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EUROHEAT & POWER Guidelines for District Heating Substations October 2008
Disclaimer: It should be noted, however, that the guidelines cannot cover all the possible special cases in which further or restrictive measures may be required. In the same line of thinking, they are not intended to hinder the development of new and better products. Applying the guidelines does not absolve anyone of responsibility for their own actions. Accordingly, Euroheat & Power disclaims any responsibility for any consequence caused by the application of the guidelines by its members or third parties. Nor can Euroheat & Power be held responsible for any advice given by the TF Customer Installations in this respect.
CHAPTER 1 – GENERAL ....................................................................................................................... 1 1.1. PURPOSE OF THE GUIDELINES ..................................................................................................................................1 1.2. APPROVAL OF THE SYSTEM AND EQUIPMENT ...........................................................................................................2 1.3. UNITS USED ...........................................................................................................................................................2 1.4. TECHNICAL DATA OF THE DISTRICT HEATING SYSTEM..............................................................................................3 1.4.1. Operating forward temperature........................................................................................................................ 3 1.4.2. Importance of low return temperature or cooling of the network ................................................................ 4 1.4.3. Differential pressure ............................................................................................................................................ 4 1.4.4. Quality of water used for district heating systems .......................................................................................... 5 CHAPTER 2 – THE DOMESTIC WARM WATER SYSTEM .......................................................................... 8 2.1. TEMPERATURES, ENVIRONMENTAL AND HEALTH REQUIREMENTS ON THE SECONDARY SIDE ......................................8 2.2. HEAT EXCHANGERS .................................................................................................................................................9 2.2.1. Types of heat exchangers (in general and for domestic warm water production) ...................................... 9 2.2.2. Storage tanks ....................................................................................................................................................... 9 2.3. DWW CONTROL SYSTEM.......................................................................................................................................12 2.4. DOMESTIC WARM WATER CIRCULATION SYSTEM .....................................................................................................12 2.5. CHOICE OF MATERIALS ..........................................................................................................................................13 2.6. HEAT EXCHANGERS, DIMENSIONING TEMPERATURES, PRESSURES AND DIFFERENTIAL PRESSURES ...........................14 2.7. DIMENSION AND CAPACITIES ................................................................................................................................14 2.7.1. Determining flow capacities for domestic warm water ...............................................................................14 2.7.2. Advantages with correct dimensions on valves and not substantially oversized dimensions on heat exchangers ...................................................................................................................................................................17 CHAPTER 3 – RADIATOR AND VENTILATION SYSTEM ........................................................................ 18 3.1. TYPES OF HEAT EXCHANGERS ................................................................................................................................18 3.2. FUNCTIONAL REQUIREMENTS................................................................................................................................18 3.3. CHOICE OF MATERIALS FOR HEATING AND VENTILATION SYSTEMS .........................................................................18 3.4. RADIATOR AND VENTILATION CONTROL SYSTEM ...................................................................................................19 3.5. DIMENSIONING OF HEAT EXCHANGERS FOR RADIATOR SYSTEMS AND VENTILATION SYSTEMS .................................19 3.5.1. Determining heat exchanger capacity ...........................................................................................................19 3.5.2. Capacity determination alternatives for radiator systems...........................................................................19 3.6. VALVES AND SENSORS .........................................................................................................................................21 CHAPTER 4 – PUMPS, SAFETY EQUIPMENT, VALVES, OTHER EQUIPMENT AND TEMPERATURE METERS
................................................................................................................................................................................................. 22
4.1. PUMPS..................................................................................................................................................................22 4.1.1. General ...............................................................................................................................................................22 4.1.2. DWW circulation pumps ..................................................................................................................................22 4.1.3. Radiator and ventilation system circulation pumps .....................................................................................23 4.1.4. Pump control .....................................................................................................................................................23 4.2. DIFFERENTIAL PRESSURE DEVICES..........................................................................................................................23 4.3. SAFETY EQUIPMENT ..............................................................................................................................................23 4.3.1. Expansion vessels ..............................................................................................................................................23 4.3.2. Safety valves for DWW systems .......................................................................................................................24 4.3.3. Safety valves for radiator and ventilation systems .......................................................................................24
.................................................................................................................................................3....................................................................28 4....3................ 48 7..............54 7...............................1.. DIMENSIONING OF TEMPERATURE SENSORS .................27 4......... Heat demand .2................................................. Installation inspection ..........5......................................................................................54 7........................................ Inspection of produced meters ................2.......... Check valves ................6............................................... Control systems................................7..............4.................................................................................................................................................................................................55 7..................................................58 7.................................... INSTALLATION OF HEAT METERS.....1... LIFETIME COST .........................25 4.........28 4......5.................................................................................................................................5......................................................................................................58 7................... vent and pressure meter valves .....2.... Temperature sensors .............................. Temperature meters ....................53 7.................61 7......................49 7........................................53 7........ 5........................................29 CHAPTER 5 – CONNECTION PRINCIPLES ................................................................4.............60 7................................2..... 5..............6...2..5... EVALUATION OF CONFORMITY WITH THE MID REQUIREMENTS ........................................................26 4........1...................................................................................................................................... DIMENSIONING OF FLOW SENSORS.............................................................. GENERAL DESCRIPTION OF THE MINIMUM STANDARD ...................................... DOCUMENTATION REQUIREMENTS........................ The district heating system .......................................................................................................................6...............................................2...................................................................................3........6................................................. Piping installation ........................................ Planning the meter position ..48 7............. General ..............................................................2...............................................4...................................................................8..............66 7....54 7............................3............................................. Pressure meters ...................... Re-verification of meters ..6...........................2.............6....6...........................................................4........................................................6....................... Shut-off valves ...................6....... Thermostatic Radiator Valve (TRV) and some importance features ............................. FUNCTIONAL REQUIREMENTS ...............................................................................57 7.................30 DIRECT AND INDIRECT CONNECTION ......................................... MARKING OF HEAT EXCHANGERS AND SUBSTATIONS .................................50 7...............1............................................................2..................................................... Hydraulic balancing and balancing valves .....51 7...........................................7..7................................................................................................60 7......1................2............................................................................5.......................................................... Selection of suitable flow sensors ........ Environmental influences..........................4........................................................... Electrical installation ............65 7.....................................................................................63 7..................................................................................7.........................6. Drain...............................3..............7..........26 4................ 5............34 VARIOUS CONNECTION ALTERNATIVES .........................27 4.7.....7.................................... GENERAL ..........................................................................................27 4................................................................................................33 SYSTEMS OF DOMESTIC WARM WATER.................. 43 CHAPTER 7 – HEAT METERING .........3............3.........................................................................................................4....32 1-STEP AND 2-STEP CONNECTION OF DOMESTIC WARM WATER..........................62 7....................................... Flow sensor .........................................67
.....................................................4............................................25 4...............................................................................4......4....2.................................................................4.......55 7.. General ................ 30 5................................ Suitable and unsuitable positions for flow sensors .................................62 7.........................................................4..1............. Identity checking .................... Calculator .......................................... Remote reading of data ....................................................................................................................................................................................................4.......................................................................................4.......................2.......................4.......................................................................1.......................................53 7.............................................................. Examination of type and design ...............................65 7....3......................................................................... VALVES AND OTHER PIPING COMPONENTS ........1.................28 4......65 7.........................................................................36
CHAPTER 6 – SERVICE AND MAINTENANCE .............. Strainers (filters)...............................8............................3........9.......................................5.................................................................................................... 5.......................................4...........5.............................58 7.................................................................................. Compatibility and interfaces between subassemblies ...........................5.........4.......4......51 7.......
installation. An example of this is provided in Chapter 7. These guidelines aim to provide best-practice and easy-to-handle recommendations for: those who are responsible for relations between district heating utilities and customers. those who manufacture. purchase. the guidelines demonstrate that the harmonization of various rules and regulations throughout Europe. instead of investment costs alone.CHAPTER 1 – GENERAL
1. The Guidelines were developed based on the most optimal operating principles of substations and meters. For instance. but in general. These guidelines do not deal with investment or cost aspects. those who own or maintain a building connected to the district heating network. is both needed and feasible. For this reason. The guidelines deal with a wide variety of issues concerning both present systems of today and district heating systems of the future.6 MPa. Nevertheless. plan. The guidelines include a chapter on the heat meter. these regulations should in all cases prevail. certain existing systems are not dealt with in these guidelines. These guidelines are intended to give the most effective overall solutions for various parts of the customer installation.
The present guidelines contain a set of recommendations focusing on planning. Euroheat & Power recommends looking at the lifetime cost of all components of the substation. The guidelines are not meant to specify the different components of the substation such as meters or heat exchangers. use and maintenance of district heating (DH) substations within district heating systems throughout Europe. The recommendations were developed in order to enable readers to develop well-functioning substations and an effective heat and domestic warm water delivery.1. including temperature levels. Specific handling and maintenance recommendations are mainly focused on present modern systems but are also intended to cover the future situation as much as is feasible. For instance. The officially prescribed temperatures should in every case prevail over temperatures taken up in these recommendations. as the meter and especially the meter installation is always installed simultaneously with the rest of the substation. At the same time however. when national regulations pose rules contrary to those recommended in the guidelines. throughout most countries in Europe prescriptions exist in order to avoid risks of diseases like Legionella. these guidelines do not cover steam systems.8. systems with temperatures exceeding 110 °C and pressure levels above 1.
. test and install substations.
all laws and rules from health and environmental authorities need to be taken into consideration. European Union (EU)-.3.
Approval of the System and Equipment
All DH equipment and the system as a whole is to be approved in accordance with international-.86 Mcal 1 Mcal = 1. National DH organisations and Euroheat & Power should make efforts towards harmonizing such rules and standards throughout the EU. CEN 311.2. bar Authority of the control valve
qv ∆p
∆pv ∆phc
HTS LTS
∆pv ∆p hc
Authority of the control valve – definition Pressure loss of the selected valve. The aforementioned organisations may also issue technical recommendations themselves. and national laws.
1 kW = 0. etc.
1.01 bar = 0. bar Pressure loss of heating circuit. Differential Pressure Temperature Flow coefficient value Flow coefficient value .1868 MJ 1 l/s = 3. regulations.These guidelines are valid from 1 October 2008. in order for these rules and standards to be as much as possible in line with the specificities of DH.1 mwp 10C = 10K kv kv = qv ∆p
Capacity Energy Energy Flow Pressure.86 Mcal/h = 102 kpm/s 1 kWh = 3600 kJ = 0. Also.6 m3/h 1 kPa = 0.163 kWh = 4. bar High Temperature Systems Low Temperature Systems
. The following standards and EU directives are relevant for the present Guidelines: Pressure Equipment Directive (97/23/EC) Measuring Instruments Directive (2004/22/EC) Energy Performance of Buildings Directive (2002/91/EC) Machinery Directive (2006/42/EC) Energy Services Directive (2006/32/EC) Eco-design Directive (2005/32/EC) EN/CEN standards: EN 1434.definition DH flow (m3/h) Dimensioning pressure difference. The guidelines are to be regarded as a working document subject to on-going adaptation and perfection. building codes and standards.
Every DH company should provide this information to the customer.
Technical Data of the District Heating System
Traditional high-temperature systems (HTS) operate at higher temperatures and pressures than low-temperature systems (LTS).4. In order to ensure that district heating substations receive a supply temperature of not less than 65°C. It is important that the heat supplier clearly specifies which operating temperature characteristic is employed. Table 1 below shows rating and design data for the systems.
1.DWW DWWC SH DH DHS DHR DH water Storage tank
Domestic Warm Water Domestic Warm Water Circulation Space Heating District Heating District Heating Supply District Heating Return District Heating water Cylinder or accumulation vessel
Depending on local conditions. the forward temperature of the water from the production plants should be about 10°C higher than the targeted supply temperature. Operating forward temperature The temperature curves in the diagram below show the supply temperatures from the production plant to the district heating substations.4. the break point can vary over the range -5oC to +10oC.1.
in accordance with the temperature and pressure levels provided below.6 MPa High-temperature system (HTS system) differential pressure 0.10 Mpa Max 85°C.4. This data should be used for determining the necessary sizes and capacities of control valves and heat exchangers.6 MPa Low-temperature system (LTS system) differential pressure 0.2. more heat subtracted) and good performance of the district heating substation are in the interests of both the customer and the heat supplier. The quality of the circulation water that carries the heat can affect performance. Differential pressure The district heating supplier will provide information on the actual minimum and maximum differential pressures. Importance of low return temperature or cooling of the network The amount of heat utilised from the circulating district heating system water depends mainly on the design and adjustment of the building's internal heating systems. Therefore.Operating and design data Euroheat & Power strongly recommends DH companies to build all new systems.3. including new parts in older systems.6 MPa Design data
1. The following diagram shows the principal ranges over which the differential pressure in a high temperature district heating system can vary. 0.3 MPa 90°C. as measured at the service connection valves. 1. but also on the performance and the condition of the district heating substation.
Table 1 District heating system Operating data 100°C.8 – 0. 1.e.4.35 – 0.6 MPa 110°C. water treatment and control and monitoring of contributory water for the system is important.
. Good cooling of the district heating water (i. 0.
1. NOTE: Existing systems are not reflected in Table 1 below. Note that the heat supplier should include the pressure drop across the heat meter in the information provided.
In modern substations this value is close to 0. Oxygen (O2) in "salty" water causes corrosion in unalloyed and low-alloyed ironwork materials (piping and radiators). The substations should be dimensioned according to the real pressures that may occur. There are also different methods to protect the system against corrosion. one generally needs less than 0.6 MPa (see Figure 2 above). the use of 0.4.8 MPa. In that case. The local heat supplier can provide further information on differential pressure making it possible to use higher levels of differential pressures for dimensioning. the system should as far as possible be closed to the penetration of oxygen. the most common range is 0. To secure the overall efficiency in all substations in a big district heating network.1.
District heating substations for HTS systems normally operate with a differential pressure in the range 0. 1.4.4. in the meter and in the piping and valves. The total pressure drop that is needed in the substation shall cover the pressure drop in the heat exchanger.1 MPa. substations at the end of the network will also be able to manage all situations. With optimal dimensioning of all these parts.10 MPa is recommended. Therefore. Gases These Guidelines identify the need to focus only on two gases: oxygen and nitrogen.05MPa for ordinary substations.4.1 to 0. Quality of water used for district heating systems There are various water qualities in DH systems.
1.1 to 0.
4. pores or in columns). under certain critical conditions (e. through diffusion from permeable membranes or plastic pipe systems. in the presence of oxygen lead to local corrosion (e. noise and erosion corrosion will be the consequences. Scale increase impedes the functioning of the heat exchanger and decreases its thermal capacity. They also disturb the function of control.2. Furthermore. Due to the fact that specific corrosion danger depends on several factors (e. In any case. operating conditions). A chloride concentration up to 50 mg/l will usually cause no corrosion damage. Oils and fats are nutrients for micro-organisms and can even cause micro-biological corrosion. Therefore it is strongly recommended to avoid the use of oils and fats in DH systems.g. In some cases overheating occurs and as a consequence the heat generator can be damaged. As a film or cover on materials. Organic substances Insoluble and soluble organic substances can impair water treatment technology. crack corrosion) with unalloyed ironwork materials. Components in the water Water soluble substances Alkali In warm water. low pressure conditions in closed systems enable the entry of air through gaskets and automatic vacuum breakers. alkali reacts with hydrogen carbonate forming calcium carbonate and resulting in the formation of scale. in case of increasing concentrations under covers.and deposit corrosion. To protect the system against scale formation. chloride ions in stainless steels can lead to pitting. 1. Circulation disturbances. Anions Anions from water-soluble substances. Oils and fats To temporarily prevent the corrosion of old armatures. oils affect the heat exchanger. However. material. a very low chloride concentration is recommended.and safety equipment.g.
.g. chloride causes corrosion with aluminium materials making this combination unadvisable. substances based on oils or fats are used. Gas blistering appears as a cause of increasing temperature and decreasing pressure. Oxygen (and small amounts of nitrogen) can enter through heat exchangers of domestic warm water systems.4. medium. the filling water and top-up water should be softened. a limit value valid for all operating conditions cannot be defined. particularly chloride and sulphates. The gas solubility decreases. In district heating substations air/gas can permeate the circulation water through the expansion tanks open to the atmosphere in the domestic system. piping or heating surfaces. Also. as well as micro-biological reactions in the circulation water.Nitrogen (N2) is an inactive gas in the water content and causes material problems when its concentration is so high that free nitrogen gas bubbles are formed.
rustproof steels and coppers.4. Another aspect is that magnetite . including the secondary side. Iron and copper can lead to deposits and failures in zones with low flows. can be applied. For DH systems two different operational possibilities exist.01 mg/l are in the normal range.02 <0.g. But this protection layer is only built at temperatures higher than 100°C.
Table 2 Standard values for district heating water quality Electrical conductivity pH-value Oxygen Alkaline Mg/L mmol/L µS/cm 100-1500 9. In extraordinary operations/situations (e. For a safe and economic operation of the circulation water the following standard values should be complied with. the system should be closed from air and cold water uptake to prevent corrosion. Compliance with the standard values for chemical water treatment (see Table 2) unalloyed ironwork materials.as a corrosion product . start-up.1. Aluminium or aluminium alloys should not be used in direct contact with the circulation water. Experience shows that concentrations of iron ≤ 0. namely low-salt and high-salt operation. separately or in combination. damage) it is possible to diverge from the values for a short time.builds a homogeneous oxygen surface layer with high corrosion resistance on metallic surfaces. Euroheat & Power recommends not using aluminium at all in any DH systems.4. So this effect cannot be used in domestic warm water systems. Therefore suitable pressure maintenance is necessary.02
The treatment of the DHW is achieved in the production plant and handled there.3.10 mg /l and copper ≤ 0. otherwise alkali-induced corrosion is possible.5-10 <0.
. Operating techniques First of all.
Environmental and Health Requirements on the Secondary Side
With the entry into force of Directive 98/83/EC. In order to achieve good comfort and health requirements for the domestic warm water system one should be able to control: temperature levels on the secondary side. There should not be any connection of equipment to the system. The domestic warm water system should not be used for other purposes than purely sanitary. some special actions should be taken regarding design and operation. If accumulation of warm water in storage tanks is used. In order to reduce the risk of Legionella infection. It is advisable to check and record these parameters. suggestions are presented on how to prevent the development of bacteria and Legionella. e. where the distances between the heat exchanger/storage tank and the tap are typically short. no connection of towel dryers or floor heating pipes to the drinking water pipe system. “Short-cuts” or “dead ends” are to be prevented in the system. For multi-family houses the outgoing temperature from the heat exchanger/ storage tank should be minimum 55˚C in order to secure the temperature at the tap of 50˚C. The contamination of the system especially with Legionella takes place in the domestic plant. Towel dryers and smaller floor heating pipes are potential risks for bacteria. temperature of the circulation flow and return in the system. In case of Legionella growth in the system. the circulation and the storage tank. the system should be operated at 55˚C.e. Bacteria and Legionella are not problems specific to district heating.CHAPTER 2 – THE DOMESTIC WARM WATER SYSTEM
2.1 The owner of the domestic plant is responsible for its good functioning. Bacteria will not be eliminated by increasing the temperature to 55˚C in a heat exchanger of warm water that has been standing still for a long time at 40˚C. For one-family houses.g. i. the water content should be heated up to at least 60˚C during two hours before the water is delivered to taps. in the drinking water pipe system. Below.1. The requirements for cold and warm water are comparable with the demands on foodstuffs. European standards for ensuring the safety of water for human consumption were enacted. They occur in all warm water systems (heating oil/natural gas/solar/electric).
Temperatures. Such heating occurs very quickly and does not give sufficient time to kill the bacteria. This is
. minimum 50˚C at the heat exchanger is usually sufficient to get a temperature of 50˚C at the tap as well. which could force the temperature below 50°C in any part of the system.
2. In such cases it is recommended to change the control system to a faster one. This type of exchanger has the advantages of reliability. Another type of plate heat exchanger is plates with gaskets which can be used when problems with lime scale occur. in low energy one-family houses. Types of heat exchangers (in general and for domestic warm water production) Regardless of the type and the material of the heat exchanger. A disadvantage is the low internal water volume. if there is an exceptionally high use of DWW at the same moment (sport halls etc.
2. fixed tap positions with a maximum temperature of 38 ˚C should be installed. retirement homes and kindergartens special care should be taken to avoid growth of the Legionella bacteria. The heat exchanger surfaces are made from acid-resistant steel or stainless steel. and large capacity for its size.1. The cooling of DHW must be as effective as possible in all conditions and all water flows should run along the heat exchange surfaces. Modern heat exchangers are brazed plate heat exchangers.an unsuitable arrangement and does not meet public health and environmental requirements. Water hardness Euroheat & Power recommends not using any chemical treatment for water hardness. If there are special demands for low temperatures at the tap or in a shower. lightweight. Below some examples are provided: if there is a lack of appropriate flow capacity of DH service connection (too small dimension).2. In buildings for especially sensitive persons like hospitals.
.2. the basic objective is that heat exchangers are to be dimensioned and built so that the customer will get sufficient warm water in all normal circumstances. In such a case the manufacturer should guarantee the durability and elasticity of gaskets and other elastic parts for operation (special attention should be paid to the lifetime of the gaskets). The mixing should occur at the shower positions in order to avoid bacterial growth.
‘Storage tank’ is taken here to have the same meaning as ‘cylinder’.
2. Storage tanks It is generally also possible to use DWW storage tanks if this is the traditional installation.2. which may cause temperature problems if the regulating system is not fast enough.). All heat exchangers used in district heating should follow the requirements of EN 1148.
2. Cold water temperature 10 °C.1 One-family house system One-family houses can use a storage tanks with 100 L – 160 L content.2.2.2.It is more efficient for the cooling of the network to use substations without accumulation than to use substations with accumulation. standard apartments.2. the number of taps and the desired temperature inside the storage tank. 2.2 Small systems – storage tank with internal heat exchanger For economic reasons storage tanks with an internal heat exchanger are recommended in small multi-family houses.
Diagram for storage tanks with internal heat exchanger
. The diagrams are based on: DHW temperature 60 °C. depending on the number of inhabitants and their behaviour. The following examples show the dimensioning of DHW systems with storage tanks.
Filling the DWW storage tank by means of a filling pump should not take more than two hours. The construction
. Figure 3b Diagram for storage tanks combined with external heat exchangers
Diagram corresponds to Figure 12 in connection drawings in Chapter 5.
The DWW tank size should guarantee the possibility of it being fully drained during daily maximum consumption periods. which is necessary for an efficient filling pump.Diagram corresponds to Figure 13 in connection drawings in Chapter 5.5. The DWW storage tank should have thermal insulation guaranteeing the maintenance of a stable water temperature. It is recommended to use a system consisting of a plate heat exchanger and a DWW storage tank (flow-storage system) to obtain the lowest possible return temperatures from the substation with storage tanks.5.
In order to ensure the best performance in 'on-demand' systems.controlled. the frequency of warm water demand. One option in the control equipment could be to prioritize the DWW over space heating. whether the domestic warm water system does not have a circulation system (as in detached house systems or apartment building systems).
. DWW may have priority over space heating. if based on limiting the maximum substation capacity.or flow.4. detached house areas with central domestic warm water production.
Domestic warm water circulation system
The domestic warm water system consists of pipes from the heat exchanger in the substation to the different taps and of circulation pipes which return unused water to the heat exchanger.
2. To guarantee the good quality of DWW a fast control system is needed. This can be ensured through a variable pump capacity. Euroheat & Power recommends that circulation systems are used in all buildings that are connected to district heating. for instance. It is important that the domestic warm water circulation system maintains the prescribed temperature in the distribution pipes and in the circulation pipes. design and setting up of domestic warm water supply and circulation systems in order to ensure circulation in all parts of the systems. the type of heat exchanger. which will ensure maximum utilization capacity and a minimum dead sediment part.shape of the DWW storage tank is to be of a vertical slim shape. which will keep the DWW temperature constant. the equipment should respond to both the incoming cold water flow rate to the heat exchanger and the temperature of the domestic warm water delivered from the heat exchanger. The task of the circulation of warm water is to keep the system active and the temperature on such a level that both comfort and health requirements are satisfied for the customer. The control valves may be either electronically or temperature.
2. thermostatic valves and balancing valves. If domestic warm water circulation systems are installed.
DWW control system
The control system should ensure a stable DWW temperature during the whole year. which is highly recommended especially in multi-family houses. The following aspects should be considered when deciding on control equipment: pressure and temperature variations in the district heating system. one should ensure that the DWW return temperature never goes below 50°C.3.
When choosing materials for a domestic warm water system. water is the most common existing solvent and can in many cases be very aggressive. this means that the installation of a circulation system is necessary. If there are significant distances in a one-family house Euroheat & Power recommends also installing circulation there. one should ensure that they can withstand the working conditions in the system for the period the system is designed and that they do not add harmful or poisonous substances to the water or contribute to the development of bacteria in the water. attention should be paid to the quality and chemical composition of the local water source to avoid corrosion of the system.
2. the materials in question should not contribute to the development of bacteria. circulation should at least exist in the lowest part that covers the horizontal pipes up to the vertical main pipes in multi-apartment buildings. In order to avoid the waste of water and to improve comfort.
. the materials in question should not release harmful or poisonous substances into the water. the materials should also withstand the maximum temperature that the system is designed for. for example. i.4301 (AISI 304).In older buildings with no circulation systems. the circulation system or heat tracing can be omitted.2 l/sec. it is not only metals that are used in domestic warm water systems. In most systems this means 1. it is recommended to design the warm water system in such a way so that the warm water reaches the tap within approximately 10 seconds (design water flow: 0. in gaskets. This can vary considerably between different systems.5 MPa) pressure on the primary side.5. but also polymers. In many cases.
To ensure a safe and healthy production of domestic warm water there are a number of criteria that should be fulfilled: the materials in question should be selected so that they can withstand the maximum pressure that the system is designed for.6 (could also be 2. The same care has to be taken in choosing gaskets for the system.).e. if there is a mix of materials they should be chosen in a way to avoid galvanic corrosion between the materials. 1. 1.4401 (AISI 316).4404 (AISI 316L) or Alloy 20/18/6 o Dezincified resistant brass o Titanium o Polymers The choice of material in house installations should also follow national requirements and regulations.0 MPa pressure on the tap water side and 1. The recommendation of a 10 seconds maximum waiting time should not necessarily result in the installation of circulation systems in all one-family houses. common materials in domestic warm water systems are: o Copper o Stainless steel. for instance in rarely used taps. In cases where waiting time or the waste of water is not important. 1.
NOTE: national and/or regional values can be used.1.7. Dimensioning Differential Pressures
Heat Exchangers. multi family houses Return Temperature. Determining flow capacities for domestic warm water The formula below is recommended for nearly all existing residential buildings in Europe. The choice of flow is recommended in accordance with the dimension slopes below. There are a number of advantages in choosing adequate sized heat exchangers and the smallest possible valves.) Calculating Temperature Calculating Temperature for LTS Return Temperature.
Domestic warm water heat exchangers should be designed to provide the following temperatures and pressure performances:
Table 3 Primary side (DH) Differential Pressure (max.7.
.6. single family houses 25 kPa 65°C 60°C <22°C <25°C Secondary side (DWW) 50 kPa 10°C 10°C Supply temperature 55°C Supply temperature 50°C
Euroheat & Power recommends dimensioning the heat exchangers according to this design.
The two slopes represent the upper and lower flows that are currently used in Western and Northern Europe for dimensioning of flow demand in residential buildings.1 = design flow rate [l/s] for n apartments number of apartments aggregated flow per apartment to determine heat exchanger data total maximum flow per apartment.15 = = 0.7. may be increased if needed probability of exceeding qm probability of exceeding q
The figures entered refer to the lower slope in the graph. By striving to make dimensions closer to the lower line in Figure 4 above. See chapter 2. Capacities of heat exchangers in residential buildings should be calculated and determined on the basis of the following conditions:
. network and production. one can obtain better economical and maintenance results for both substations.20 = = 0.015 = = 2. The different flows are originally calculated by the following formula:
q = qm + O(n * Qm − qm) + A O * qm n * Qm − qm
q n qm Qm O A = = = 0.2.
2.36 0. differential pressure lower than the design minimum differential pressure.0. it should be acknowledged that it is the heat exchanger for which this formula intends to provide design data: rules for determining design capacities of the domestic warm water system piping in the building(s) are set out in prEN 806-3. High flow-rate tap water systems may be encountered in older buildings and allowance should be made for them when deciding on the necessary flow-rate capacity of the heat exchanger.1.89 .73 0.2.58 0.2.84 0.0.73 .49 Number of apartments 80 90 100 110 120 130 140 150 160 Domestic warm water.0.1.78 .67 .37 1.2.60 0. In addition.22 Number of apartments 170 180 190 200 210 220 230 240 250 Domestic warm water.2.00 1. a temperature drop of more than 5°C between the heat exchanger and the tap.1.56 .99 .1. In many places in Europe there are extensive residential areas with very big apartment buildings.2. l/s 1. such as non-residential buildings.Part 3: Determining the Sizes of Tap Water Pipes.57 1. The 'single' apartment shown in Table 4 represents a detached house or an individual apartment district heating substation unit.40 .61 .91 0.44 1.47 .1.38 .14 .1. If the system supplies more than 250 apartments.2. l/s 0.77 1. the domestic warm water and circulation piping has a smoothing effect on the domestic warm water temperature.31 .39 0. In addition. The flows have been calculated from the following formula and are valid for apartment buildings with more than five apartments.51 .1.2.2.2.2. and should be specified.84
Several conditions must occur or be present simultaneously before a shortage is likely to arise: a district heating supply temperature of less than the normal minimum °C.25 .67 0.Table 4 Number of apartments 1 5 10 20 30 40 50 60 70 Domestic warm water. some
.94 .19 .71 1.60 .76 0.18 0.15 1.2.84 .20 .51 1.09 .05 0. The required performance parameters for buildings with a recognised higher domestic warm water demand. a cold water temperature lower than 10°C. the requirements should be checked using the formula above.29 0.1.1.08 1. a warm water flow rate exceeding ql/s as used in the above calculation.30 1.64 1.2.28 .33 .1.04 .92 1. Requirements for Systems and Components Inside Buildings Conveying Water for Human Consumption .55 .0. can be different.42 .24 .48 . l/s 0.
better regulation of both warm water and heating in the substation means better. it is possible to obtain better economic and maintenance results for substations. It can be concluded that by making the dimensions closer to the lower slope in Figure 4 above. decreased morning peaks. the warm water circulation functions better. Advantages with correct dimensions on valves and not substantially oversized dimensions on heat exchangers Present dimensioning varies considerably throughout Europe. It also allows starting up the network after “a blow-out“ much earlier than before. This leads to a longer lifetime for valves and other equipment. In some cases there is no good domestic warm water circulation and this. decreased risk for laminar flow when low flow conditions occur.
2.2.7. The advantages of using correct dimensions.
.containing more than 500 apartments per building. especially for valves. less pumping costs. smoother and more stable conditions. creating more capacity which can be used for new connections or transmission purposes. This means that the highest demands now are lower and easier to supply than before. and possible other circumstances. could demand higher flows than calculated. are the following: smoother and more dynamic network that better responds to changes in forward temperature and flow. less service costs and ensures a better economy to the owner of the substation. the network and production.
common materials in heating systems are: o Stainless steel.6 MPa pressure on the heating/ventilation side and a 1. heat exchangers should be built so that cooling of the DH water is as effective as possible in all conditions and so that all water flows run along the heat exchange surfaces.2.
Choice of Materials for Heating and Ventilation Systems
To ensure safe and reliable operation a number of criteria should be fulfilled: the materials in question should be selected so that they can withstand the maximum pressure the system is designed for. 1. Secondary supply water should not be mixed with secondary return water. care should be taken to the quality and chemical composition of the local water source to avoid corrosion of the system.6 MPa (could also be 2.1. if there is a mix of materials they should be selected in such a way as to avoid galvanic corrosion between these materials. 1.4404(AISI 316L) o Copper o Carbon steel o Dezincified resistant brass o Polymers
Regardless of type and material of the heat exchanger.3. for example. the materials should also withstand the maximum temperature that the system is designed for.
3. In most systems this means a 0. to ensure that they can withstand the working conditions in the system for the period the system is designed.
Please refer to Chapter 2. gaskets. i. 1.
3. but also polymers in. When choosing materials for a heating system. water can be very aggressive in many cases. The same care has to be taken in choosing gaskets for the system. This can vary greatly between different systems. not only metals are used in heating systems.4301(AISI 304).CHAPTER 3 – RADIATOR AND VENTILATION SYSTEM
3.2 (the same type of heat exchangers as for DWW except for shell and tube heat exchangers). Heat exchangers should have thermal insulation and all connections are to be clearly marked.5 MPa) pressure on the primary side.4401(AISI 316).
Radiator and Ventilation Control System
The control system should assure stable space heating temperatures according to customer needs during the whole year, independent of changes in the outside weather conditions or inside heat loads. The preferred method is to use outside-temperature-compensated radiator flow temperature (connected to the thermostatic radiator valves in every radiator). For this, the outside temperature sensors should be placed in a suitable reference place (for instance the northern wall). A flow water temperature sensor and a control centre should also be considered. Modern control centers are digital with additional functions. Reference room temperature sensors complement the outside temperature sensors. If possible through agreement or ownership, it is advantageous to install a controller for DH or other utilities with a temperature trend log that enables to register controllable parameters in order to carry out technological optimization. Reference room temperature sensors are recommended as an option. One should always pay attention to the cost-benefit situation.
Dimensioning of Heat Exchangers for Radiator Systems and Ventilation Systems
3.5.1. Determining heat exchanger capacity Heat exchanger capacity should be such that the heating power requirements of the building can be met at the design outdoor temperature. In some cases, however, there may be an operating mode that does not necessarily occur at the lowest ambient temperature that determines the necessary design capacity. The local climatic conditions should also be considered. Calculations should also be made to ensure that part-load power demands could be met. Requirements resulting from the Buildings Directive and national applications for heat demands should be taken into account. Table 5 shows a number of alternatives for determining the necessary design capacities for different types of building and heating systems. The specified return connection temperatures apply for new heat exchangers with clean heat exchange surfaces.
3.5.2. Capacity determination alternatives for radiator systems The design parameters used for the dimensioning of the radiator system are related to the DHsystem as a whole. The necessary DH supply temperature and the aimed return temperature have a significant impact on the: heat losses; production efficiency; pipe capacity/construction cost; pumping capacity; the cost of heat installations.
In general, low temperature-set means less heat losses. The supply temperature is set by taking into account: the fact that a low supply temperature means a demand for more pipe and pumping capacity, whereas a low return temperature in all aspects is advantageous for the DHsystem. The only disadvantage of a low return temperature is that it demands a higher radiator surface area. The design parameters for choosing the optimal return temperature are therefore a compromise. In general, the energy demand is decreasing. Specifically, the consumption for new buildings has decreased. This increases the significance of having lower return temperatures, because a smaller consumption rate leads to smaller radiators. In new one-family houses the focus on the differential temperature is even more important in order to reduce the service pipe dimension, resulting in lower construction costs and lower heat losses. The necessary capacities of radiator systems in buildings already connected to a district heating system, or for which such connection is planned, can be determined in accordance with Table 5.
Table 5 Target design temperature Max. radiator and ventilation system supply temp. Max. radiator and ventilation system return temp. 40°C 30°C
Max. district heating supply temperature, HT/LT system
Max. district heating return temp.
Max. floor heating system temp.
100/80°C 100/80°C
70°C 60°C*
28 - 35°C
Max. pressure drop in district heating side 25 kPa
Max. pressure drop in radiator and ventilation side 20 kPa
* 55°C for drier circuits When the buildings are dimensioned for less optimal solutions (e.g. designed for using natural gas boilers), the existing in-house radiator system will be used. It is preferable, however, to redesign the existing system to suit the new conditions. When considering 60-40°C or 70-30°C systems, the factors that particularly need to be considered are the larger radiator surface areas and the lower flow rates, as well as the improved temperature efficiency. It improves the efficiency of the district heating system and reduces the return temperatures; the operation costs of the secondary system are in a heat exchanger also lowered.
As with heat exchangers for domestic warm water systems, the temperature difference on the return side of the radiator heat exchanger should not exceed 3°C at the design rating. At lower loads, this temperature difference should be proportionally less. If the temperature difference on the return side of the radiator heat exchanger is increased to 5°C at the design rating, this will lead to a reduction of the heating surface of only 15%. The life-time cost of the system will increase substantially as this will lead to increased pumping costs and increased return temperature on the primary side. Balancing the system has a decisive effect on operating performance, regardless of the choice of design temperatures for the radiator circuit. Over the years, various principles have been applied in order to achieve a good result: the high-flow and the low-flow principles, for example, are two ways of achieving good cooling of the radiator circuit water. There can be advantages in choosing a low-flow system for the building's heating system. A characteristic of such systems is the relatively high design supply temperature and the low return temperature, which assists the overall performance of the district heating system and reduces costs in the whole system. If a low-flow heating system providing very low return temperatures is used, there will be little further benefit from the use of a two-stage connection in terms of further cooling of the return water. In such cases, it is recommended that the more cost-efficient parallel connection should be selected.
Regulating valves are to be dimensioned according to the needs of space heating systems and design values of the heat exchanger and heat flows: minimum pressure drop on open valves (valve authority) – should not be lower than 50% of the total pressure drop of the regulated unit. Valve characteristics should consider the right consumption function. The valve should minimize the risk of fissures and leaks from closed valves and should not exceed 0,05%Kvs at 1,0 MPa of pressure difference. Range ability of the valves should not be lower than 50:1 (control ratio which is defined as a ratio between maximum flow to minimum controlled flow). Temperature sensors The time-constant of DWW temperature sensors is recommended to be maximum 2 seconds. In order to ensure the correct measurement of temperature values, the proper construction and installation of the temperature sensor is crucial. It is recommended to use an immersed casing of stainless steel, operating in direct contact with the heating medium (with an additional protective pocket) and installed in the pipeline axis. Pockets are only recommended for large installations as compatibility is the greatest advantage for service purposes.
1. DWW circulation pumps The pump is to be designed for the same pressure and temperature class as the domestic water system: PN 10 or higher. VALVES. General Energy saving pumps should be considered in all circumstances in order to save energy and to reduce the lifetime operation costs of the system. Normally 20% of the total flow of the DWW heat exchanger is utilized. OTHER EQUIPMENT AND TEMPERATURE METERS
4. The flow for DWW circulation pumps should be calculated on the basis of both heat losses and pressure drops. including motor. The manufacturer of the substation shall adjust the pressure (i.e. The class of electrical components. DWW-circulation pipes should have a balancing valve in order to ensure the correct flow for the DWW-network. It is recommended to use a voltage of 1x230 V. The pump should be placed before the heat exchanger in order to reduce the risk of fissures and reduce thermal stress of the electronic components.
4. All pumps in the system should have sufficiently low noise levels so that no noise is transferred into the living quarters of the building.1. Such type of pumps enable the adjusted flow to provide better conditions for space heating. SAFETY EQUIPMENT.CHAPTER 4 – PUMPS. as pressure drops could vary between design specifications and manufacturers’ specifications. retirement homes etc. The circulation pump should be in continuous operation and is recommended to have speed and noise control functions. lifting height) of the pump in accordance with the existing heat exchanger.) where it is very important to maintain continuous and effective functioning. It is also recommended to use adjustable DWW-pumps. should be IP34 or higher.1.
4. it is recommended to use double pumps with an automatic start function for the second motor. The wet part of the pump should be made of water-resistant materials with a high oxygen content. For critical buildings (hospitals.2. The use of low energy pumps is strongly recommended.
Dimensioning of the expansion vessel should be carried out by considering both the possible difference between the highest and lowest temperatures that
.4.3. A very high differential pressure may result in an additional systematical meter error. when pumps run intermittently during summer time via presostat or thermostat controlling.2. In case of external switches for pump control. The pump control box should fulfil all local and national electricity requirements. The pump control box should be included in.1 MPa (and/or if noise occurs). to avoid interaction between differential pressure valves located in the same area. in the ECO-function in heating. Expansion vessels Expansion vessels should be installed in closed loop systems to accommodate the thermal expansion of the water. in the switches for each motor.4. Pump control Pump control components are typically located inside the pump control box with terminal connections.
For indirect systems with variations in differential pressures that are larger than 0. The protection class of the pump control box should be IP34 or higher. The pumps should be dimensioned and selected in accordance with the secondary flow through the heat exchanger.1. the main switch.
4. All pumps have to be protected against overload situations.1. for instance.
4.1. This occurs.3.4 MPa and for direct systems with variations larger than 0. Radiator and ventilation system circulation pumps The pump is to be designed for the same pressure and temperature class as the radiator/ventilation system: PN 10 or higher. This can be handled inside the pump control box with overload protections or inside the pump motor.
4. in the indication lamps and in the alarm connection points for each pump motor. The devices should be placed in the substation. or a part thereof. it is an option to use differential pressure devices. at least.
4.3. the pump control box should be equipped with transmitters for controlled motors.
a check for the pressure level should be made. e. It is recommended to use two parallel safety valves on the space heating side in large buildings.3. Safety valves for radiator and ventilation systems The safety valve should preferably be installed in the incoming pipe to the heat exchanger on the secondary side. The expansion pipe should be connected to the return pipe before the pump. otherwise one extra safety valve between the heat exchanger and shut-off valve will have to be installed.
4. If the design pressure of the DH network is higher than the parameters of the customer installation. including pumps.could occur in the system and the total volume of the loop in question.g. The expansion vessel should be placed on the suction side of the pump so that it need not also control the pressure drop over the heat exchanger and the strainer. It is necessary to control and measure the pressure of gas inside the expansion vessel. When changing old installations. controls and expansion tanks. Closed expansion systems are recommended in case of new installations due to the fact that open systems can increase the oxygen level of domestic space heating systems. The resting pressure is kept constant in the heat generating system. There should not be any shut-off valve between the safety valve and heat exchanger. Safety valves for DWW systems The safety valve is to be installed in the cold water supply pipe connected to the domestic warm water heater. the power plant or network substation.3.2.
4. Pressure control Euroheat & Power recommends the use of the same design parameters for pressure on the primary side of the substation and for direct connections as the maximum system pressure of the DH network. There should not be any shut-off valve between the safety valve and the water heater. then the safety valve should be installed between the heat exchanger and the service valve.
. For high buildings (pressure <= 450 kPa) it is also possible to use systems with pressurisation sets. An adequate resting pressure has to be ensured to prevent evaporation or vacuum formation. If a service shut-off valve is used for an expansion vessel.3. then special safety equipment has to be installed in accordance with the Pressure Equipment Directive and/or local regulations.
The number of components and places are described in the connection principles under Chapter 5. carbon steel.The secondary side should be protected against excessive operating pressure by safety valves.
Table 7 Materials and connections for all components Primary side Size DN 20 and smaller all sizes Domestic warm water up to DN 50 all sizes Sec. cast iron. General It is recommended that the size of valves and other piping components be the same as the pipes and be based on the flow. threaded
welded. flanged
welded. stainless steel threaded. stainless steel
Dezincification proof brass. stainless steel
Valves and Other Piping Components
Dezincification proof brass. cast iron. stainless steel
Dezincification proof brass. The design of safety valves and connection pipes should be done in accordance with the Pressure Equipment Directive and national regulations.4. flanged
Cast iron. Regulating valves for space heating systems can have a longer closing time.1. carbon steel. welded. welded. flanged
threaded. flanged.4.
Regulating valves for DWW should have a short closing time. carbon steel. cast iron. stainless steel
Dezincification proof brass. flanged
welded. carbon steel. Heating up to DN 50 DN 65 and higher
Dezincification proof brass.
By installing thermostats on each radiator. control unit with a remote sensor. Maximum pressure drop for check valves is recommended to be 3 kPa. automatically controls the flow through the radiator in order to maintain the room temperature in accordance with the desired and set value of the TRV. connected to the main control unit with a capillary tube. Thermostatic Radiator Valve (TRV) and some importance features System improvements can be carried out by installing radiator thermostats (to control room temperature).2. e. The sealing (gland seal) around the spindle. In both 1-pipe and 2-pipe systems. Check valves Check valves should include an inspection hole in order to check for possible leakages. 2. so the room temperature is kept constant.
. which supports and guides the cone. the room temperature will be controlled automatically since the thermostat is a proportional controller. Valve body There are several types and sizes of valve bodies. For energy savings it is a possibility to have pre-programmed thermostat radiator valves. This enables the room set point to be lowered and the forward temperature to the heating circuit to be reduced. straight and elbow.4.
4. is designed as one unit making it easily exchangeable during operation.g.4. they result in considerable energy savings compared to unbalanced systems that are controlled by manual valves. By installing radiator valves that can be pre-set. Control unit There are several kinds of control units. The most common are: control unit with a built-in thermostat sensor. The thermostat radiator valve. By installing radiator thermostats on each radiator. Well-balanced heating systems where the room temperature is controlled by radiator thermostats provide a highly energy efficient solution. thereby reducing the amount of water needed to flow in the system and the energy needed to run the pump.4. consisting of a sensor unit and a valve body. the maximum flow through the radiator can be limited to the actual amount needed to heat up the room.3. two large energy saving gains are obtained: 1. or hydraulic balancing valves (to balance the heating system and secure heat distribution in buildings). connected to the remote setting unit with a capillary tube. control unit with a valve adaptor. It even cuts off the flow to the radiator when free heat (for example sunshine or bodily warmth) is heating up the room.
4. These valves should be fitted with a removable plug. A balancing valve can also function as a normal shut-off valve. manual balancing valves are an acceptable solution in many situations. Ball valves should be made of stainless steel. awareness about sufficient heat authority by the use of balanced flow and presetting facilities. if the balancing valve can fulfil the same requirements set for shut-off valves. system balancing of flow and pressure and reducing influence from a change in load. automatic types do not.
4. manual balancing valves need additional work at starting-up. When designing an effective and energy efficient heating application. Euroheat & Power recommends installing automatic hydraulic balancing valves. to install thermostatic radiator valves with presetting as a minimum requirement and.5. The connection type should be threaded. it will always be a great advantage. Shut-off valves Types of shut-off valves are ball valves or butterfly valves.4. Butterfly valves should be fitted with metal gaskets. Hydraulic balancing and balancing valves An optimally controlled heating system has the following control performances: steady heat and pressure supply. Balancing valves Balancing valves are to be installed on the secondary side of the space heating and DWW circulation system in order to carry out hydraulic balancing of the internal installation. controlling flow temperature according to changes in outdoor temperature.4. The size of a draining valve should be DN 15. but due to the commissioning process which is set to average application conditions. Manual versus automatic hydraulic balancing valves have the following characteristics: manual balancing valves are cheaper than automatic types. In larger installations/buildings the hydraulic balancing valves (manual + commissioning and automatic solutions) are a means of balancing flow and pressure in the entire system.
. The use of grease or rubber gasket material for shut-off devices is unsuitable. vent and pressure meter valves Drain valves are assembled at the lowest point in all networks: primary side. outdoor temperature controls. DWW and secondary heating side. in most cases.
4. regardless of the size of the installation/building. Drain. Drops in pressure should be easily measurable from the valve.4.4. larger changes in the system are not accounted for.6. In such cases the automatic types provide for an optimal solution.
The meter should meet the accuracy requirements of 1. Pressure meter valves are assembled for each pressure meter in all networks: primary side. The drain pipe from filters should be suitable to ensure a thorough flushing of the filter. Strainers (filters) Strainers should be fitted on the primary inlet at the secondary side to avoid foreign particles passing into the system.Vent valves are assembled near the heat meter section at the primary side. The measuring range should be in accordance with the design pressure. The size of a draining valve should be DN 15. The material of the mesh should be stainless steel.
.4.10 Booster pump If the supply conditions are low and it is not economically practicable to raise the supply conditions.4. These valves should be fitted with an inspection connection. The filter should be positioned in such manner that flushing the filter will not harm equipment.4. there is the possibility of employing a booster pump. The reading accuracy of the meter should be at least 0. Temperature meters The temperature can be displayed either directly via a thermometer. It is recommended that the density of the mesh is to be between 0. The connection type should be threaded. or via a sensor.
4. It should be equipped with a flushing valve for cleaning without dismantling the filter.0 mm. Pressure meters The clock diameter of a pressure meter should be >= 100 mm.4. These valves should be fitted with a removable plug.
4.9. 4. The reading accuracy of the meter should be at least 1°C. Scale units should be MPa or bars.
4.5 1.6% of scale. The range of the temperature meters should at least cover the maximum temperature variations.8. DWW and secondary heating side. The connection type should be threaded. The size of these valves should be DN 15 or in accordance with the meter connection.05 MPa. For one-family houses smaller clocks of around 50 mm can be used.7.
Heat load for heating. Maximum design pressure. Manufacturing year.3. Design pressure. Volume per side. Manufacturing No.
Marking of Heat Exchangers and Substations
Heat exchangers should have a permanent and visible attached plate containing the following information: Manufacturer. Minimum design pressure.3. Temperature program for heating. Test pressure..4. Manufacturing No. Safety valves settings. Type.PED Category or article 3. Maximum design temperature. Leakage test pressure. Type.5.PED Category or article 3. Manufacturing year.. ventilation and DWW. Substations should have a permanent and visible attached plate containing the following information: Manufacturer. Directive 97/23/EC .. Fluid group. Voltage. ventilation and DWW. Article No. Volume per side. Fluid group. Directive 97/23/EC . Article No. Design temperature.. Minimum design temperature.
Such connection principles are designed for the following purposes: to ensure safe and reliable use. Table 8 shows the main differences between the most common connection principles.
. Euroheat & Power recommends a connection drawing of the substation to be visible in every heating room in multi-family houses. to utilize the most cost efficient solutions. to maintain good quality of district heating. The recommended positions of components within the substation are exemplified in section 5 of this Chapter. floor heating and pool heating. for example. It is possible to add more functions and components to substations if the customer desires. it is recommended to use those. In case of more than one heating network. The connection principles are designed to ensure the most preferable means of cooling district heating water. or if special conditions are present. This applies. to simplify design work. By-pass connections over the substation should not be used in the primary or secondary sides. If better solutions are found from the cooling point of view.CHAPTER 5 – CONNECTION PRINCIPLES
5.1. The connection principles contain minimum standards that each substation should fulfil. Such solutions decrease the cooling capacity of district heating water. substations should have their own heat exchanger for each network. The position of components can be modified for construction reasons. to minimize energy consumption. to ventilation.
General Description of the Minimum Standard
These Guidelines include the most highly recommended connections with which to connect customers to the primary network.
Return temperatur e >= 45°C Indirect. LTS
One stage heat exchanger
Small house One stage heat exchanger. LTS
Small house One stage heat exchanger. max 20 kW
HTS. max 60 kW Large One stage heat exchanger One stage heat exchanger
Indirect. max 25 kW
Direct. LTS
Charging system Direct. max 8 kW
. LTS
HTS. Return temperatur e < 45°C Indirect. prim.4. prim.Table 8 DOMESTIC WARM WATER Suitable for district heating system (see Table 1 in Chapter 1.1) HTS. LTS HEATING
HTS. max 8 kW
The maximum capacities in small houses are 60 kW for DWW and 20 kW for heating. max 40 kW Small house Heat exchanger inside tank.
Directly connected systems are recommended to have some kind of leakage alarm system.
direct connection of the customer heating circuit to the district heating network.
Direct and Indirect Connection
Customers can be connected to the primary network using two main connection principles: indirect connection of the customer heating circuit to the district heating network: a heat exchanger provides the hydraulic separation.). This principle does not include any heat exchanger.
.2.5. floor heating etc. so the same district heating water is inside the secondary network (radiators.
6 MPa max 3°C higher as secondary return temperature normally not needed
0. including two parts for DWW heating: pre-heater and after-heater.3. The two-stage heat exchanger includes two parts that are inside the same pressure vessel. including one part for DWW heating.6 MPa same temperature as secondary return needed to decrease pressure in secondary side Excessively high pressure may cause pipe or radiator damages and water leakage
Risk of damages and leakages
no risks because of hydraulic separated networks
1-step and 2-step Connection of Domestic Warm Water
The main indirect connection principles of DWW are: one-step heat exchanger.Table 9 Design levels of indirect and direct connections
less than 90°C – generally 80°C
Design pressures Cooling of district heating water Differential pressure controller
1. The district heating flow from space heating flows through the pre-heater of DWW and improves the total cooling of the district heating system. two-step heat exchanger.
normal values are valid.
Euroheat & Power recommends using a 2-step connection in multifamily houses where the return temperature from the space heating system is high.4. Pre-heater improves the cooling of district heating.
Systems of Domestic Warm Water
The indirect heating for domestic warm water may be made in two ways: instantaneous water heaters. No differences.
. and return temperature from space heating side. Pressure drop on the primary side can become high: if the flow from the space heating side is greater than the dimensioned flow through the DWW heat exchanger.Table 10 Indirect connection principles
1-step connection (parallel) Design Temperatures Design pressures
2-step connection
Cooling of district heating water
Total pressure loss over substation
No extra pressure drops due to separated flows from DWW and space heating. then the pre-heater can have problems in managing the whole flow passing through the heat exchanger for the consumer heating circuit. In other types of buildings it is recommended to use a 1-step connection. The influence depends on: consumption of DWW.
5. heaters with warm water accumulation. normal values are valid.
The same applies to consumers with long service pipes (30 m+).
Safe solution to keep good cooling of district heating.). It is an option to use storage tanks when consumers are located relatively far away from the district heating plant. There is a lack of appropriate flow capacity from the DH service connection (too small dimension). low energy one-family houses. running of charging pump is controlled by temperature in bottom of storage tank.
In normal district heating circumstances no problems to get enough DWW.
Euroheat & Power recommends using instantaneous water heaters.Table 11 Alternative warm water production
Instantaneous water heaters Design Temperatures Design pressures
Heaters with accumulation
No differences. where the differential pressure might be low. Normal cooling of district heating if: inlet temperature for heat exchanger is normal cold water temperature. momentary exceptionally high use of DWW (sports halls etc. normal values are valid. No differences. normal values are valid. instantaneous water heaters can be used. In the case of consumers located close to the district heating plant where the differential pressure is high.
Indirect 2-step
Indirect parallel
Indirect small house
DWW charging
Direct parallel small house
DWW charging small house
2 3. All necessary steps for a comprehensive inspection and maintenance are described in Table 12 below. Apart from smaller maintenance work. Therefore. specified periods of time are not prescribed. Valid technical regulations contain only a recommendation to carry out inspections.1 3. it is possible to develop individual inspection and maintenance plans as well as calculations.2. only those steps that apply to the substation or the ownership structures should be selected.4 3.6 3. For this. In order to ensure a high quality level of maintenance.1 3. Guaranteeing a smooth and economically efficient operation of the district heating supply requires regular inspection and maintenance of the substations and their components.2
3 3.1.1. From this Table. Various schemes regarding substation structures are addressed in Chapter 5. drain -. it is recommended that a specialist should make regular inspections to optimise the operation. many district hearing companies prescribe the certification of such personnel.3 3.1.5 3.2.1.1. und air escape valves (look over) Check of mounting (look over) Check non return valves Shut off . Although the substations are extremely reliable and have a long lifetime.CHAPTER 6 – SERVICE AND MAINTENANCE
Customer satisfaction is essential for maintaining and increasing the market position of DH.1.2 3. Table 12 Inspection and maintenance checklist for district heating substations A – Domestic Warm Water Working hours look over [h] Domestic warm water system Pipe system Check for corrosion (look over) Check of insulation (look over) Potential equalisation available (look over) Check of fill-. developing malfunctions will be recognized and eliminated at an early stage.armatures Test function (practicability) Check for leaks (look over) Working hours test function [h]
Pos. it is recommended to use qualified personnel.1 3.
4 3.TC/TM/STL
Check of time control (on-/off times) 3.3.1
Filling pump (AS/ACS) Check for leaks (look over) Check noise behaviour Circulation pump Check for leaks (look over) Check noise behaviour Check on-/off temperatures Circulating pump
Check for leaks (look over) Check noise behaviour Manometer. thermometer Check for leaks (look over) Test function Mechanical fasteners Check flanges.4 Test priority circuit 3.3.1 3.4.8.2 3.3
.10.7.2 3.2 3.6.3.3 3.1 Check for leaks (look over) 3.1 3.2 3.10.5.10 Control valve 3.8 3.2
Test function .4.3 3.2 3.1 3.9.6.9.9 3.9.2 Test safety function 3.5 3.1 3.3 3.9.1 3.3 Check of wiring (look over) 3. Controller / Monitor / Limiter (with safety function) valves
3.4.8. screws and immersion sleeves for leaks (look over) Flow regulation valve Check for leaks (look over) Check volume flow and correct if necessary (supply side) Check volume flow and correct if necessary (circulation) Control Check of parameters a) temperatures (supply-/return-) b) on-/off temperatures c) return temperature limitation Temp.1 3.7 3.5.10.8.6 3.
2 Check for leaks inside Notice: Shut off extraction-.1 over) 3.12.12 connection) Check for leaks outside (look 3. Abrupt rising pressure on secondary side indicates leak.1. 3.1.2 Test function Heat exchanger (indirect 3.1. The customer has to be informed immediately to remedy deficiencies.1 Check for leaks 3.13.1.1.1 2.11.3 Check inside (look over) Clean sedimentary deposit if 3.6
.1 2.and cold water pipes and relieve pressure. B – Space Heating Heater curcuit:______ direct indirect Room heating Pipe system Check for corrosion (look over) Check of insulation (look over) Potential equalisation available (look over) Check of fill drain and air escape valves (look over) Check of mounting (look over) Check air venting Working hours look over [h] Working hours test function [h]
2 2.5 2.11.1.13 Storage tank 3.3 2.4 possible Notice: Log actual values during inspection in the checklist.1 Check for leaks (look over) 3.13. Additional defects. circulation.4 2.2 2. like damaged electrical equipment or installation in the domestic connection room also have to be logged.2 Check anode 3.3.13.12.11 Safety valves 3.13.
1 2.4.6.2 2.2 2. clear filter and if necessary renew sealing Non return valve Check for leaks (look over) Test function Notice: turn off pump. renew the non return valve.4
Control valve Check for leaks (look over) Test safety function Check of wiring (look over) Test stop position
Check for leakages Shut off .4.1 2.8.1.7 2.3
Test function . screws and immersion sleeves for leaks (look over) Weather induced control Check of parameters a) temperatures (supply-/return/outside) b) heating curve c) on-/off temperatures d) return temperature limitation Check of time control a) reduced temperature times b) summer-/ wintertime Temp.3 2. thermometer Check for leaks (look over) Test function Mechanical fasteners Check flanges.armatures Test function (practicability) Check for leaks (look over) Dirt trap Check for leaks (look over) Check filter.2 2.9 2.9.3.8.2.1 2. shut off pump armatures.2.9.1 2.4 2.TC/TM/STL
2.7 2.5.8.3.7.5 2.9.1
2.1 2.6 2. if return flow temperature raises.1 2.6.1 2.3 2.2 2.1 2.9. Controller / -Monitor / Limiter (with safety function) valves
2. Circulating pump Check for leaks (look over) Check noise behaviour Manometer.2.5.8 2.2 2.
3 temperatures (indicates dirt evaluation of the heat exchanger) 2.and domestic plant return 2.2 over) a) test function Log district heating .Heat exchanger (indirect connection) 2. Additional defects.1 Check for leaks (look over) Check safety valve for leaks (look 2. The customer has to be informed immediately to remedy deficiencies.
.10. such as damaged electrical equipment or installation in the domestic connection room also have to be logged.10 2.11 Diaphragm type expansion tank a) Check for leaks (look over) b) Shut off armature (look over and test practicability) c) Check secondary pressure/ nitrogen Notice: Log actual values during inspection in the checklist.10.10.
a volume and hour counter is needed. It is important to have consumption data in order to keep the customer informed about energy use and saving opportunities and to assist them in detecting failures.1. invoicing the m3 consumption. Data logging.
The Energy Services Directive includes goals concerning the reduction of primary energy consumption. For temperature-related tariffs such as peak load. Proper information about individual energy consumption. of both consumption data and instantaneous reading values. It also allows for improvements in cooling of the district heating water.
. thereby contributing to the detection of errors. Heat allocators are an additional way of introducing individual metering and are not covered by these Guidelines. In this way the meter data could be used to optimise the operation of the network from an economical point of view. and is therefore no longer recommended. Other important issues to be aware of are: security of metering data. conservation of data. should be readily available. In most countries heat allocators are used in larger buildings with a large number of flats.CHAPTER 7 – HEAT METERING
7. The installation and the operation of the system are normally carried out by the building administration company. The meter is useful for the surveillance of operations in district heating networks and for monitoring temperatures and flows. is necessary in order to motivate customers into saving energy. for instance based on metering. Heat metering allows for the customer to be invoiced for consumed heat in an accurate manner. To invoice according to basic data energy. The previous metering principle measures only the accumulated flow. flow temperatures are required. The district heating company then has only one main meter measuring the total consumption of the building. and assurance of the quality of the data.
the flow sensor .measuring the amount of district heating water running through the meter. As required by the MID A measuring instrument shall be suitable for its intended use. conform to the relevant Essential Requirements of the Measuring Instruments Directive (MID). the temperature sensor pair in the forward and the return pipe.2. A recommendation is given in Section 8.
. Reference to the Measuring Instruments Directive (MID) and standards The meters (or subassemblies) shall. For meters with data communication. by complying with all the normative clauses in Parts 1. Part 3 shall also apply.Figure 14
Main components of the energy meter
Components: the calculator calculating energy consumption.
7. and shall not require unreasonable demands from the user in order to obtain a correct measurement result. In order to ensure that the running meters are working correctly it is necessary to introduce a control system. 2. The system should be based on a statistical test programme.4. 4 and 5 of EN 1434. The communication system and remote reading of meters should comply with EN 13757.
As required in the MID The needed measuring range in temperature. temperature difference and flow rate as well as the maximum admissible working pressure.3 for the countries that have no national regulations on this. shall be determined by the distributor or the person legally designated for installing the meter. so that the meter is appropriate for the accurate measurement of consumption that is foreseen or foreseeable. taking into account the practical working conditions.
5°C (the maximum permissible error in the temperature difference should be within the limits of EN 1434). 2-wire method of connection without the need for shielded cable. head connection used for long sensors. The complete heat meter does not have separable sub-assemblies. The heat meter can either be a combined. the maximum recommended sensor thermal response time should be 50% of the shortest projected peak load. after verification. In case of short peaks in consumption (e. for the purpose of pattern approval and verification.5.
.2. The minimum recommended measuring range in the flow rate is dependent on foreseeable consumption.6 1. the calculator and the temperature sensor pair or a combination of these.1. Some recommendations to optimise the interchange-ability: Pt100 or Pt500 type sensors. Temperature sensors The temperature sensor pairs are to be tested in accordance with EN 1434-4 and EN 1434-5 and the types and dimensions should be in accordance with EN 1434-2 to have full compatibility and replacing ability. its sub-assemblies are to be treated as inseparable. a complete or hybrid meter. Euroheat & Power recommends the usage of combined heat meters or hybrid heat meters. However. The combined heat meter has three separable sub-assemblies: the flow sensor.6
PS in bar 1) 16 (25) 16 16
1) In EN 1434 (as in the Pressure Equipment Directive) PS is used for maximum admissible working pressure. If the temperature information is used for performance checking.
7. A hybrid heat meter is a heat meter which. diff 3 – 100 K 3 – 60 K 2 – 20 K
PS in MPa 1) 1. Guidelines for this are taken up in Section 7.6 (2. generating warm water for washing hands) the heat meter should be able to follow these short loads where a duration of 5 seconds is reported as normal.Table 13 Recommended measuring range
Type of system HTS LTS Cooling
Temperature 20 – 120°C 20 – 80°C 5 – 30°C
Temp.5) 1.g. To be able to handle short peaks in consumption. PN is used as a numerical designation for reference purposes only. The complete meter and hybrid meter are often called ‘compact meters’. the maximum permissible error in the temperature should be ± 0. can be treated as a combined instrument.
There is no standardized relationship between qp and qs and they can have the same value.
. under which no registration is allowed. 25. e. qp for permanent flow (where the sensor is to be able to work continuous without exceeding the maximum pressure drop).) NOTE: EN 1434 and MID use the following definitions for flow levels: a flow threshold value. or with the standardized flow conditioner package defined in Annex B of EN 1434-1. The lowest pressure for which the flow sensor is to function should be specified.2. Flow rates greater than qs are not to result in a positive error greater than 10 % of the actual flow-rate. the behaviour of the meter. For smaller substations accuracy class 3 should be accepted.
7. 100 or 250. To be able to handle short peaks in consumption the flow sensors should be classified as “fast response meter” and the test in 6. but for larger substations class 2 is recommended.4 of EN 1434-4 should be included at the type testing. for flow rates greater than qs. Flow sensor The flow sensors are to be tested in accordance with EN 1434-4 and EN 1434-5 and the types and dimensions should be in accordance with EN 1434-2 to have the full compatibility and replacing ability.7. Depending on the foreseeable variations in thermal load the dynamic flow range (qp/qi) should be at least 25 or 50. Calculator The calculator is to be tested in accordance with EN 1434-4 and EN 1434-5. the flow sensors should be approved to be used in either of the following ways: without any requirements for straight pipes before and after the meter. (MID specifies > 10.3. Euroheat & Power recommends specifying a “long-life flow sensor” which typically lasts for more than 5 years. qi for minimum flow (over which the sensor is to be within the maximum error limits). EN 1434 has the standardized values 10. qs for maximum flow (“overrange” where the sensor is to be able to work for shorter times and be within the error limits). should be declared by the manufacturer. by producing spurious or zero signals.2. Depending on the installation possibilities. 50.2.4.g. Euroheat & Power recommends that no meters should be selected that indicate zero flow at flow rates over qs.2.
Input and output test signals A high resolution energy signal should always be provided for automatic and multitesting purposes. error codes. operation time. Additional values are recommended to be available after some additional display button operations: power. Such connections are not to modify the metrological qualities of the heat meter. accumulated volume. peak flow rate with timestamp. M-bus address. The energy signal as specified above should be available either directly at the calculator connection terminal or at the terminal of a testing adapter as stated in Annex B of EN 1434. The supplier should declare the lifetime of the batteries. baud-rate for data exchange.We recommend that the display at least should have at least the following information easily accessible: accumulated energy (basic information). The test signal should either be pulses with a defined value of pulses/energy increment or preferably data output. The resolution should be sufficiently high so that at the lower limit of temperature difference and/or flow rate. Pulse output names used at output connections are provided in Annex B of EN 1434. the time interval between the calculations and measurements of temperatures should be in the same order as or faster than the duration of the peaks. they should be replaceable without causing damage to the verification markings. pulse value. The supplier should state the nominal relationship between the high-resolution signal and the energy reading. the additional error caused by the energy signal can be shown to be insignificant. Heat meter calculators may be fitted with interfaces allowing the connection of supplementary devices. flow. If short peak loads should be registered correctly. Batteries If a heat meter has interchangeable batteries. specially defined. the frequency of input pulses from flow sensor and the frequency of calculations. or a display with correspondingly high resolution. temperatures. peak value of power with timestamp.
. The lifetime may differ depending on: how often the data communication is used.
permissible adjustments.
7. instructions for correct operation and any special conditions of use. conditions for compatibility with interfaces. this should be specified by the supplier. mechanical and electromagnetic environment classes. If the battery lifetime is dependent on the usage of remote reading.Data-logging We recommend the calculator to have some data logging functions that can store at least: peak values of power and flow with timestamp. Information shall be easily understandable and shall include where relevant: rated operating conditions.3. The data-logging function stores data in an extended memory. error codes with time stamp. the upper and lower temperature limit.2. In such way. This means that not only installation instructions but also manuals for testing.
7.1. sub-assemblies or measuring instruments.4. maintenance.
7. Remote reading makes it possible to provide more information and services to the customers. General As required in the MID If necessary. the meter data could be used to optimise the operation of the network from an economical point of view. mean value of flow under a number of periods of about 15 minutes. the instrument shall be accompanied by operational guidelines. thus contributing to the detection of errors. and Euroheat & Power recommends that the in-service life should be at least 10 years if allowed by national regulations and if in accordance with testing procedures. open or closed location.
. setting parameters. reset or programmed through the optical interface or by means of other communication options. Remote reading of data We recommend that a new calculator should at least have the possibility to install a remote reading facility. All recorded data cannot be displayed but can be read. repairs. Durability and reliability The total lifetime of a calculator should be at least 15 years. Remote reading of the meters allows surveillance of operations in district heating networks as well as monitoring temperatures and flows. service and necessary testing adapters should be available to the district heating companies. instructions for installation.3. whether condensation is possible or not.
as well as on the system operating conditions.
Dimensioning of Temperature Sensors
The size of the sensors should be adapted to the size of the pipe so that the sensing element is situated in the middle of the streaming water. it is normally possible to work out what the likely district heating flow rate will be. Most sensors on the market have a sufficient temperature range. however in connection with a large substation they may be used. preferably by referring to the standard solutions in EN 1434. Once these parameters and factors are known.5.
.2. EN 1434 recommends: type DS without pockets with a length of 39 mm for pipes with DN 15 … 25.7. The most commonly used combinations between the flow sensor and the calculator are put forward in Table 14 below.5.3. It is also necessary to know the customer's requirements and consumption characteristics. For compatibility between subassemblies. EN 1434 defines a number of input and output classes for the signals.
Dimensioning of Flow Sensors
Determining the necessary capacity of a flow sensor depends on the temperature rating and design of the district heating system.1.2. 120 or 210 mm for larger pipes o mounted in bend or angled for DN 32 … 50 o mounted perpendicular for DN 65 … 250 Euroheat & Power does not generally recommend the use of pockets.4. In case of replacement of the meter there is good historical data from which the needed sensor capacity can be determined exactly – see Section 8. type DL without pockets or PL with pockets with a length of 85. See Section 8. Table 14 Flow sensor output OA: reed or electric switch with no polarity specified IB: “slow” input with pull-up resistor OC: open collector with specified polarity Calculator input
7. Compatibility and interfaces between subassemblies The type of signals between the calculator. the temperature sensors and the flow sensor should be clearly defined by the supplier.
1. behaviour over qs. rather than always selecting sensors that are too large. with pressure drop at qp.
7. The district heating system Analyse the operating conditions in terms of production and distribution conditions (pressure drops and temperature levels) that can affect the meter. with allowance for any special operating requirements. Check the data for the calculations determining the necessary capacity of the district heating substation unit itself. The thermal power value used for determining the necessary meter capacity is to stand in reasonable relation to the actual demand.In new installations.2. Flow demand for domestic warm water production. but as knowledge of domestic warm water and space heating demands and capacity determination improves. it becomes possible to use smaller flow sensors. together with temperature variations in the system and water quality. It is essential to have pressure drop diagrams for the flow sensors for this.
There can never be totally accurate model values for heating and domestic warm water requirements as each building is different: it is necessary to know what the consumption patterns are in each. It is better occasionally to choose flow sensors that are too small. Flow demand for radiators / space heating.5. The following rough calculation can be used to check the power demand: Heat load [kW] = Heated area [m2] *x [W/m2]/1000
. the energy certificate required by the Buildings Directive can provide a very good basis for determining the needed capacity. Flow sensors' measurement ranges (qi – qp). with a value of 40 W/m2 being more suitable for more energy-efficient buildings.5.
Heat demand: Domestic warm water: Control: Flow sensors:
7. the trend has been to install flow sensors that are too large. Valve sizes and response times. In some situations a flow regulator could be used to limit the flow. Data required for determining the needed capacity of flow sensors The district heating system: Maximum and minimum pressure differences across the service valves. with allowance for any special operating requirements / strategies. etc. The size of this limit value affects the choice of meter. An upper limit value of 100 W/m2 can be used for some older residential buildings. Historically.
. to some extent. This provides a good indication of how well the necessary capacities of the metering equipment. A flow sensor of one step smaller will generally provide a better distribution within the flow range. Typical results of this procedure are shown in Table 15 below. e.g. However. they show that the flow has exceeded qp for only 1 % of the operating time.When calculating the water flow rate in the district heating system (m3/h) to a substation unit.g. there are other. the behaviour of the meter. shall be declared by the manufacturer. night set-back of heating and/or starting of ventilation units). it may be worthwhile replacing them with smaller valves. One way of checking the flow range by means of operational monitoring is to measure. Check what flows can occur in the space heating circuit when night set-back is withdrawn. The critical operating state can occur just before the district heating system operator starts to increase the supply temperature. In some cases even a reduction with two steps may be possible! Table 15 Total duration Flow level Typical One step smaller 1%* 3% 35 % 95 %
>qs 0% >qp 1% > q p/ 2 25% >qi 90% *Check with the flow sensor specification if this is advisable
NOTE: The manufacturer should. 15-minute demands and to compare them with the capacity of the meter. and that it has been less than qi for 10 % of the operating time.5.e. If the control valves in a system are oversized.e. This means that it is possible. when the control valve is fully open. i. at the system’s knee point. to assess how well the flow sensor is matched to the necessary measuring range. Monitoring systems in operation Heat meters often incorporate a storage facility for storing maximum values of flows. ways of checking the flow sensor's working range by using remote reading or logging of the flow via supervisory systems or mobile data-loggers.2. allowance should also be made for cooling of the water and for the overall operating strategy (e. Flow rates greater than qs are not to result in a positive error greater than 10 % of the actual flow-rate. This can pay for itself through improved metering accuracy. while at the same time providing a better flow range for the flow sensor. inform about the behaviour over qs: “For flow rates greater than qs.2 in Part 1). and often better. by producing spurious or zero signals. improved comfort and greater abstraction of heat from the district heating supply. for instance. 7. control valves and heat exchangers have been determined. In this case.1. in accordance with EN 1434 (Clause 6. i. better control.
which means that the fitting size can often be smaller. The required measurement range and pressure drop across the flow sensor are the decisive factors. In such cases. at which the heat meter shall function for short periods (< 1h / day. ultrasonic flow sensors are not affected in the same manner as are mechanical flow sensors.5.2. qs.5. while for larger buildings the capacity can be determined on the basis of the flow
. Heat demand for industrial premises and office buildings. depending on their design. or by using an integrator that registers maximum flows.3. it is necessary to identify the specific type and rating etc. Euroheat & Power recommends choosing one of the higher dynamic ranges specified in EN 1434. When deciding on the necessary measurement range for the flow sensor. < 200 h / year). Complicated installations should be fitted with ultrasonic flow sensors.2. For buildings with around 10 to 20 apartments.1. for process plants that are heated by ventilation units. and so it is important to obtain full data from the supplier when purchasing meters. space heating and domestic warm water production do not normally occur simultaneously in industrial premises or office buildings. If brief flow peaks in excess of qs occur. qs at the likely maximum load could perhaps be used. with a capacity as determined by the likely aggregated load. requiring a rapid temperature rise in the mornings. The upper limit of the flow-rate.3. Selection of suitable flow sensors Different types of meters have different working ranges and different requirements in respect of the working environment and it is these factors that determine the type of meter to be used. the capacity of flow sensors in the district heating return connection can be determined on the basis of the domestic warm water flow requirement. is the highest flow-rate. However.
7. Maximum demands for ventilation. If the premises are normally heated by both radiators and tempered ventilation air. ultrasonic flow sensors have no problems with continuous measurement at their maximum flow rates. This would be the case. Some ultrasonic flow sensors continue measuring in the overload range. the two loads should be added and used as a guide when calculating and selecting the meter's qp rating (this does not apply for unusual loads such as swimming pools etc. As opposed to mechanical devices. it is advisable to start from the expected highest demand flow rate for any one of these loads. After obtaining details on the particular factors governing the type of flow sensor needed. Check the flow range after installation by logging the flow. of the sensor. for example. without the maximum permissible errors being exceeded.General info from EN 1434 about qs: “5.).” 7. and so the maximum permissible pressure drop should be considered. the pressure drop across the meters can vary.
0 m3/h up to 25 apartments qp = 2.1. Flow profile at the metering position For our purposes. The design flow rate should be close to qp. such as single-beam ultrasonic meters. The shape of the flow profile at the metering position has a very considerable effect on the performance of all types of flow meters.5 m3/h up to 65 apartments qp = 6.1. Examples of standard stock flow sensors will provide coverage as follows qp = 0.1. the positions of components and the design of the electrical
.1.6. the term 'flow profile' is taken to mean: the velocity distribution across a cross-section of liquid flowing through a pipe. Environmental influences 7.
7. a few sizes of flow sensors will suffice for metering heat supplies to buildings containing up to 100 apartments.6.1 Figure 4. and the distance between such interference sources and the meter is very important.6.6. or a little higher for static sensors. For larger substations Euroheat & Power recommends using class C.6. Protection classification According to EN 1434 the minimum forms of enclosure protection is to be IP54 for equipment that is to be installed into pipe work and IP52 for other enclosures 7.2. Provided that the pressure drop across the flow sensor does not exceed 25 kPa. Different forms of potential interference affect the flow profile in different ways. are very dependent on the flow profile over the metering range being representative of the full flow area. Environmental classification In accordance with EN 1434. Planning the meter position The meter can be placed on either the forward or return pipe depending on the temperature level.0 m3/h up to 100 apartments The values in the example are related to the lower dimensioning slope in chapter 2.3.requirement for delivery of the building space heating load. 7. a heat meter is to conform to one or more environmental classifications according to its application.7. Piping arrangements. Meters that measure the flow velocity at only a part of the cross-sectional area.6.2.
7.1.6 m3/h from one detached house up to 5 apartments qp = 1.
or to replace it if necessary with the least possible disturbance to the heat supply. to perform maintenance on it. Possible places for manometers (measuring outlets for pressure)
. distribution unit etc. (See EN 1434.
10. In principle. the same rules apply for the installation of heat meters in detached houses as for the installation of meters in larger installations. When the heat meter is ready for use. Wire size 0. 4. can be locked or sealed Temperature sensor pair Flow straightener a) Straight pipes before and after the flow sensor a) Should be used for flow sensors where this is specified (in datasheets or type examination certificates) Differential pressure controller. It should be possible to read the meter without difficulty. 11.5 m. the installation should be inspected and approved by the heat supplier or the installer in accordance with quality demands of the heat supplier. switch etc. DN = sensor connection size Safety switch (maintenance/service switch). 9. 8. for more detailed instructions) Flow sensor. Figure 15 Example of schematic diagram of a meter position for larger district heating substations with flow sensor in return pipe
1. 7. if required. 5. including space for flow sensors.75 mm2. Calculator Wire size 1. page 10. Part 2. with sealable cover. distribution unit etc.installation are important elements for consideration when planning the position of the meter. Power supply from switchboard.5 mm2. 6.
Switchboard. they too should be installed in a manner that allows for straightforward maintenance and service. 3.5 mm2 if the lengths exceed 7. 2. in order to ensure that the meter will measure with the prescribed accuracy. Use 1. As district heating substations for detached houses and for smaller buildings are supplied as complete units.. fused.
shut-off valves fitted upstream of the flow sensor should be fitted outside the straight length of the pipe run. Piping installation The heat supplier generally installs the flow sensor. at least 15 cm from the wall and with an unobstructed space of at least 0. In case of long pipe runs. fit separate valves as shown by the dotted lines in the schematic diagram. Valves fitted in pressure measurement pipes should have welded connections.1. the distance should consider the meter type F. If they are installed outside the substation room.8 m above floor level.
Suitable and unsuitable positions for flow sensors
A.4. as bubbles can collect to form air pockets Unsuitable position. Meters should be positioned well away from bends in two planes
Turbine sensors should be installed horizontally with a vertical turbine axis. D.3.7 m in front of it. as bubbles can collect to form air pockets Valves should not be fitted immediately upstream of the meters.7. The main service valves for district heating substations are normally positioned about 1.0 . too.6. calculator and temperature sensors.
Suitable position for most types of meters This position works well for inductive and ultrasonic meters Unsuitable position. A meter should not be positioned before a pump G.
7. The flow direction should be respected. C. The vertical Woltman meters should be installed at the lowest point of the pipe work in order to avoid the risk of trapped air in the meter. Vertical Woltman sensors should be installed in horizontal pipes with the Woltman axis vertical.6. The flow sensor should be positioned so that it is easily accessible.
Electrical installation Heat meters requiring a mains connection should be connected in accordance with all applicable electrical regulations. an outlet pipe of 3xDN is needed. To accept all EN 1434 approved sensors there should be. a thin (0. directly upstream of the meter.
7. in a bend with the tip against the flow direction. Mains power supplies should be protected against accidental interruption. and should be independently supported. The pipes in which the sensors are installed should be of the same size and should have very similar flow profiles. Signal wires should not be run immediately adjacent to power cables and should be secured separately. Details for temperature sensors The sensors should be positioned in the centre of the flow. This information should be provided by the heat supplier. Clean the filter. either: perpendicular to the pipe. Behind the meter. 7.5. Adjust the length of the pipe sleeve so that the actual sensing elements of the sensors are in the centre of the pipe. The insulation should not cover the threaded connection of the pocket or sensor due to leakage risks.1. Measurement signal cables should be separated by at least 50 mm from other cables such as mains supply cables. in an angle of about 45 º with the tip against the flow direction. Pipes connecting to the flow sensor should be fitted with pipe supports. the heat meter should be protected from shocks and vibrations originating from its surroundings. A sensor should be mounted in a welded-in boss or pipe fitting. the piping contractor needs to know the size of the flow sensor's connection flanges. Thoroughly flush the circuit in which the flow sensor is to be installed in order to remove dirt before fitting the sensor. The two sensors should be installed in a similar manner in each pipe.4. low voltage supply cables and data communication cables.If a meter is to be correctly installed. if there is one.12xDN) flow straightener plate followed by an inlet pipe without flow disturbances with a length of 5xDN (min.6. A good quality sealable means of disconnection should be provided for use when it is necessary to disconnect the supply to the meter in order to deal with electrical problems or when performing service work. NOTE: See Annex B of EN 1434-1 for details.6.
. In order to minimise the risk of damage. The flow sensor should not be exposed to unnecessary mechanical loading caused by stresses in the pipes or connections. The temperature sensors should be fitted in the district heating supply pipes in easily accessible positions.).
Check that the documentation for the fitted meter corresponds to its certificate and enter the details in the heat supplier's meter list. The results of the above inspections should be recorded. a check should be made to ensure that the correct meter has been installed. Identity checking Before using the meter. electric motors.6. fluorescent lights). that the meter is installed at a safe distance from possible sources of electromagnetic interference (switchboards. Installation inspection The following points should be checked by duly authorised persons: that the flow sensor is correctly positioned and orientated. either accidentally or without authorization.Mains and external signal cables longer than 10m should.
7. It should not be possible to disconnect signal connections between parts of a heat meter installation.6. by comparing the manufacturer's type and size numbers with the capacity data and system specification. be protected with an external lightning surge protection at the cable entrance to the building. that the temperature sensors are correctly installed. for both mains operation and/or battery operation. the meter is correctly earthed. when so specified. that the meter seals are intact. If combination meters are in use. each part of the meter should display its own certification symbol. and that it is connected and installed in accordance with the schematic diagram for the meter installation. in accordance with the meter supplier's and heat supplier's instructions. that any accessories are correctly installed. that all parts of the meter work when the heating system is started.6. and that the transmitted measured values are the same as the actual measured values. that the communication unit is installed. that. the cables should be of the same length. Follow this by checking that the meter displays the correct certification symbol. For two-wire connections. that the meter is correctly programmed. without joints.
7. Each signal cable between the temperature sensors and the calculator should have one continuous length.7.
. that the power supply and wiring are correctly installed. in areas where lightning is frequent.
The specification should also be used when dimensioning the sites where the meter is to be installed so that standardised meter components will fit.
. and shall not require unreasonable demands from the user in order to obtain a correct measurement result. Such specifications should include dimensions and other properties to ensure that the meter fits the intended installation.7. The essential conditions of MID contain many metrological requirements specified in Annex I and some more details for heat meters in Annex MI-004. There are also more general requirements such as: A measuring instrument shall be suitable for its intended use. Alternatively. Governmental authorities should ensure that the appropriate measuring range for a heat meter will be “determined by the heat supplier or the person legally designated for installing the meter. Only Module F requires verification to be made outside the manufacturer. taking into account the practical working conditions. MID has to be implemented in current national regulations for meters (or sub-assemblies) after 31 October 2006. the final testing should be done by an approved testing institution independent of both the manufacturer and the user. so that the meter is appropriate for the accurate measurement of consumption that is foreseen or foreseeable” (MID Annex MI-004 §8).
Evaluation of Conformity with the MID Requirements
Since 31 October 2006. meters need to be subjected to a conformity assessment procedure. The manufacturer has free choice of the modules (B+D or B+F or H1).7. MID has detailed requirements for the manufacturer. Before use.” To make the initial verification in a testing laboratory connected to the manufacturer. There are also some detailed requirements for instrument users. MID has replaced the earlier national regulations. A measuring instrument shall be robust and its constituent materials shall be suitable for the conditions in which it is intended to be used. This means the buyer should use the correct specifications. as stated at the beginning of the MID text: “The responsibilities of the manufacturer for compliance with the requirements of this Directive should be specifically stated. which replaces the earlier procedures of pattern approval and initial verification. the manufacturer should have an approved quality system for production and final testing. D. F and H1 of the MID. It consists of the combinations of modules described in Annexes B.
Made by the manufacturer under supervision of a notified body of his choice. manufacture.
Made by the manufacturer under supervision of a notified body of his choice. The manufacturer should have quality system for design. manufacture.
. This should be approved by a notified body of his choice. The manufacturer should have a quality system for design. Made by the manufacturer under supervision of a notified body of his choice.
Initial verification Made by a notified body of the manufacturers choice. carrying out verification tests (module F). final product inspection and testing. This should be approved by a notified body of his choice. carrying out supervision of a quality system for production. The manufacturer should have a quality system for production. manufacture. final product inspection and testing (module H1). The tasks can be listed as: carrying out type approval tests (module B).
Made by a notified body of the manufacturers choice.Table 16 Testing and conformity assessment procedures according to MID
Inspection of produced Examination of type and meters design Checking that the produced Checking that the design of the meters are conform with the type type meets the MID requirements and meet the MID requirements
Old ► ▼ New according to MID B+F
Type approval Made by a notified body of the manufacturers choice. final product inspection and testing. The Commission will publish a list of the notified bodies in the EU Official Journal. carrying out supervision of a quality system for design. final product inspection and testing (module D). final product inspection and testing. This should be approved by a notified body of his choice
A notified body designated by the Member State to carry out these tasks will have an identification number provided by the European Commission and will be notified to the other Member States.
The control system works through the statistical control of several meters. If not prescribed differently by the national regulations.7. or sub-assembly. is to pass. If the result is rejected as being outside the double error limits as specified in EN 1434 the entire lot has to be taken out for re-verification within a year and the next control for that lot of meters should be within the next 5 years. However. supplier. as part of the conformity assessment procedure. the verification procedure of EN 1434-5 can also be used here. The checklist in Annex A of EN 1434-4 should be followed to ensure that the specific requirements are fulfilled. These include meters / sub-assemblies that are: installed within a year. of the same type from the same meter supplier. of the same flow sensor size.
. If the result inside the error limits as specified in EN 1434. The first control should be within 6 years of installation.2. the old national regulations are still in force. installer or user of the measuring instrument that they inspect and any of their authorised representatives. the procedure in EN 1434-5 under the responsibility of the notified body. the following procedure is recommended as a minimum. Examination of type and design The type and design examination is to include the type testing procedure in EN 1434-4 carried out under the responsibility of the notified body.
7.Notified bodies are to be independent of any designer. If the result is accepted as being inside the double error limits as specified in EN 1434. manufacturer.1. since nearly all recent national regulations were based on EN 1434. NOTE: Specifying meters with a reference to a European Standard does not contradict the Measuring Instruments Directive or the Procurement Procedures Directive (2004/17/EC). For meters with type approvals older than 21 October 2006. Inspection of produced meters Each individual meter. Meters taken out for this statistical control should be re-verified before reinstallation.7. comparable in terms of water quality and operating parameters.
7.3. the remainder can be left in the installation for an additional 3 years before the next check.7. the remaining meters can be left in the installation for an additional period of 6 years. Control systems A control system for monitoring the quality of installed meters should be considered as a must.
A random sample is to be made from the lot. To compensate for possible totally broken meters.7. Re-verification of meters If not prescribed otherwise by national regulations.
7. the re-verification of meters or subassemblies should be made in accordance with EN 1434-5. it is economically preferable to repair and recalibrate the more expensive heat meters than to use non-reusable meters. The size of the sample and the maximum permissible number of meters outside the error limits are dependent on the size of the lot: Table 17 Lot size up to 5 25 50 90 150 280 500 1200 3200 Reject the lot if the No of faulty meters exceeds 0 0 0 1 2 3 5 7 10
No of samples 5 5 8 13 20 32 50 80 125
Table 17 is based on ISO 2859.4. the verification requirements need to follow those of the approval used. The maximum intervals between actions prescribed in national regulations in some countries are listed in Table 18 below: Table 18 Country Austria Denmark Finland France Interval 5 years 6 years
Action to be taken Replace all meters with new or re-verified meters 1) Sample test on installed meters 2) The samples should be replaced with new or re-verified meters No legal regulation The intention is to draft a new regulation on this matter probably in 2008
. For meters with older approvals not following EN 1434. NOTE: Compared to gas or electricity metering. it is recommended to take few additional samples.
Three different scenarios based on 2006 figures from Helsinki. Table 19 The quality of the DH water. the result of sample tests may shorten the interval 2. an increase of the verification period is only possible for heat distributors that can demonstrate an appropriate survey procedure of the meters installed in their network
The examples in Table 19 below specify lifetime costs. It might be helpful to insert one’s own figures. the installation and the meters allow a technical life time for the meter of at least 15 years
The national regulations prescribe the use of sample check to verify that the meters could be used for another period a re-verification every 5th year a re-verification every 5th year
at least 15 years shorter than 10 years
.Germany Italy Poland Slovakia Slovenia
1) Replace all meters with new or re-verified meters 2) Sample check on the replaced meters
Replace all meters with new or re-verified meters Replace all meters with new or re-verified meters Replace all meters with new or re-verified meters 1) Replace all meters with new or re-verified meters 2) At least a sample check on the replaced meters Replace all meters with new or re-verified meters No legal regulation
5-10 years1
5 years 3 --
1.8. the result of sample tests may increase the interval 3.
Scenario 1 + Investment + Installation + Putting into use + *) + Sample test + Reinstallation of sampled units + *)
€/meter 567 240 26 17 9 26
Scenario 2 + Investment + Installation + Putting into use + *) + Re-verification without any renovation work + Installation + *) + Re-verification without any renovation work + Installation + *) + Re-verification without any renovation work + Installation + *)
€/meter 567 240 26 200 108 26 200 108 26 200 108 26
Scenario 3 + Investment + Installation + Putting into use + *) + Re-verification with renovation OR new meter + Installation + *) + Re-verification with renovation OR new meter + Installation + *) + Re-verification with renovation OR new meter + Installation + *)
€/meter 567 240 26 284 108 26 284 108 26 284 108 26
+ Sample test + Reinstallation of sampled units + *) + Sample test + Reinstallation of sampled units + *)
17 9 26 17 9 26
989 /15 = 66
1835 /15 = 122
2087 /15 = 139
* Each year there will be a cost for repair of some meters broken down during the year (2% per annually?).
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