PUBLIC REVIEW DRAFT, SEPTEMBER 2008KENYA STANDARD  KS 1855-2:2008  
ICS 27.160; 97.100.99 
  
 
 
  
 
  
 
  
 
Thermal solar systems and components — 
Custom built systems — Part 2: Test methods 
 
 
 
 
 
 
  
 
  
 
Public Review Draft, September 2008  
 
 
 
 
  
 
  
 
  
 
© KEBS 2008 Edition 1.0 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
ii © KEBS 2008 — All rights reserved  
TECHNICAL COMMITTEE REPRESENTATION 
 
The following organizations were represented on the Technical Committee 
 
Kenital Solar (K) Ltd  
ASP Solar (Kenya) Ltd  
Sollatek Ltd  
Department of Electrical & Electronic Engineering, JKUAT  
Renewable Energy Department, Ministry of Energy  
Chloride Exide Kenya Limited  
Energy Alternatives Africa Ltd  
Solarnet  
Automotive and Industrial Battery Manufacturers (AIBM) (K) Ltd 
RENCON Associates  
Telesales Solar Ltd 
Kenya Industrial Research and Development Institute, KIRDI 
Kenya Bureau of Standards — Secretariat 
 
 
 
 
  
 
 
 
 
  
REVISION OF KENYA STANDARDS 
 
In order to keep abreast of progress in industry, Kenya standards shall be regularly reviewed. Suggestions for 
improvement to published standards, addressed to the Managing Director, Kenya Bureau of Standards, are 
welcome. 
 
© Kenya Bureau of Standards, 2008 
 
Copyright. Users are reminded that by virtue of Section 25 of th e Copyright Act, Cap. 12 of 2001  of the Laws of Kenya, copyrig ht 
subsists in all Kenya Standards and except as provided under Section 26 of this Act, no Kenya Standard produced by Kenya Bureau  of 
Standards may be reproduced, stored in a retrieval system in any form or transmitted by any means without prior permission in w riting 
from the Managing Director. 
 
 
 
 
 
 
   
 
 
 
 
 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
ICS 27.160; 97.100.99  
© KEBS 2008 — All rights reserved iii  
 
 
 
 
 
 
 
 
  
 
 
Thermal solar systems and components — 
Custom built systems — Part 2: Test methods 
 
 
 
 
 
 
 
  
 
  
 
KENYA BUREAU OF ST ANDARDS (KEBS) 
 
Head  Office:  P.O. Box 54974, Nairobi-00200, Tel.: (+254  020) 605490, 602350, Fax: (+254 020)  604031 
E-Mail: info@kebs.org,  Web:http://www.kebs.org   
 
KEBS Coast Region 
P.O. Box 99376, Mombasa 80100 
Tel: (+254 041) 229563, 230939/40 Fax: (+254 041) 229448 
E-mail: kebs-msa@swiftmombasa.com
 KEBS Lake Region 
P.O. Box 2949, Kisumu 40100 
Tel: (+254 057) 23549,22396 Fax: (+254 057) 21814 
E-mail: kebs-ksm@swiftkisumu.com
 KEBS North Rift Region P.O. Box 2138, Nakuru 20100 
Tel: (+254 051) 210553, 210555
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
iv © KEBS 2008 — All rights reserved  
Foreword 
 
This Kenya standard was developed by the Renewable Energy Resources Technical Committee under the supervision of the Electrical Industry Standards Committee and is in accordance with the procedures of the 
Bureau. 
 
Quality assurance is of primary importance for large custom built systems. The total investment cost for such 
systems is higher than for smaller ones, although the specific investment cost (i.e., per m
2 collector area) is 
lower. The potential of large custom built systems from the point of view of conventional energy savings is 
much larger than for smaller ones. Moreover, the return-on-investment is in many cases more favorable for 
large systems than for small ones. Hence, the purchasers of large custom built systems are interested in 
efficient, reliable and durable systems, the thermal performance of which may be accurately predicted, 
checked and supervised. 
 The test methods in this standard provide a means of verifying the compliance of large custom built systems 
with the requirements in KS 1855-1. 
 
As large custom built systems are by definition unique systems, only general procedures on how to check 
and supervise them may be given. An additional difficulty in the formulation of procedures is the fact that they have to be adapted to the dimension of the large custom built system considered, which may vary from 
typically 30 to 30000 m
2 of collector area. Therefore, several possible levels of analysis are included 
(annexes C and D). 
 
The objective of the two short-term system tests presented in Annex C is the characterization of system performance and/or the estimation of the ability of the system to deliver the ener gy claimed by the designer. 
In principle, two approaches for short-term system testing are referred to in this standard: 
 
a) A simplified check of short-term system performance, carried out by intercomparison of the measured 
solar system heat gain with the one predicted by simulation, using the actual weather and operating 
conditions as measured during the short-term test. 
 
b) A short-term test for long-term system performanc e prediction. The performance of the most relevant 
components of the solar heating system is measured for a certain time period while the system is in 
normal operation. More detailed measurements encompass a) energy gain of collector array(s) and b) 
energy balance over storage vessel(s). Intercomparison of the observed and simulated energy quantities provides the indirect validation of collector and storage design parameters. The measured data within the 
collector array are also used for direct identification of the collector array parameters. As far the component parameters are verified, the long-term prediction of the system gain as well as the detection 
of possible sources of system malfunctioning are possible. 
 
Annex D describes a procedure for long-term monitoring as a part of the supervision of a large custom built 
solar heating system. The objectives of supervision may be: a) the early recognition of possible failures of 
system components, in order to get the maximum benefit from the initial solar investment as well as to 
minimize the consumption of non-solar energy and the resulting environmental impact; b) the measurement 
of system performance (solar gains or other system indicators), if requested by a contractual clause, e.g. guaranteed results. The long-term monitoring in Annex D is limited to the solar energy specific aspects, 
especially to the determination of the solar contribution to the total heat load. Instrumentation used in the long-term monitoring should be an integrating part of the system, a part included from the very beginning of 
the design process. If adequately foreseen, it may also be used for system adjustment at start time. 
 
Drinking water quality 
 
In respect of potential adverse effects on the quality of water intended for human consumption, caused by the 
product covered by this standard: 
 
a) This standard provides no information as to whether the product may be used without restriction; PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008  
© KEBS 2008 — All rights reserved v  
b) It should be noted that, while awaiting the adoption of verifiable criteria, existing national regulations 
concerning the use and/or the characteristics of this product remain in force. 
 
Factory Made and Custom Built solar heating systems 
The standards KS 1852-1 as well as KS 1852-2 and the standards KS 1855-1 to KS 1855-3 distinguish two categories of solar heating systems: Factory Made  solar heating systems and Custom Built  solar heating 
systems. The classification of a system as Factory Made or Custom Built is a choice of the final supplier, in accordance with the following definitions.  
Factory Made solar heating systems  are batch products with one trade name, sold as complete and ready 
to install kits, with fixed configurations. Systems of this category are considered as a single product and 
assessed as a whole. If a Factory Made Solar Heating System is modified by changing its configuration or by 
changing one or more of its components, the modified system is considered as a new system for which a new 
test report is necessary. Requirements and test methods for Factory Made solar heating systems are given in KS 1852-1 and KS 1852-2. 
 
Custom Built solar heating systems  are either uniquely built, or assembled by choosing from an 
assortment of components. Systems of this category are regarded as a set of components. The components are separately tested and test results are integrated to an assessment of the whole system. Requirements for Custom Built solar heating systems are given in KS 1855-1; test methods are specified in KS 1855-2 and KS 
1855-3. Custom Built solar heating systems are subdivided into two categories:  
⎯ Large Custom Built systems  are uniquely designed for a specific situation. In general HVAC 
engineers, manufacturers or other experts design them. 
 
⎯ Small Custom Built systems  offered by a company are described in a so-called assortment file, in 
which all components and possible system configurations, marketed by the company, are specified. 
Each possible combination of a system configuration with components from the assortment is 
considered as one Custom Built system. 
 Table 1 shows the division for different system types: 
 
Table 1 ⎯ Division for factory made and custom built solar heating systems 
 
Factory Made Solar Heating Systems 
(KS 1852-1, -2) Custom Built Solar Heating Systems (KS 1855-1, -2, -3) 
 
Integral collector-storage systems for 
domestic hot water preparation Forced-circulation systems for hot water preparation and/or space heating, assembled using components and 
configurations described in a documentation file (mostly small 
systems) 
Thermosiphon systems for domestic hot 
water preparation  
Forced-circulation systems as batch 
product with fixed configuration for 
domestic hot water preparation Uniquely designed and assembled systems for hot water 
preparation and/or space heating (mostly large systems) 
 
NOTE 1 Forced circulation systems can be classified either as Fa ctory Made or as Custom Built, depending on the market approach  
chosen by the final supplier. 
 
NOTE 2 Both Factory Made and Custom Built systems are performance tested under the same set of reference conditions as specifie d 
in Annex B of KS 1852-2 and Annex A of KS 1855-2. In practice, the installation conditions may differ from these reference cond itions. 
 
NOTE 3 A Factory Made system for domestic hot water preparation may have an option for space heating, however this option shoul d 
not be used or considered during testing as a Factory Made system. PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
vi © KEBS 2008 — All rights reserved  
Contents 
 
1 Scope ......................................................................................................................... ................................ 1  
2 Normative references .......................................................................................................... ....................... 2  
3 Terms and definitions ......................................................................................................... ........................ 2  
4 Symbols and abbreviations ..................................................................................................... ................... 2  
5 System classification ......................................................................................................... ......................... 4  
6 Test methods .................................................................................................................. ............................ 4  
7 Optional performance test of small custom built solar he ating systems .................................................. 10  
8 Performance test report ....................................................................................................... ..................... 16  
Annex A (normative)  Reference conditions for performance pr ediction ..........................................................  18 
Annex B (normative)  Testing of solar loop controllers with temperature sensors ........................................... 22  
Annex C (informative)  Short-term system testing .............................................................................. .............. 27  
Annex D (informative)  Long-term monitoring ................................................................................... ................ 38  
Bibliography .................................................................................................................. .................................... 40  
 
 
  
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KENYA STANDARD KS 1855-2:2008  
© KEBS 2008 — All rights reserved 1  
 
Thermal solar systems and components  — Custom built systems — Part 
2: Test methods  
 
 1 Scope 
 
This Kenya Standard applies to small and large custom built solar heating systems with liquid heat transfer 
medium for residential buildings and similar applications, and gives test methods for verification of the 
requirements specified in KS 1855-1. 
 
This Kenya Standard includes also a method for thermal performance characterization and system performance prediction of small custom built systems by means of component testing and system simulation. 
 
Furthermore, the Kenya Standard contains methods for thermal performance characterization and system 
performance prediction of large custom built systems. 
 This Kenya Standard applies to the following ty pes of small custom built solar heating systems: 
 
⎯ systems for domestic hot water preparation only; 
 
⎯ systems for space heating only; 
 
⎯ systems for domestic hot water preparation and space heating. 
 
This Kenya Standard applies to large custom built solar heating systems, primarily to solar preheat systems, 
with one or more storage vessels, heat exchangers, piping and automatic controls and with collector array(s) 
with forced circulation of fluid in the collector loop.  
This Kenya Standard does not apply to: 
 
⎯ systems with a store medium other than water (e.g. phase-change materials); 
 
⎯ systems for space heating with a distribution fluid other than water for the space heating subsystem 
(e.g. air systems); 
 
⎯ small custom built systems with a circulation line entering any store having a feedback on the solar 
heated store. 
 Principally, systems with circulation line may be tested in accordance to the methods described in this Kenya 
Standard, if the connecting port for the circulation line is kept closed during the tests. This should, however, 
stated in the test report. 
 
⎯ thermosiphon systems; 
 
⎯ integral collector-storage (ICS) systems. 
 The test procedure of Annex C cannot be applied to solar heating systems with concentrating collectors. 
 
NOTE The two test methods presented in annex C ("Short-term system testing") have only been validated, so far, two laboratories , at 
the Danish Technological Institute DTI and at the Chalmers University of Technology Goteborg ([9], [14]). DTI is confident that  the 
procedures are promising and very efficient. However, the full verification and a round robin test within Europe are urgently n eeded. 
 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
2 © KEBS 2008 — All rights reserved 2 Normative references 
 
The following referenced documents are indispensable for the application of this Kenya Standard. For dated 
references, only the edition cited applies. For undated re ferences, the latest edition of the referenced document 
(including any amendments) applies.  
 
EN 806-1, Specifications for installations inside buildings conveying water for human consumption — Part 1: 
General  
 
ISO 15783, Seal-less rotodynamic pumps — Class II — Specification  
 
ISO 9906, Rotodynamic pumps — Hydraulic performance acceptance tests — Grades 1 and 2  
 
EN 1717, Protection against pollution of potable water in drinking water installations and general 
requirements of devices to prevent pollution by backflow  
 ISO 6612, Windows and door height windows — Wind resistance tests  
 
ISO 16528, Boilers and pressure vessels  
 
KS 1851-1, Thermal solar systems and components — Solar collectors — Part 1: General requirements  
 KS 1851-2, Thermal solar systems and components — Solar collectors — Part 2: Test methods  
 
KS 1852-1, Thermal solar systems and components — Factory made systems — Part 1: General 
requirements  
 KS 1852-2, Thermal solar systems and components — Factory made systems — Part 2: Test methods  
 
KS 1855-1, Thermal solar systems and components — Custom built systems — Part 1: General 
requirements  
 
KS 1855-3, Thermal solar systems and components — Custom built systems — Part 3: Performance 
characterization of stores for solar heating systems  
 IEC 60335-1, Safety of household and similar electrical appliances — Part 1: General requirements  
 IEC 60335-2-21, Safety of household and similar electrical appliances — Part 2: Particular requirements for 
storage water heaters  
 
ISO 9459-5, Solar heating — Domestic water heating systems — Part 5: System performance by means of 
whole system testing and computer simulation  
 ISO 9488, Solar energy — Vocabulary  
 
3 Terms and definitions 
 
For the purposes of this Kenya Standard, the terms and definitions given in ISO 9488 and ISO 9459-5 as well 
as KS 1851-1, KS 1852-1 and KS 1855-1 apply. 
 
4 Symbols and abbreviations 
 
al algebraic constant for the determination of the collector heat loss coefficient 
 A
c collector reference area 
 
Cc collector array heat capacity PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 3  
fsol solar fraction 
 
G solar irradiance 
 
Gd diffuse irradiance 
 
Gg global irradiance (i.e. horizontal) 
 
Gh hemispherical irradiance, e.g. on tilted plane 
 H
c hemispherical solar irradiation in collector plane 
 
Kατ incidence angle modifier 
 
Paux power of the auxiliary heater 
 P
c thermal power of the collector or collector array 
 
Prc circulation heat loss power 
 Q
sol heat delivered by the collector loop to the store 
 
Qaux net auxiliary energy demand of a solar heating system delivered by the auxiliary heater to the store or 
directly to the heat distri bution system (see 7.5.3) 
 
QL energy delivered at the outlet of the solar heating system 
 
Qd heat demand 
 
Ql store heat losses 
 
Qohp heat diverted from the store as active overheating protection, if any 
 
Qpar parasitic energy (electricity) for the collector loop pump(s) and control unit 
 
ϑaverage  yearly average cold water temperature on reference location 
 
ϑc,mb collector ambient air temperature 
 
ϑs,amb store ambient air temperature 
 
ϑci/co collector or collector array inlet/outlet fluid temperature 
 
ϑcw mains water temperature 
 
ϑd desired hot water temperature 
 
ϑm mean collector fluid temperature; ϑm = (ϑci + ϑco) / 2 
 
ϑrci fluid temperature at circulation loop inlet 
 
ϑrce fluid temperature at circulation loop outlet 
 
θreq required temperature for sensor high-temperature resistance (see annex B) 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
4 © KEBS 2008 — All rights reserved ϑS store outlet fluid temperature 
 
θsens sensor temperature (see annex B) 
 
ϑstart/stop  temperature for which controller operation starts/stops (see annex B) 
 
ϑtank temperature of the storage tank (see annex B) 
 
T* reduced temperature of collector; T* = (ϑm ⎯ ϑc,amb) /Gh 
 
(UA)hx heat transfer rate of a heat exchanger 
 (UA)
S store heat loss rate 
 
UL overall heat loss coefficient of collector array 
 
Vd demanded (daily) load volume 
 
VS store volume 
 
VC volume flow rate in collector loop 
 V
rc volume flow rate in circulation loop 
 V
s volume draw-off flow rate from storage 
 
v surrounding air speed 
 
Δϑ temperature difference 
 
Δϑamplit average amplitude of seasonal variations on reference location 
 
η zero-loss collector efficiency (efficiency at T* = 0) 
 
5 System classification 
 
See clause 5 of KS 1855-1. 
 
6 Test methods 
 
Subsequent test methods refer to the requirements given in KS 1855-1. 
 
NOTE The numbering of the following clauses is kept in direct correspondence to the numbering in KS 1855-1. 
 
6.1 General 
 
6.1.1 Suitability for drinking water 
 
See EN 806-1. 
 
6.1.2 Water contamination 
 
For small custom built systems see EN 1717. 
 
Large custom built systems: Check the hydraulic scheme or any other part of the documentation of the system according to 6.7.3 of KS 1855-1. (See also the introduction about water quality). 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 5 6.1.3 Freeze resistance 
 
See 5.1 of KS 1852-2. 
 
6.1.4 Overheating protection  
6.1.4.1 Scald protection  If the temperature of the domestic hot water in the system can exceed 60 °C, check the design plan or the system documentation to see whether the system is provided with an automatic cold water mixing device or 
any other device capable for limiting the water temperature to 60 °C at most. 
 
6.1.4.2 Overheating protection of materials 
 Ensure by checking the hydraulic scheme and/or by calculation and taking into account the most adverse conditions for the materials of all parts of the system, that the maximum temperatures which may occur do 
not exceed the maximum permissible temperatures for the respective materials. 
 
NOTE Both transients (high-temperature peaks of short duration) and stagnation of longer duration may create adverse conditions  for 
the respective material. 
 
6.1.5 Reverse flow prevention 
 
Check the hydraulic scheme included in the documentation (see 6.7) to ensure that no unintentional reverse 
flow will occur in any hydraulic loop of the system. 
 
6.1.6 Pressure resistance 
 
See ISO 16528.  
If any component of the system is not covered by ISO 16528 or KS 1851-1, check the technical data to see whether the component for the part of the system in which it is used will withstand the lowest of the following pressures  
 
⎯ 1.5 times the manufacturer's stated maximum working pressure 
 
⎯ the manufacturer's stated maximum test pressure 
 
In addition, for large custom built systems only: 
 
⎯ Regarding safety valves, check the hydraulic scheme or any other part of the documentation of the 
system according to 6.7.3 of KS 1855-1. 
 
⎯ Regarding pressure resistance, check whether the collector array can withstand short and high 
pressure peaks. Calculate the highest pressure that can occur in the individual loops in the system 
and compare it with the maximum allowed pressure of the individual loops (see also NOTE 2 in 6.1.6 
of KS 1855-1). Alternatively, an experimental test with 1,3 times the maximum allowed pressure of 
each loop may be applied. 
 6.1.7 Electrical safety  
See IEC 60335-1 and IEC 60335-2-21. 
 
6.2 Materials 
 
Check the work certificates provided by the manufacturer whether the requirements on UV radiation and 
weather resistance as well as on the choice of materials for the collector loop are fulfilled. For small custom built systems this check shall in  any case be performed, for large ones as far as applicable. 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
6 © KEBS 2008 — All rights reserved 6.3 Components and pipework 
 
6.3.1 Collector and collector array 
 
The collector shall be tested according to KS 1851-2. 
 
In addition, the maximum disparity of the mass flow rate in parallel collector rows should be calculated by 
means of the corresponding pressure drops. 
 
6.3.2 Supporting frame 
 Check the calculation proving the resistance of the frame to wind loads in accordance with ISO 6612.  
6.3.3 Collector and other loops 
 
The optional collector loop test comprises the following steps: 
 
⎯ Determination of the nominal power needed by the collector loop pump 
 
⎯ Calculation of the highest heat power which can be delivered by the collector array P
c,max: 
 
Pc,max = η0AcGref (1) 
 
where Gref is the reference irradiance of 1000 W/m2 (for other symbols see Clause 4). 
 
⎯ Check of the values calculated by formula (1) in comparison with the values listed in Table 4 of KS 
1855-1. 
 
For other heat transfer loops, the nominal parasitic power of their pump(s) should be directly compared with 
the calculated highest transmitted heat power, based on Table 4 of KS 1855-1.  
6.3.4 Circulation pump 
 
See ISO 9906 and ISO 15783. 
 
6.3.5 Expansion vessel 
 
For drain-back systems without a separate expansion vessel, check both by calculation and the hydraulic 
scheme to see whether the drain-back facility is able to fulfil its additional task as an expansion vessel. 
 
6.3.5.1 Open expansion vessel 
 
Check the volume and design of the open expansion vessel by calculation and by checking the hydraulic 
scheme. 
 In addition, check the connection of the vessel to th e atmosphere, the spill line an d the expansion lines on the 
hydraulic scheme. 
 
6.3.5.2 Closed expansion vessel 
 
For small custom built systems only: Check the fulfilment of the requirements given in 6.3.5.2 of KS 1855-1 by calculation and by visual check of the hydraulic scheme and operating instruction. 
 
6.3.6 Heat exchangers 
 
Apart from the tests in compliance with ISO 16528, check the design of the heat exchanger(s) with respect to 
scaling or the availability of cleaning facilities.  PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 7 In addition, the drop in system efficiency Δη induced by a heat exchanger in the collector loop of a small 
custom built system should be estimated by formula (2): 
 
Δη =  
hxC
UAaA
)(1 0η × 100 % (2) 
 
where η0 and al, are given from the collector performance test of KS 1851-2. For small systems ( UA)hx is 
delivered by the store performance test of KS 1855-3 (( UA)hx to be chosen for fluid temperatures of 20 °C). 
For large systems ( UA)hx is taken from the heat exchanger performance data sheet provided by the 
manufacturer. 
 
NOTE 1 In the latter case, since performance data of external heat exchangers (which are mostly used in large custom built syst ems) 
are generally quite reliable, no additional measurements are needed. 
 For heat exchangers in other loops (e.g., a load side heat exchanger), the mean temperature rise on the 
primary side Δ
ϑ which is induced by the presence of the heat exchanger should be estimated by calculation. 
The drop in efficiency may then be estimated by: 
 
Δη = (a l Δϑ/Gref) × 100% (3) 
 
where the reference irradiance Gref is set to 1000 W/m2. 
 
NOTE 2 More accurate calculation methods are given in [1]. In special cases the thermal stratification in the store should be t aken into 
account, to obtain an accurate figure for the efficiency drop. 
 
6.3.7 Store 
 
With the exception of the heat loss rate, stores for drinking water shall be tested according to ISO 16528. For 
small custom built systems, this test applies in any case, for large custom built systems as far as applicable. 
 In addition, for small custom built systems only:  
⎯ the performance of their hot water stores should be characterized according to KS 1855-3. 
 
⎯ the heat loss rate of these hot water stores, obtained from performance characterization according to 
KS 1855-3, should be compared with the requirements given in 6.3.7 of KS 1855-1. 
 
6.3.8 Pipework 
 
Check the design plan, manufacturer's works certificates and system documentation in respect of design and 
material of pipes and fittings.  
6.3.9 Thermal Insulation  
Check the design plans and system documentation. 
 
6.3.10 Control system 
 
6.3.10.1 Controller 
 
For small custom built systems only: The optional controller test is described in annex B. 
 
6.3.10.2 Temperature sensors 
 
The design plans and components shall be visually checked in respect of location, installation and insulation of the sensors according to the requirements in 6.3.10.2 of KS 1855-1. 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
8 © KEBS 2008 — All rights reserved Additionally: 
 
⎯ For small custom built systems: Test the sensor resistance to high temperature as described in B.3. 
This test is, however, not necessary if a documentation delivered with the sensor indicates that it can 
withstand 100 °C or stagnation conditions (whichever the greatest) without altering by more than 1 K. 
 
⎯ For large custom built systems: Check the suitability of the temperature sensors in respect of 
stagnation conditions or maximum temperatures in connection with the quality declaration given by 
the supplier. 
 6.4 Safety equipment and indicators  6.4.1 Safety valves 
 
Check the design plan and the system documentation to verify that each collector or group of collectors is fitted with at least one suitable safety valve. 
 Check the specification of the safety valves, whether the materials fulfil the requirements given in 6.4.1 of KS 
1855-1. 
 Check whether the size of the safety valve is correct, in compliance with the requirements given in 6.4.1 of KS 1855-1. 
 Check whether the temperature of the heat transfer medium at the release pressure of the safety valve 
exceeds the maximum allowed temperature of the heat transfer medium. 
 Additionally, for large custom built systems: For testing the system behaviour after release of one or more 
safety valves according to the requirements given in 6.4.1 of KS 1855-1, check the electric and hydraulic schemes or any other part of the documentation according to 6.7.3 of KS 1855-1. 
 6.4.2 Safety lines and expansion lines 
 Check the hydraulic scheme and system documentation to verify that safety and expansion lines cannot be shut-off. 
 
Check the internal diameter of the safety and the expansion line with respect to the requirements given in 6.4.2 of KS 1855-1. 
 Check the hydraulic scheme and system documentation to verify that the expansion line and the safety line 
are connected and laid in such a way that any accumulation of dirt, scale or similar impurities are avoided. 
 6.4.3 Blow-off lines 
 Check the hydraulic scheme and system documentation to verify that the blow-off lines fulfil the requirements given in 6.4.3 of KS 1855-1. 
 
6.4.4 Store shut-off valve 
 
For large systems only: Verify the existence of a shut-off valve by checking the system documentation in accordance with 6.7.3 of KS 1855-1. 
 
6.4.5 Indicators 
 
6.4.5.1 Indicators for collector loop flow 
 
Check the hydraulic scheme and system documentation in respect of the position and installation of the 
recommended indicators for the collector loop flow. PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 9  
6.4.5.2 Pressure gauge 
 Check the hydraulic scheme and system documentation in respect of the position and the installation of the 
pressure gauge or, in the case of some drain-back systems without pressure gauge, of the other means 
provided for checking drain-back and the fluid level in the collector loop. 
 
6.4.5.3 Heat meter 
 
If the collector loop of a large custom built system is equipped with a heat meter (see 6.4.5.3 of KS 1855-1), 
this should be mentioned in the system documentation. 
 
6.5 Installation 
 Check the design plans and the system documentation to see whether the leak tightness of the roof may be affected by the installation of the collector. 
 6.5.1 Lightning 
 For small custom built systems see 5.5 of KS 1852-2.  
For large custom built systems verify the compliance with the requirements given in 6.5.1 of KS 1855-1 by checking the documentation included in 6.7.3 of KS 1855-1. 
 
6.5.2 Wind loads 
 See ISO 6612. Moreover, check the documents for the installer whether they comply with 6.5.2 of KS 1855-1.  
6.6 Initial operation, inspection and commissioning 
 
This clause applies to large systems only.  
Before initial operation:  
⎯ Check whether the system layout and components are as described in the documentation. 
 
⎯ Check the record of the adjustments for the corresponding fittings. For each fitting a recorded 
adjustment shall exist. 
 
⎯ If there is a supervisor of the system, ensure that he has been sufficiently instructed. 
 The procedure for short-term system testing referred to in 6.6 of KS 1855-1 (only if needed or required) is 
given in annex C. 
 The procedure for long-term system monitoring referred to in 6.6 of KS 1855-1 (only if needed or required) is 
given in annex D. 
 
6.7 Documentation 
 
Check all documents, as to whether they fulfil the requirements given in 6.7 of KS 1855-1 and whether they 
are complete and understandable. 
 
6.8 System performance 
 
This clause applies to small systems only.  PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
10 © KEBS 2008 — All rights reserved The optional performance test methods for small custom built systems are described in Clause 7. The test 
results shall be presented in a test report as described in clause 8. 
 
7 Optional performance test of small custom built solar heating systems 
 
The test method is based on component tests of the solar collector, the store(s), the controller and other components as necessary. These component tests are described in 7.1, 7.2 and 7.3. The whole system is 
then simulated using a validated simulation program as described in 7.4. The long-term performance of the 
whole system is predicted for reference conditions as described in 7.5. 
 
If the carrying out of this performance test is required, the specification included in 7.4 and 7.5 shall be adhered to. 
 
In general, the system does not need to be installed as a whole for testing.  
For systems for hot water preparation only (class A) the full tests should be carried out including the long-
term performance prediction for reference conditions.  
For systems for space heating only (class B) and systems for combined domestic hot water preparation and space heating (class C) the components should be tested and the results be stated in the test report. The 
long-term performance prediction is a further option. If the performance prediction is carried out, the results 
should be stated in the test report stating also the chosen boundary conditions for the simulation. The 
following remark should be added to the results of performance predictions for systems of class B and C: 
 Intercomparison of the results of the long-term performance prediction is only possible, if validated simulation 
models and the same boundary conditions are used. 
 
NOTE 1 The procedure for space heating systems as described abov e allows national solutions with respect to the definition of 
reference conditions. This is a preliminary step for the s tandardization of this procedure within the CEN countries. After enou gh 
experience has been gained on national level, the reference conditions for all CEN countries can be elaborated. 
 
Before starting the performance testing all tests specified in 6.1 to 6.7 shall be completed. In case a system fails one or more of these tests, the malfunction or defect shall be eliminated by the manufacturer prior to 
performance testing. If this is not possible 
 
⎯ the malfunction shall be stated in the performance test report, 
 
⎯ the performance of the system shall be determined with the method as described in this clause. 
However, the reduction of the system performance induced by the malfunction or defect shall be 
estimated and the results of the performance test corrected accordingly. 
 
NOTE 2 If the system fails one of the following tests described in clause 6, a significant reduction of the system performance can be 
expected: 
 
⎯ Collector array: balanced flow (see 6.3.1) 
 
⎯ Temperature sensors: thermal contact of the sensors to the part of which the temperature is measured (see 6.3.10.2) 
 
⎯ Reverse flow prevention (see 6.1.5) 
 
⎯ Thermal insulation (see 6.3.9) 
 
7.1 Separate test of the solar collector 
 
For the collector test according to KS 1851-2, all data for dynamic simulation of the thermal behaviour of the 
collector as listed below should be determined: 
 
⎯ standard steady-state parameters 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 11 ⎯ collector heat capacity 
 
⎯ incidence angle modifier for beam and diffuse irradiance 
 
⎯ wind speed dependence of the collector heat loss coefficients (for collectors with non-selective 
absorbers or unglazed collectors) 
 
⎯ influence of flow rate if relevant  
 
⎯ influence of collector tilt angle if relevant 
 
If a solar collector is offered in different dimensions, the performance parameters of the smallest unit may be 
used as representative for the whole series of collectors. 
 
7.2 Separate test of the hot water store 
 The store should be tested in accordance with KS 1855-3. Thereby all data for dynamic simulation of the thermal behaviour of the store as described in KS 1855-3 should be determined. 
 7.3 Separate test of the control system 
 
The control system should be tested according to the methods described in annex B. Thereby all data for 
dynamic simulation of the behaviour of the control system as described in annex B should be determined.  7.4 System simulation model 
 
The modelling of the system should be carried out using a detailed transient simulation programme in which it 
is possible to model the different system and store configurations involved, and in which all parameters 
determined in the component tests can be adjusted. 
 
NOTE 1 The level of detail needed for most system types is similar to that used in the programmes TRNSYS or EMGP3 or equivalent . 
 
The component models for collector and store used in th e system simulation shall be respectively the same 
as for the characterization of the collector according to KS 1851-2, and for the characterization of the store 
according to KS 1855-3. The store model shall be able to adequately simulate thermal stratification in the 
store. 
 
The control concept tested according to annex B shall be included in the simulation programme. 
 
For other components, e.g. pipework or external heat exchanger, the level of detail in the simulation model 
shall correspond to the available technical data. 
 
The following features shall be implemented in the model: 
 
NOTE 2 The computation of the irradiance on the tilted plane s hould be as detailed as possible. Up-to-date models and any simpl ified 
tools should be avoided. A radiation model is given in [2], [3,] [4], and [5]. (See Bibliography.) 
 
⎯ A thermostat mixer which reduces the store outlet temperature i9s to the desired temperature $, 
during draw-offs. For solar preheat systems and solar-only systems this thermostat mixer shall be located directly at the outlet of the solar part of the system. 
 
⎯ The collector loop operation shall be stopped when the store temperature exceeds 100 °C if no other 
temperature is specified by the manufacturer. 
 
The system simulation model shall have been previously validated. 
 
7.5 Long-term performance prediction 
 
The recommended long-term system performance prediction is described only for system class A (domestic 
hot water preparation only). However, for system classes B and C the same general principles apply. PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
12 © KEBS 2008 — All rights reserved  
7.5.1 Calculation procedure 
 Use the simulation model selected according to 7.4. The component parameter values used for the 
simulation are those given by the separate component tests according to 7.1 to 7.3. Data on other 
components of the system, e.g. pipework or external heat exchanger, should be used as given by the 
manufacturer. 
 
The reference conditions as specified in annex A shall be used when calculating or reporting the performance of a system by computer simulation. 
 7.5.2 Prediction of yearly system performance indicators 
 
NOTE In the following paragraphs, performance indicators for solar heating systems for hot water preparation only are specified . The 
text of these paragraphs is identical for this Kenya Standard and for Factory Made Systems (KS 1852-2), except that the calcula tion of 
the performance indicators is mandatory for Factory Made Systems, being, on the contrary, optional here. Performance indicators  for 
space heating systems are presently excluded, since there is not y et enough experience available. This is a preliminary step fo r the 
standardization of this procedure. After enough experience has been gained, the performance indicators for space heating system s will 
be determined. 
 
Uniform reference conditions for the calculation of the performance are specified in the identical annexes, 
Annex A of this standard or Annex B of KS 1852-2. For these conditions, the following performance indicators should be derived from the performance test results: 
 For solar-plus-supplementary systems: 
 
⎯ the net auxiliary energy demand Qaux, net  
 
⎯ the parasitic energy Qpar  
 
For solar-only and preheat systems: 
 
⎯ the heat delivered by the solar heating system QL 
 
⎯ the solar fraction fsol 
 
⎯ the parasitic energy Qpar if any 
 
7.5.3 Calculation of the net auxiliary energy demand for solar-plus-supplementary systems 
 
Calculate the yearly net auxiliary energy demand Qaux,net  directly by computer simulation (long-term 
performance prediction) as specified in 7.5.1 of this Kenya Standard (for Custom Built Systems) or 5.9.3.2 of 
KS 1852-2 (for Factory Made Systems). Additional indication to the quantities entering the energy balance of 
one-store and two-stores solar-plus-supplementary heating systems is given in Figure 1. 
 
If a solar-plus-supplementary system cannot meet the heat demand to such a degree that the energy 
delivered to the user is less than 90 % of the yearly heat demand, this should be stated in the test report. 
 
NOTE The energy delivered to the user can be less than the heat demand for example when the power of the auxiliary heater is no t 
sufficient or when strong mixing occurs in the store during draw-offs. PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 13  
 
 
Key 
1 Collector  4 Auxiliary heater 2 Pump  5 Control Unit 
3 Store  6 Cold Water 
 
a)    Energy balance for one-store solar-plus-supplementary systems 
 
 
 
Key 
1 Collector  4 Auxiliary heater 
2 Pump  5 Control Unit 
3 Solar Store  6 Cold Water 7 Auxiliary store 
 
b)    Energy balance for two-store-solar-plus-supplementary systems 
 
Figure 1 ⎯ Energy balance for one-store and two-stores solar-plus-supplementary systems 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
14 © KEBS 2008 — All rights reserved 7.5.4 Calculation of the solar fraction for solar-only and preheat systems 
 
Compute the system energy balance on a yearly basis. This includes the following energy quantities (see 
Figure 2 and Figure 3), calculated using the reference data and conditions given in annex A of this Kenya 
Standard or Annex B of KS 1852-2 
 
Qd heat demand; 
 
QL heat delivered by the solar heating system (load) 
 
Qpar parasitic energy (electricit y) for pump and controls; 
 
The parasitic energy Qpar shall be calculated according to 7.5.5 
 
NOTE 1 The reference location for calculating the load QL are the store ports or the load-side heat exchanger ports, if provided. The 
reference temperature for calculating the loads is the cold water temperature. Heat losses of the circulation line, if any, are  not included 
in the loads, as the test is carried out with this line kept closed. 
 
NOTE 2 According to ISO 9488, a solar preheat system is a solar system to preheat water or air prior to its entry into any othe r type of 
water or air heater. This water or air heater is not part of the solar preheat system itself. Hence, for this type of system th e energy 
delivered by the solar heating system QL is calculated at the outlet of the solar heating system and the store heat loss QL is the heat loss 
of the solar store itself (see Figure 3). 
 NOTE 3 The yearly heat demand is calculated using the load volume, cold water temperature and the desired temperature for hot w ater 
as specified in annex A. 
 
 
 
Key 1 Collector 4 Cold water  2 Pump 5 Control unit 
3 Store 
 
Figure 2 — Energy balance for solar-only systems 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 15 
 
Key 
1 Collector 5 Control unit 
2 Pump 6 Cold water 
3 Solar store 7 Solar preheated system 
4 Auxiliary heater 8 Series-connected auxiliary heating system 
 
Figure 3 — Energy balance for solar preheat systems 
 
Calculate the solar fraction, fsol by using the definition of ISO 9488: 
 
Solar fraction, fsol: The energy supplied by the solar part of a system divided by the total system load ( Qd = 
heat demand). 
 
fsol = QL/Qd 
 7.5.5 Calculation of the parasitic energy 
 
Calculate the yearly parasitic energy Q
par needed by pumps, controllers etc, in conformity with 4.6.3 h) 3) of 
KS 1852-1. 
 
7.6 Presentation of performance indicators 
 
The results from 7.5.1 to 7.5.5 should be presented for the load volume(s) as specified in Annex A in the way 
shown in Table 2 and Table 3. PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
16 © KEBS 2008 — All rights reserved  
Table 2 ⎯ Presentation of system performance indicators for solar-plus-supplementary systems 
 
Performance indicators for solar-plus-supplementary systems on annual base for a volume demand of 
....... l/d 
 
Location (latitude) 
 Qd 
MJ 
 Qaux, net  
MJ 
 Qpar 
MJ 
 
Stockholm  (69.6° N) 
 ..... 
  
   
Würzburg 
(49.5° N) 
 ..... 
  
   
Davos 
(46.8° N) 
  
     
Athens 
(38.0° N) 
 ..... 
  
   
……. 1) 
  
     
1) For a location free to choose 
 
 
Table 3 ⎯ Presentation of system performance indicators for solar-only and solar preheat systems 
 
Performance indicators for solar-only and solar preheat systems on annual base for a volume 
demad of ....... l/d 
 
Location (latitude) 
 Qd 
MJ 
 Ql 
MJ 
 fsol 
% 
 Qpar 
MJ 
 
Stockholm  (69.6° N)          
Würzburg 
(49.5° N)  ..... 
       
Davos 
(46.8° N) 
 ..... 
  
     
Athens  
(38.0° N)          
…… 1) 
  
       
1) For a location free to choose 
 
 
8 Performance test report 
 This clause describes the report of results from the optional tests performed according to Clause 7. This test report applies to small custom built systems only as also the system performance test methods given in 
Clause 7 are applicable to small custom built systems only (see 6.8). PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 17  
The test report shall include: 
 
⎯ a detailed description of components and system configuration 
 
⎯ the prediction method used. The simulation programme shall be specified and an input file shall be 
enclosed. 
 
⎯ the complete reference conditions used as specified in Annex A including information about the location 
for which the performance prediction is made and the reference weather data used. 
 
⎯ for the reference conditions as specified in Annex A, the performance indicators on a yearly base as 
specified in 7.5.2. PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
18 © KEBS 2008 — All rights reserved  
Annex A 
(normative) 
 
Reference conditions for performance prediction 
 
A.1 General 
 
The conditions given in Table A.1 shall be used when calculating, reporting or comparing the performance of 
a system, either from a test or from a computer simulation. These conditions should also be applied to the 
system during any system performance test, if not specified otherwise.  
NOTE The following reference conditions are identical for testing and simulating of Factory Made Systems in KS 1852-2 and Custo m 
Built Systems in this Kenya Standard. However, some aspects related to systems considered in only one of the two standards, hav e 
been deleted from the other standard. 
 
Table A.1 ⎯ Reference conditions for performance presentation 
 
Reference condition Value Remarks 
SYSTEM 
 
Collector orientation 
 South    
Collector tilt angle 
 45°  For testing, (45 ± 5)° if not fixed for the system or specified by the manufacturer.  
Total length of collector circuit 
 20m = 10m + 10m 
 If piping is not delivered with the system or specified by the manufacturer. 
 
Pipe diameter and insulation thickness of 
collector circuit 
 See A.2 
 If piping is not delivered with the system or specified by the manufacturer. 
 
Location of the collector 
circuit pipes 
 Indoors, for systems 
with the store 
located indoors; 
outdoors, for systems with the 
store located 
outdoors As far as possible at the test rig 
 
Store ambient temperature 
 15 °C  For systems where the store is located outside, the ambient temperature from the climate shall be used. 
 
For systems with indirect 
(hydraulic) auxiliary 
heating: Power to be 
applied on auxiliary heat 
exchanger 
 (100 ± 30) W per 
liter of store volume 
above the lowest 
end of heat 
exchanger 
 If the auxiliary heater is not delivered with the system and 
no restrictions have been given in the documentation. 
The auxiliary heater shall be  modeled as an ideal heat 
source with no heat capacity and constant heating power.
 
Flow rate through auxiliary 
heat exchanger 
  The flow rate through the heat exchanger shall be 
chosen such that the temperature difference between the inlet and outlet of the auxiliary heat exchanger is (10 ± 2) 
K under steady state conditions, unless specified 
otherwise by the manufacturer. 
(continued) PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 19 Table A.1 (continued) 
 
  
 
For systems with electrical 
auxiliary heating: Power of electrical element 
 If an electrical element is normally delivered with the system or specified by 
the manufacturer, this element shall be used. Otherwise, (25 ± 8) W per liter of store volume above the electrical element apply. 
 
For solar-plus-
supplementary systems: 
Status of the auxiliary 
heater 
 Permanently 
activated 
 This is for performance prediction 
 
Temperature of integrated 
auxiliary heating 
 52,5 °C (minimum 
temperature of 
hysteresis) 
 Or a higher temperature, if recommended by the 
manufacturer 
 
CLIMATE 
Reference locations 
 Stockholm, Würzburg, Davos, Athens 
 In the reporting form, the performance of a different 
location of choice may also be given.  
Climate Data 
 For Stockholm: CEC Test Reference Year; for Davos, Würzburg and Athens: Test Reference Year. 
 
HEAT LOAD 
Daily load pattern  For all systems: - 100 % at 6 h after solar noon For testing, the load patterns shall be as specified in the test procedure. 
 
Cold water supply temperature 
 See A.3 
 For testing, the temperature shall be as specified in the test procedure 
 
Desired (mixing valve) temperature 
 45 °C 
 If the daily or yearly loads are calculated in terms of energy, this energy shall be calculated using the cold 
water supply temperature and the desired temperature.
Daily load volume  The load volumes in liters per day shall be chosen from the following series: 50 l/d, 80 l/d, 110 l/d, 140 l/d, 170 l/d, 200 l/d, 250 l/d, 300 l/d, 400 l
/d, 600 
l/d. If larger loads are required, the series may be extended by repeatedly 
multiplying by the square root of 2 and rounding to the nearest multiple of 10. 
 The manufacturer shall give a design load for the system. The nearest value 
given in the above series shall be used, as well as the next lower and higher 
values. It is recommended to use all lowe r and higher values from the series, 
which lie between 0.5 and 1.5 times the design load. 
 
NOTE fixed load volumes have been chosen to facilitate comparison of the performance of 
different systems. 
For testing, the load volumes as specified in the test procedures shall be 
used. 
 
A.2 Pipe diameter and insulation thickness 
 
If the pipe and insulation for the collector circuit are delivered with the system, or the pipe diameter and the 
insulation thickness to be used for the collector circuit are clearly specified in the installation manual for the 
system, the delivered hardware or the specified values shall be used. 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
20 © KEBS 2008 — All rights reserved When piping and insulation are not delivered with the syst em or clearly specified, the pipe diameter, the pipe 
thickness and the insulation thickness given in Table A.2 shall be used for forced-circulation systems. 
 
The material for the collector circuit piping shall be copper, unless specified otherwise in the installation 
manual. 
 
Table A.2 ⎯ External pipe diameter and insulation thickness for forced-circulation systems 
 
Flow rate in collector 
circuit 
l/h 
 External pipe diameter1)
 
mm 
 Pipe thickness 
 
mm 
 Thickness of one layer 
insulation2) 
mm 
 
<90 
 10 
 1 
 20 
 
90 - 140 
 12 
 1 
 20 
 
140-235 
 15 
 1 
 20 
 
235 - 405 
 18 
 1 
 20 
 
405 - 565 
 22 
 1 
 20 
 
565 - 880 
 28 
 1.5 
 30 
 
880 - 1445 
 35 
 1.5 
 30 
 
1445 - 1500 
 42 
 1.5 
 39 
 
> 1500 
 Such that the flow 
velocity is approximately 
0.5 m/s 1.5 
 as the internal pipe 
diameter 
 
1) Tolerance 1 mm  
2) Tolerance 2 mm 
 
 
 
A.3 Calculation of cold water temperature at reference location 
 
The cold water temperature shall be calculated according to: 
 
ϑCW = ϑaverage + Δϑamplitsin(2π (Day - D s) / 365) 
 
where 
 
ϑCW is the cold water temperature to be used for performance presentation 
 
•ϑaverage is the yearly average cold water temperature on reference location 
 Δ
ϑamplit is the average amplitude of seasonal variations on reference location 
 
Day is the day number of the year 
 
Ds Shift term 
 The yearly average cold water temperature, average amplitude of seasonal cold water temperature variations and shift term given in Table A.3 shall be used for the reference locations. PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 21  
Table A.3 ⎯ Data for calculation of the cold water temperature at the reference locations 
 
Reference location 
 ϑaverage  
°C 
 ϑamplit 
°C 
 Ds 
d 
 
Stockholm 
 8.5 
 6,4 
 137 
 
Würzburg 
 12.0 
 3.0 
 137 
 
Davos 
 5.4 
 0.8 
 137 
 
Athens 
 17.8 
 7.4 
 137 
 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
22 © KEBS 2008 — All rights reserved  
Annex B 
(normative)  
 
Testing of solar loop controll ers with temperature sensors 
 
B.1 Purpose 
 
The testing of solar loop controllers in cludes the following two partial tests: 
 
a) Testing of capability of temperature sensors to resist high temperatures (mandatory test) to prove 
that a sensor installed in the solar collector will to lerate stagnation temperature, i.e. temperatures of 
up to 200 °C. 
 
b) Function testing of differential thermostats (optional) to determine starting and stopping differentials 
in dependence on temperature level, to demonstrate that the temperature indication is correct and that the function and operation comply with the manufacturer's guidance. 
 
Furthermore, it should be documented that starting and stopping differentials are unchanged in relation to the 
above statement at 6 % over nominal mains voltage, 230 V, and 10% below.  B.2 Field of application 
 
Testing of temperature resistance in sensors can be applied to all kinds of sensors. 
 
Function testing can be applied to differential thermostats independent of sensor type (resistance sensors or 
voltage supplier etc.) ⎯ the simulation box method can only be applied to resistance sensors, however. 
 
Other types of controller systems for solar heating systems may be tested " ad hoc ", for instance clock 
controllers, light sensor contro llers and solar cell controllers. 
 
NOTE Basic information is given in [11] to [13]. 
 
B.3 Testing the sensors' capability to resist high temperatures  
B.3.1 Temperature requirements 
 
The temperature requirements for the sensor depends on its application as shown in Table B.1:  
Table B.1 ⎯ Temperature requirements 
 
Application: 
 Temperature requirement:  
Selective absorber with single cover  ϑ > 200 °C( ϑreq = 200 °C) 
 
Non-selective absorber with single cover  ϑ > 150 °C( ϑreq =150 °C) 
 
Uncovered absorber; store sensors  ϑ > 100 °C( ϑreq = 100 °C) 
 
 
B.3.2 Equipment 
 
For the testing of the high-temperature resistance of sensors the following items shall be used (Figure B.1): 
 
⎯ “High temperature device”. A device able to provide a stable temperature of at least 200 °C. This 
could be an oven with integrated heating element and fan (see Figure B 1) a temperature bath, or a 
temperature calibrator. PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 23 ⎯ Temperature calibrator. 
 
⎯ Digital multi-meter (for voltage, current and electrical resistance measurements). 
 
 
Key 
1 Thermostat 6 Collector sensor 
2 Sensor and control for oven temperature 7 Oven 200 °C 
3 Controller 8 Heating element 4 Tank sensor 9 Fan 
5 Optional: Sensor for space heating control 
 
 
Figure B.1 ⎯ Example of oven-arrangement for sensor high-temperature resistance testing 
 
 
B.3.3 Test procedure for sensor resistance to high temperatures 
 
The test procedure applies to sensors irrespective of the type of solar collector in which they are used. 
 
a) Both solar collector sensor and tank sensor shall be connected electrically to the controller in accordance 
with the manufacturer's guidelines. The controller unit shall be connected to mains supply and put into 
operation. Thus the sensors are exposed to the normal sensor current with the consequent self-heating. 
 b) The solar collector sensor shall be placed in the temperature calibrator at 20 °C, 50 °C and 90 °C 
respectively. If the controller has a temperature display for the collector sensor the corresponding 
temperatures can be read directly from the controlle r display, if not the sensor shall be electrically 
disconnected from the controller and the corresponding resistances measured by means of an Ohm-
meter. 
 c) The solar collector sensor shall be installed in the "high temperature device" so that the active part of the 
sensor is totally exposed to the high temperature and the cable will not be destroyed by the heat. The temperature of the tank sensor shall remain at 20 °C. 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
24 © KEBS 2008 — All rights reserved d) The temperature shall be increased from 20 °C to ϑreq (see Table B.I). 
 
e) The sensor shall be exposed to the temperature ϑreq for 4 hours, and then the test in item b) shall be 
repeated. 
 
The measured values before and after temperature influence shall be compared and the results assessed as 
follows: 
 
⎯ If the measured values after exposure differ by less than 1 K from the corresponding values before, 
then the sensor may be accepted. 
 
⎯ If the sensor does not meet the above criterion, the sensor may not be accepted. 
 
⎯ Besides the test of the electric function, the sensors shall be subject to a visual inspection of sensor 
box, gasket and cables so that any decomposition due to temperature influence can be incorporated 
in the test report. 
 
B.4 Optional function testing of differential thermostats 
 
B.4.1 Principle 
 
The function testing at various operation situations can be performed in two ways: 
 
⎯ By means of a simulation box (can only be applied to resistance sensors) 
 
⎯ With a temperature calibrator 
 
B.4.1.1 Simulation box approach 
 
The test equipment comprises a custom-built simulation box, which allows the simulation of every occurring 
temperature sensor resistance (see Figure B.2). 
 
 
 
Figure B.2 ⎯ Example of a simulation box for testing differential thermostats of solar heating 
systems PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 25  
In Figure B.2, S indicates a four-pole switch. In the position shown, the resistors R 1 and R 2 are connected to 
the control unit of the solar heating system. In the other position, these resistors are connected to a 
multimeter. The resistors R 1 are chosen in such a way that they correspond to the lowest resistance of the 
sensors under test within the test temperature range. R 2 are wire-wound multiturn potentiometers, the 
resistance range of which is chosen so that the resistance range of all sensors under test is covered by the potentiometers connected in series to R
1. 
 Hence, the differential thermostat (controller) is connected to the simulation box, so that the controlling 
sensors are replaced by the variable resistances of the simulation box. 
 
In the "Simulation box" approach the test procedure is as indicated below. This procedure is related to the case for which the on- and off- temperature differences for a sensor pair (for instance a solar collector sensor 
and a tank sensor) are determined. In cases of testing "multifunction" controllers, each operational situation 
(described in the manufacturer's gu idance) should be tested separately. 
 
a) The "tank sensor resistor" is switched to the desired temperature level for the tank sensor, 
ϑtank; the 
temperature/resistance conversion takes place on the basis of the actual data sheet for the sensor type. 
 
b) The resistance of the solar collector sensor is slowly changed corresponding to increasing temperature in 
the solar collector, until the pump relay of the differential thermostat turns on. The corresponding 
resistance is observed and converted to a "start temperature" ϑstart. 
 
c) The resistance of the solar collector sensor is slowly changed corresponding to decreasing temperature 
in the solar collector, until the pump relay of the differential thermostat turns off. The corresponding 
resistance is observed and converted to a "stop temperature" ϑstop. 
 
d) The on- temperature difference is calculated by ϑstart - ϑtank and the off-temperature difference is 
calculated by ϑstop - ϑtank. 
 
The procedure is repeated with tank temperatures of 20 °C, 50 °C and 90 °C. 
 
B.4.1.2 Temperature calibrators / temperature baths approach 
 
The testing equipment comprises temperature calibrators or temperature baths. 
 
The correct installation of the sensors according to the manufacturer's guidance should be checked. 
 In the "Temperature calibrators/temperature baths" approach the test procedure is as indicated below. This 
procedure is related to the case for which the on- and off- temperature differences for a sensor pair (for 
instance a solar collector sensor and a tank sensor) are determined. In cases of testing "multi-function" controllers, each operational situation (described in the manufacturer's guidance) should be tested 
separately. 
 a) The two temperature sensors are placed into separate temperature baths of equal temperatures. The 
temperature of the solar collector sensor is slowly increased according to increasing temperature in the 
solar collector until the pump relay of the differential thermostat turns on. The sensor temperatures i9tank 
(tank sensor) and i9start (collector sensor) are read. If a calibrator is used the temperature should be 
raised step by step by no more than 1 K respec tively. After each step, temperature stability in the 
calibrator should be awaited. The slow increase in a temperature bath can be made continuously provided that the bath temperature is measured close to the sensor. 
 
b) The temperature of the solar collector sensor is slowly decreased equivalent to decreasing temperature 
in the solar collector until the pump relay of the differential thermostat turns off. The sensor temperatures 
ϑtank (tank sensor) and ϑstop (collector sensor) are read. 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
26 © KEBS 2008 — All rights reserved c) The on- temperature difference is calculated by ϑstart - ϑtank and the off- temperature difference is 
calculated by ϑstop - ϑtank. 
 
The procedure is repeated with tank temperatures of 20 °C, 50 °C and 90 °C. 
 
B.5 Optional testing of the mains voltage dependence 
 
B.5.1 Principle 
 
According to temporary regulations after the revision of the IEC 60038, which states an interval of 230 V + 10 
%, function testing of the differential thermostat is performed at the mains voltage of 230 V + 6 % and 230 V - 10 %. 
 
NOTE According to information provided by IEC, the temporary regulations will be completed in the year 2003 (see DEMKO 
notification No 30/88). 
 
B.5.2 Equipment 
 
a) Mains voltage stabilization box 
 b) Variable AC voltage supply 0 V to 260 V/300 W at 220 V supply 
 
c) Temperature calibrator or simulation box 
 
d) Digital multi-meter for supervision of mains voltage level 
 
B.5.3 Preparation of the unit 
 
Depending on the function test according to B.4.1, the differential thermostat is connected to the simulation 
box, or the associate temperature sensors are installed in the temperature calibrator, correctly installed 
corresponding to the manufacturer's guidance. 
 B.5.4 Test procedure 
 
⎯ The variable voltage supply is connected to the mains voltage st abilization box and switched to 207 
V. 
 
⎯ The solar loop controller is connected 1 hour before start of function testing. 
 
⎯ A function testing of the differential thermostat (see B.4) is performed at 3 different tank temperatures 
at 20 °C, 50 °C and 90 °C respectively. 
 
⎯ The variable voltage supply is now switched to 244 V, the control system being connected, o 
 
⎯ After one hour the function testing is repeated at the same 3 tank temperatures of 20 °C, 50 °C and 
90 °C respectively. 
 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 27  
Annex C 
(informative) 
 
Short-term system testing 
 
 
C.1 General 
 
The objective of short-term system testing is to estimate the long-term system performance. 
 A system inspection should be performed and any error detected should be corrected before the beginning of the short-term system test (see, e.g. [6]). 
 In principle, two approaches for short-term system testing are referred to in this Kenya Standard: 
 
a) the check of short-term system performance;  
b) a short-term test for long-term system performance prediction. 
 Both approaches are applicable to systems including auxiliary heating only in the case that heat contribution 
by auxiliary source can be measured with an accuracy of at least 5 %.  
The first test method is a simplified one. A check of the system performance is carried out by comparing the 
measured solar heating system gain with the one predicted by simulation using the actual weather and 
operating conditions as measured during the short-term test. 
 By the second test method, performance of the most relevant components of the solar heating system is 
measured for a certain time period while the system is in normal operation. These detailed measurements 
include the energy gain of the collector array(s) and the energy balance of the store(s). Comparing the observed and simulated energy gives a validation of collector and storage design parameters and the 
measured data for the collector array are also used for direct identification of the collector array parameters. 
When the parameters of the components are verified, the long-term prediction of the system gain is enabled as well as a detection of possible sources of system malfunctioning. 
 C.2 Instrumentation, data acquisition and processing  
C.2.1 General 
 
This clause includes instructions and recommendations on instrumentation, data acquisition and processing 
to be applied if any of the measurements described in this annex is carried out.  
NOTE If possible, these instructions and recommendations should be reviewed already at system design time, and used to minimize the test expenses and maximize the outcome of the test. 
 
C.2.1.1 Location of sensors 
 Sensors designated to take data for irradiance, surrounding air speed and ambient air temperatures should be mounted as described in C.2.1.2 to C.2.1.7. 
 C.2.1.2 Pyranometer for hemispherical irradiance 
 
The pyranometer for the measurement of the hemispherical irradiance should be installed at the same 
geometrical plane as the collector array. It should be installed near the upper part of the collector array. If more arrays are situated on a different orientation, the test engineer has to decide whether irradiance will be 
measured for each array or computed on the basis of measurements on the horizontal plane. PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
28 © KEBS 2008 — All rights reserved  
C.2.1.3 Pyranometer for diffuse irradiance 
 The pyranometer for the measurement of the diffuse solar irradiance should be installed in the same 
geometrical plane as the collector array. It should be installed near the upper part of the collector array in the 
vicinity of the pyranometer measuring hemispherical irradiance. 
 
For collector arrays situated significantly off-south (azimuth is off-south by more than 10°) the diffuse 
irradiance should be measured at the horizontal plane instead of the tilted plane together with an additional 
pyranometer used for measuring the global irradiance (i.e. on horizontal plane). The fraction of diffuse 
irradiance at the tilted plane is then to be computed based on the measured fraction at the horizontal plane.  
C.2.1.4 Ambient air temperature 
 The ambient air temperature in the vicinity of the collector array should be measured, if possible, using a shaded and ventilated sensor approximately 1 m above the array, not closer than 1.5 m to the collector array 
and not further away than 10m away from the array. 
 
The sensor measuring the ambient air temperature in the vicinity of storage unit(s) should be situated in a 
manner to be shielded from heat radiation sources such as stores, lights, auxiliary heaters etc.  
C.2.1.5 Fluid temperatures 
 
The sensors for measuring the fluid temperature should be located as close as possible to the inlet and outlet 
of the collector array and respective storage loop inlet(s)/outlet(s). Mixing devices mixing the fluid before the sensor are recommended. The piping between measurement points and the collector array or the storage 
respectively, should be properly insulated.  
NOTE Measurement accuracy increases if the sensors are so close to the array (or to the storage) that they are thermally couple d to 
the array (or to the storage) even when there is no fluid circulation. 
 
C.2.1.6 Volumetric flow meter 
 
The volumetric flow meter should directly be installed in the loop's coldest part (e.g. mains cold water line, or 
for the collector loop, the collector array).  
The additional pressure drop introduced by the flow meter and its connecting pipes should be negligible 
compared to the pressure drop in the remaining of the hydraulic loop, so that the flow rate is the same with 
and without the flow meter. 
 
C.2.1.7 Anemometer 
 
The surrounding air speed should be measured on a flat surface (min. dimension: 1m × 1m) fixed in the same 
plane as the collector array front cover. The anemometer should be positioned at a height approximately 
equal to the height of the centre of the collector array. The height of vanes should be 15 cm above the 
surface to which the anemometer is mounted. The anemometer should be located as close as possible to the 
collector array, the distance should not exceed 1 m.  
C.2.2 Accuracy and calibration of sensors  
The requirements on sensor accuracy stated in ISO 9459- 5 should be fulfilled and the calibration procedures 
described in that standard should be followed. 
 
C.2.3 Data acquisition and processing 
 
The data specified in Table C.1 and Table C.2 should be measured and recorded by the data logger. All 
measured data during a test sequence should be recorded with time intervals not exceeding the values 
specified in Table C.1 or Table C.2. PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 29  
C.3 Check of short-term system performance  
C.3.1 Principle 
 
The principle of the method is indicated in Figure C.1. 
 
 
 
Figure C.1 ⎯ Principle of the short-term system performance check: Check and intercomparison of 
useful energy gain 
 
The principle of this method is to compare the measured output of the solar heating system with the output 
predicted by a simulation program. 
 
The components parameters required for simulation of system performance are derived from the system 
documentation or the manufacturer's data. If they are not available they can be estimated. The simulation 
should be carried out using weather data and solar heating system operating conditions (draw-off profile, mains water temperature, etc.) as occurred during the measuring period. 
 
NOTE The main advantage of this method is that expensive measur ements are avoided. Therefore, it is appropriate to use it for 
smaller systems where the cost of the test is the most critical factor. 
 
The measurement of data as requested in C.3.2.2 should be carried out continuously until the criteria for 
termination of the measurement, as indicated in C.3.3, are met. The measurement should take place under 
"operation conditions" of the system. "Operation conditions" is defined as follows: 
 
⎯ For solar water heating systems: the consumer daily draw-off volume is between 50 % and 150 % of 
the corresponding daily draw-off volume as expected for the system and/or as predicted by the solar heating system designer. 
 
⎯ For solar space heating system: the solar space load is between 50 % and 150 % of the 
corresponding load as expected for the system under particular weather conditions and house 
occupancy. 
 This method is applicable for solar-preheat systems (e.g., systems without auxiliary energy source inside the 
storage) and for storage without a circulation loop. 
 However, the systems with auxiliary heat source and circulation loop may be treated in a similar way if the 
following is assured:  PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
30 © KEBS 2008 — All rights reserved ⎯ The uncertainty of measurement for the auxiliary heating should be better than 2 % if immersed 
electrical heaters are used. For other types of aux iliary heating the uncertainty should be better than 
5 %. 
 
⎯ The uncertainty of measurement for the heat loss power in a circulation loop should be better than 3 
%. 
 
⎯ The circulation loop is not connected to the solar (part of the) store, hence heat from auxiliary heating 
cannot be transferred to the solar (part of the) store. 
 
C.3.2 Measurement of the system energy gain 
 C.3.2.1 Conditioning 
 
For the dynamic simulation of the system performance the initial energy content of the store (i.e. the mean store temperature) is one of the required inputs. As measurements inside the store should be avoided, the 
initial state of the store may be found by forced store conditioning or it may be estimated on the basis of fluid 
temperature measurements at the collector inlet (piping leaving the lower part of the storage vessel) and the draw-off inlet/outlet (for hot water heating systems). 
 In order to minimize the influence of the error in determination of the initial energy content of the store(s), conditioning should be performed, whenever possible, prior to the measurement sequence. 
 The conditioning period encompasses the withdrawal of at least 3 storage volumes. The withdrawal should 
be carried out by night or during day periods with low hemispherical irradiance, i.e. less than 200 W/m
2. 
 
NOTE Due to high water costs, conditioning should be avoided whe never the initial energy status of the store can be approximate ly 
estimated ⎯ e.g. if the daily load consumption exceeds the storage volume and after several (2-3) days of proceeding measurements 
the daily irradiation was lower than 5 MJ/(m2 d). 
 
Conditioning applies only if the store volume is less than 5 m3. If conditioning is not carried out, the initial 
energy state of the store(s) should be estimated using the store draw-off temperature and the collector fluid 
inlet temperatures by means of the particular storage mo del (i.e. taking into account the stratification effect). 
 
C.3.2.2 Measurements  The measurement data indicated in Table C.1 should be continuously recorded on a data logger.  
Table C.1 ⎯ Variables to be measured and corresponding maximum sampling intervals 
 
Symbol 
 Unit 
 Variable 
 Maximum sampling interval 
s 
ϑcw 
 °C 
 mains water temperature 
 5 
 
ϑs 
 °C 
 storage draw-off temperature 
 5 
 
SV& 
 m3/s 
 volume draw-off flow  rate from storage 
 5 
 
Gg, Gh 
 W/m2 
 global or hemispherical irradiance 
 5 
 
Gd 
 W/m2 
 diffuse irradiance 
 5 
 
ϑc,amb °C collector ambient air temperature 30 
ϑs,amb °C storage ambient air temperature 30 
Paux W auxiliary power 5 
Pre W circulation heat loss power 5 
NOTE Integrating instruments should be applied for auxiliar y power, circulation losses and draw-off quantities. 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 31 C.3.3 Criteria for termination of the test 
 
For termination of the test, the fo llowing criteria should be met: 
 
⎯ The irradiation integrated over the measurement sequence should be greater than 150MJ/m2. 
 
⎯ At least 50 % of irradiation should occur during the time intervals with an irradiance exceeding 500 
W/m2. 
 
Due to the possible error in estimation of the initial energy content of the store, the two first days of 
measurements should not be taken into account. 
 
C.3.4 Simulation of the system useful energy gain using components data 
 
The performance of the system can be predicted by means of a validated simulation program. 
 
The store and collector parameters should be available in the system documentation.  
If data for other system components such as piping, external heat exchanger etc. are not included in the 
system documentation, those data given by the manufacturer should be used. If data are not available, they may be estimated. 
 
The performance of the system, e.g., the useful energy gain, can be predicted for weather and load conditions as observed over the monitoring period. 
 
C.3.5 Comparison of measured with simulated data 
 The useful energy gain delivered by the store over the test period should be compared with the observed data on daily basis. 
 
The solar heating system under test is considered to behave as predicted by the simulation program if the 
difference (on the basis of daily values) between the observed and predicted system power does not exceed 
10 %.  
As errors in estimation of the initial energy status of the store may occur, the first three days of 
measurements should not be taken into account.  
The comparison on daily basis should be done only for days at which error in estimation of the initial energy status of the store at the beginning of measurement sequence may be neglected and, additionally, if the daily 
irradiation exceeds 15 MJ/m
2. 
 
Finally, the difference between predicted and measured useful energy gain over the complete monitoring 
period (excluding the first three days as mentioned above) should not exceed 10 % in relation to the 
observed energy gain.  
C.3.6 Test report 
 
The test report should include the following items: 
 
⎯ Detailed description of components and system configuration 
 
⎯ Prediction method used: The simulation program used should be specified and an input file enclosed. 
 
⎯ Weather data and space heating load and/or hot water demand profile: The file(s) containing data 
concerning monitoring of the system performance should be enclosed. 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
32 © KEBS 2008 — All rights reserved ⎯ Predicted solar energy output of the solar heating system: The daily predicted output (by the 
simulation program) as well as the observed one should be presented by graph and table. 
 
⎯ List of the measuring equipment and sensors, with the corresponding accuracy 
 
⎯ Interpretation of possible reasons for discrepancy of the predicted and observed power 
 
C.4 Short-term test for long-term system performance prediction 
 
C.4.1 General 
 The performance of large solar hot water and/or space heating systems depends on their design parameters and on various weather and operating conditions, e.g. irradiance, ambient temperature, wind speed, and fluid inlet temperature. 
 In order to evaluate long-term system performance and detect sources of system malfunctioning, it is 
primarily necessary to 
 a) check the energy delivered by the collector array, 
 
b) check the energy balance over the storage vessel(s) and, if possible,  
c) identify the most important system parameters.  
NOTE Ideally, both collector and storage parameters would be identified under in-situ conditions. Unfortunately, the state-of-t he-art 
does not allow accurate and repeatable results of in-situ test of the storage vessels. Therefore, in this Kenya Standard the sh ort-term 
system test is limited to the above points a) and b) and the identification of the collector array parameters only. 
 So, the storage simulation model is verified by checking the storage energy balance while the collector array parameters are id entified 
directly. With the identified collector parameters and the validated storage model, both an accurate prediction of long-term sy stem 
performance and a detection of sources of system malfunctioning are possible. 
 
For more information, see [14]. 
 
C.4.2 Principle 
 
The principle of the method is indicated in Figure C.2. 
 
Measurement data should be collected under non-stationary operation. A wide range of operation conditions 
representative for the system being tested should be covered. 
 
 
 
Figure C.2 ⎯ Principle of the short-term test and of the subsequent long-term system performance 
prediction 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 33  
Measurement of data as requested in C.4.3.2 should take  place continuously over a certain time interval until 
the criteria for termination of the measurement, indicated in C.4.4, are met. The measurement should be carried out under "operation conditions" of the system, according to C.3.1. 
 
After the criteria for termination of the test have been met, the collector array parameters should be identified. 
The identified parameters are thereafter used for the prediction of the long-term performance of the system. 
Local input data are hourly values of meteorological da ta, which are available, e.g., from test reference year 
(TRY), and the load data specific for the system being tested. 
 
C.4.3 Measurements  
 C.4.3.1 Conditioning  See C.3.2.1.  
C.4.3.2 Procedure 
 
During the monitoring period the measurement data indicated in Table C.2 should be continuously recorded. 
 
Table C.2 ⎯ Variables to be measured during system test, and corresponding maximum sampling 
intervals 
 
Symbol 
 Unit 
 Variable
 Maximum sampling interval
s 
ϑcw 
 °C 
 mains water temperature  5 
 
ϑS 
 °C  store draw-off temperature  5 
 
ϑrci 
 °C 
 fluid temperature at circulation loop inlet  5 
 
ϑrce 
 °C  fluid temperature at circulation loop outlet  5 
 
ϑci 
 °C 
 collector fluid inlet temperature  5 
 
ϑCO 
 °C  collector fluid outlet temperature  5 
 
V&C 
 m3/s 
 volume flow rate in collector loop 
 5 
 
v&re 
 m3/s 
 volume flow rate in circulation loop 
 5 
 
V&S 
 m3/s 
 volume draw-off flow rate from store 
 5 
 
Gh 
 W/m2 
 hemispherical irradiance on tilted plane 
 5 
 
Gg 
 W/m2 
 global irradiance, i.e. horizontal (optional) 
 5 
 
Gd 
 W/m2 
 diffuse irradiance on tilted plane 
 5 
 
ϑc,amb 
 °C 
 collector ambient air temperature  30 
 
ϑS,amb 
 °C 
 store ambient air temperature  30 
 
v 
 m s-1 
 surrounding air speed  10 
 
Paux 
 W 
 auxiliary power  1 
 
NOTE Integrating instruments should be applied for auxiliary power and flow rates. PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
34 © KEBS 2008 — All rights reserved  
The values needed for determination of the system power, such as temperature difference, volume draw-off 
flow rate and auxiliary power should be obtained with a period not exceeding 1 s. The data for other variables 
should be obtained with periods of at least 30 s for further processing. 
 
The sampled values should be continuously integrated and averaged. 
 
The integrated values for each variable should be computed over a recording interval and stored. 
 Maximum recording interval is 1 min. The data recording interval may vary during the measurement 
sequence. 
 The monitoring of the collector array and collecting of data should be continued until the criteria for 
termination of the test as described in C.4.4 are met. 
 
C.4.4 Criteria for termination of the test 
 In order to be able to check the store energy balance and the collector array energy gain, it is necessary to 
collect data continuously over a certain time period with reasonably good weather conditions. 
 So, the first criterion for termination of the test applies to weather requirements during the test. The weather 
conditions which should prevail during the test are:  
⎯ The irradiation integrated over the test should be higher than 200 MJ/m
2. 
 
⎯ The total time with irradiance exceeding 500 W.m2 should exceed 50 % of the total test period. 
 
The second criterion applies to the collector operation conditions necessary for accurate identification of the 
collector parameters. 
 
These general operation conditions are fully represented by four driving variables: 
 
a) the difference between the mean collector fluid temperature ϑm and the collector ambient air temperature 
ϑc, amb, 
 
b) the reduced temperature T* = (ϑm - ϑc,amb)/G h, 
 
c) the surrounding air speed, and 
 
d) the angle of incidence of the direct solar radiation on the collector plane. 
 
The wind speed range depends on the climate where the system under test is located. The range scanned 
during the test should be representative for that climate. 
 The requested ranges of variation for other driving variables are listed in Table C.3. 
 
Table C.3 ⎯ Range of variations of the driving variables to be scanned during a test outdoors 
 
Driving variable 
 Requested range of variation  
(ϑm - ϑc,amb (while Gh > 500 W/m2) 
 10 K to 45 K or 65 K 1)
 
reduced temperature T* (G h>500W/m2) 
 0.02 m2K/W to 0.12 m2K/W or 0.2 m2K/W1) 
 
angle of incidence of direct solar radiation  10° to 70°  
1) Whenever possible, the requested range of vari ation should be extended up to that value. 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 35 C.4.5 Identification of collector array parameters 
 
The theoretical model of the collector ("dynamical collector test model") should be used as defined in KS 
1851-2. 
 
The identification of the parameters of the theoretical model should be carried out by an appropriate 
mathematical tool for identification of parameters as defined in KS 1851-2 ("dynamical collector test model"). 
 
The collector array parameters determined by the parameter identification program should be listed together with the associate standard deviations. 
 C.4.6 Criteria for the acceptance of the test results 
 
The main aim of the test is to enable a prediction of the long-term system performance under actual weather 
and load conditions.  
An incorrect prediction of long-term system performance are mostly caused by: 
 
a) incorrect computation of irradiance on the tilted plane, 
 b) the collector array does not deliver the energy expected by the designer and 
 c) the in-situ storage performance does not correspond to the designed one. 
 
In order to eliminate these possible sources of error the basic criteria for acceptance of the test results, given in C.4.6.1 to C.4.6.3, should be fulfilled. 
 If one of these criteria is not met, the corresponding simulation model should be checked. If the simulation 
model is correct, and no error is detected in the operation of the system, the test should be prolonged for 2 
additional days (daily irradiation exceeding 12MJ/(m
2.d)). This procedure should be repeated until the criteria 
are met. 
 
C.4.6.1 Irradiance on the tilted plane 
 
Only the days where the irradiance exceeds 12 MJ/(m2.d) should be considered. 
 
C.4.6.2 Collector array 
 
The energy delivered by the collector (on the daily basis) should not differ by more than 10 % from the energy 
predicted by the collector array design parameters over the operational conditions during the test period.  
 In addition, the identified collector parameters should  be accurately determined. The identified parameters 
are acceptable if the standard deviations do not exceed the following values: 
 
a) 1 5 % for the overall heat loss coefficient of collector array U
L, 
 
b) 20 % for the incidence angle modifier Kτα 
 
c) 10 % for the collector array heat capacity Cc and 
 
d) 3 % for the zero-loss efficiency of collector array η0. 
 
If the standard deviations of any of the identified parameters listed in Table C.4 exceed their permissible 
values the identification procedure should be repeated using reasonable assessed values for these 
parameters in equation (22) of KS 1851-2. Hence the remaining parameters only should be calculated by the identification procedure. 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
36 © KEBS 2008 — All rights reserved  
Table C.4 ⎯ Permissible standard deviation for secondary collector parameters 
 
Parameter 
 Symbol*) 
 Permissible standard 
deviation 
 
Temperature dependance of the overall heat loss coefficient  C
2 
 15%  
Wind speed dependance of the overall heat loss coefficient  C
3 
 15%  
Sky temperature dependance of the overall heat loss 
coefficient  C
4 
 15%  
Wind speed dependance of the zero-loss collector efficiency 
 C6 
 15%  
*) According to equation (22) in 6.3.4.8.2 of KS 1851-2 
 
 
C.4.6.3 Store 
 
Energy drawn-off from store (on a daily basis) should not differ by more than 10 % from the energy predicted 
using the store design parameters over the particular operational conditions during the test period. Here, the 
energy delivered by the collector array is used as a measured input variable.  
C.4.6.4 Final check 
 
After the criteria in C.4.6.1 to C.4.6.3 are met, the co mplete solar heating system model should be validated 
comparing the measured with the predicted useful energy gain and using the following data: 
 
a) component data, 
 
b) weather data (the irradiance on the horizontal plane should be used), and 
 
c) the load conditions as occurred during the validation test. 
 
The energy predicted by simulation should not differ by more than 10 % from the measured energy output on 
a daily basis.  C.4.7 Test report 
 
The test report should include: 
 
⎯ Detailed description of the system under test. 
 
⎯ Detailed description of the test  installation and instrumentatio n specifications (manufacturer, 
accuracy). 
 
⎯ Graphical presentation of the measured energy gain of the collector array, as well as that predicted 
using the collector design parameters. 
 
⎯ Graphical presentation of the measured energy delivered to the user from the storage vessel(s) as 
well as that predicted using the storage design parameters. 
 
⎯ The identified parameters of the collector array with associate standard errors and their correlation 
matrix, if available. A Comparison with the design collector array parameters should be stated as well. 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 37 ⎯ A diskette with data files and the file(s) resulting from the statistical data evaluation. 
 
NOTE Clause 8 gives additional information on the contents of the test report. 
 
C.4.8 Prediction of the yearly system gain 
 
On the basis of the component data (either by in-situ measurement or manufacturer data) the detailed 
simulation should be performed by the same computer program as in 4.6, using actual load volume and profile and the test reference year for a particular site. 
 Additionally, simulation runs should be performed with the load level varying from 70 % to 120 % of the actual 
one and the yearly irradiation from 90 % to 110 % of that of the test reference year. 
 
NOTE Figure C.3 gives an example of the predicted performance dependence on load level and irradiation. 
 
 
 
Key 
1 Out in % 
2 Load scale factor in % 
 
Figure C.3 ⎯ Example of the predicted performance dependence on load level and irradiation for a 
solar domestic hot water heating system (see [8]). 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
38 © KEBS 2008 — All rights reserved  
Annex D 
(informative) 
 
Long-term monitoring 
 
 
D.1 General 
 
Long-term monitoring gives the company operating the solar heating system after commissioning (referred to 
below as the "client") a simple supervision tool  a) to determine the solar contribut ion to the total heat load, and 
 
b) to get an indication on malfunctions or degradations of the solar heating system. 
 
The final long-term goal is to get the maximum benefit from  the initial solar investment as well as to minimize 
the consumption of auxiliary energy an d the resulting environmental impact. 
 
Long-term monitoring of a solar heating system is very similar to that of a common heating plant. In this annex, solar energy specific aspects are emphasized. 
 In order to reduce the cost of long-term monitoring as much as possible, the physical key quantities 
monitored should be integrated continuously, and the figures displayed by the integrators be recorded at 
regular time intervals (mostly in coincide nce with the supervision time intervals). 
 The data which should be monitored include:  
a) the hemispherical solar irradiation in the plane of the collector array(s) 
 b) the total load of that part of the system to which solar energy is supplied, and 
 
c) the solar contribution of the solar heating system.  
The interface where the heat transferred from the solar part to the conventional part of the system (i.e. the 
solar contribution) is measured, should be specified individually for each system, depending on the hydraulic 
scheme and the control concept. 
 
NOTE 1 It is always possible to include more physical quantities into the measuring programme, giving a higher priority to some  of 
them according to additional supervision objectives. In that cas e, the additions (in comparison to this annex) should be fully documented. 
 
Long-term monitoring starts when the expected system performance has been confirmed by the short-term system testing according to annex C. 
 
The monitoring procedure is described for a large custom-built system with short-term storage (Class A or B 
according to 5.2 of KS 1855-1). 
 
NOTE 2 Future updates of this Kenya Standard may consider other system types, e.g. such with seasonal storage, when more 
experience on those types is available. 
 
D.2 Evaluation chart 
 
The evaluation chart is a diagram showing the solar contribution of the solar heating system as a function of 
the solar irradiation in the collector plane for different load levels. It should be used as a reference to evaluate 
the system performance (see D.4). The evaluation chart should be established at design time and delivered 
to the client with the system technical documentation. It is obtained similarly to the system energy balance 
and should be based on the same weather data and load assumptions (see 6.7.3.1 in KS 1855-1). PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
© KEBS 2008 — All rights reserved 39  
The evaluation chart should display different trends of solar contribution variation as a function of the load 
level and other possible parameters having a strong influence on the system performance. 
 
NOTE The range of load level variation should be 70 % to 120 % of the nominal value used for dimensioning. 
 
Weekly data are preferred in evaluation charts, as they match up to the most common time interval in use in heating plant supervision. However, daily and monthly data may also be plotted in those charts. 
 
If monthly performance data have been obtained at design time, they may be converted to weekly average 
values for the corresponding months, in order to display only weekly data in the evaluation chart. Similarly, 
daily values may be grouped to weekly data in the evaluation chart. Finally, values from short-term testing according to annex C, related to any time intervals, may be converted to weekly (average) values and 
included in the evaluation chart. 
 D.3 Monitoring equipment 
 
The monitoring equipment described here is kept at the lowest possible level of instrumentation in order to minimize cost; accordingly, simple methods of evaluation have been chosen (see D.4). 
 
More sophisticated equipment with a higher time resolution, additional physical quantities to be monitored and/or automatic data acquisition and display, is always possible. Accordingly, the evaluation chart should be 
supplemented at design time. At least all data considered in the evaluation chart should be monitored, and most data monitored should be considered in the evaluation chart. 
 
The simplest monitoring equipment includes: 
 
a) a heat meter to measure the heat load of the system. If solar energy is supplied to a part of the system 
only, e.g. for hot water preparation, the load of this part should be monitored. 
 b) heat meter to measure the solar contribution related to the above mentioned heat load.  
c) an integrator of the solar irradiance in the collector plane. If different collector orientations exist within the 
system, the solar irradiance can be measured in the di fferent planes and considered in evaluation charts, 
according to the client's wishes. 
 
Instrumentation used in the long-term monitoring should be an integral part of the system, a part included 
from the very beginning of the design process. If adequa tely foreseen, it may also be used for adjustments at 
the initial operation time. 
 
D.4 Data analysis 
 
The monitored data should be plotted in the evaluation chart for direct visual comparison with the expected 
values. For their interpretation the different load levels as well as other parameters included in the evaluation charts (see D.2) should be considered. 
 
The system is working properly if the monitored data fit to the values given by the evaluation chart, within the accuracy limits agreed to by the client. If a larger disc repancy is observed, there is evidence for malfunction 
or degradation of the solar heating system. 
 PUBLIC REVIEW DRAFT, SEPTEMBER 2008KS 1855-2:2008 
40 © KEBS 2008 — All rights reserved  
Bibliography 
 
[1] John A. Duffie and William A. Be ckman: Solar Engineering of Therma l Processes. Wiley-Interscience 
ed., 1991 
 
[2] R. Perez, R. Stewart, C. Arbogas, R. Seals and J.  Scott: An anisotropic hourly diffuse radiation model 
for sloping surfaces: Description, performance validation, site dependency evaluation. Solar energy, 
36, 6, 481-497, 1986 
 
[3] R. Perez, R. Seals, P. Ineichen, R. Stewart and D. Menicucci: A new simplified version of the Perez 
Diffuse Irradiance Model for tilted surfaces. Solar energy, 39, 3,221-231, 1987 
 
[4] R. Perez, P. Ineichen, R. Seals, J. Michalsky,  R. Stewart: Modelling daylight availability and 
irradiance components from direct and global irradiance. Solar energy, 44, 5, 271-289, 1990 
 
[5] R. Perez, P. Ineichen, E. Maxwell, R. Seals and A. Zelenka: Dynamic models for hourly global-to-
direct irradiance conversion. Proc. of the ISES world congress; Vol. 2, Denver, USA, 1991 
 
[6] U. Frei, J. Keller and R. Brunner: Inspection Procedure for Solar Domestic Hot Water Heating 
Systems. International Energy Agency, Solar Heating and Cooling Programme, Report No. T.3.E.2, edited by J.-M. Suter, April 1990  (available from the Swiss Federal Office of Energy, Bern) 
 [7] G. Brouwer and J.H. Liefting: Guaranteed Solar Results for Collective Solar Hot Water Installations in 
the Netherlands. EC ALTENER Project, Proceedings of the conference "EuroSun '96", 16-19.9.1996, 
Freiburg, Germany 
 
[8] M. Bosanac and J.E. Nielsen: Guaranteed Yields of Solar Hot Water Systems under Reference 
Conditions. Danish Technological Institute, Final Report to ALTENER EU Project, Feb. 1996 
 
[9] M. Bosanac and J.E. Nielsen: In-Situ Check of Collector Array Performance. Solar Energy, Vol. 59 
(1997), pp 135-142 
 
[10] M. Bosanac, J.E. Nielsen and H.D. Stein: Sourc es of the Inaccuracies of the ISO CD9459/5. Final 
Report of IEA Task XIV, November 1996. 
 [11] DIN 43, Elektrische Temperaturaufnehmer, September 1987 
 [12] DIN IEC 751, Industrielle Platin-Widerstandsthermometer und Platin-Messwiderstande, December 
1990 
 
[13] BS 5918:1989, British Standard Code of practice for Solar Heating Systems for domestic hot water. 
Appendix G: "Methods of testing for differential temperature control systems" 
 
[14] J. Dahm: Evaluation of a Solar Heating System for a Small Residential Building Area. Document 
D39:1997, Dpt. of Building Services Engineering, Chalmers University of Technology