Heating system of the type for apartments or offices in buildings

A water heating system for a number of apartments or offices 10 each having a water store 15 for receiving hot water from a common boiler 12. The system includes a temperature sensor S2 for sensing the temperature of incoming water from the boiler, with a valve V1 between the temperature sensor S2 and the water store 15. A further temperature sensor S1 senses the temperature of water within the store 15. An electronic controller 30 controls the flow of water via valves V1, V2 dependent on the temperature detected by both the first and second sensors to prevent water being received by the store when the temperature differential is too small. This avoids the risk of reduction of the water temperature within the store 15, and meter 21 will not register utilization under these circumstances as valve V2 allows the return of the water other than via store 15.

This application is based on International Application PCT/GB95/02941, 
having international filing date of Dec. 15, 1995, and a priority date of 
Dec. 23, 1994. 
The invention relates to a heating system of the type used for supplying a 
number of separate flats, apartments or offices in a building from a 
common boiler plant. Each apartment may be billed separately for the heat 
utilized. 
According to the invention there is provided a heating system having a 
boiler for supplying heated water to a number of apartments, offices or 
the like and each apartment or the like including (a) first sensor means 
for sensing the current water temperature in that respective apartment; 
(b) second sensor means for sensing the arriving water temperature to that 
apartment; (c) first control means for controlling the incoming water to 
allow this to pass for utilization only when the temperature thereof is 
above a selected temperature for that apartment; and (d) second control 
means for returning the incoming water without utilization when the 
temperature thereof is below a selected temperature for that apartment and 
wherein each apartment includes a water store for receiving hot water from 
the boiler, the first sensor means sensing the temperature within the 
water store. 
Further according to the invention there is provided a method of heating a 
number of apartments, offices or the like from a common boiler, the method 
including: sensing the current water temperature in a water store in a 
respective apartment; sensing the incoming water temperature received by 
that apartment controlling the incoming water in that apartment to allow 
this to pass for utilization only when the temperature thereof is above a 
selected temperature; and controlling in that apartment the incoming water 
so as to return it without utilization when the temperature thereof is 
below a selected temperature.

FIG. 1 shows a system including a number of heating arrangements 10 
connected to a common boiler 12 via pipes 13, 14. Although only two 
arrangements are shown, in practice the number utilized will be equal to 
the number of apartments in the building, e.g. 40. 
Each arrangement 10 includes a hot water store 15 with associated 
thermostat S1. Hot tap water can be drawn via outlet 16 and water for 
radiators 17 are provided via pipes 19, 20. A meter 21 is provided on the 
return pipe 22 which also includes closure valve 23. 
The hot water from boiler 12 is received by each apartment and the hot 
water store 15 therein will contain a reserve of this hot water for 
heating the tap water and radiators. 
Thermostat S1 will be set to a desired temperature and will indicate to the 
boiler when temperature in the store has fallen so that the common supply 
will be heated further. The hot water for the taps will typically be 
heated within the store via coils from a cold source to avoid utilizing 
the water from the boiler itself. The radiator water is circulated and 
passes back to the hot water store. The meter 21 measures the water 
circulation or heat or the user is charged accordingly. 
Problems with levels of demand can cause operational problems in that if 
the boiler cannot cope with demand, or if the water in the pipes 13 and 14 
is cold, cool water could be circulated through the apartment system can 
be paid for. Also, if the water store temperature is relatively high this 
heat could be `robbed` by the boiler water. To avoid these problems, it 
may be necessary to keep the boiler water temperature and the water 
temperature in pipes 13 and 14 artificially high so that on many occasions 
heat is being wasted when demand is low as the hot water will be 
continually circulating in the pipework (i.e. pipes 13 and 14 would be 
joined at the end of the run). 
In the modified system of FIG. 2, additional measures are taken to avoid 
these problems. 
With the water store 15 is now provided an electronic controller 30 which 
is connected to two thermostats (S1 and S2) to allow the water store 
temperature (T1) to be determined by sensor S1 and the temperature T2 
determined by S2 for the incoming water from the boiler 12 received via 
buffer store 26. The electronic controller 30 can control the water pump 
27 by cable connection 33 thereto. Electric valves V1 and V2 are provided 
and controlled by controller 30. The system also includes a pump 32 for 
the radiator circulation. A water coil 35 receives a supply of cold water 
at inlet 36 and coil 35 acts as a heat exchanger to heat the water which 
passes from outlet 37 to taps for basins, bath and so on. A manual 
thermostatic mixer 38 can adjust the heated water temperature. 
With the system now described, when the water store temperature drops (when 
water is being drawn, for example) this will be sensed by S1 and a signal 
sent to the boiler plant pump 27 to pump water to the water store 15. If 
there are no requests for water resulting from a drop in temperature the 
water in pipes 13 and 14 does not circulate. S2 the sensor specific to 
that apartment senses the incoming water temperature when a request is 
generated and only allows V1 to open if this incoming water temperature is 
sufficiently high. V2 operates under the controller 30 to return this 
water should it be too cold. V2 only returns water following a request for 
hot water (sensed by S1). Normally water does not return via V2. 
Typically S1 and S2 can be ganged so that a higher temperature setting on 
S1 will require a higher setting on S2 also. It is to be noted that there 
is a sensor S1 and S2 associated with each apartment and the control of 
valves V1 and V2 is taken by the local controller. An arrangement for the 
controller 30 is shown in FIG. 3. 
The temperature T1 is converted by the sensor S1 to an electrical signal 
which is received by comparator 50. The output of comparator 50 controls 
the coil of a relay RL1. 
The temperature T2 is converted by the sensor S2 to an electrical signal 
which is received by comparator 51. The output of comparator 51 controls 
the coil of a relay RL2. 
The comparator setting is controlled by variable resistor 53 which 
typically is ganged to variable resistor 54 but offset thereto. Hence, for 
example, a temperature setting of 75.degree. C. can be set for the 
comparator 50 and a setting of 70.degree. for comparator 51. Power is 
supplied to relay contacts RL2A via RL1 contacts RL1A and also to operate 
the pump 27 via contacts RL1B utilizing connection cable 33. 
Hence in operation when the water store temperature falls below the set 
value (e.g. 75.degree. C.) then RL1 operates and dependent on the sensed 
temperature T2 at sensor S2 measuring the incoming water temperature 
either the valve V1 will open if the sensed temperature is high enough to 
raise the temperature in the water store or will cause valve V2 to open 
instead to return the water to the boiler system to be reheated (without 
it actually being passed through the water store). This avoids the user 
having to pay for water that is below the desired temperature. Nor does it 
allow the heat already paid for to be `robbed` by heating the returning 
water. Hence the meter 21 in the return path from the water store will not 
be active in this improved system under these circumstances. Nor does it 
require the supply pipe 13 and the return pipe 14 to be permanently heated 
to supply water at correct temperature, hence saving on energy. 
The controller could be configured to allow a preselected temperature band 
to be used rather than a specific temperature to avoid unnecessary 
switching about a specific temperature. 
As the decisions on water flow and temperature are effected by the 
controller associated with a particular apartment, it is possible for the 
temperature settings in one apartment to differ from that required in 
another apartment. The arrangement also has the advantage that utilizing 
local decisions prevents the need for water to continuously circulate in 
pipes 13 and 14 which would require constant heating, a wasteful 
technique.