GB2301430A

GB2301430A - Central heating control system

Info

Publication number: GB2301430A
Application number: GB9509308A
Authority: GB
Inventors: Nicholas Julian Jan F Macphail
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-05-06
Filing date: 1995-05-06
Publication date: 1996-12-04
Anticipated expiration: 2015-05-06
Also published as: GB9509308D0; GB2301430B

Abstract

A central heating system comprising a boiler (1), a pump (3) and radiators (7) also includes a bypass arrangement which includes a spring-loaded valve (5). In milder weather, when the thermostatic radiator valves close, the water pressure in the system correspondingly increases. Valve (5) is able to progressively open the bypass. A flow switch or sensor (6) senses the flow of water through the bypass and automatically sets the boiler to a lower operating temperature. A time circuit may also be actuated to control operation of the pump or boiler.

Description

Improved Heating System Efficiency by Reducing Input Temperature at Part Load" I NICHOLAS JULIAN JAN. FRANClS MacPHAIL, a British Subject of La Girouette, Grandes Rocques, Guernsey of the Channel islands, do hereby declare the invention for which we pray that a patent may De granted to me and the method by which it is to be performed to be particularly described in and by the following statement: - THIS INVENTION relates to control of the input temperature of central heating systems by sensing the flow in a bypass control lea by an adjustable spring bypass valve: In a typical wet central heating system a circulating pump is used to accelerate the heat energy carrying water around a pipe circuit incorporating heat emitting radiators.Improvements in thermostatic radiator valves have made their use as the room temperature control more common. Thermostatic radiator valves function by progressively restricting then finally ciosing off the water flow to each radiator to which they are fitted as the set room temperature Is approached then reached. The output from a circulating pump is commonly set to provide sufficient volume flow to meet the system s maximum potential heating requirements against the resistance of the system with fully open control valves. in milder weather under partial load conditions most of the thermostatic radiator valves will be closed or partially closed.A pump set for maximum potential load under these circumstances characteristically produces iess flow at greater heao pressure. Tis in turn can cause, in addition to variations to system balance, high velocity flow through the narrowing openings of the thermostatic valves causing turDuRent flow noise across the vaive seating.

it is Known that to overcome the problem of such noise a spring loaded Dypass valve may be fitted to bypass or short between the iow ana return of the system pipework or between the output and input ports of the system pump, set to progressively open at ; fixed heaa pressure which wilt bypass the volume of water proportionate to that which is lost round the main circuit by the increase in system resistance. Also in a typical wet central heating system the boiler temperature is set by a manual control thermostat to be able to cope with the optimum system load.This normally is 1800 Farenheit which together with 200 F drop across the system between the flow and return is the design criteria for most heat emitters, eg radiators, cylinder heat exchanger coils etc. The system control thermostat is usually backed up in case of control thermostat failure by a limit thermostat. The thermal efficiency of a boiler is governed in part by the temperature required as the output water temperature from the boiler. The higher this temperature is the lower the boilers thermal efficiency.As the boiler control thermostat is normally set to enabie the boiler output temperature to be able to cope with the maximum thermal demands of the heating system it means that under all other part load conditions the boiler is running at an unnecessarily high temperature with an attendant lower thermal efficiency and higher thermal iosses to fiue ventilation, boiler jacKet losses ano pipe losses etc.

It is shown that to gain maximum efficacy from condensing boilers tney neea to be run at as low a temperature as is feasible to enable them to run in their most efficient condensing mode. The prior art requires oversized heat emittors or provides limited condensing conditions.

It is the object of the present invention to overcome or obviate the problems of the prior art.

Accoraing to the present invention there is provided a flow switch or sensor to sense the flow of water through a system bypass incorporating an automatic spring ioaded bypass valve and to use the sensed flow to alter the thermal input into a heating system.

Preferably said flow switch or sensor sets the system boiler to a lower operating temperature when bypass flow is detected.

Conveniently when bypass flow is detected by the said switch or sensor a time circuit may be actuated to hold off the circulating pump organo boiler for a set or adjustable time.

Advantageously the lower temperature operation may be disabled to supply fuil temperature demand by, for exampie, domestic hot water cylinder to enaDie fast recovery of the cylinder water after a demand or to service other high temperature requirements.

Conveniently the said flow switch or sensor inlay De integral to or a part of the spring loaded bypass aevice.

in a further preferred form of the present invention the bypass instep of orioging between the flow and return pipes to a heating system Bridge Detween the inlet and outlet of the pump of a neatlng system.

Convenienty the aforementioned pump bypass form may incorporate the spring loaoec bypass valve within its pump casing.

Advantageously the aforementioned pump bypass form may incorporate the flow sensor or flow switch and or a spring loaded bypass valve within the pump structure.

Conveniently the said means of providing spring loaded bypass and flow switch or sensor is integral or external to the pump body and incorporated within the pump's standard dimensions to aid repiacement or retro fitting.

Advantageously where multiple boilers are linked to a common header in a heating system, multiple bypass valves together with the said flow switches or sensors may be used to bring on progressively more boilers at increasing load or conversely fewer boilers and/or lower temperatures at decreasing load by having the bypass valves set to progressively increasing differentiais.

Although for simplicity the invention has been described in a flow switch form it should be understood that where the system enables it and where it is deemed suitable a proportional electronic sensor and proportional temperature control may be sunstituted for the flow switches and switch thermostats.

In order that the invention may be more readily understooc and so that further features may be appreciated the invention will now be aescriDed by way of example with reference to the accompanying drawings of which: Figure i is a diagramatic representation of a wet heating system incorporating the present invention with a conventional bypass between flow and return.

Figure 2 is a diagramatic representation of a wet heating system incorporating the present invention having the bypass linking between the pump outlet and pump inlet.

Figure s is a line only drawing of a electrical circuit as might be used for the present invention.

Figure 4 is a diagramatic representation of a multiple boiler heating system incorporating the present invent ion.

Referring first to Figure 1 there is shown diagramaticaily a representation of wet heating system as might incorporate the present invention. The boiler 1. provided with an expansion system 2. supplies heated water via a pump 3. being provided with isolating valves 4. to a heating circuit 7. Bridging between the flow and return is a bypass being provided with a spring loaded bypass valve 5. and flow sensor or flow switch 6. Pump 3. and spring loaded bypass valve 5. would normally be set to satisfy the maximum heating load presented by the heating circuit /.

Should a motorised valve knot shown) normally operated to control the cylinder (not shown) and/or thermostatic valves on the radiators knot shown) in the heating circuit 7. be ciosed or neariy closed then the frictional resistance of the heating system would be higher than the spring setting on te spring ioadea bypass valve 5. The spring leased bypass vave 5. would therefore ze pushed open by the higher differential pressure across it causing flow through the flow sensor or flow switch 6.

ine flow sensor or switch 6. being wired through the low level thermostats on the boiler i. would cause the boiler i. to run to a lower temperature improving thermal efficiency of the boiler and reducing heat losses from both the boiler jacket 8. via the flue and from the pipework in the heating system.

In Figure 2 there 1S shown a diagramatic representation of a wet heating system representing the present invention wherein the bypass incorporating spring loaded valve 5. and/or bypass switch or sensor 6. is between the outlet and the inlet of a pump 3.

either integrally to the pump 3. or as a separate circuit. The switch or sensor 5. and 6. carry out a similar function to those shown in Figure 1 and therefore function as above described.

In Figure 3 there is shown a diagramatic representation of a line oniy electrical wiring diagram of a typica heating system incorporating the present invention as shown in Figure 1 or Figure 2. On demand for heat from either the room thermostat cr cylinder thermostat the motorised valves are actuated providing power to the pump and to the flow switch. On sensing a bypass flow taking place the power is diverted via the flow contact to a low temperature Doiler thermostat of approximately 160 F although lower temperatures may be used where the boiler structure permits).This then flows through the higher standard boiler thermostat contacts which would De ciosed under such low temperature conditions via the iimit thermostat which would also have its contact classed under such low temperature conditions to power the Doiler. When no flow is detected across the bypass unoer high system loao conditions the no flow contact bypasses the ' ow temperate thermostat ana runs the Roller to the higher temperature of 180 F the limit thermostat stii: being in circuit.A demand for heat from a high temperature requirement circuit, eg from a cylinder thermostat, may bypass the low temperature boiler thermostat and be taken directly to the standard boiler thermostat to provide faster recovery of the cylinder.

The use of the invention shown in Figure 1 and Figure 2 would be very useful to more up-to-date "system" boilers incorporating the pumps within the boiler casing and this type of system boiler application is to be regarded as a preferred form.

In Figure 4 there is shown a diKgramatic representation of a multiple boiler heating system incorporating the present invention. The boilers la, lb,and Ic are, together with their shunt pumps, linked to a common header being provided with a neating circuit pump 3. and bypasses a, b and c each having an automatic bypass valve 5. and flow switch 6. The automatic bypass valves 5. are set at increasing differentiais so that at full load no bypass flow takes place and all boilers fire at full temperature. As the system load reduces as the builaing nears oesign temperature the thermostatic valves in the heating system progressively close increasing the differential pressure across the bypasses causing flow through the flow switches 6. which are wirea to progressively switch the boilers to a lower temperature.

In Figure 5. there is shown diagramaticaiiy an example line only wiring diagram as would provide the progressive temperature setback for a multiple boiler application of the present invention.

It should be understood that the above multiple boiler application of the present invention is described in a arrangement of three boilers by way of an example only and that the present invention is applicable to any other multiple boiler configuration.

Claims

1. Means to sense the flow of water through a heating system bypass incorporating an automatic spring loaded bypass valve and to use the sensed flow through the bypass to alter the thermal input to the said heating system.

2. Means according to Claim 1 that sets the system boiler to a lower operating temperature when bypass flow is sensed.

3. Means according to Claim 1 indoor 2 that actuates a timer to hold off the circulating pump andzor boiler for a set or adjustable time.

4. Means according to the above claims together or individually that incorporates the facility to disable the lower temperature operation to temporarily supply temperature requirements.

5. Means according to Claim I being integral to a spring loaded bypass device.

6. Means according to the above claims having the said bypass between the flow and return of a heating system.

7. Means according to the above claims having the bypass between the inlet and outlet of a circulating pump of a heating system.

8. Means according to Claim 7 wherein said bypass and flow sensor indoor flow sensor is integral to the pump.

9. Means according to the above claims utilised where multiple boilers are linked to a common header using single or multiple bypasses to progressively increase or decrease the number of boilers operating to meet a given load.

10. Means according to the above claims where the bypass flow sensor is a flow switch.

II. Means according to claims 1-9 where the bypass flow sensor is a thermostat.

12. Means according to claims 1-9 where the bypass flow sensor is a thermister or other thermal sensor.