HEATING SYSTEM

Abstract

A heating system comprises a hot water cylinder having a first input coil whereby water within the cylinder can be heated using solar energy, a second input coil whereby water within the cylinder can be heated by a boiler, and a third, output coil whereby heat can be extracted from the water within the cylinder, the system further comprising a heat demand, and control means operable to determine whether the heat demand is supplied from the boiler, from the third coil, or from a combination thereof.

Description

This invention relates to a heating system, and in particular to a system suitable for use in supplying heat and hot water to a building in an environmentally efficient manner.

It is known to provide a heating system including a hot water storage tank or cylinder in which a heat exchange coil is provided to permit water within the cylinder to be heated by hot water or another fluid heated by a boiler, for example a gas or oil fired boiler. The output from the boiler may also be supplied to a space heating system, for example including a series of radiators, to provide heat to a building.

It is also known to provide, in the cylinder, an additional input coil connected, in use, to a solar water heater panel or other device whereby the water within the cylinder can be heated using solar energy. Depending upon the environmental conditions and upon the quantity of hot water required, the solar input may be sufficient, alone, to heat the water within the cylinder, or at least part thereof, to the desired temperature. Alternatively, the water may be heated using the solar energy driven circuit in combination with the output of the boiler. In such a mode of operation, the solar derived energy raises the base temperature of the water within the cylinder, thereby permitting a reduction in the energy requirement from the boiler to achieve a given water temperature and so permitting energy savings to be made. Under some conditions, the boiler output alone may be used to provide the hot water.

The cylinder may include a further coil to permit heat to be extracted from the hot water within cylinder for use by another heat demand, for example, to operate a space heating system, an underfloor heating system, a swimming pool, or other heat demands.

The control systems used in such heating systems are relatively complex.

It is an object of the invention to provide a heating system of this general type of simple and convenient form. In particular, the invention relates to a control system associated with the heating system to permit operation thereof in a simple, convenient and efficient manner.

According to the present invention there is provided a heating system comprising a hot water tank or cylinder having a first input coil whereby water within the cylinder can be heated using solar energy, a second input coil whereby water within the cylinder can be heated by a boiler, and a third, output coil whereby heat can be extracted from the water within the cylinder, the system further comprising a heat demand, and control means operable to determine whether the heat demand is supplied from the boiler, from the third coil.

Preferably, the control means comprises a mixer valve operable to control the supply of hot fluid from the boiler to the heat demand. The mixer valve preferably further controls the supply of cooled fluid from the heat demand back to an input thereof. The control means preferably comprises a control valve operable to control the supply of heated fluid from the third coil to the heat demand. Preferably, the control means additionally includes a control pump operable to return cooled fluid from the heat demand to the third coil.

A controller is preferably provided to control the operation of the components of the control means. The controller preferably receives temperature signals representative of the fluid temperature in parts of the system and uses the temperature signals in controlling the operation of the control means. The temperature signals are preferably derived from temperature sensors operable to sense the fluid temperature at the third coil and at the output from the mixer valve. Preferably, a differential temperature sensor is provided, the output of which is used to control the operation of the control pump and the control valve.

Preferably the heat demand comprises an underfloor heating system. However, this need not always be the case and the invention is also applicable to the operation of, for example, a series of radiators. Further, by appropriate design, the invention could be used in controlling the operation of two or more heat demands of different types.

The invention will further be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic representation of a heating system in accordance with one embodiment of the invention;

FIGS. 2 to 4 are views similar to FIG. 1 illustrating alternative configurations; and

FIGS. 5 and 6 illustrate wiring schemes suitable for use in the heating systems of FIGS. 1 to 4.

Referring to FIG. 1 there is illustrated a heating system comprising a hot water cylinder 10 to which cold water can be supplied through an inlet 12, and from which hot water can be drawn through an outlet 14. Hot water from the cylinder 10 is supplied, in use, to the sinks, basins, baths and/or showers of a domestic building, and/or to dishwashers, washing machines, etc.

The cylinder 10 includes three heat exchanging coils 16, 18, 20. Although three such coils are illustrated, it will be appreciated that a greater number of coils may be provided, if required or desired. The first coil 16 is an input coil and is connected to a solar panel 22 operable to heat the fluid passing along a solar circuit 24 including the panel 22 and the coil 16. The fluid preferably comprises water, ideally incorporating an anti-freeze liquid, but it will be appreciated that this need not be the case and that other fluids could be used. In use, the fluid passing around the solar circuit 24 is heated in the panel 22, heat from the fluid passing to the water within the cylinder 10 as the fluid passes through the coil 16. The precise details of the solar panel 22 and the solar circuit 24 are not of importance to the invention and so will not be described in further detail.

The second coil 18 is, likewise, an input coil connected, through a control valve 26 to the output of a boiler unit 28, for example in the form of a gas or oil fired boiler. The boiler unit 28 includes a pump 30 operable to supply hot fluid under pressure therefrom along or through a boiler circuit 32 to the second coil 18, depending upon the operation of the control valve 26. A space heating circuit 34 including a series of radiators 36 is connected to the boiler circuit 32 via a second control valve 38 such that, depending upon the position of the second control valve 38, the operation of the boiler unit 28 and associated pump 30 can be used to supply heated fluid to the radiators 36. It will be appreciated that the output from the boiler unit 28 can be supplied to either or both of the second coil 18 and the radiators 36, depending upon the operation of the control valves 26, 38.

It will be appreciated that the heating system described thus far is capable of heating the water within the hot water cylinder 10 either by using heat energy derived from the solar circuit 24 or by using heat energy derived from the boiler unit 28, or a combination thereof. When the environmental conditions are such that sufficient hot water can be supplied at the desired temperature using just the solar circuit 24, then the boiler unit 28 is either not used or is used to supply heat to the radiators 36. Where the environmental conditions do not permit hot water to be provided from the solar circuit 24 alone, the boiler unit 28 may be used to boost the provision of hot water, and where the environment conditions are poor, the boiler unit 28 may used to provide the majority or all of the hot water requirement.

In addition to the features described hereinbefore, the heating system further includes an additional heat demand in the form of an underfloor heating circuit 40. Although the additional heat demand described herein is in the form of an underfloor heating system, the invention is also applicable to other arrangements, for example arrangements in which the additional heat demand is a network of radiators, a swimming pool heating circuit, or the like. The underfloor heating system 40 is arranged to derive heat energy from either the water stored in the hot water cylinder 10 via the third coil 20 thereof or from the boiler unit 28, a control means 42 being provided to control this. As illustrated in FIG. 1, the underfloor heating system 40 includes a feed line 44 and a return line 46. The feed line 44 is connected to the third coil 20 via a line 48 incorporating a third control valve 50, forming part of the control means 42. The feed line 44 is also connected to the boiler circuit 32 via a mixing valve 52 forming another part of the control means 42. The return line 46 is connected to the return side of the third coil 20 via a line 54 incorporating a control pump 56 forming another part of the control means 42, and is also connected to the return side of the boiler circuit 32. The return line 46 is further connected to the mixing valve 52 so that, depending upon the operation of the mixing valve 52, a proportion of the relatively cool fluid returning from the underfloor heating system 40 along the return line 46 can be returned to the feed line 44 thereof.

The operation of the control means 42 comprising third control valve 50, the control pump 56 and the mixing valve 52 is controlled by a control unit 58 dependent upon demand signals and temperature information derived from a series of temperatures sensors 60, 62, 64 operable to sense the temperature at, at least, the third coil 20 and the feed line 44 of the underfloor heating system 40. The control unit 58 further controls the operation of the first and second control valves 26, 38 to determine whether or not the boiler unit 28 is used to heat the water within the cylinder 10 and the radiators 32. In part, in order to achieve this, the control unit 58 uses signals representative of the water temperature within the cylinder 10 and room thermostats. In use, the operation of the system to provide hot water and to drive the radiator circuit is as described hereinbefore. When it is desired to operate the underfloor heating system 40, the control unit 58 switches on the pump 40a of the underfloor heating system 40. If the temperature at the third coil 20 as detected by the sensor 60 is higher than that at the feed line 44 of the underfloor heating system 40 as sensed by the sensor 62, then the third control valve 50 is opened and the control pump 56 is switched on with the result that heat extracted from the water within the hot water cylinder 10 is used to heat the underfloor heating system 40. The temperature at the feed line 44 of the underfloor heating system 40 is monitored by sensor 64 and, if it is at a predetermined target level, then the underfloor heating system 40 is driven using just the heat energy extracted from the hot water cylinder 10. If the measured temperature is lower than the target temperature, then the boiler unit 28 is switched on and the mixing valve 52 is opened so as to temporarily supplement the heat derived from the cylinder 10 with additional heat from the boiler unit 28. The degree by which the mixing valve 52 is opened is controlled to ensure that the desired target temperature is maintained. The opening of the mixing valve 52 in this manner results in the temperature at the feed line 44 of the underfloor heating system 40 exceeding that at the third coil 20, and hence in the third control valve 50 being closed and the control pump 56 being switched off. Heat energy will then be derived just from the boiler circuit. If the temperature sensed by the sensor 64 is higher than the desired temperature, then the boiler unit 28 is switched off and the mixing valve 52 is controlled to return a proportion of the relatively cooler fluid from the return line 46 to the feed line 44, thereby ensuring that the feed line temperature is maintained at approximately the desired target temperature. The target temperature at the feed line 44 to the underfloor system 40 is determined by the control unit 58 and is related to the temperature in the area being heated using the underfloor heating system 40. As the temperature rises, the target temperature at the feed line 44 to the underfloor heating system reduces. When a point is reached where the target temperature, and hence the feed line temperature as achieved by the operation of the mixing valve 52, is lower than the temperature at the third coil 20, the third control valve 50 is opened and the control pump 56 operated with the result that the underfloor heating system 40 derives its heat energy just from the hot water within the cylinder 10 rather than directly from the boiler unit circuit.

If a point is reached at which the temperature at the third coil 20 exceeds the target temperature, the room controls will ensure that overheating of the room does not occur, for example by switching off the underfloor heating system 40.

It will be appreciated that, in use, where the temperature in an area heated using the underfloor heating system 40 needs to be raised by a relatively large amount, then the majority of the heat energy required to achieve the heating will be derived from the boiler unit circuit. However, once the area is at substantially its desired temperature, maintenance of that temperature can often be achieved to a large extent using the heat energy derived from the hot water within the cylinder. Consequently, significant energy savings can be made.

It will be appreciated that, whilst the boiler unit is operating, any excess heat can be used to heat the water within the hot water cylinder, thus the heat energy can be stored for subsequent use. Appropriate lagging or insulating of the cylinder 10 is provided in order to minimise heat loss from the cylinder, thereby maximising the efficiency of the heating system. It is envisaged that, for operation of the underfloor heating system, the boiler unit will be switched on when the mixing valve opens beyond a 20% open position, and switches off when the mixing valve is moved to less than a 10% open position. However, other operating schemes could be used.

It will be appreciated that, in determining whether or not to open the third control valve and operate the control pump all that it required is information representative of whether the temperature at the coil exceeds that at the inlet to the underfloor heating system. The absolute temperatures at these locations are not required. Consequently, it is envisaged that the sensors 58, 60 will form part of a differential thermostat operable to sense the temperature difference between these locations, rather than sensing the absolute temperature at these locations.

FIG. 2 illustrates an arrangement similar to FIG. 1 but in which the radiator circuit is omitted.

FIG. 3 illustrates and arrangement similar to FIG. 1 but in which the third coil 20 is used to extract heat from the water within the cylinder for use by either the radiator circuit or the underfloor heating system, in either case the boiler unit being able to supply heat in the event that insufficient heat energy can be derived from the cylinder to meet the demand.

FIG. 4 illustrates an arrangement similar to that of FIG. 2 but in which an alternative, four-port mixing valve 52 is used instead of the version shown, diagrammatically in FIGS. 1 and 2.

FIGS. 5 and 6 illustrate wiring diagrams or schemes suitable for use in controlling the operation of the heating systems of FIGS. 1 to 4.

A number of modifications and alterations may be made to the arrangement described hereinbefore without departing from the scope of the invention.

Claims

1. A heating system comprising a hot water cylinder having a first input coil whereby water within the cylinder can be heated using solar energy, a second input coil whereby water within the cylinder can be heated by a boiler, and a third, output coil whereby heat can be extracted from the water within the cylinder, the system further comprising a heat demand, and control means operable to determine whether the heat demand is supplied from the boiler, from the third coil, or from a combination thereof.

2. A system according to claim 1, wherein the control means comprises a mixer valve operable to control the supply of hot fluid from the boiler to the heat demand.

3. A system according to claim 2, wherein the mixer valve further controls the supply of cooled fluid from the heat demand back to an input thereof.

4. A system according to claim 1, wherein the control means further comprises a control valve operable to control the supply of heated fluid from the third coil to the heat demand.

5. A system according to claim 1, wherein the control means additionally includes a control pump operable to return cooled fluid from the heat demand to the third coil.

6. A system according to claim 1, further comprising a controller operable to control the operation of the components of the control means.

7. A system according to claim 6, wherein the controller receives temperature signals representative of the fluid temperature in parts of the system and uses the temperature signals in controlling the operation of the control means.

8. A system according to claim 7, wherein a differential temperature signal is used by the controller.

9. A system according to claim 1, wherein the heat demand comprises an underfloor heating system.

10. (canceled)

11. (canceled)