GB2157456A

GB2157456A - Control of multiple energy source heating system

Info

Publication number: GB2157456A
Application number: GB08409604A
Authority: GB
Inventors: Peter Short; Roger Houston
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-04-13
Filing date: 1984-04-13
Publication date: 1985-10-23

Abstract

A central heating system a first heat source A (e.g. a gas boiler) and a second heat source (e.g. open fire back boiler), the letter being connectable (e.g. by valves I,J) directly to a hot watertank C and radiators D when it produces a usable output. The connection of the second heat device is determined by the use of truth tables to describe the overall system, and the various inter- dependent relationships, electrical, electronic, mechanical or water flow. By so doing, a system can be made universal or tailored to specific requirements. The control system may comprise relay, non- intelligent electronic, or micro- processor control. The input output devices may be standard items, such as room or boiler thermostats, gas or motorised water valves; or specialised components, such as solid state remote temperature sensors. <IMAGE>

Description

SPECIFICATION Multiple energy control systems This invention relates to control of multiple energy systems used for central heating, without the need for independent plumbing systems for each energy source.

Central heating control systems are well defined. The temperature of one or more rooms is controlled via a thermostatic device in the room(s), which in turn control the central heating boiler, be it solid fuel, gas or electric central heating.

However, when a second energy source is added to the system, a second heat exchanger is normally required to accept the hot water from the second source. Alternatively, the second source is used to heat water in a separate water tank which is used to supply fresh, warm rather than cold, water to the primary system. Sometimes, a manual direct control is added, to allow the second source to be manually connected when needed, for example when a central heating system is installed where earlier hot water was derived from an open fire back boiler.

This invention provides a means, where appropriate, of directly coupling the second energy source's hot water supply to the primary system, and automatically controlling the water flow.

The root of the invention is the application of well-known control techniques with wellknown plumbing techniques using logic truth tables to establish the exact relationship between both areas of central heating technology to allow simple modification of an existing system to accomodate the alternative energy source(s).

The attached diagram illustrates a typical example. An existing gas central heating system (Fig. 1) heats water in the boiler (A) to a temperature controlled by boiler thermostat (B). The water is circulated to the hot water tank (C) and the radiators (D) either directly or according to the instruction supplied by a hot water tank thermostat (E) and/or room thermostat (F), which may in turn control a circulation pump (G). The hot water tank thermostat (E) controls a motorised valve (K) to allow water to flow by convection to the tank.

When the temperature of the water in the boiler (A) drops below the pre-determined temperature set by thermostat (B), the gas valve (K) is activated to restore the boiler temperature. Hot water flow out of the boiler is controlled by the hot water thermostat (E) and the room temperature thermostat (F).

When (E) and/or (F) demand hot water, it is provided by means of, usually, convection to the hot water and pump (G) to the radiators.

A new alternate energy source, for example, an open fire back boiler (H), is added to the system-Fig. 2. Instead of connecting the new source to a second heat exchanger in the hot water system, it is coupled directly, via motorised valves (I 8 J). The problem now is to control the second energy source, i.e. the back boiler, such that when it is capable of supplying hot water to the heating system that it does so. The boiler (H) is fitted with two thermostats (M) and (N). Thermostat (M) senses that the water in boiler (H) is at a high enough temperature to supply the needs of the system.Thermostat (N) is provided for safety purposes and overrides the control unit if the water is approaching boiling point, pumping the excessively hot water into the hot water tank (C) and/or radiators (E) until the temperature again drops to a safe level.

The control unit is depicted as (Q) with the various control lines to and from the various devices in the system.

When thermostat (M) detects that the water in boiler (H) is at a suitable temperature, it must operate motorised valves (I) 8 (J) to complete the water circuit through boiler (H).

The flow is then controlled by pump (P), via the other thermostats in the system. Operation of thermostat (M) must also inhibit the gas valve.

A plumbing system embodying motorised valves and thermostats to control the flow of water can be expressed, exactly as the attaching control systems, in terms of logic truth tables. If water is to flow, it is a logic '1', if not it is a '0'. If a thermostat is on, it is at a logic '1', off, it is a 'O'. Therefore, logically, it is -possible to link the desired water flow to the desired temperature by using logic truth tables to link them together. Having done so, it is possible to develope a controller, using well known electrical/electronic techniques, to control the overall heating system. Fig. 3 illustrates a truth table used to determine the variable conditions found in, and the control functions required by Fig. 2.

1. An integrated central heating control system capable of linking a gas central heating and/or hot water system directly to an open fire back boiler, and controlling the water flow such that when the open fire boiler is able to supply water to the system, it is automatically linked to the system. When the back boiler is not able to supply hot water, it is disconnected automatically from the water system. The control unit uses simple relay techniques to control the various electrical items and link them together as required and described above. By using a simple relay system, existing standard electrical items, such as room and boiler thermostats, gas valve and motorised water valves can be used without modification.

2. A system as described in 1. above but utilising non-intelligent electronic circuitry to control the system.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Multiple energy control systems This invention relates to control of multiple energy systems used for central heating, without the need for independent plumbing systems for each energy source. Central heating control systems are well defined. The temperature of one or more rooms is controlled via a thermostatic device in the room(s), which in turn control the central heating boiler, be it solid fuel, gas or electric central heating. However, when a second energy source is added to the system, a second heat exchanger is normally required to accept the hot water from the second source. Alternatively, the second source is used to heat water in a separate water tank which is used to supply fresh, warm rather than cold, water to the primary system. Sometimes, a manual direct control is added, to allow the second source to be manually connected when needed, for example when a central heating system is installed where earlier hot water was derived from an open fire back boiler. This invention provides a means, where appropriate, of directly coupling the second energy source's hot water supply to the primary system, and automatically controlling the water flow. The root of the invention is the application of well-known control techniques with wellknown plumbing techniques using logic truth tables to establish the exact relationship between both areas of central heating technology to allow simple modification of an existing system to accomodate the alternative energy source(s). The attached diagram illustrates a typical example. An existing gas central heating system (Fig. 1) heats water in the boiler (A) to a temperature controlled by boiler thermostat (B). The water is circulated to the hot water tank (C) and the radiators (D) either directly or according to the instruction supplied by a hot water tank thermostat (E) and/or room thermostat (F), which may in turn control a circulation pump (G). The hot water tank thermostat (E) controls a motorised valve (K) to allow water to flow by convection to the tank. When the temperature of the water in the boiler (A) drops below the pre-determined temperature set by thermostat (B), the gas valve (K) is activated to restore the boiler temperature. Hot water flow out of the boiler is controlled by the hot water thermostat (E) and the room temperature thermostat (F). When (E) and/or (F) demand hot water, it is provided by means of, usually, convection to the hot water and pump (G) to the radiators. A new alternate energy source, for example, an open fire back boiler (H), is added to the system-Fig. 2. Instead of connecting the new source to a second heat exchanger in the hot water system, it is coupled directly, via motorised valves (I 8 J). The problem now is to control the second energy source, i.e. the back boiler, such that when it is capable of supplying hot water to the heating system that it does so. The boiler (H) is fitted with two thermostats (M) and (N). Thermostat (M) senses that the water in boiler (H) is at a high enough temperature to supply the needs of the system.Thermostat (N) is provided for safety purposes and overrides the control unit if the water is approaching boiling point, pumping the excessively hot water into the hot water tank (C) and/or radiators (E) until the temperature again drops to a safe level. The control unit is depicted as (Q) with the various control lines to and from the various devices in the system. When thermostat (M) detects that the water in boiler (H) is at a suitable temperature, it must operate motorised valves (I) 8 (J) to complete the water circuit through boiler (H). The flow is then controlled by pump (P), via the other thermostats in the system. Operation of thermostat (M) must also inhibit the gas valve. A plumbing system embodying motorised valves and thermostats to control the flow of water can be expressed, exactly as the attaching control systems, in terms of logic truth tables. If water is to flow, it is a logic '1', if not it is a '0'. If a thermostat is on, it is at a logic '1', off, it is a 'O'. Therefore, logically, it is -possible to link the desired water flow to the desired temperature by using logic truth tables to link them together. Having done so, it is possible to develope a controller, using well known electrical/electronic techniques, to control the overall heating system. Fig. 3 illustrates a truth table used to determine the variable conditions found in, and the control functions required by Fig. 2. CLAIMS

3. A system as described in 1. above but employing micro-processor control to control the system.

4. A system as described in 1, 2, or 3 above employing other than standard devices, ie solid-state room temperature sensing, solid state boiler temperature sensing, outside of the central control unit.

5. A system as described in 1, 2, 3, and 4 above, linking an electric hot water central heating system to a solid fuel back boiler.

6. A system as described in 1, 2, 3, and 4 above, linking a gas central heating boiler to a heat pump system.

7. A system as described in 1, 2, 3, and 4 above, linking an electric hot water central heating system to a heat pump system.

8. A system as described in 1, 2, 3, and 4 above, linking a gas central heating system to a solar energy system.

9. A system as described in 1, 2, 3, and 4 above, linking an electric hot water central heating system to a solar energy system.

CLAIMS Superseded claims claim 1 New or ammended Claims:- claims 1,10 and 11 1. An integrated central heating control system capable of linking a gas central heating and/or hot water system *directly* to an open fire back boiler, and controlling the water flow such that when the open fire boiler is able to supply water to the system, it is automatically linked to the system. When the back boiler is not able to supply hot water, it is disconnected automatically from the water system. The control unit uses simple relay techniques to control the various electrical items and link them together directly. By using a simple relay system, existing standard electrical items, such as room and boiler thermostats, gas valve and motorised water valves can be used without modification. Existing plumbing systems are used, the additional plumbing is connected directly to the existing system via motorised valves.

10. A system as described in 1, 2, 3, and 4 above, directly linking any combination of two energy sources for central heating/hot water.

11. A system as described in 1, 2, 3, and 4 above, directly linking more than two energy sources for central heating/hot water.