GB2263963A

GB2263963A - Water heating arrangement

Info

Publication number: GB2263963A
Application number: GB9201497A
Authority: GB
Inventors: Gerald Uttley
Original assignee: FORMAT DRAW Ltd
Current assignee: FORMAT DRAW Ltd
Priority date: 1992-01-24
Filing date: 1992-01-24
Publication date: 1993-08-11
Also published as: GB9201497D0

Abstract

A water heating arrangement for combined central heating and hot water supply systems includes a water storage vessel or tank 20 housing a boiler 22 and an expansion vessel 29 above the water boiler and within the storage vessel or tank. As shown, the vessel 20 is a pressure vessel. The boiler 22 is gas- or oil-fired. The expansion vessel 29 is filled with nitrogen and is open at 30. A plate heat exchanger 39 for a domestic hotwater supply system may be housed within a casing 21. In an alternative embodiment (Fig. 6, not shown), a non-pressure vessel (60) has an expansion space (65) and a central heating expansion vessel (66) above the level of water in the vessel (60). The central heating water is heated indirectly by water from the vessel (60) in a heat exchanger (82). <IMAGE>

Description

WATER HEATING ARRANGEMENT This invention relates to water heating arrangements and in particular to water heating arrangements for combined central heating and hot water supply, especially domestic hot water supply, systems.

It is an object of the present invention to provide a simple water heating system arrangement which is more compact than known water heating arrangements having the same or similar water heating output and which has an enhanced water heating output compared with such known same or similar water heating arrangements.

According to this invention there is provided a water heating arrangement for combined central heating and hot water supply systems, the water heating arrangement comprising a water storage vessel or tank housing a water boiler to provide a hot water storage and, above the water boiler and also within the storage vessel or tank, an expansion vessel.

Preferably the boiler comprises a heat exchanger and a fuel burner assembly, preferably a gas-fired burner assembly, there being in water flow communication with the boiler heat exchanger a secondary water-to-water heat exchanger external of the water storage vessel or tank. Alternatively the secondary water-to-water heat is located inside the water storage vessel or tank.

Preferably the storage vessel and tank is a pressure vessel, preferably insulated.

Preferably the secondary heat exchanger is a plate heat exchanger, preferably housed in a casing also enclosing the storage vessel or tank.

Preferably, the secondary heat exchanger forms part of a hot water supply system.

Preferably the hot water supply system has a cold water input to the secondary heat exchanger and a hot water output therefrom, the cold water being heated by hot water pumped from the store through the secondary heat exchanger for return to store.

Preferably the hot water supply system comprises a mixing valve in the hot water output with the cold water input connected to the mixing valve.

Preferably, a central heating system is connected to the water heating arrangement such that hot water is drawn off from the hot water store in the pressure vessel or tank by a pump for delivery to one or more heating radiators, the water return from the latter being back into store below the water boiler.

Preferably, the hot water inlet to each of the central heating system and hot water supply system from store is above the water boiler and below the expansion vessel.

The central heating system and the hot water supply system may alternatively incorporate a single common pump and a diverter valve.

Alternatively the diverter valve is replaced by a motorised valve in each system or only in the central heating system. In the first alternative the motorised valve is preferably in the hot water outlet side of the hot water supply system, and, in both alternatives, in the hot water inlet side of the central heating system.

The storage vessel or tank may be an insulated vessel or tank of a non-pressure nature.

The central heating system may include a water-to-water heat exchanger, preferably of the plate type, and through which the feed water from store and the return water to store passes to heat the circulating central heating which also passes through the heat exchanger.

Preferably a central heating expansion vessel is housed in the non-pressure storage vessel or tank adjacent an expansion space above the stored hot water.

Preferably a filling circuit is provided for the central heating system.

Preferably the hot water supply system includes downstream of the secondary heat exchanger in terms of water flow a mixing valve in the hot water outflow, the cold water inflow being connected to the mixing valve.

Preferably 3-operational mode control circuitry is provided for gas-fired water boiler and associated pumps and thermostats as described hereafter.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which Figs. 1 and 2 are respectively side and front elevations of a first embodiment of combined central heating and domestic hot water systems according to this invention; Figs. 3 and 4 are side elevations corresponding to Fig. 1 showing two modes of the water store arrangement; Fig. 5 is a side elevation showing three modifications of the systems of Figs. 1 to 4; Fig. 6 is a front view of a second embodiment of a combined central heating and domestic hot water system according to this invention; and Figs 7 to 9 are respectively control circuit diagrams for the systems shown in Figs. 1 to 4, Fig. 5 and Fig. 6.

Referring to Figs. 1 to 4 of the drawings, the water heating arrangement for the combined central heating and domestic hot water supply systems comprises a pressure vessel or tank 20, suitably insulated and enclosed within a casing 21 openable for access purposes.

Within the pressure vessel 20 is a water boiler 22 constituted by an upper heat exchanger 23 and a lower gas-fired burner assembly 24.

The burner assembly 24 may be fired by a fuel other than gas, for example oil.

The boiler 22 is fitted with a multi-directional flue system 25 incorporating a multi-choice flue turret or connector 26 and terminating in a balanced flue arrangement 27 traversing the exterior wall 28 of, say, a house, the flue system 25 at its lower end and adjacent the boiler 22 being fitted with a suction fan 25A for the extraction of flue products.

Within the pressure vessel 20 and above the water boiler 22 there is provided an expansion vessel 29 communicating with the lower region of the pressure vessel 20 via an opening 30.

A door 23A is provided for accessing the heat exchanger 23 and flue assembly 25 for maintenance and repair purposes.

The above described water heating arrangement serves to provide a primary hot water store for a central heating system CH and a domestic hot water supply system HW.

Fig. 1 illustrates the pressure vessel 20 empty of water and the expansion vessel 29 filled with nitrogen or other suitable inert gas.

Fig. 3 illustrates the pressure vessel 20 filled with cold water and with consequent partial filling of the expansion vessel 29 and compression or reduction of the nitrogen volume contained therein.

Fig. 4 illustrates the pressure vessel 20 with the water contained therein heated by the boiler 22 to working temperature with consequent expansion of the water volume and further compression or reduction of the nitrogen volume contained therein.

There is thus provided, according to this invention, a water heating arrangement comprising a pressure vessel 20 containing and enclosing a pressure vessel 29 and a hot water boiler 22 and serving to provide a hot water store for both the central heating system CH and the domestic hot water supply system HW.

The central heating system or circuit CH (primary system) is supplied with hot water via a feed pipe 32 incorporating a pump 33 with the usual upstream and downstream shut-off valves 34, 35 from the hot water store contained with the pressure vessel 20 from the region above the boiler 22, the water return from the central heating system or circuit CH being to the pressure vessel 20 via a return pipe 36 to the region below the hot water boiler.

A pressure relief valve 37 is incorporated in the hot water supply side of the central heating system or circuit CH.

The domestic hot water supply system HW (secondary system) has a cold water inlet pipe 38 connected to a heat exchanger 39, preferably but not essentially a plate heat exchanger, from which there is a heated water outlet pipe 40 incorporating a mixing valve 41 to which the cold water inlet pipe 38 is connected by a pipe 42. The hot water outlet pipe 40 terminates in one or more draw-off taps or faucets 43 (only one shown).

The domestic hot water is heated by hot water from store which is delivered from above the boiler 22 via a pipe 45 into the plate heat exchanger 39 and from there back into the boiler heat exchanger 23 via pipe 46 which incorporates a pump 47 with the usual upstream and downstream valves 48A,48B.

The gas supply to the gas burner assembly 24 is indicated at 24A, which supply is controlled by a double solenoid valve 49 as is customary.

The plate heat exchanger 39 is normally housed within the casing 21 as shown in Figs. 2 to 4.

As an example, the water heating arrangement (casing dimensions) of the invention is 900 mm (high) x 450 mm (side-to-side) x 350 mm (back to front), and compactness is achieved by the incorporation in the pressure vessel or tank 20 of the hot water boiler 22 and the expansion vessel 29.

Referring now to Fig. 5 of the drawings, the water heating arrangement is as disclosed with reference to Fig. 1 to 4 save that only a single pump 49A is provided for both the central heating system CH and the domestic hot water supply system HW.

The pump 49A is connected to a diverter valve 50 whereby hot water from store (pressure vessel 20) can be supplied either to the central heating system CH or to the domestic hot water supply system HW with priority being given to the latter.

Alternatively, a motorised valve is fitted, as indicated at A and B, in the central heating system CH and domestic hot water supply system HW respectively, or simply at A to permit, in the first case, hot water supply from store (pressure vessel 20) to either (CH or HW) or both systems (CH and HW) or in the second case hot water supply from store to either system CH or system HW.

An alternative water heating arrangement is shown in Fig. 6 which is more economic to manufacture in that it does not employ a pressure vessel.

This water heating arrangement comprising an insulated casing or tank 60 defining a hot water store and incorporating a gas-fired water boiler 61 constituted by a heat exchanger 62 with a bottom gas burner assembly 63. The boiler 61 is fitted with a multi-directional, or fan-assisted flue assembly generally indicated at 64.

An expansion space 65 is provided in the tank 60 above the hot water store level, and also above this level there is provided a separate expansion vessel 66 forming part of a central heating system CH.

Like the previous embodiments, the water heating arrangement is combined with a central heating system CH and a domestic hot water supply system HW.

In this embodimant the central heating system CH (primary system) incorporates in its hot water supply line 67 a pump 68 with upstream and downstream shut-off valves 69. 70.

The pump 68 is connected to a filling loop comprising a cold water supply pipe 71 connected to a cold water supply (mains supply) 72 and incorporating a double check valve 73 and an on/off valve 74, the former ensuring no backflow to the supply 72 and the latter no flow to the central heating system CH when the latter is filled.

The cold water supply pipe 71 is connected via a pipe 71A to the water tank 60 for filling or topping-up purposes under the control of a ball float controlled valve 75.

The hot water store tank 60 is fitted with an air vent 76 and an overflow warning pipe 77.

The hot water supply system HW (secondary circuit) comprises the cold water supply 72 connected to a water-to-water heat exchanger 78 with a hot water outlet pipe 79 from the latter terminating in one or more faucets 80 and incorporating a mixing valve 81 to which the cold water supply 72 is connected by a pipe 72A.

The water flow of the central heating system CH (primary circuit) comprises a water-to-water heat exchanger 82 from which heated water is delivered to the pump 68 by a pipe 83, the return water flow to the heat exchanger 82 being via a pipe 84.

The central heating system CH incorporates a pressure relief valve 87 and pressure and temperature gauges 88 connected to the expansion vessel 66 to which the cold water supply pipe 71 is also connected.

Hot water (boiler water) is delivered to both heat exchangers 78, 82 to heat the domestic hot water and the central heating water via an intermediate circuit IC in which boiler water is delivered from store (tank 60) via a pipe 85 incorporating a pump 86 with upstream and downstream shut-off valves 87A, 87B to the water-to-water heat exchanger 78 via a pipe 87, the return from the heat exchanger 78 being via a pipe 88 into the boiler heat exchanger 62.

The pump 86 is connected, downstream of the pipe 87 to a motorised or diverter valve 89 disposed in a boiler water supply pipe line 90 which delivers boiler water to the water-to-water heat exchanger 82 with return from the latter being via a pipe 91 into the pipe 88 which feeds the boiler heat exchanger 62.

The motorised or diverter valve 89 is used, when necessary, to give priority of boiler water supply to the domestic hot water system HW over the central heating system OH.

Referring now to Fig. 7 there is shown details of the control circuitry for the combined central heating and hot water systems CH and HW of Figs. 1 to 4 (primary hot water store).

This circuitry in addition to controlling the gas valve 49 also controls (a) ignition spark and sensing 112; (b) the fan 25A; (c) the pump 47 for the boiler and domestic hot water supply; (d) the central heating pump 33.

The electrical mains supply 99 is connected via a storage tank thermostat 115 and a double pole relay 116 to a printed circuit board 117 to which is electrically connected the fan 25A, the gas valve 49 which is of the double solenoid type, a gas pressure switch 118 and the ignition spark and sensor 112. A normally-closed overheat thermostat 119 is in circuit with the gas valve 49. The thermostat 119 may alternatively be disposed, in series arrangement, between the storage tank thermostat 115 and the double pole relay 116.

The double pole relay 116 is electrically coupled to the pump 47 which is provided with an overrun thermostat control 120 and a flow switch or water heating thermostatic control 121.

The electricity mains supply 99 is also connected directly to the central heating pump 33 with which is also electrically coupled a room thermostat 122 and a clock control 123.

The circuitry is shown in Fig. 7 in a bulk water store heating mode, in which mode the gas boiler 22 for example is on (operational), the pump 47 is on and the central heating pump 33 is off (nonoperational).

Other operational modes of this control circuitry are as follows:1. Domestic hot water run off, or pump 47 overrun.

In this mode, pump 47 is on, pump 33 is off and gas boiler 22 is off.

Compared with the circuitry shown in Fig. 7, the double pole relay 116 is open, tank thermostat 115 is open and the pump overrun thermostat 120 and flowswitch or hot water thermostat 121 are both closed (operational).

2. Domestic hot'- water and central heating store temperature satisfied.

In this mode, the circuitry compared with that shown in Fig. 7 has the double pole relay 116 open, the tank thermostat 115 open, the flow switch of water heating thermostat 121 open, the room thermostat 122 may be closed, the clock control 123 may be operational, and the pump 33 may be operational.

Briefly, other possible operational modes are: (a) all systems calling for heat gas boiler 22, pump 47 and central heating pump 33, all on; (b) central heating only operational-gas boiler 22 and pump 47 both off but central heating pump 33 on; (c) pump overrun-gas boiler 22 and central heating pump 33 both off but pump 47 on.

Fig. 8 shows the control circuitry for the Fig. 5 combined control heating and domestic hot water supply systems CH and HW, i.e. with single pump 49A.

In this control circuitry, only motorised valve A is shown, the domestic hot water store flow being indicated at HW and central heating water flow at CH.

The hot water store thermostat 115 operates on/off modes of the boiler 22 and the pump 49A.

Thermostat 120 serves to control residual heat pump overrun/timer.

Thermostats 121A and 121B respectively serve to function in response to cold water flow (circuit to pump 49A actuated), and to control the central heating water store temperature limits.

Fig. 9 is the control circuitry for the combined arrangement central heating and domestic water heating systems CH and HW described with reference to Fig. 6 incorporating pumps 68 and 86.

The control circuitries disclosed in Figs. 8 and 9 also provide the three operational modes described with reference to Fig. 7.

Claims

CLAIMS:

1. A water heating arrangement for combined central heating and hot water supply systems, the water heating arrangement comprising a water storage vessel or tank housing a water boiler to provide a hot water storage and, above the water boiler and also within the storage vessel or tank, an expansion vessel.

2. An arrangement as claimed in claim 1, wherein the boiler comprises a heat exchanger and a fuel burner assembly, preferably a gas-fired burner assembly, there being in water flow communication with the boiler heat exchanger a secondary water-to-water heat exchanger external of the water storage vessel or tank.

3. An arrangement as claimed in claim 1, wherein the secondary water-to-water heat is located inside the water storage vessel or tank.

4. An arrangement as claimed in any one of the preceding claims, wherein the storage vessel and tank is a pressure vessel, preferably insulated.

5. An arrangement as claimed in any one of the preceding claims, wherein the secondary heat exchanger is a plate heat exchanger.

6. An arrangement as claimed in claim 5 wherein the plate heat exchanger is housed in a casing also enclosing the storage vessel or tank.

7. An arrangement as claimed in any one of claims 2 to 6 wherein the secondary heat exchanger forms part of a hot water supply system.

8. An arrangement as claimed in any one of claims 2 to 7, wherein the hot water supply system has a cold water input to the secondary heat exchanger and a hot water output therefrom, the cold water being heated by hot water pumped from the store through the secondary heat exchanger for return to store.

9. An arrangement as claimed in any one of the preceding claims, wherein the hot water supply system comprises a mixing valve in the hot water output with the cold water input connected to the mixing valve.

10. An arrangement as claimed in any one of the preceding claims connected to a central heating system such that hot water is drawn off from the hot water store in the pressure vessel or tank by a pump for delivery to one or more heating radiators, the water return from the latter being back into store below the water boiler.

11. An arrangement as claimed in claim 10, wherein the hot water inlet to each of the central heating system and hot water supply system from store is above the water boiler and below the expansion vessel.

12. An arrangement as claimed in claim 10 or 11 wherein the hot water supply system alternatively incorporates a single common pump and a diverter valve.

13. An arrangement as claimed in claim 12 wherein the diverter valve is replaced by a motorised valve in each system or only in the central heating system.

14. An arrangement as claimed in claim 13, wherein in the first alternative the motorised valve is preferably in the hot water outlet side of the hot water supply system, and, in both alternatives, in the hot water inlet side of the central heating system.

15. An arrangement as claimed in any one of the preceding claims, wherein the storage vessel or tank is an insulated vessel or tank of a non-pressure nature.

16. An arrangement as claimed in any one of claims 10 to 15, including a water-to-water heat exchanger, preferably of the plate type, and through which the feed water from store and the return water to store passes to heat the circulating central heating water which also passes through the heat exchanger.

17. An arrangement as claimed in any one of the preceding claims, wherein a central heating expansion vessel is housed in the nonpressure storage vessel or tank adjacent an expansion space above the stored hot water.

18. An arrangement as claimed in any one of claims 10 to 17, wherein a filling circuit is provided for the central heating system.

19. An arrangement as claimed in any one of the preceding claims, wherein the hot water supply system includes downstream of the secondary heat exchanger in terms of water flow a mixing valve in the hot water outflow, the cold water inflow being connected to the mixing valve.

20. A water heating arrangement substantially as herein described with reference to the accompanying drawings.