GB2342429A

GB2342429A - Flow control for boiler of central heating/hot water system

Info

Publication number: GB2342429A
Application number: GB9922262A
Authority: GB
Inventors: George Curtis
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-09-23
Filing date: 1999-09-22
Publication date: 2000-04-12
Also published as: GB9922262D0; GB9820611D0

Abstract

A boiler comprises a housing 11, a heat exchanger 18, a valve 16 regulated gas burner 12, a cold water inlet 26 to the heat exchanger, a hot water outlet 25 from the heat exchanger which splits into two flow outlets 30, 34 and flow control means 36, 38 located between the hot water outlet 25 and the two flow outlets 30, 34. A central heating system comprises the above boiler 10, a central heating circuit 54, 56, 58 connected to one flow outlet 30, a hot water circuit 60, 64, 66 connected to the other flow outlet 34 (wherein cooled water from both circuits returns to the cold water inlet 26 of the heat exchanger) and at least one thermal storage unit 66 located in the hot water circuit in close proximity to a hot water outlet (tap) 63. The flow control means preferably comprises one or more pumps 36, 81 with or without one or more valves. The valves can be motorised and 3-way. Control apparatus such as flow sensors, thermostats and programmable timers may be used to control the flow control means and supply of hot water. An expansion vessel 23 may be provided. The thermal storage unit preferably comprises a hot water jacket at 80, a blender (mixer) valve 76 and a heat exchange coil 68. Hot water from the hot water circuit 60 and cold mains water 70 flow through the thermal storage unit providing hot water 74 for the hot water outlet 63.

Description

"Central Heating and Hot Water Apparats" This invention relates to apparatus for use in a central heating and hot water system. More particularly, the invention relates to an improved central heating and hot water boiler and to an improved central heating and hot water system incorporating such a boiler.

When assembling a central heating and hot water system, the various components such as a circulation pump, motorised hot water and heating valves, flow and return pipes and electrical components all have to be fitted separately which involves substantial labour costs and time.

Once fitted, the central heating and hot water system, with all the components, attached pipework and cables connected, leaves an unsightly appearance and, depending on its location, may not render easy access for maintenance procedures.

A further problem associated with central heating systems is that the source of domestic hot water, whether this comprises a hot water storage tank or a "combi-boiler"or other type of"instant"water heater, is normally located some distance from the hot water tap at the point of use. This results in a significant wastage of water and energy when cold water is run off from the pipes connecting the tap to the hot water source.

It is a first object of the present invention to provide an improved boiler which facilitates the installation and maintenance of central heating and hot water systems.

It is a further object of the present invention to provide an improved central heating and hot water system which reduces the wastage arising from the distance between hot water taps and hot water sources.

According to a first aspect of the present invention there is provided a boiler for use in a central heating system, comprising a housing enclosing: a gas burner and pipework, including a gas control valve, for connection to an external gas supply; a heat exchanger having an inlet end and an outlet end, whereby heat from said gas burner may be transferred to water flowing through said heat exchanger; return pipework having an outlet end connected to the inlet end of said heat exchanger and having an inlet end for connection to an external return pipe; and flow pipework having an inlet end connected to the outlet end of said heat exchanger and having an outlet end for connection to external flow pipework; wherein: said flow pipework includes a first flow outlet for connection to an external central heating flow pipe and a second flow outlet for connection to an external hot water flow pipe; said flow pipework further including flow control means for controlling the flow of water between the outlet end of said heat exchanger and said first and second flow outlets.

Preferably, said flow control means includes at least one pump means incorporated between said outlet end of said heat exchanger and said first and second flow outlets.

In certain embodiments of the invention, said flow control means includes a single pump having an inlet side connected to the outlet end of said heat exchanger and an outlet side connected to valve means located between the outlet side of the pump and the first and second flow outlets. In one embodiment, said valve means comprises a first motorised valve located in a heating branch of said flow pipework downstream of said pump between the outlet side of the pump and said first flow outlet, and a second motorised valve located in a hot water branch of said flow pipework downstream of said pump between the outlet side of the pump and said second flow outlet. In another embodiment, said valve means comprises a three-way valve having an inlet connected to the outlet side of said pump and first and second outlets connected respectively to said first and second flow outlets.

In a preferred embodiment, said flow control means comprises a first pump located in a heating branch of said flow pipework extending between the outlet end of the heat exchanger and said first flow outlet, and a second pump located in a hot water branch of said flow pipework extending between the outlet end of the heat exchanger and said second flow outlet.

Preferably, the boiler further includes control apparatus for controlling the operation of said pump (s) and/or valve means.

When adapted for use in a sealed system, the boiler is preferably further provided with an expansion vessel.

In accordance with a second aspect of the invention, there is provided a central heating and hot water system including a boiler in accordance with the first aspect of the invention, wherein said first flow outlet of the boiler is connected to flow pipework of a central heating circuit and said second flow outlet is connected to flow pipework of a hot water circuit, and wherein said return inlet is connected to return pipework of said central heating and hot water circuits; wherein: said hot water circuit includes at least one thermal storage unit located in close proximity to at least one hot water outlet (tap).

Preferably, said thermal storage unit comprises a hot water jacket having an inlet connected to said flow pipework and an outlet connected to said return pipework, and enclosing a heat exchange coil having an inlet connected to a cold water supply and an outlet connected to said hot water outlet.

Preferably, said thermal storage unit further includes blender valve means having a first inlet connected to said water jacket outlet, a second inlet connected to said cold water supply and an outlet connected to said hot water outlet.

Preferably also, said hot water jacket is adapted to contain water at a temperature of at least about 80 C.

Preferably also, the system includes sensors and control means whereby operation of the boiler is controlled to supply hot water to said heating and hot water circuits in accordance with predetermined criteria.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a schematic front view of the interior of a first embodiment of a central heating and hot water boiler in accordance with the first aspect of the invention; Figs. 2a, 2b and 2c are diagrams illustrating variations of the embodiment of Fig. 1; and Fig. 3 is a diagram illustrating a simplified central heating and hot water system incorporating the boiler of Figs. 1 and 2, in accordance with a second aspect of the invention.

Referring now to the drawings, Fig. 1 shows a central heating and hot water boiler 10 in accordance with the first aspect of the invention, comprising an outer casing (typically of stove enamelled steel) enclosing a gas burner 12, adapted to be connected to a gas supply via pipework 14 including a gas control valve 16, and a heat exchanger 18. Water enters the heat exchanger 18 at an inlet end 20 thereof and exits from an outlet end 22, such that heat from the gas burner 12 is transferred to the water passing through the heat exchanger. Water enters the heat exchanger 18 via a return pipe 24 having an inlet end 26 adapted for connection to the return pipework of external central heating and hot water plumbing. Water exits the heat exchanger 18 via a flow pipe 25. The boiler described thus far corresponds to the basic components of a conventional boiler, and may further include a substantially conventional expansion vessel, illustrated schematically at 23, where necessary.

In accordance with the first aspect of the present invention, the flow pipework provided integrally with the boiler further includes a central heating flow branch 28 having a first flow outlet 30 and a hot water flow branch 32 having a second flow outlet 34, the inlet ends of the flow branches 28 and 32 being connected to the outlet end of the main flow pipe 25.

Further in accordance with the first aspect of the invention, the flow of water through the respective flow branches 28 and 32 is controlled by flow control means.

In the embodiment of Fig. 1, the flow control means comprises a first water pump 36 incorporated in the central heating flow branch 28 and a second water pump 38 incorporated in the hot water flow branch 32. The respective pumps 36 and 38 may be operated independently of one another such that water heated in the heat exchanger 18 may be directed to the first flow outlet 30, or to the second flow outlet 34, or to both flow outlets 30 and 34. The operation of the pumps 36 and 38 and of the gas control valve may be controlled by substantially conventional electrical, electronic or electro-mechanical control devices (not shown), which may also be incorporated into the boiler 10 or may be located externally thereof. Such control means may include programmable timers and/or thermostatic controls etc., as is well known in the art.

Figs. 2a, 2b and 2c illustrate variations of the flow control means of the boiler 10. The various flow pipes and branches are designated by the same reference numerals as in Fig. 1.

Fig. 2a shows an embodiment in which the flow control means comprises a single pump 40 incorporated in the main flow pipe 25, and first and second motorised valves 42 and 44 incorporated in the heating and hot water flow branches 28 and 32 respectively. The pump 40 and valves 42 and 44 can be controlled so as to direct water from the flow pipe 25 to either the first or second flow outlets 30,34, or both.

Fig. 2b shows an embodiment in which the flow control means again comprises a single pump 40 incorporated in the main flow pipe 25. The outlet end of the flow pipe is connected to an inlet port of a three-way valve unit 46 having one inlet and two outlets. The outlets of the three-way valve are connected to the inlet ends of the heating and hot water flow branches 28 and 32 respectively. The pump 40 and three-way valve unit 46 can again be controlled so as to direct water from the flow pipe 25 to either the first or second flow outlets 30,34, or both.

Fig. 2c shows a comparative diagram of the embodiment of the flow control means of Fig. 1, as already described, with separate pumps 36 and 38 in the heating and hot water flow branches 28 and 32.

The incorporation of the flow control means, comprising one or more pumps and control val-, into the boiler assembly simplifies and facilitates the installation and maintenance of a central heating and hot water system. It is only necessary for the return inlet 26 and flow outlets 30 and 32 to be connected to the conventional return and flow plumbing of central heating radiators and hot water circuits in order to provide an operational heating and hot water system.

As previously mentioned, the necessary programmers or other controllers can also be incorporated into the boiler, or could be installed separately at other locations if desired.

In a conventional hot water system, the hot water flow from the second flow outlet 34 would be directed to a hot water storage tank in which heat from the hot water passing through the flow pipework is transferred to cold water in the tank. The hot water tank is normally located some distance from the hot water taps. When hot water is required at a particular tap, it is necessary to run off cold water (which has previously been heated in the storage tank and has subsequently cooled) from the pipes connecting the storage tank to the tap. This is inconvenient and is wasteful of both water and energy.

Fig. 3 illustrates a simplified version of an improved central heating and hot water system in accordance with a second aspect of the present invention, incorporating the boiler 10 of Figs. 1 and 2. The gas inlet 14 is connected to a mains gas supply 50. The return inlet 26 of the boiler 10 is connected to return pipework 52 of the external plumbing. The first flow outlet 30 is connected to a substantially conventional central heating circuit comprising flow pipework 54, at least one radiator or the like 56, and return pipework 58 connected to the main return pipe 52. Instead of being connected to a central hot water storage tank, as in a conventional hot water system, the second flow outlet is connected via hot water flow pipework 60 to an inlet of a thermal storage unit 62 located closely adjacent to the tap 63 which is to be supplied with hot water.

The outlet of the thermal storage unit 62 is connected to hot water return pipework 64 which is in turn connected to the main return pipe 52. If more than one tap is required to be supplied with hot water, then additional thermal storage units would be installed closely adjacent to each tap.

The thermal storage unit 62 comprises a hot water jacket 66 through which hot water is circulated from the boiler 10. The hot water jacket 66 encloses a heat exchange coil 68, having an inlet 72 connected to a cold water mains supply 70 and an outlet 74 connected to the tap 63. Cold water passing through the coil 68 when the tap 63 is opened is heated by the transfer of heat from the hot water jacket 66. The amount of energy stored in the thermal storage 62 unit depends on the volume of the water jacket 66 and the temperature of the water contained therein. The volume of the unit can be reduced by increasing the temperature of the water. In order to regulate the temperature of the hot water exiting the tap 63, the thermal storage unit 62 further incorporates a three-way blender valve 76, having two inlets and one outlet. One of the inlets is connected to the outlet 74 of the heat exchange coil; the other inlet is connected to the cold water mains supply 70 ; the outlet is connected to the tap 63. In this way, the amount of hot water which can be drawn from the tap 63 at any one time can be determined by adjusting the volume and operating temperature of the water jacket 66. If water is supplied to the water jacket at a temperature of about 80 C then the thermal storage unit 62 can be made compact enough to fit in a typical under-sink space while providing a sufficient volume of hot water at a suitable temperature. The relatively small volume of the water jacket 66 also means that it can be replenished quickly after its stored energy has been depleted by running off hot water from the tap 63. The water jacket 66 can be thermally insulated to a high standard so that the water therein remains sufficiently hot until the tap 63 is operated, and its close proximity to the tap eliminates wastage in running off cold water from the pipework connecting it to the tap 63. Wastage of water and energy is further reduced if the boiler is located relatively close to the hot water taps (and hence to the associated thermal storage units). This is often the case where kitchens and bathrooms are located adjacent to one another, with the boiler located in one or the other (as compared with conventional systems where the boiler and taps may be relatively close to one another but the hot water storage tank is remote from both the boiler and the taps).

The control systems for controlling the flow control means and gas burner of the boiler may be responsive to temperature and/or water flow sensors associated with the thermal storage unit 62, so as to supply hot water to the water jacket 66 as and when required. For example, flow sensors would be fitted to either the hot or cold pipework of the thermal storage unit to detect when water is being drawn off, causing the boiler 10 to supply hot water to the water jacket 66. Typically, the hot water flow from the second flow outlet 34 of the boiler 10 would take priority over the central heating flow from the first flow outlet 30, until the water jacket 66 reaches its operating temperature.

Thereafter, the boiler will operate on demand in response to the central heating control system (timers and thermostats).

If the boiler 10 is used with a conventional indirect hot water cylinder (storage tank) then both the heating and hot water circuits can be supplied by the boiler 10 on demand, independently of one another under the control of appropriate timers and thermostats, with neither taking priority over the other.

The first aspect of the invention thus provides an improved central heating and hot water boiler, which may be employed advantageously in either an otherwise conventional central heating and hot water system or in an improved system in accordance with the second aspect of the invention.

Improvements and modifications may be incorporated without departing from the scope of the invention.

Claims

Claims 1. A boiler for use in a central heating system, comprising a housing enclosing: a gas burner and pipework, including a gas control valve, for connection to an external gas supply; a heat exchanger having an inlet end and an outlet end, whereby heat from said gas burner may be transferred to water flowing through said heat exchanger; return pipework having an outlet end connected to the inlet end of said heat exchanger and having an inlet end for connection to an external return pipe; and flow pipework having an inlet end connected to the outlet end of said heat exchanger and having an outlet end for connection to external flow pipework; wherein: said flow pipework includes a first flow outlet for connection to an external central heating flow pipe and a second flow outlet for connection to an external hot water flow pipe; said flow pipework further including flow control means for controlling the flow of water between the outlet end of said heat exchanger and said first and second flow outlets.
2. A boiler as claimed in Claim 1, wherein said flow control means includes at least one pump means incorporated between said outlet end of said heat exchanger and said first and second flow outlets.
3. A boiler as claimed in Claim 2, wherein said flow control means includes a single pump having an inlet side connected to the outlet end of said heat exchanger and an outlet side connected to valve means located between the outlet side of the pump and the first and second flow outlets.
4. A boiler as claimed in Claim 3, wherein said valve means comprises a first motorised valve located in a heating branch of said flow pipework downstream of said pump between the outlet side of the pump and said first flow outlet, and a second motorised valve located in a hot water branch of said flow pipework downstream of said pump between the outlet side of the pump and said second flow outlet.
5. A boiler as claimed in Claim 3, wherein said valve means comprises a three-way valve having an inlet connected to the outlet side of said pump and first and second outlets connected respectively to said first and second flow outlets.
6. A boiler as claimed in Claim 2, wherein said flow control means comprises a first pump located in a heating branch of said flow pipework extending between the outlet end of the heat exchanger and said first flow outlet, and a second pump located in a hot water branch of said flow pipework extending between the outlet end of the heat exchanger and said second flow outlet.
7. A boiler as claimed in any preceding Claim, further including control apparatus for controlling the operation of said flow control means.
8. A boiler as claimed in any preceding Claim, further including an expansion vessel.
9. A central heating and hot water system including a boiler as claimed in any preceding Claim, wherein said first flow outlet of the boiler is connected to flow pipework of a central heating circuit and said second flow outlet is connected to flow pipework of a hot water circuit, and wherein said return inlet is connected to return pipework of said central heating and hot water circuits; wherein: said hot water circuit includes at least one thermal storage unit located in close proximity to at least one hot water outlet (tap).
10. A system as claimed in Claim 9, wherein said thermal storage unit comprises a hot water jacket having an inlet connected to said flow pipework and an outlet connected to said return pipework, and enclosing a heat exchange coil having an inlet connected to a cold water supply and an outlet connected to said hot water outlet.
11. A system as claimed in Claim 10, wherein said thermal storage unit further includes blender valve means having a first inlet connected to said water jacket outlet, a second inlet connected to said cold water supply and an outlet connected to said hot water outlet.
12. A system as claimed in Claim 10 or Claim 11, wherein said hot water jacket is adapted to contain water at a temperature of at least about 80 C.
13. A system as claimed in any one of Claims 9 to 12, further including sensors and control means whereby operation of the boiler is controlled to supply hot water to said heating and hot water circuits in accordance with predetermined criteria.
14. A boiler for use in a central heating system, substantially as hereinbefore described with reference to the accompanying drawings.
15. A central heating and hot water system, substantially as hereinbefore described with reference to the accompanying drawings.