GB2147090A - Water heating systems - Google Patents

Abstract

A water heating system utilizing a pump P2 and an electric heater H which preferably operate during times of cheap-rate electric mains supply to charge a heat store S with energy. A heat load L is supplied with heated water via a mixer valve V5 which takes energy from the store S or direct from the heater H in case of need. <IMAGE>

Description

SPECIFICATION Water heating systems The present invention relates to water heating systems for domestic or other use.

It is well known to utilize electric immersion heaters to heat water and also to mount such heaters directly in a hot water storage tank or vessel. In conventional central heating systems, installation is time-consuming and a general object of the present invention is to provide a simpler system which can be quickly installed in a variety of different sites and applications.

A heating system according to the invention comprises at least one electric heater and a pump connected in a circuit via pipework and subjected to control to supply energy to a separate heat store during one cycle of operation and a heat load such as radiators, connected in a circuit via pipework and a mixer valve which supplies heated fluid to the load; the heat energy for the fluid being derived from the store or direct from the heater. The aforesaid cycle of operation is intended to be determined by an economy rate mains supply, say overnight. Preferably, the system utilizes a self-contained unit with a housing containing said at least one heater and its associated pump as well as pipework and control devices connectible with detachable joints and connections to the separate heat store and other components of the system.In its simplest form, the unit is compact and has a housing with external connectors for connecting to the heat store and accepts an electric power cable. The housing can be rendered suitable for outdoor use.

The heat store itself can be an insulated hot water tank or vessel or a PCM (phase-change material) store. In a conventional installation with a water tank or vessel storing heated water, the water storage facility is entirely separate from the unit, which means the facility can take a variety of forms say, one or more 40 gallon cylinders or a larger vessel which needs no special adaptation.

In a preferred form the system or the unit has an additional pump to feed the load such as radiators with heated water drawn from the store and through the heater or vice versa.

Various valves can be employed to control the water flow paths such as are described hereinafter.

A heater unit constructed in accordance with the invention comprises a first circuit with an electric heater and a pump with an inlet and outlet connectible to a separate heat store to supply energy thereto and a second circuit with a mixer valve and a pump with inlets and outlets to said heat store and said first circuit and to an external heating load; wherein the circuits are isolated from one another and are controlled to operate at different times.

The invention may be understood more readily, and various other features of the invention may become apparent, from consideration of the following description.

Embodiments of the invention will now be described, by way of examples only, with reference to the accompanying drawings, wherein: Figure 1 is a schematic representation of one form of heating system and unit thereof constructed in accordance with the invention, and Figure 2 is a schematic representation of another heating system and unit constructed in accordance with the invention.

In the accompanying drawings, only the water pipework, flow paths, connections and associated devices are shown and for the sake of clarity, the electrical connections, thermostats and associated devices are omitted. The system as depicted in Fig. 1 employs a selfcontained unit with a casing K represented in dotted outline. The casing K has two connectors 10, 11 which lead to a separate heat store S. As discussed hereinbefore, the heat store S may take the form of one or more insulated water storage vessels or a PCM heat store. The connector 10 provides the main inflow IN to the unit and the connector 11 provides the main outflow OUT from the unit.

The connector 10 leads through an isolating valve V, to an electrical heater H composed of two 6KW heating elements. The outlet from the heater H is connected directly to an upstanding vent pipe 'VENT' and via a nonreturn valve V3 to a pump P2. The outlet of the pump P2 is connected through a nonreturn valve V4 back to the connector 11. A drain valve V2 is provided on the heater H and is conveniently accessible exteriorly of the casing K. Normally, electric controls (not shown) would operate the heater H and the pump P2 for one or more preset times during the day and preferably on an economy tariff to cause the store S to store heat energy.

The unit also has another circuit or loop which as shown is associated with additional connectors 12, 1 3. The valve V3 is connected through a mixer valve V5 which leads back to the connector 11 via a non-returnable valve V6. The valve V5 is also connected to a further pump P1 which is coupled to the connector 12. A heating system load, such as a series of radiators as shown in dotted outline L is connected between the connector 12 and a control valve or motorized valve V7 which also connects to the connector 1 3 leading to the valves V5 and V6. Another connector 14 leads to the inlet of the pump Pt. An auxiliary boiler, such as an oil-fired boiler designed AB can be connected between the connector 14 and the control valve V7.

The electrical controls would cause the pump P to operated for one or more other pre-set times to supply water heated with energy from the store S or the heater H to the load L. The supply to the load L passes through the valve Vt, the heater H, the valves V3 and V5 and the return passes through the valves V7 and V6.

The heater H operates under thermostatic control to maintain the water temperature at a pre-set level. The mixer valve V5 is designed to mix water from the outlet of the heater H with water returned to the connector 1 3 in a proportion to maintain the temperature of the water at the inlet to the pump P1 at a predetermined temperature.

In a typical system the water return at the connector 1 3 is at about 40"C, the water supplied from the store S is in the range of about 40 C to 97'C and the water at the inlet to the pump P1 is at a temperature of about 70'C. The thermostatic control acting on the heater can serve to operate the heater H to maintain the forward temperature at 70"C if the temperature of the water supplied from the store S is below 70"C.

Fig. 2 depicts a somewhat simplified installation where like reference numerals are used to identify like parts to the Fig. 1 arrangement. By way of example, the heat store is a water storage vessel S which is shown in this installation in its operative association with the unit K. A single one-way valve V9 is connected in parallel with the vessel S and a flow-sensor control switch F1 is connected in series with the pump P2 and the heater H.

The main connections 10, 11, 12, 1 3 are supplemented by additional connectors 8,9 with the store S between the circuits 10, 11; 8,9 and 12, 13.

The system again operates so that the advent of the economy rate supply activates the pump P2 and the heater H to charge up the vessel S with hot water over a typical cycle of 5 hours. The pump P1 feeding with the load L in the form of radiators is controlled by means of a time switch to operate for say the last two hours of the charging cycle if needed and for other set times when the pump P2 is inoperative.

Under the conditions when both pumps P and P2 operate, the water flow through the vessel is shown in dotted lines denoted D and the stored heat is not utilized. When the economy cycle terminates the heater H and the pump P2 cease operating and heated water is available to feed the load L under control of the pump P1. If the temperature of the stored water falls below say 70"C, the pump P, and the heater H are operated automatically by thermostatic control to maintain the heat supply under overall control of a user.

Claims (8)

1. A heating system comprising at least one electric heater and a pump connected in a circuit via pipework and subjected to control to supply energy to a separate heat store during one cycle of operation and a heat load such as radiators, connected in a circuit via pipework and a mixer valve which supplied heated fluid to the load; the heat energy for the fluid being derived from the store or direct from the heater.

2. A system according to claim 1, wherein the heated fluid is supplied with the aid of a further pump subjected to control independent of the first-mentioned pump.

3. A system according to claim 1 or 2, wherein said one cycle of operation in determined by an economy rate mains supply.

4. A system according to any one of claims 1 to 3, wherein there is provided within the system a self-contained unit with a housing containing pipework, the heater, the first-mentioned pump and control devices and having detachable connections with other components of the system.

5. A system according to any one of claims 1 to 4, wherein the heat store is at least one water storage tank or vessel.

6. A system according to any one of claims 1 to 4, wherein the heat store is a PCM store.

7. A heater unit comprising a first circuit with an electric heater and a pump with an inlet and outlet connectible to a separate heat store to supply energy thereto and a second circuit with a mixer valve and a pump with inlets and outlets to said heat store and said first circuit and to an external heating load; wherein the circuits are isolated from one another and are controlled to operate at different times.

8. A heating system or unit substantially as described with reference to and as illustrated in Fig. 1 or 2 of the accompanying drawings.