EP0828116A2

EP0828116A2 - A heating system

Info

Publication number: EP0828116A2
Application number: EP97306944A
Authority: EP
Inventors: William John Lloyd; Roy Bratley
Original assignee: Caradon Ideal Ltd
Current assignee: Caradon Ideal Ltd
Priority date: 1996-09-09
Filing date: 1997-09-08
Publication date: 1998-03-11
Also published as: GB9618773D0; EP0828116A3

Abstract

A water heating system has an instantaneous water heater 1 for heating potable water in a potable hot water supply line 2. The supply of potable hot water can be supplemented by potable hot water contained in a supply vessel 4 connected to the supply line 2 downstream of the boiler 1. The invention allows the combination of the advantages of heating systems having a storage vessel and heating systems having an instantaneous water heater by providing a high initial potable hot water flow rate and a continuous supply of potable hot water at a lower flow rate thereafter.

Description

This invention relates to heating systems, and it is concerned particularly with systems for heating water for domestic use.

Previously known heating systems can be divided into two categories: heating systems having a hot water storage vessel; and heating systems comprising an 'instantaneous' water heater, e.g a gas boiler. In heating systems of the first kind, the water in the storage vessel is heated to a desired temperature, e.g. by an electrical heating element or by hot water passed through a heating coil located in the vessel, and on demand heated water is drawn from the vessel, and the vessel is replenished with unheated water. Although such systems function adequately, a long recovery period, during which no heated water at the desired temperature is available, follows periods of heavy demand, and a large space is required to house a storage vessel of sufficient capacity to supply even normal levels of demand of an average household.

Instantaneous water heaters provide a relatively compact alternative, and they can supply heated water for an unlimited period of time. However, heating systems utilising instantaneous water heaters suffer the disadvantage of a low heated water flow rate in comparison with heating systems having a hot water storage vessel. Although the flow rate from instantaneous water heaters is sufficient to meet modest levels of demand, an extended period of time is required to produce a large volume of heated water, e.g. in order to fill a bath.

The present invention addresses the disadvantages of the two known types of heating systems by providing a heating system comprising a gas boiler for heating water flowing through a potable hot water supply line, a potable hot water storage vessel comprising means for heating water contained in the vessel, the vessel being connected to the hot water supply line downstream of the boiler for hot water to flow from the vessel into the supply line when water heated by the boiler is flowing therethrough.

Advantageously, the water in the storage vessel is heated by a heat exchange with a fluid heated by the boiler.

A heating system according to the present invention can satisfy an initial demand for potable hot water at a high flow rate, allied with the ability to provide a continuous supply of heated potable water at a lower flow rate, thereby combining the advantages of both the known types of heating systems. Also, a smaller storage vessel than would be required in a known system consisting of a storage vessel can be used.

A clear understanding of the invention will be gained from the following detailed description of a preferred embodiment of the invention given with reference to the accompanying schematic illustration of the preferred embodiment (figure 1).

A boiler 1 has a gas burner for heating water flowing through a potable or sanitary hot water supply line 2 for domestic consumption and for heating water circulated through a

primary heating circuit

5,8. In a manner known per se, the water in the supply line and the heating circuit can be heated directly by the gas burner in distinct flow paths through a duplex heat exchanger surrounding the burner, or the water in the supply line can be heated in a secondary heat exchanger by indirect heat from the water in the heating circuit. The following description is given with reference to a boiler having a duplex heat exchanger.

An insulated hot water storage vessel or tank 4 is connected in parallel with the heat exchanger to the potable hot water supply line 2 by an inlet pipe 9 and an outlet pipe 6. The outlet pipe 6 includes a wax thermostat 7.

The heating circuit includes two flow paths: the heat exchanger is connected in series with a diverter valve 11 and a heating coil 12 located within the vessel 4 to complete a

first flow path

3,5; and a

second flow path

3,8 is defined by the connection in series of the diverter valve 11 and a plurality of space heaters (not shown).

When a demand for heated water in the potable hot water supply line 2 is sensed, the gas burner is ignited and the water flowing through the heat exchanger of the boiler is heated. If the temperature of water in the outlet pipe 6 of the storage vessel 4 is above a threshold determined by the wax thermostat 7, the flow path through the outlet pipe will be open and heated water from the storage vessel 4 will supplement the flow of heated water flowing from the boiler in the potable hot water supply line 2. As the water is drawn from the storage vessel it is replenished with unheated potable water. When the temperature of water in the outlet pipe 6 drops below the predetermined temperature threshold, the wax thermostat 7 closes to prevent flow of water from the storage vessel until the temperature of water therein rises above the threshold again. Thus, water from the storage vessel 4 adds to the flow of water from the heat exchanger of the boiler to provide a high initial potable water flow rate, and thereafter potable hot water can be supplied from the heat exchanger of the boiler alone at a lower constant flow rate for an unlimited period of time.

When there is no demand for domestic hot water, the water in the central heating circuit can be heated and circulated around the

first flow path

3,5 or the

second flow path

3,8 depending on the position of the diverter valve 11. Heated water circulated around the

first flow path

3,5 passes through the coil 12 within the storage vessel 4 to thereby heat the water therein. The heating of water in the storage vessel could take priority over the supply of the space heaters or vice versa. The diverter valve is preferably controlled to shut off delivery of hot water to the heating coil of the water storage vessel when the water contained in the vessel is at a predetermined temperature.

Modifications to the described heating system are possible without departing from the scope of the claims. For example, the invention is equally applicable to dedicated domestic water heating systems as it is to combined domestic and central heating system. Also, the storage vessel 4 could be heated by any suitable means, e.g. an electric element. Further, the wax thermostat 7 could be replaced by any suitable separate thermostat and valve.

Claims

A heating system comprising a gas boiler (1) for heating water flowing through a potable hot water supply line (2), a potable hot water storage vessel (4) comprising means (12) for heating water contained in the vessel, the vessel being connected to the hot water supply line downstream of the boiler for hot water to flow from the vessel into the supply line when water heated by the boiler is flowing therethrough.
A heating system according to claim 1, wherein a thermostatic means (7) is provided for controlling the minimum temperature of water leaving the storage vessel.
A heating system according to any one of claims 1 or 2, wherein the thermostatic means (7) comprises a sensor for sensing the temperature of water leaving the storage vessel, and a valve coupled to the sensor.
A heating means according to any one of claims 1 or 2, wherein the thermostatic means (7) comprises a wax thermostat.
A heating system according to any one of claims 1 to 4, wherein the water in the storage vessel is heated by heat exchange with a fluid heated by the boiler and flowing in a closed heating circuit (3, 5, 8).
A heating system according to claim 5, wherein the heating circuit comprises a diverter valve (11) for switching the flow of heated fluid between a first flow path (3, 5) passing through the storage vessel, and a second flow path (3, 8) including a plurality of space heaters.
A heating system according to claim 1 or 4 wherein the heating means is an electric element.