GB2195172A - Hot water containers; self- priming of primary water system - Google Patents

Abstract

In a hot water container 1 comprising a heat exchanger 3a capable of connection to a primary water heating system, self priming means for the primary system is located within the principal container interior. A pair of communicating upper and lower chambers 9, 10 are capable of receiving or transferring water and/or air, the two chambers communicating through a first duct 12. A second duct 16 extends from or near the bottom of the upper chamber to communicate to atmosphere 18 and provide a hot water draw-off 17. The lower chamber 10 is capable of connection to both a primary heating circuit and an external auto-vent 25. The upper chamber 9 is in communication via a third duct 15 with the main body of the container 1. Separation of potentially contaminated primary heated water from a secondary hot water supply may be maintained by air pocket(s) within the chambers and a sealed partition if required. Water replenishment may be automatic and boiling malfunction is particularly catered for. <IMAGE>

Description

SPECIFICATION Hot water containers and systems This invention is concerned with a container such as a tank or cylinder suitable for a domestic water heating system, and to hot water and heating systems incorporating such containers. Indirect domestic water heating systems conventionally employ a domed copper sealed cylinder for storage and supply of domestic hot water in a secondary circuit, the available water heater by heat exchanger supplied with boiler-heated water in a separate, primary circuit. It is necessary to prime. a cylinder after initial installation or substantial repair and to replenish water drawn off from the secondary hot water supply circuit. There is also a requirement to prevent unwanted mixture of secondary supplied water with potentially contaminated primary water in the heating circuit.

Domestic water heating systems are known which can supply primary and secondary water from a common feed and which automatically replenish water drawn off from the secondary circuit. The arrangements for maintaining primary/secondary separation have not always been successful under all operating conditions particularly during malfunction.

One known form of indirect cylinder which maintains separations of primary from secondary water by means of air pocket is the Primatic (Trade Mark) cylinder supplied by Range Boilers, Ltd. In this arrangement the heat exchange unit is formed from sheet copper metal as a pair of spaced open chambers.

Apart from employing a heat exchanger largely replaced now by coiled types, the open chambers employed may lead to contamination, particularly during boiling malfunction.

An alternative arrangement of heating system incorporating a self-priming means is disclosed in GB-A-2001 740. In the arrangement disclosed in this prior specification, a flow control device is located externally of the cylinder. In use, initial filling of the primary and secondary systems is possible with subsequent maintained separation of primary from secondary water by closed air pocket. Although this known priming device may operate satisfactorily it needs additional space in the instaliation and associated connecting pipework.

It is from a consideration of existing domestic hot water cylinder, and water heating systems that has led to the development of the present invention.

According to this invention there is provided a principal container for a water heating system comprising a heat exchanger capable of connection to a primary water heating system, self priming means located within the principal container interior comprising, when the said container is in an upright position, a pair of communicating upper and lower chambers capable of receiving or transferring water and/ or aird, the said two chambers communicating through a first duct, a second duct extending from or near the bottom of the upper chamber which can communicate to atmosphere and provide a hot water draw-off, the lower chamber capable of connection to both a primary heating circuit and an external auto-vent.

The container may usefully comprise a metal tank or cylinder such as a standard domestic hot water copper cylinder.

In order that the invention may be illustrated and readily carried into effect embodiments, by way of example only, will now be described with reference to the accompanying drawings, in which: Figure 1 is a principal container suitable for connection to gravity fed primary circuit, and Figure 2 shows a principal container and connections for a pumped primary domestic hot water system.

Referring firstly to Fig. 1 of the drawings, an indirect cylinder 1 is shown as principal container for housing domestic water 2 in a secondary circuit. Cold water is fed to the cylinder 1 from a header tank 4 by means of supply pipe 3. A tubular, spiral heat exchanger 3a is located within the cylinder and forms junctions 4a at the flow side and 5 on the return side of a primary water heating circuit.

Junction 5 is connected to return pipe 6 and junction 4a is connected, via branch duct 7, to a branched flow pipe 23.

A self-priming means 8 is located within the cylinder comprising an upper 9 and lower 10 chamber divided and/or separated by walls 11 and 1 lea. Communication is provided between lower and upper chambers by means of a first duct 12 extending from the wall 1 1a (passing through wall 11) and having an open end spaced from the roof of the container, i.e. in the upper part of the upper chamber 9. The spacing provides for an air pocket or pockets in use to separate primary from secondary water.

The upper chamber 9 is in communication via a third duct 1 5 with the remaining section of the container 1. A second duct 1 b is connected to a hot water draw-off 17 and expansion vent 18 which communicates to atmosphere over the cold feed tank 4. The lowermost end of duct 16 is located at or near the bottom of the upper chamber. Expansion vent 18 serves as atmospheric outlet in the event of expansion/overheating of water in the primary or secondary circuits.

The lower chamber 10 of the self priming means 8 has a base aperture 20 in communication with external junction 22, for connection to a primary heating circuit and with an automatic air-vent 25 by ancillary ducts 21 and 24 respectively. Auto-vents are known to those skilled in the art and may comprise a valve which opens when dry but-seals when wet. Provision may be made in such auto-vent for manual operation to override the automatic function.

A modification of this system is shown in Fig. 2 particularly suited for domestic hot water system having a pumped primary circuit.

In this embodiment pipework 7 from junction 4a is connected to the primary (central heating) flow incorporating a pump 27, flow share valve 28, L.S. valve 29, primary flow 30, primary return 31 and boiler flow pipe 26. The upper chamber constituted by partition wall 11, extending the full internal width of the container 1, and the roof 32 serves as an internal metal 'dome' for positive separation of primary and secondary water in both Fig. 1 and Fig. 2 embodiments.

Operation from initial priming is now described. Water is fed directly into the cylinder 1 at 3 from a normal cold feed tank 4. This causes the cylinder to become pressurised and water then passes through third duct 15 into the upper chamber 9 venting at atmosphere above the cold tank 4. Water then passes from the upper chamber internally into the lower chamber 10 (of the self-priming means 8) via the first duct 12. As pressure is continualiy being exerted from the cold water tank via the hot cylinder, this will continue to fill the self-priming means which in turn will fill the central heating system.

The auto-vent, for example as sold under the Trade Mark "Purg-O-Mat", will allow all air to be discharged from the central heating circuits and automatically cut off any further supply of water to the central heating system, once this primary circuit is filled.

Such continuous filling will automatically take place at any time water is removed from the central heating circuit and requires no further manual priming or adjustment. Normal expansion and contraction of the heating water takes place within the self-priming means and cannot mix with hot water stored in or supplied from the secondary circuit. In the event of thermostat failure, on the boiler, overheating of the boiler or central heating circuits may result which will automatically discharge through the self-priming means and pass via the vent pipe to atmosphere.

When the malfunction has been corrected, the self-priming means will automatically re replenish any loss of water within the primary central heating circuit. As all feed and expansion from the heating circuit is fed into the self-priming means, this prevents contamination of primary heating water with secondary domestic hot water stored in the container.

In another embodiment of the invention the container comprises a rectangular-shaped tank instead of a cylinder as described.

Claims (8)

1. A principal container for a water heating system comprising a heat exchanger capable of connection to a primary water heating system, self priming means located within the principal container interior comprising, when the said container is in an upright position, a pair of communicating upper and lower chambers capable of receiving or transferring water and/or air, the said two chambers communicating through a first duct, a second duct extending from or near the bottom of the upper chamber which can communicate to atmosphere and provide a hot water draw-off, the lower chamber capable of connection to both a primary heating circuit and an external autovent.

2. A container as claimed in Claim 1 in which the upper and lower chambers are spaced apart by one or more partitions.

3. A container as claimed in Claim 1 or 2 in which the upper chamber comprises a divided part of the principal container.

4. A container as claimed in any preceding claim in which the lower chamber is or forms part of a separate internal container having a sidewall spaced from the interior surface of the principal container.

5. A container as claimed in any preceding claim further including a third duct communicating the upper part of the upper chamber with the remaining section of the principal container.

6. A principal container for a water heating system substantially as herein described and illustrated.

7. A hot water storage and supply system incorporating a container as claimed in any preceding claim.

8. A hot water storage and supply system substantially as herein described and illustrated.