GB2181824A

GB2181824A - Water heater providing automatic feed for a central heating system

Info

Publication number: GB2181824A
Application number: GB08525814A
Authority: GB
Inventors: Jeffrey Baguley
Original assignee: Baguley & Sons Ltd J
Current assignee: Baguley & Sons Ltd J
Priority date: 1985-10-19
Filing date: 1985-10-19
Publication date: 1987-04-29
Also published as: GB8525814D0

Abstract

An immersion water heater 10 is supplied with hot water from a central heating system to heat water within a tank 14 and includes a helical conduit 11 wrapped around a cylindrical hollow body 16 having upper and lower chambers 18, 19, the lower chamber 19 being open at its lower end. A first flow conduit 20 provides a flow path from an upper part of the lower chamber 19 to a position near the top of chamber 18 and a second flow conduit 21 provides a fluid flow connection between a lower part of the upper chamber 18 and a lower part of the helical conduit 11 so that automatic filling and replenishment of the central heating system from the tank 14 occurs but the arrangement provides an air-lock to prevent mixing between the two systems. <IMAGE>

Description

SPECIFICATION Water heater This invention relates to a heater which can be immersed in a water tank, for example a domestic hot water tank, and be supplied with hot water from a central heating system to heat the contents of the tank indirectly.

When domestic hot water and central heating systems exist together it is usual for each to have a separate header cistern for each providing a respective cold water feed. Such duplication is costly and undesirable and a heater structure has been developed and used which incorporates an automatic feed for the central heating system from the hot water tank. An airlock within the heater structure prevents mixing between the contents of the two systems.

This known structure comprises a hollow body having an annular, cylindrical part and, within the annular part, at a lower end thereof, a pair of upwardly extending domed plates. A conduit provides for water flow upwardly from the top exterior of the lower dome to close to the top interior of the upper dome. This conduit serves on fitting and replenishment of the central heating system, to allow flow into the heating system from the tank. During expansion and contraction of the water in the heating system in use, air is transferred between the two domes, at all times preventing mixing between the two systems' contents.

It is an object of the present invention to provide an improved water heater providing for automatic filling and replenishment of a central heating system connected thereto.

Accordingly the invention provides a heater for immersion in a water tank and adapted to be connected to a heating circuit to heat water in the tank indirectly, the heater comprising a helically disposed conduit having upper and lower fluid flow connections by which it can be connected as part of a heating circuit, a hollow body within the helix divided by a baffle into separate upper and lower chambers, a first fluid flow conduit providing a flow path extending from an upper part of the lower chamber to a position near to the upper interior of the upper chamber and a second fluid flow conduit providing a flow path from a lower part of the upper chamber to a lower part of the helical conduit.

The heater of the invention operates hydraulically in exactly the same way as the prior known indirect, feed and vent heater. However, the heater is more efficient, giving a faster re-heat time for an equal heat transfer area, or giving the same reheat time with a smaller heat transfer area.

The body can have generally cylindrical side walling contacting or being disposed close to the conduit forming the helix.

The fluid flow connections to the conduit can be fittings adapted to pass through walling of a hot water tank and be sealed thereto in conventional manner. The upper connection can have or have connected to it an automatic air vent valve to allow escape of air but not water from the heating circuit.

The invention will be described further, by way of example with reference to the accompanying drawings, wherein the single figure is a schematic vertical cross-section through a preferred heater of the invention.

A preferred heater 10 to the invention is made form a material of good thermal conductivity and good resistance to corrosion such as copper. The heater has a main heat transfer portion in the form of a helical coil 11 of circular section tube terminating at its lower end in a fitting 12 and at its upper end in a fitting 13. Fittings 12 and 13 enable the heater to be mounted inside a water tank, a part of whose walling is illustrated at 14, and connected conventionally to a central heating circuit (not shown) in which hot water circulates. The upper end of the coil 11 connects with or has connected to it and automatic airvent valve 15 of conventional construction.

Such valve 1 5 is shown inside the tank, but could easily be connected, for example, to fitting 13 or an adjacent conduit outside the tank.

The coil 11 surrounds and contacts or lies close to the outer cylindrical wall of a hollow central body 16 also made from metal such as sheet copper. Body 16 is divided internally by a baffle 17 into an upper chamber 18 and a lower chamber 19. The lower chamber 19 is open at its base to the interior of the tank and a conduit 20 leads upwards from its top to a position near to the domed top of the upper chamber 18. A second conduit 21 leads from the base of the upper chamber 18 to a lower end part of the coil 11.

The turns of coil 11 are close to and may contact and be secured (as by brazing all along or at intervals) to the material of the body 16.

The heater 10 of the invention operates hydraulically in a manner comparable to that of known indirect automatic feed heaters. In use, hot water from the heating circuit flows in coil 11 transferring heat to the water in the tank indirectly ie without mixing. The body 16 allows flow of water from the tank into chamber 19 and into chamber 18 and to coil 11 upon commissioning to fill the heating circuit.

Thereafter, the air entrapped in chambers 18 and 19 prevents mixing, although replenishment of any shortage of water in the heating circuits occurs. Thermal expansion and contraction of the water in the heating circuit in use is accompanied by and accommodated by transfer of the air trapped between chamber 18 and 19.

Thermally the heater of the invention is con siderably more efficient that the previously known indirect automatic feed heater and can thus give a faster re-heat time at equivalent cost, or give the same reheat time at reduced cost.

Claims

1. A heater for immersion in a water tank and adapted to be connected to a heating circuit to heat water in the tank indirectly, the heater comprising a helically disposed conduit having upper and lower fluid flow connections by which it can be connected as part of a heating circuit, a hollow body within the helix divided by a baffle into separate upper and lower chambers, a first fluid flow conduit providing a flow path extending from an upper part of the lower chamber to a position near to the upper interior of the upper chamber and a second fluid flow conduit providing a flow path from a lower part of the upper chamber to a lower part of the helical conduit.

2. A ;heater as claimed in claim 1, wherein the body has generally cylindrical side walling contacting the conduit forming the helix.

3. A heater as claimed in claim 1 wherein the helical conduit is near to but spaced from the side walling of the body.

4. A heater as claimed in claims 1, 2 or 3 wherein the fluid flow connections to the conduit are fittings adapted to pass through walling of a hot water tank and to be sealed thereto.

5. A heater as claimed in any preceding claim wherein the upper connection has, or has connected to it, and automatic air vent valve to allow escape of air but not water from the heating circuit.

6. A heater substantially as hereinbefore described with reference to the accompanying drawings.