GB2052230A

GB2052230A - Fluid heating equipment

Info

Publication number: GB2052230A
Application number: GB8019090A
Authority: GB
Original assignee: IMI Santon Ltd
Current assignee: IMI Santon Ltd
Priority date: 1979-06-15
Filing date: 1980-06-11
Publication date: 1981-01-21

Abstract

An electrical heating element 11 for an instantaneous water heater includes a helical portion 14 together with a U-shaped portion 15 which is arranged so that it has thermal contact with the uppermost face of the container 10. The water inlet 20 is arranged so as to direct incoming cold water towards this thermal contact region which is in contact with a thermal cut-out device 17. <IMAGE>

Description

SPECIFICATION Fluid heating equipment This invention relates to improvements in fluid heating equipment. It is especially concerned with improvements in electrical water heaters of the "instantaneous" type, i.e. heaters where the water is heated immediately before use as it passes through a container of small volume. Instantaneous water heaters have recently come into general use for hot showers, hand washers and other domestic appliances where relatively small flow rates are required.

Instantaneous water heaters need to be both safe and efficient. High wattage heaters up to 7 kW and above are employed to heat water as it passes through a small container, so that if for any reson the power remains connected to the heating element when the water cannot leave the - container, as for example in closed outlet heaters, there is a risle that the container could rupture under the high pressure which can rapidly develop, A thermal cut-out or other temperature-related safety device is normally installed at the hottest part of the container to ensure that this cannot happen, but the presence of these cut-outs or other devices can lead to other problems associated with the operation of the heater, particularly where the element has a relatively high heat input.

Although cut-outs of rapid response can be provided, the heat stored in the element at the instant of cut-out may be sufficient to cause the temperature or the relatively small volume of water to rise significantly after the operation of the cut-out. If a cut-out responsive to a lower temperature is installed to overcome this problem, the water heater may be prone to what is known as "nuisance tripping" i.e. the thermal cut-out is triggered during normal use, or by a slight drop in the inlet water pressure.

It is an object of the invention to provide both an improved heating element and a container for housing said element for an instantaneous water heater, which significantly ameliorates the problems set out above.

According to one aspect of the invention, an electrical heating element for a water heating container includes a helical portion together with a U-shaped portion extending in a plane parallel to the principal axis of the helix and arranged so that the closed part of the U-shaped portion can lie closely adjacent to or in contact with a face of the container extending in a plane perpendicular to the principal axis of the helix.

The closed part of the U-shaped portion may include a linear length of element extending in a plane perpendicular to the principal axis of the helix, so that it can be brazed by a heat transmitting material to a face of the container co extending in a plane parallel to the linear length.

The U-shaped portion bf the element preferably extends from within the helical portion thereof.

According to a second aspect of the invention we provide a heating element as defined above in combination with a water heating container, both terminal portions of the element extending through one planar end of the container. The U shaped portion of the element preferably has a linear length lying adjacent the same planar end.

The container may incorporate means four directing, inlet water into the region where the linear length of the U-shaped portion lies adjacent to or in The container may be made in several parts and may comprise a right cylinder with plane ends.

contact with the plane end of the container. A thermal cut-out device, responsive to disconnect the electrical supply to the element at a pre determined temperature, may be secured to the outside of the planar end of the container adjacent the linear length of the element. Such a cut-out device may be two or three pole isolator.

An outlet to the container may be provided extending from close to the planar end of the - container adjacent which lies the closed part of the U-shaped portion of the element, said outlet extending in conduit form through an opposite planar end of the container. Alternatively the outlet from the container may extend through the cylinder wall adjacent the ends of the container through which the terminal portions of the element project.

One embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side-elevation, partly cut-away, of a heating element according to the invention within a container; Figure 2 is a plan view of the element of Figure 1;and Figure 3 is a plan view of the element viewed in the direction indicated by arrow A of Figure 2.

A copper container 10 in the shape of a right cylinder is mounted vertically so that its plane ends face respectively upwards and downwards.

The container 10 may be made in two or more pieces which can be soldered or brazed together.

A pre-formed electrical heating element 11 made with a sheath of copper or other corrosion resistant material is positioned within the container 10 so that its two straight terminal portions, 12 and 13 respectively, project through the upper end of container 10. After entering the container from terminal portion 12, the element 11 has a helical portion 14 extending about a vertical axis in a direction towards the base of container 10. The number of turns in the helical portion 14 will depend on the power requirements of the water heater.

Adjacent the container base, the helical portion 14 terminates as the element 11 bends vertically upwards within the helical portion 1 4. Element 11 continues until it reaches the upper end of container 10 where it is bent back through 1860C towards the base of container 10 to form a U shaped portion 15, the closed part of the U touching or positioned very close to the upper end of container 10.A further 1 800 bend in element 1 within the helical portion 14, takes the element 11 to the other terminal portion 1 3. The U-shaped portion 1 5 has a linear portion 16 extending parallel to the inside surface of the upper end of container 10, which portion 1 6 is brazed to the container to provide a good thermal contact at this point.

A thermal cut-out device 1 7 is mounted on the outside of the upper end of container 10 adjacent the linear portion 16 brazed to the inside surface of the upper end. The cut-out device 17 is designed to operate at a pre-determined temperature to isolate the electrical supply to the heating element 11. This temperature will not be reached in normal use of the water heater, since the element is only connected to the electrical supply whilst water is flowing through the container 10. A flow-responsive switch (not shown) is incorporated in the water circuit for this purpose.

If however, for any reason the electrical supply to element 11 is not cut off when the water flow ceases, the thermal cut-out device 1 7 will isolate the electrical supply to element 11 upon reaching the pre-determined temperature. The cut-out device 1 7 can be re-set manually but this facility is not usually exposed to the user, since the container 10 and its associated switches, cut-outs etc is housed in a closed casing.

The container 10 has a water inlet extending through its cylindrical wall adajacent the base The inlet is in the form of a conduit 18 running parallel to the base, which terminates at an end cap 19.

An orifice 20 in the uppermost side of the conduit 1 8 directs the inlet water, which is under pressure, upwardly towards the U-shaped portion 15 where it lies adjacent the upper end of the container 10.

The orifice 20 is positioned so that the helical portion 14 of the element 11 does not baffle the inlet water, so that cold inlet water moves upwardly inside the helical portion 14. We have found that this arrangement of the water inlet, and the direction of the inlet water flow, is important in preventing "nuisance tripping" of the termal cutout.

A heated water outlet conduit 21 extends from a position centrally within container 10 above the helical portion 14 of the element 1 1, through the base of container 10. A control valve (not shown) may be incorporated in the outlet conduit either remotely from or close to the water heater.

Claims

1. An electrical heating element for a water heating container, said element including a helical portion together with a U-shaped portion extending in a plane parallel to the principal axis of the helix and arranged so that the closed part of the - U-shaped portion can lie closely adjacent to or in contact with the face of the container extending in a plane perpendicular to the principal axis of the helix.

2. An electrical heating element as claimed in Claim 1 in which the closed part of the U-shaped portion includes a linear length of element extending in a plane perpendicular to the principal axis of the helix.

3. An electrical heating element as claimed in Claim 1 or Claim 2 in which the U-shaped portion of the element extends from within the helical portion thereof.

4. An electrical heating element as claimed in any of Claims 1 to 3 in combination with a water heating container, in which the terminal portions of the element extend through one planar end of the container.

5. The combination of Claim 4 in which the Ushaped portion of the element has linear length lying adjacent the planar end of the container through which the terminal portions of the element extend.

6. The combination as claimed in Claim 4 or Claim 5 in which the container comprises a right cylinder with plane ends.

7. The combination as claimed in Claim 5 in which the container incorporates means for directing inlet water into the region where the linear length of the U-shaped portion of the element lies adjacent to or in contact with the plane end of the container.

8. The combination as claimed in any of Claims 4 to 7 in which a thermal cut-out device, responsive to disconnect the electrical supply to the element at a pre-determined temperature, is secured to the outside of the planar end of the container adjacent the closed part of the U-shaped portion of the element.

9. The combination as claimed in any of Claims 4 to 8 in which the outlet to the container extends from close to the planar end of the container adjacent which lies the closed part of the Ushaped portion of the element.

10. The combination as claimed in Claim 9 in which the outlet extends in conduit form through an opposite planar end of the container.

11. An electrical heating element as claimed in Claim 1 and as hereinbefore described with reference to and as shown in the accompanying drawings.

12. An electrical heating element in combination with a water heating container as claimed in Claim 4 and as described with reference to and as shown in Figure 1.