GB2542161A

GB2542161A - An immersion heater unit

Info

Publication number: GB2542161A
Application number: GB1516009.6A
Authority: GB
Inventors: Murphy Thomas
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-09-09
Filing date: 2015-09-09
Publication date: 2017-03-15
Anticipated expiration: 2035-09-09
Also published as: IE20160223A1; GB2542161B; GB201516009D0

Abstract

An immersion heater for a water cylinder or water tank comprises a base section 2 having heating elements 7, a thermostat, and thermostat pocket (6, figure 3), a detachable middle section 3 connected to a power supply, thermostat sleeve and an electrical inspection chamber, and a removable cover section 24 having a thermostat reset button and securing fixings, where detaching the middle from the base disconnects the mains power supply to the immersion. The base may comprise an upper section having a rod thermostat and plug pins, and a lower section comprising heating elements and a rod thermostat pocket. The heating element may comprise single, dual, or multiple element rods. The connection means in the middle section may comprise hollow connection points receiving the plug pins. When the middle is detached from the base, the earth pin may be the last to disengage and closure means on the hollow connection points may close to prevent access to the power supply. The cover 24 may comprise a large cover section covering the supply connections and a small cover section 5 covering the thermostat and an over cut out reset button, the small cover section allowing safe inspection of the thermostat.

Description

An immersion heater unit

Introduction

The invention relates to an immersion heater unit for a hot water cylinder or tank.

The lifespan of an electric immersion heater in a water cylinder in a domestic household can be short. In many households the element fails and the immersion needs to be replaced every couple of years or sooner depending on usage. In areas where the water is particularly hard this can happen more often.

The task of inspecting or replacing the heating element or thermostat in a water cylinder can be a difficult, unsafe and complex task and quite costly.

There is a need for an improved immersion heater which is easier and faster to replace which also has safer access to the electrical terminals and thermostat.

Statements of Invention

According to the invention there is provided an immersion heater unit for a water cylinder or tank comprising; a base section comprising heating elements, electrical connections, thermostat, and a thermostat pocket; a detachable middle section comprising connection means to a power supply, electrical connections, thermostat sleeve and an electrical inspection chamber; and a removable cover section comprising a surface mounted thermostat reset button and a holding down bolt and securing fixing which are flush with the cover; wherein detaching the middle section from the base section disconnects mains power supply to the immersion.

In one embodiment of the invention the middle section comprises a thermostat cover sleeve. This ensures the correctly sized and compliant thermostat is fitted to the immersion.

In one embodiment of the invention the base section comprises an upper and lower section, the upper section comprising a rod thermostat, plug pins and electrical connections, the lower section comprising heating elements and a rod thermostat pocket. Preferably the plug pins comprise any one or more of Earth, Live and/or Neutral connections. Most preferably the earth pin is the last pin to disengage when the middle section is detached from the base section.

In one embodiment of the invention the heating element comprises single, dual or multiple element rods.

In another embodiment of the invention the connection means in the middle section comprise hollow connection points connectable to a power supply. Preferably the hollow connection points receive the plug pins in the base section connecting the heating element to a power source. Most preferably the immersion heater unit comprises closure means on the hollow connection points wherein when the middle section is detached from the immersion head section the hollow connection points are closed to prevent access to the power supply.

In one embodiment of the invention the removable cover section comprises a large cover section and a small cover section, the large cover section covering the electrical power supply connections and having a power indicator light, the small cover section covering the thermostat with an over cut out reset button wherein removal of the small cover section provides safe means to inspect and access the thermostat without coming into contact with the power supply connections.

In another embodiment of the invention the removable cover section comprises grooves, overlaps and raised areas to prevent any leaking water to come into contact with the electrical connections.

In one embodiment of the invention the over cut out thermostat reset button is flush with the raised area on the cover section when the over cut out thermostat trips. Preferably the large cover section comprises a holding down fixing which is flush with the cover.

In one embodiment of the invention the immersion heater unit comprises at least one thermostat. Alternatively the immersion heater unit comprises at least two thermostats.

In one embodiment of the invention the immersion heater unit comprises an acoustic alarm means.

In one embodiment of the invention the base section comprises a threaded fitting manufactured from any one or more of brass, bronze, stainless steel, heat resistant thermoplastic material.

In one embodiment of the invention the removable cover section and electrical inspection chamber are manufactured from any one or more of a flame resistant, heat resistant thermoplastic material.

In another embodiment of the invention the heating element is manufactured from any one or more of stainless steel, incoloy, titanium, copper.

In one embodiment of the invention the immersion heater unit comprises an indicator light placed below the lid.

In another embodiment of the invention the immersion heater unit comprises a surface mounted indicator light.

In a further embodiment of the invention the immersion heater unit comprises a hinged cover.

In one embodiment of the invention the immersion heater unit comprises a single cover attached to the middle section.

Brief Description of the Invention

The invention will be more clearly understood from the following description thereof with reference to the accompanying drawings in which: -

Fig. lisa side perspective view of an immersion unit of the invention;

Fig. 2 is a side perspective exploded view of the immersion unit of Fig. 1;

Fig. 3 is an exploded perspective view of the immersion unit of Fig. 1 from the below;

Fig. 4 is a side perspective view of the immersion unit of the invention in situ on a hot water tank;

Fig. 5 is a top plan view of the immersion unit of the invention with the small access cover removed; and

Fig. 6 is a top plan view and sectional view through the cover lids of the immersion unit of the invention.

Detailed description

The present invention provides an improved immersion heater unit which makes the inspection, thermostat re-setting and/or replacement of an immersion heater element in a hot water tank faster, easier and safer to perform. The immersion heater unit of the invention is intended to replace the conventional immersion electrical terminal box typically found on a hot water tank. The immersion heater unit of the invention may be used in a domestic, industrial or agricultural setting.

The most common type of domestic immersion heaters commercially available are the dual element immersion and the single element immersion. The dual element immersion has a long element for heating enough water for a bath and a small element for heating water for a sink.

The conventional domestic immersion heater on the market at the moment comprises an element body, a threaded hexagonal brass boss and a steel or plastic terminal box which covers the electrical connections and is held in place by a surface mounted hexagonal nut. The electrical connection points are welded onto the element rods and the wires are securely fixed to the connections with screws. The four connections on the dual immersion are the Earth- green and yellow, Live to bath- Brown, Live to sink- Black and Neutral to the thermostat -Blue. On the single immersion there is only one live wire and therefore only three connections to be made.

The typical immersion heaters are screwed onto the hot water cylinder or tank and the wiring to the mains power supply is then directly connected to the terminal points by the installer. The typical immersion head contains a thermostat unit which has two separate thermostats built into it or the immersion may contain two separate thermostats one of which has a re set button. One of the thermostats functions when the water temperature reaches 60 degrees Celsius which is what it is normally set at and it will reset itself when the water cools down. The other thermostat is an over cut out thermostat. This thermostat trips out the power supply to the immersion elements if the water should reach 85 degrees Celsius. This is to stop a situation where scalding may occur. This thermostat needs to be reset manually be pressing the reset button on the thermostat. In most instances the cover lid on the immersion will have to be removed to press the thermostat reset button or to check the wiring. The cover on a conventional terminal box is typically made of steel or plastic and secured by a hexagonal nut to the immersion body. When the cover on the terminal box is removed all the wiring connections are exposed and live if the electrical power supply has not been manually turned off.

Typically in order to replace an immersion element the wiring has to be exposed and disconnected before the immersion heating element can be removed from the water tank. This is to allow the large hexagonal immersion spanner to fit down on to the head of the immersion. Accidents resulting in electrocution have occurred with people forgetting to switch off the power supply to the immersion heater when they want to access and disconnect the wiring or someone else inadvertently switching the power back on at the main consumer unit.

For this reason plumbers sometimes are not prepared to interfere with the wiring and power supply to the immersion and the services of an electrician are therefore required. Employing the services of an electrician as well as a plumber add significantly to the cost of replacing or simply inspecting an immersion heater.

Figs. 1 to 6 show the immersion unit of the invention. Figs. 2 and 3 show the inner workings of the immersion unit of the invention in more detail. The base section 2 (Fig. 1) comprises an upper and lower section, the upper section comprising a rod thermostat 9 and three individual plug pins 10 and earth pin 18 (Fig. 2), the lower section comprising the heating elements 7 and rod thermostat pocket 6 (Fig 3) which extend into the water cylinder/tank 19 (Fig 4). The heating element 7 may be a single, dual or multiple element rods and vary in length depending on the requirements and size of the cylinder. The immersion base section 2 has a threaded bolt 20 for securing the middle section 3 to the base section 2. The middle section 3 is then secured to the base section 2 using a securing fixing 14 (Fig 1).

The base section 2 comprises plug pins 10 and 18 corresponding to the different connections Earth, Live to bath, Live to sink and Neutral to the thermostat. Two of the plug pins are fixed to the heating element rods 7 and the other two plug pins are fixed to the immersion base section 2. The round plug pins 10 are mechanically fixed to the element rods and immersion body by means of threaded fixings or any other suitable means. The base section 2 also has a rod thermostat 9 with a built in over cut out re-set button 21 (Fig 2). The plug pins 10 and 18 are typically manufactured in brass or steel however any other material commonly used in the field may also be used.

The immersion unit has a thread 8 on the underside of the base section 2 (Fig 1) which allows it to be connected to a cylinder or tank which has a corresponding threaded fitting using a large hexagonal immersion spanner. Alternatively the immersion base section 2 may have a flange fitting with a number of holes which will allow it to be fitted to a cylinder or tank which has a corresponding flange fitting by use of bolts or other suitable fittings.

The middle section 3 has hollow connections 22 (Fig 3) which are connected to a mains power supply 16. The hollow connections 22 are manufactured from brass or any other suitable material and fit snugly over the plug pins 10 and 18 in the base section 2 when the middle section 3 is placed over the base section 2. There may be three or four connections depending on the type of immersion heater used. The middle section 3 has an electrical inspection chamber 23 (Fig 2).

By detaching the middle section 3 from the base section 2 the hollow connections 22 are easily disconnected from the plug pins 10 which ensures that the power supply connection to the base section 2 is instantly and safely broken. The earth pin 18 is longer than the plug pins 10 and will always be the last pin to disengage. All the wiring within the middle section 3 is self-contained and no electrical connections are exposed when a person is changing the immersion or checking the thermostat.

An additional safety element on the middle section 3 comprises a self-closing spring loaded device which closes over concealing the hollow live connections 22 immediately the middle section 3 is lifted from the plug pins 10. The middle section 3 operates like a typical wall socket. Only when the earth plug pin 18 is partially engaged with the corresponding earth connection on the middle section 3 will the hollow connections 22 for the other plug pins (neutral and live) be open. When the middle section 3 has been removed from the base section 2 the hollow connections are automatically closed.

The middle section 3 may be manufactured from a heat resistant and flame proof thermoplastic or any other suitable material. It may be approximately 80mm in diameter and approximately 55mm high. It is not ideal to have a steel lid covering live connections. When replacing a steel lid if the power is not disconnected and if the lid should make contact with a live terminal the person working on the immersion could be electrocuted.

Once the middle section 3 has been detached from the base section 2 then the mains power supply will have been safely disconnected. While the drawings show a top entry type immersion heater the immersion heater of the present invention may also be used for side-entry immersion elements.

Since 2004 an additional over cut out safety thermostat is now required on all immersions as it plays an essential role in the safety of the units. The safety over cut out thermostat operates if the normal thermostat fails and prevents the water reaching a dangerously high temperature. Immersion manufacturers now have to supply immersion heaters that contain two thermostats, some immersion manufacturers will provide one thermostat unit with two thermostats built into it while others will provide an immersion with two separate thermostats. On immersions containing two separate thermostats some tradesmen have been known to by-pass the over cut out safety thermostat and wire the current immersion directly into the normal thermostat, which is something that should never be done. On immersions containing a single thermostat with a built in over cut out thermostat and reset button reset button when the thermostat fails and the tradesman is replacing the thermostat some have been known to fit a standard thermostat with no safety over cut out thermostat or reset button This is highly dangerous. With the immersion unit of the present invention it is not possible to by-pass the thermostat, or fit an incorrect thermostat on.

In the past young children asleep in their beds have died by scalding as a result of water storage tanks in the attic filling up with boiling water which had travelled up through the expansion pipe from the hot water cylinder causing the water tank to melt and water cascading down through the ceiling onto the sleeping children in beds beneath. The problem was caused by a faulty thermostat on the immersion heater which had been left turned on.

The problem with both of these thermostats is that when the safety thermostat fails there is nothing to prevent the electrician, plumber or householder from buying a thermostat without a safety over cut out thermostat which is readily available and fitting it in place of the safety thermostat . It will work perfectly but is highly dangerous as it does not have the over cut out thermostat fitted to prevent a repeat of the scalding incidents above.

The immersion unit of the present invention has a thermostat sleeve 13 (Fig 3) which fits snugly around the thermostat. The thermostat sleeve 13 ensures that only the correctly sized suitable and compliant thermostat is used.

The cover section 24 (Fig 1) has two parts, a small cover section 5 and a large cover section 4. The small cover section 5 comprises an independent thermostat reset button 11 which connects with the built in over cut out reset button 21 on the rod thermostat in the base section 2 ( Fig 5). The small cover section 5 can be removed when checking for current across the rod thermostat terminals with a multi meter. The large cover section 4 sits neatly down onto a power indicator light 12 (Fig. 5) detachably connected to the internal wiring of the immersion. When the thermostat trips out the indicator light 12 illuminates to indicate a problem. In addition in the event that the bulb in the indicator light 12 does not light up another indication of a fault is when the thermostat reset button 11 pops up. This is a second indication to alert the homeowner that something is wrong with the immersion heater.

When the smaller section 5 is removed as shown in Fig. 5 the live connections supplying power to the plug pins 10 remain covered by the larger cover section 4 so there is no risk of accidental electrocution. The larger cover section 4 should only be removed by a qualified or competent person carrying out more complex electrical investigation if required.

The cover sections 4 and 5 are secured to the middle section 3 by four small screws 15 (Fig5) and can be easily removed to inspect either the rod thermostat or the electrics. All the lid securing fixings are flush with the cover. When the thermostat reset button 11, which is normally in a depressed position, pops up to indicate a problem with the immersion the button 11 is flush with the raised area of the cover section 25 (Fig 6).

The cover section 24, when the small 5 and large 4 cover sections are in place, has an overlap 26 , groove 17 and raised areas 25 (Fig 6). The grooves and raised areas prevent water ingress into the electrical compartment. Any water that may get between the cover sections is channeled away over the side of the lid by the groove 17. The raised area 25 prevents any water entering through the reset button or indicator light. The screws 15 and flush securing fixing 14 each tighten down on a gasket to make them watertight. The overlap 26 on the lid prevents any water running off the lid from entering the electrical compartment thereby ensuring that any water from leaks or other source is safely diverted away from the inner workings of the immersion heater. The cover of the immersion heater of the present invention is manufactured from a heat resistant and flame proof thermoplastic or any other suitable material.

Conventionally domestic immersions are mounted on the top of a water cylinder however they can also be mounted on the side of a cylinder. Depending on the height of the cylinder there can be more than one immersion mounted on the side of a cylinder. Almost all domestic immersions currently on the market have a steel or plastic lid covering the electrical connections which is secured in place by a 5mm hexagonal nut threaded down onto a holding down bolt.

The problem with this type of fixing is that it is surface mounted on the lid and sometimes it may come loose as a result of expansion and contraction caused by heat transfer from the hot cylinder or it may not have been tightened down properly the last time the lid was removed to re-set the immersion. When the cylinder is located on the floor of a hot press or airing cupboard or the immersion heater is side mounted at a low level on the water cylinder the immersion can pose a health and safety risk. A child could easily remove a loose nut and remove the lid of the immersion exposing the electrical connections. If the immersion was turned on when this happened the child would be electrocuted if they touch the live connections.

To prevent such an incident the immersion heater of the present invention has a slightly recessed flush fitting 14 (Fig. 5) on top of the electrical compartment which can be opened by a screwdriver or similar tool. Even if the middle section 3 containing the electrical connections was removed there is no risk of electrocution as the power is automatically disconnected as soon as the electrical compartment is removed.

The present invention provides an improved immersion heater 1 which is intended to replace the conventional steel or plastic terminal box set up on a water heater.

All the parts of the immersion heater of the invention comply with the required regulations. The thermostat complies with BS EN 60335- 2- 73. The plug pins comply with BS1363. The wiring on the immersion complies with BS7671.

The immersion heater of the present invention is cost effective. Currently when a new heating element is required for a hot water cylinder or tank the whole immersion heater unit including the rod thermostat will be removed and replaced as at present all replacement immersion heaters are supplied with a rod thermostat fitted. In comparison with the immersion heater of the present invention only the base section 2 containing the plug pins 10 fixed to the element rods 7 needs to be replaced. No new thermostat, cabling or wiring would be required and the middle section 3 containing the electrical connection is re-useable when just needing to replace the heating element. The immersion heater of the present invention is more economical to replace.

The immersion heater of the present invention has many advantages over the conventional immersion heater currently available. It is safer to work with , it is much easier and faster to inspect the thermostat and/or replace the heating element. After the initial wiring there is no need for any electrical work to be carried out thereby eliminating the cost of an electrician’s services. By simply removing the middle section 3 from the base section 2 of the immersion heater the householder has safely disconnected the mains power supply to the immersion. This may also have insurance benefits as the semi-skilled person or plumber does not have to deal with live wiring in examining and replacing the heating element.

The semi-skilled person or plumber is able to examine and replace the immersion element themselves and in the case of many dispense with the need of an electrician to carry out what is essentially a very simple task.

The invention is not limited to the embodiments herein before described which may be varied in detail.

Claims

1. An immersion heater unit for a water cylinder or tank comprising; a base section comprising heating elements, electrical connections, thermostat, and a thermostat pocket; a detachable middle section comprising connection means to a power supply, electrical connections, thermostat sleeve and an electrical inspection chamber; and a removable cover section comprising a surface mounted thermostat reset button and a holding down bolt and securing fixing which are flush with the cover; wherein detaching the middle section from the base section disconnects mains power supply to the immersion.

2. An immersion heater unit as claimed in claim 1 wherein the middle section comprises a thermostat cover sleeve.

3. An immersion heater unit as claimed in claim 1 wherein the base section comprises an upper and lower section, the upper section comprising a rod thermostat, plug pins and electrical connections, the lower section comprising heating elements and a rod thermostat pocket.

4. An immersion heater unit as claimed in claim 3 wherein the plug pins comprise any one or more of Earth, Live and/or Neutral connections.

5. An immersion heater unit as claimed in claim 4 wherein the earth pin is the last pin to disengage when the middle section is detached from the base section.

6. An immersion heater unit as claimed in any of claims 3 to 5 wherein the plug pins on the upper section of the immersion head are connected to the heating element and immersion head section.

7. An immersion heater unit as claimed in any preceding claim wherein the heating element comprises single, dual or multiple element rods.

8. An immersion heater unit as claimed in any preceding claim wherein the connection means in the middle section comprise hollow connection points connectable to a power supply.

9. An immersion heater unit as claimed in claim 7 wherein the hollow connection points receive the plug pins in the base section connecting the heating element to a power source.

10. An immersion heater unit as claimed in claims 7 or 8 comprising closure means on the hollow connection points wherein when the middle section is detached from the immersion head section the hollow connection points are closed to prevent access to the power supply.

11. An immersion heater unit as claimed in any preceding claim wherein the removable cover section comprises a large cover section and a small cover section, the large cover section covering the electrical power supply connections and having a power indicator light, the small cover section covering the thermostat with an over cut out reset button wherein removal of the small cover section provides safe means to inspect and access the thermostat without coming into contact with the power supply connections.

12. An immersion heater unit as claimed in any preceding claim wherein the removable cover section comprises grooves, overlaps and raised areas to prevent any leaking water to come into contact with the electrical connections.

13. An immersion heater unit as claimed in claim 10 or 11 wherein the over cut out thermostat reset button is flush with the raised area on the cover section when the over cut out thermostat trips.

14. An immersion heater unit as claimed in any of claims 10 to 12 wherein the large cover section comprises a holding down fixing which is flush with the cover.

15. An immersion heater unit as claimed in any preceding claim comprising at least one thermostat.

16. An immersion heater unit as claimed in any preceding claim comprising at least two thermostats.

17. An immersion heater unit as claimed in any preceding claim comprising an acoustic alarm means.

18. An immersion heater unit as claimed in any preceding claim wherein base section comprises a threaded fitting manufactured from any one or more of brass, bronze, stainless steel, heat resistant thermoplastic material.

19. An immersion heater unit as claimed in any preceding claim wherein the removable cover section and electrical inspection chamber are manufactured from any one or more of a flame resistant, heat resistant thermoplastic material.

20. An immersion heater unit as claimed in any preceding claim wherein the heating element is manufactured from any one or more of stainless steel, incoloy, titanium, copper.

21. An immersion heater unit as claimed in any preceding claim comprising an indicator light placed below the lid.

22. An immersion heater unit as claimed in any preceding claim comprising a surface mounted indicator light.

23. An immersion heater unit as claimed in any preceding claim comprising a hinged cover.

24. An immersion heater unit as claimed in any preceding claim comprising a single cover attached to the middle section.

25. An immersion heater unit substantially as hereinbefore described with reference to the drawings.