Immersion thermostat and thermal cut out

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My hot water is only heated by an immersion.

When a new tank and immersion were fitted about 1 year ago I started to get problems with the thermal cut out on the immersion being triggered at random stages during the heating process. Sometimes this would be even with the temperature of the water still only tepid.

I understand these thermal cut outs are a fairly new safety requirement.

I was able to initially solve the problem by not using the shelf immediately above the top of the immersion in the airing cupboard. More air seemed to thus circulate and stopped the thermal cut out tripping.

Now despite the same setup it has started tripping again and I keep on having to reset by pressing the little black button down again.

The immersion is a Thermtec Type HS 3kw.

Can anyone help with this problem please?

If I replace the thermostat which I believe can be done without needing to remove the immersion itself or drain the tank does it need to be the identical make of thermostat?
 
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It just needs to be the same length, ensure the power is off and then undo the two terminal screws on the top of the stat, remove the wires and slide the stat out and measure it, they are normalls 7" or 18"
 
It just needs to be the same length, ensure the power is off and then undo the two terminal screws on the top of the stat, remove the wires and slide the stat out and measure it, they are normalls 7" or 18"

Thanks for this. Whats confusing me though is that this thermal cut out does not seem to be integral to the thermostat. It is mounted on top of a brass "lump" next to it with the wiring going through it. Does this make any difference to changing the thermostat to one of a different make to the immersion?
 
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post a picture, the stat normally has the reset switch on it, a dial and two terminals for the live in and out
 
Hi

This immersion element and stat as a 2yr or 5yr guarantee, find out the receipt.


HTH
 
Hi

This immersion element and stat as a 2yr or 5yr guarantee, find out the receipt.


HTH

It was fitted by the plumber so don't have a receipt for the actual immersion etc. So does this type of thermostat have to be replaced like for like or otherwise replace the whole immersion?
 
Turn off water supply to cylinder
Turn off electric, via fused spur, (remove fuse)
Dis-connect wire
With the cylinder full of water, turn the immersion with a box spanner (APPROX 1/4 OF A TURN- DO NOT REMOVE)
You do the above as its easier to turn the immersion with water in.
Drain cylinder with a hose pipe connected to the drain cock. This may take up 45mins (If it is a bottom entry)
If not then drain for 5 mins.
Remove the immersion and buy a new one the SAME length.
You can vacuum out all the lime scale if you want.
Fit new drain cock washer and tighten closed.
Fit an alloy immersion as it will last longer than a copper one.
Smear LSX around base of new immersion then fit new fibre washer and smear more LSX around fibre washer
Fit into cylinder and tighten, don't over tighten it.
Turn on water supply and check for leaks
Connect wiring and replace fuse and turn on.
You should be able to hear a humming sound from the cylinder.
After 1hr go and have a nice shower.
As I tell all my customers "when your having a shower, think of me"
Some people don't find that funny.

If anything above is unclear then please come back.


Andy
 
Turn off water supply to cylinder
Turn off electric, via fused spur, (remove fuse)
Dis-connect wire
With the cylinder full of water, turn the immersion with a box spanner (APPROX 1/4 OF A TURN- DO NOT REMOVE)
You do the above as its easier to turn the immersion with water in.
Drain cylinder with a hose pipe connected to the drain cock. This may take up 45mins (If it is a bottom entry)
If not then drain for 5 mins.
Remove the immersion and buy a new one the SAME length.
You can vacuum out all the lime scale if you want.
Fit new drain cock washer and tighten closed.
Fit an alloy immersion as it will last longer than a copper one.
Smear LSX around base of new immersion then fit new fibre washer and smear more LSX around fibre washer
Fit into cylinder and tighten, don't over tighten it.
Turn on water supply and check for leaks
Connect wiring and replace fuse and turn on.
You should be able to hear a humming sound from the cylinder.
After 1hr go and have a nice shower.
As I tell all my customers "when your having a shower, think of me"
Some people don't find that funny.

If anything above is unclear then please come back.


Andy

Thank you for your comprehensive reply.

Are you saying that it is not possible to just replace the thermostat and thermal cut out with this type of immersion. I understand that can be done without removing the immersion and draining the tanK?
 
9 times out of 10 the immersion is corroded and needs changing. I always change the complete unit, it saves 'go backs'

Andy
 
9 times out of 10 the immersion is corroded and needs changing. I always change the complete unit, it saves 'go backs'

Andy

Thanks - The immersion (and tank) is only about 15 months old and previous immersions have lasted at least 15 years. Is it absolutely not possible with this model (see picture above) to replace just the thermostat or even just the thermal cut out? If I can would it have to be like for like or could I use a different make of thermostat that has the thermal cut out on the thermostat itself rather than to one side where it seems to pick up excess heat causing it to trip?
 

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