Immersion heaters an safety cut outs

[revjames]

Just been to a house where my brother (plumber) had been called as there was no hot water. I tried to help him ove rthe phone and diagnosed a faulty stat. He went back and changed it. Still not working.

I went there today and found there was a safety cut out built in to the top of the element. There was a button on top and I had a fiddle with it but was not aware of a positive 'click' to indicate I had re set it. Put my meter across the element and there was 240V. Putmy ear on the tank and you could hear that it was working.

Customer told me that the last time it worked it got really hot. Makes me wonder if thermostat failed closed and cut out operated. Plumber came and changed stat. But still not working as cut out still o/c. Will have to wait and see now. can the cut outs themselves be replaced? tested element which seems fine.

 

[ProDave]

I've only ever seen the safety cut out built into the normal thermostat.

Do you have a pic of this one? Was it a mains pressure tank as they have different types of thermostat.

 

[bengie]

i've seen both types and found the ones with the seperate cut-outs to be more reliable, at work we fit heatrae immersions with RDT stats and they are a bloody nightmare, they trip for the hell of it with the top loading elements being far worse than side loading ones, its got so bad we are no longer fitting tanks with top loading elements.

 

[revjames]

Sorry didnt take a pic. The cut out was fitted into the main element housing. It looks like it might unthread but do I need to drain it first? Not a mains pressure tank, header in loft.

 

[Riggy]

Sorry didnt take a pic. The cut out was fitted into the main element housing. It looks like it might unthread but do I need to drain it first? Not a mains pressure tank, header in loft.

Yes you can unscrew them, the thread goes into the immersion metalwork only so you can remove without draining. As stated above, much more reliable (in my experience) than those built into 'stat.

 

[batty]

These cut outs do seem to be a problem have been to quite a few and some plumbers don't seem to know they exist.

 

[sparkytim]

BS Regulation FOR ALL NEW immersions and REPLACEMENTS.

 

[mikep]

water temperature stat set at 55 degree's and there is a secondary safety stat set at 65 degrees in case the first one fails which is manual reset so if the 55 degree goes over limit then the safety one cuts the circuit otherwise it boils the water, not good in certain conditions.

When water turns to steam it expands by 1400 times

see vid.

https://www.youtube.com/embed/jbreKn4PoAc?feature=oembed

 

[bengie]

but we don't have sealed cylinders.

 

[mikep]

Does not say what type of cylinder it is at the start could be a Megaflo, they should all now be fitted with the safety cut out, the vids only an extreme situation which sometimes happens.

Mike.

 

[revjames]

Thanks for the replies, havent heard anything back so fingers crossed all is well.