Immersion heater overheating

Zippymark · Sep 13, 2020

Hello, i have a job that had an immersion heater overheating, i didn't know how old it was so just replaced it as they don't seem to last these days. Within a week it had overheated, so i reset it. Now a month later it has gone again, and maybe once more.

It's a 14" immersion, incoloy/titanium this time, on a direct combination cylinder, so the only source of heat. There is not a shower pump or anything. Going by the amount of plastic immersion heater caps littering the loft, this happens pretty often.

Can anyone think of any other reasons this keeps on happening? The only other thing i can think to check is the state of the ballvalve, i guess if that's getting stuck or running slowly it might be emptying and overheating because of that?

Any help appreciated, thankyou.

Murdoch · Sep 13, 2020

Turn the setting down ?

PETE 123 · Sep 13, 2020

I had the same so removed to fit new one found elements had moved/warped to very near where stat slides through pocket so may of picked up extra heat to trip that way.

steadyon · Sep 13, 2020

1. Is it in a hard water area? If so, then then cylinder may have so much limescale in it that it is surrounding the element and causing it to overheat.
2. If so, then:
2a. Remove immersion and try and scoop out limescale through opening. OR
2b. Replace cylinder.

Zippymark · Sep 15, 2020

steadyon said:
1. Is it in a hard water area? If so, then then cylinder may have so much limescale in it that it is surrounding the element and causing it to overheat.
2. If so, then:
2a. Remove immersion and try and scoop out limescale through opening. OR
2b. Replace cylinder.

London, so yes. I've visitied yesterday and turned to almost its lowest setting so we'll see if that helps but in future i'll definitely shine a torch in to see how much limescale there is 👍

John.g · Sep 15, 2020

Also check/take a picture of immersion head, some (normally, older type) had a separate hi limit stat attached to the immersion boss, if fitted, change this and the control stat to a combined control/hi limit stat which may cure the problem.