Immersion heater thermostat problems

[Peter.N.]

I have recently replaced three immersion thermostats and two of them have failed again, one going open circuit and the other going short circuit. I have very rarely had one fail before in the 45 years I have been here. My voltage is a bit high at 240+ volts but it always has been, we are the only ones on the 11kv transformer.

The replacements I have used are Backer which are generally OK, is there a problem with them, has anyone else had this trouble?

I checked the resistance of the heaters and it was about right for 3kw although I can't remember exactly what it was now, I think about 20 ohms.

Peter

 

[Burnerman]

When I need particular reliability for electrical gear (hopefully) I head for C.E.F. guess what, they supply Backer.....never had a problem!
The curse of the orient, maybe?
John

 

[Peter.N.]

Hi John, do you run these forums single handed? This a very strange situation, first the one on my off peak water heater failed, at least I thought it had but it turned out to be the spur box that had melted! I tested the heater and it was OK but the daytime heater which wasn't connect anyway was leaking. Then my sons off peak immersion failed, he lives over the border in Devon but only about 3 miles away, anyway that was an o/c thermostat so I took the one out of my redundant heater and fitted it - it didn't work, o/c, I then took the one from his daytime heater which he wasn't using and fitted that - still didn't work, that one was o/c.

I ordered three new ones, the first one failed after a few days, o/c again, fitted another one, that worked for a few weeks and then went s/c, it doesn't switch off and keeps tripping the over temperature sensor, so he resets it every night and gets a tank full of near boiling water - can't remember what happened to the third one but I am now thermostatless again.

I don't think I have had a thermostat fail in 50 years so what is going on. I have been looking for a different make but there doesn't seem to be one.

Peter

 

[Burnerman]

Bizarre, that one.....are you getting any voltage surge, do you think? Mind you, that sounds a bit corny as surely other more delicate items would bite the dust first.....
I'm just wondering - based on no facts whatsoever - that the pocket that the stat lives in is getting hot spots.....limescale or whatever? I believe that the better immersion elements have a high titanium content just to correct that very cause, but I've no personal experience. My own immersion is 25 years old, infrequent use but I never give it a thought. Our water is pretty soft, I think.
John

 

[Peter.N.]

Martins water is soft and there was a lot of calcium piled up at the bottom of the tank, I got a digger in and cleared it out! The tube itself is OK in fact I may have fitted a whole new unit - I can't remember any more. Our water is just the opposite and leaves brown stains on everything and eats through the fittings - and the tanks! It comes from our well.

I think I will just have to bite the bullet and get yet another thermostat.

Peter