General question about repeated Immersion Heater failure

[Ian]

I'm wondering if anyone can help me with a slightly vague question about Immersion Heaters. The information I have is secondhand and concerns my mother's ageing Immersion Heater. Seemingly it has run without a glitch for about 25 years but earlier this year failed. At this time both the heating element and thermostat were replaced. A month or so later, however, the thermostat had apparently failed again and was once again replaced. A couple of months later the system had failed again and this time a wire supplying the unit had 'burnt out' and was trimmed and reconnected. This was about 6 weeks ago and now today the system has failed once again.

I have no specific knowledge of this kind of thing myself but it does seem odd that the Immersion Heater has now failed four times in almost as many months. Could there be some underlying cause for all these repeated failures which hasn't been detected? Would it be better getting rid of the whole thing and getting a new one? Would really appreciate any help or suggestions from those with more knowledge of such things.

[mrcheerful]

sounds like a badly fitted mickey mouse part/parts.

mrcheerful

[David W.E. Roberts]

If you replace parts, then you have no proof that the next failure was not due to a fault in the rest of the immersion heater.

If you fit a new heater and it fails you can get it replaced under the 'sale of goods' act..

Labour and parts costs for repair must by now have outstripped the cost of a new heater.

New heater sounds the way to go.

HTH Dave R

[Set Square]

You seem to have overlooked the fact that, on the initial failure earlier this year, the whole lot (i.e. element + stat) *was* replaced - but didn't prevent subsequent failures.

My suspicion is that there is a problem further back in the wiring - switch/timer?/fuse etc. which is causing the contact to be intermittent. The whole circuit - right back to the CU - needs to be tested and examined.

[N. Thornton]

it worked fine with the old heater, so its unlikely the system design's amiss. So I'd have to agree with duff parts. Make sure the replacement element is as long as the original was, clean all wire ends up bright before connecting them, and get decent quality parts in there. And set the stat temp to something reasonable like 60 or 65, not to 95 degrees. You dont by any chance have a stat separate to the heater element do you? If its a separate bolt on one, its always possible it might not be making proper clean contact with the tank or something. Best use a heater/stat in one.

Regards, NT

[John]

"Cooking" of the end of the connecting flex indicates a poor connection. Possibly the old flex was heat damaged by the first failure and/or the new unit was not correctly installed/tightened. Once the connection started to heat up it would quickly take out the new bit. I dont think there is much likelihood of any trouble being located further away than the flexible connecting to the unit. My suggestion would be to replace the flex and any other parts showing heating damage, making sure the flex is of no less than 1.5mm^2 heat resisiting type. BTW any immersion in frequent use in a hard water area will fail in short order by comparison to one in soft water (Wolds water causes a copper sheath immersion to fail in about 15 months) If you are in a hard water area I'd suggest an Incoloy element or similar