Hi All what connection, if any, is there likely to be a connection between the following two events:
- Immersion heater seems to have failed (power going to terminals OK)
- a small leak around the top of the tank, where the heater is fitted ?
Of course my next step is to try and unscrew the heater with a view to replacing; I'm just wondering what failure mode might account for both symptoms.
Cheers Jon N
I have replaced my immersion heater many times. Once, it was so stuck that I tore the copper tank trying to unscrew it. I was able to solder copper patches to repair the breaks, but later, an unknown leak allowed water to get between the copper and the surrounding foam insulation, which then broke into pieces at the top. I eventually replaced the whole cylinder.
Your leak might be just a failure of the fibre ring washer under the heater, in which case the new heater should come with a new one. On the other hand the leak could be due to a tear in the copper caused by a brutal torque during the replacement of your existing heater.
I live in a hard water area, and the heater tubes just corrode away eventually.
None. And it's moot anyway.
NT
Age and general crustyness!
The Leak: age can cause corrosion of the copper or disintegration of the fi bre washer. The heating device itself is not likely to be the cause. Crusti ness acts to plug leaks.
Open circuit: crustiness does raise element operating temp, but too much cr ust normally breaks off, and the element is designed to survive this proces s. It will however accelerate aging to an extent. Age is the killer on this one, these things have finite life.
NT
You talkin' to me?
;-/
Jon N
Which terminals have you checked - the element itself or just the input, which includes a thermostat in series with the element? Check that the stat hasn't failed before doing anything else, because that's much easier to replace than the whole thing.
If you *do* need to remove the immersion heater, start to unscrew it with the tank still full of water so that the weight of the water holds the tank in place. Use a proper immersion heater spanner and tap it round with a rubber mallet. Be prepared for the tank to split in the process!
And don't do it if the element enters the *side* of the tank, low down, otherwise hundreds of litres of water will shoot out of the hole :-(
I had a tank like this so obviously I drained it completely first of all. But when I was describing the hassle to someone at work he said that he knew someone (cue the apocryphal story) who didn't drain the tank. The thread was fairly watertight till he'd almost undone it (otherwise the seepage might have alerted him to what he was about to do!), and then the final turn of thread couldn't withstand the pressure and the element shot out and broke the man's arm, and several hundred litres of scalding hot water (heated by the central heating) cascaded out in a 4"-wide plug of water, burning him in various unfortunate places and running in a torrent down the stairs into the living room.
For the avoidance of doubt, I was not using "crusty" as a synonym for scale. Just as a general comment on the state of the installation. I.e. if its old / nearing end of life that is one factor that connects both events.
Beyond that, there is unlikely to be any direct connection unless say the immersion heater boss is suffering serious corrosion - that may account for the leak and its non functioning.
There is probably one good message to take from that... don't work on a cylinder when its still full of *hot* water - it only magnifies the problems when something goes pair shaped! Let it cool down first.
So much more fun when it's scalding.
NT
Before removing an immersion heater, you need to saw out the packing ring between the heater flange and the tank. Hacksaw blade with one end wrapped in tape is the tool. Clean up flange before fitting replacement heater.
Fair point - except that now the thing is leaking, which I don't think is related to any Thermostat issues...
Good stuff about removal snipped. FWIW mine is at the top of the tank.
Ideally I would like a method of determining the length (for obtaining a replacement) before removing the one at fault, but I doubt that exists...
J^n
Did it heat just the top of the tank or lower down?
I don't think you can buy that many lengths. Personally I would use a short one, so to heat just the top as it would only be used for emergencies.
Or pear shaped, even.
It's still advisable to loosen the heater with the tank full, such that it can be removed more easily after the tank has been drained - but obviously don't unscrew it fully with the tank full!
Yup not disputing that - just full though rather than full of hot water. If the tank decides to split on you big time as you loosen it, you have far more options open to you than you do if water at 60+ deg C is spewing everywhere!
;-)
I once replaced the temperature sensor probe in the DHW part of a combi. I forgot to shut off the mains cold feed to it. Needless to say, when it finally pulled free of its socket, things got damp rather fast, and sticking my thumb over the source of the jet of water only served to spread it around over a wider area!
Pulling the stat out will give you some indication - at least you know it won't be shorter than that!
I have had reasonable success in swapping elements (only one failure) and I give the spanner a sharp knock to tighten the element before uncrewing it.
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