immersion heater problem


My hot water immersion heater has packed up three times in two years. On two occasions it required a new thermostat; on one it apparently needed a whole new unit.
Now, I'm not saying I don't trust plumbers :-) but something's wrong somewhere.
Any suggestions please?
Also - does anybody know of a good site that will walk me through the process of removal and replacement? At least my own time is free....
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I don't know of any sites but: - Firstly, you need to close off the entry water to the cylinder, then attach a piece of garden hose pipe to the drain point, which should drain to a bucket or preferably outdoors. The discharge point of the hose, should be below the "head height" of the heater screwed connection to the cylinder. Then; and most important to avoid excess shearing stress on the cylinder copper, before emptying any water from the cylinder - just loosen the heater, using a box spanner which can be bought from the sheds or a plumbing supplier, until there is a slight seepage of water, at the joint between the heater and the cylinder, Now drain the water to a level to just below the heater thread, i.e. when the seepage stops. Finally, slowly unscrew and remove the heater completely. Follow the manufacturer's instructions for replacing. Ensure that the cable supplying the heater is of the heat resistant type; and is not brittle or showing signs of overheating of the cable or the cores. Check the thermostat setting is still the same and re-install. The drain point should still be closed off, refill the cylinder by opening the inlet valve and switch on/test.
Immersion Heater Element Notes
They all have the same mounting boss, but there are different lengths. The most common lengths are 11", 18" and 27", but there are also 30" and 36". You need to get the one that suits your cylinder.
If you have a side entry element, mounted near the base of the cylinder, then the length is probably 11". If you have a top entry element, then it's probably 27".
If you have a dual element (top entry only), then you need to replace the whole assembly - they're a bit more expensive but you have no choice.
BTW, get an Incaloy coated element - they last much longer. Titanium coated ones even longer.
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Seaside Peter wrote:

immersed heaters. As can fitting too long a heater and bending it to fit in. As can buying cheapest possible imports, rather than quality products. Do you often change the temperature settings on the thermostat? Ever drain down the system with the heater still on?
There are many possible reasons for an early failure.
The good news is that, since the units have been replaced recently, the whole lot shouldn't have had time to corrode and seize solid. So getting the bits out to replace them shouldn't be too tricky. However, you will probably need to buy the correct tool to remove the heater.
If you drain the tank down, a dentist mirror and a lamp should allow you to have a quick look at the condition of the inside of the tank and more importantly the condition of the central heating heat exchanger coil. If they look to be in a bad state, now might be a good time to swap out the entire tank. eg before the rust inhibitor in the central heating loop starts appearing out of the hot water tap...
--
Sue





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On Thu, 17 May 2007 10:31:58 +0000, Palindrome wrote:

replaced the thermostat - still no dice. Then I replaced the whole unit - success.
What I still don't know is why it packed up so quickly - visually, it looks in perfect nick. Probably got what I paid for...
Thanks again.
--
peter

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