Immersion heater overheating

[david.genet]

My friend just moved into his new flat and is having problems with the shower pump overheating. This is being caused by the temperature of the water flowing out of the immersion. The immersion has two elements, one at the top and one at the bottom. The bottom one is controlled by economy 7 power, while the top is controlled by a switch which is off. Both are wickes elements and were set to 65, so thinking this might be the problem I dialled them down to 40, but the water is still as hot as ever, and the pump still overheats. The pump is fine if all power to the immersion is cut and the water has a chance to cool down.

Is this just a simple case of the elements and their thermostatic cut-offs being shot ? Is it a common problem on immersion heaters ? If so I guess its just the simple job of relacing both elements. Any other suggestions ?

Cheers

[Stuart]

You know that immersers have separate thermostat rods ?

[david.genet]

Yeah, I noticed that the thermostat could be pulled out. I take it I can just replace the rod then ? Or is it better to replace the complete unit ? I have no idea how long it has been in situ.

[Stuart]

You might find it's not much more expensive to buy the complete thing .Check

for prices .

Stuart .

[jim]

Yes, decide which one (or both) is dud. Take out the rod & buy a replacement the same size. I can't say for sure without knowing exactly what your units are, but due to recent EU/gold plated UK regulation changes in specs for immersion heaters, you may have some trouble finding a stockist. Almost certainly you will need to seek out an electrical wholesaler. I didn't find it easy this summer.

Or is it better to replace the

due to said changes you may find it even harder to find replacement immersion units of the right size, though YMMV. & it's a much harder job to replace the heater unit. & there's no need. A reasonably good make of heater will outlast several thermostats.

NB turn off the switch AND switch off the MCB (or pull out the fuse) AND sketch or - better - photograph the existing electrical connections before handling.

HTH

[Stuart]

Did you not try here .

[david.genet]

Thanks.

There is a tlc around the corner so I'll try there first. If not I'll give bes a go.

Cheers

[Pete C]

Hi,

If you have a cooking thermometer and cheap multimeter, you could heat the thermostats in a pan of water and see what temperature they open.

Is the shower and immersion newly fitted?

cheers, Pete.

[david.genet]

No idea how long they have been in, although the shower looks about 15 years old, but the immersion/tank/pump all look quite newish.

Might just throw in a new thermostat as they only cost a few quid each. Will just replace the bottom one initially as that is the one being used for heating at the moment.

Cheers

[Christian McArdle]

Note that modern immersions should have two thermostats. One is a working adjustable stat and should be set around 60C to determine the temperature. The second is a manual reset overheat stat and trips around 80C (often fixed temperature, but sometimes adjustable).

If you only have one thermostat, but have a tube for a second, make sure you buy one of each type, as it is vastly safer. Stuck on immersions can actually be very dangerous, both because of extreme temperature/steam at the taps and also because vent blockage will lead to an explosion that is more than capable of entirely demolishing a house.

Christian.

[noelogara]

Christian McArdle wrote: Stuck on immersions can

can you explain Christian how an explosion of a copper cylinder could possible demolish a house.

[James Salisbury]

Have a read

[noelogara]

built of bricks and mortar.

[Christian McArdle]

There is easily enough pressure released in such an explosion to blow out the wall sideways. The Ronan Point rules on disproportionate collapse pressure resistance don't apply to houses, either.

Christian.

[Bob Mannix]

AFAICR a brick wall of "normal" size (ie room size) will give way at a 2psi pressure difference across it (or thereabouts). Sudden expansive incidents (such as gas explosions and instantaneous steam generation when an overheated tank goes) can easily provide this.

Bob Mannix

[Mark Carver]

Unless you live in a hard water area. My parents' IM heaters lasted lasted just two-three years. They fitted a water softener 10 years ago and haven't replaced the IM heater since.