Possible to get an immersion heater with external temp control?

[dave]

Our immersion heater has a thermostat fitted in the "head" of the unit. Are there ones that have some kind of external control setting? Appreciate a link to one if so. thanks

[ARWadsworth]

Why do you need to alter the temperature?

However

work. It would need to be wired in series with your existing stat to be safe.

If you have already not got one of the new immersion stats with the safety cutout then I suggest you get one.

[TheOldFellow]

There is nothing to stop you adjusting the existing TS to a safe max, and then wiring it through another TS. Just make sure the new TS is actually measuring something heated by the IH (i.e not the bottom of the tank).

R.

[dave]

The tank is one of those that is encased in a solid foam "jacket". So can't don't think I could get to the copper to measure it properly.

The reason I need to alter the temp is that the tank is not really up to delivering enough water for a bath (and so thermstat is set high for that). The water is thus too hot for other normal use. Yes it needs replacing by a new system - but that's a big job - maybe for the summer. For now I could do with an adjustable IH. thanks anyway.

[ARWadsworth]

You just cut out a section of the foam where you want the stat to be in contact with the cylinder.

[dennis]

It isn't because you have the wrong length of heater in it? If the heater is in the top you need one long enough to nearly reach the bottom. A short heater will only heat the water at the top.

[Tabby]

You could add a strap-on stat. Cut away a patch of foam where its to touch the copper tank.

New stats tend not to go very high tempwise, that can be solved by mounting the stat further down - but not below the bottom of the heater element.

NT

[Huge]

Seconded.

After a melted insulation event, I replaced mine with such a 'stat, and then had a number of apparently false trips. I eventually discovered that one of the connectors on the element itself was not as well spot-welded onto the element as it appeared, was high resistance and regularly overheated. Without the safety cutout, there could well have been a fire.

[Tabby]

to

Those prevent the HW being set hot enough for the OP.

NT

[ARWadsworth]

That's why I gave a link to one that can switch 15A :-)

[ARWadsworth]

I suppose you could wire a new stat in series with the existing stat and add an extra switch in parallel with the new stat. Once you have got the temperatures setup correctly you can then turn the switch on to bypass the new stat for "bath hot water" and off for normal use.

[Ian Jackson]

Or simply make a note of the 'normal' setting, and - for a bath - turn the new thermostat to maximum.

[dave]

A)

B)

Yes to both. I had (after seeing the link to the 15A strap-on!) decided on the two stats in series soln with an override on the new one. That will work with the proviso that certain people (including me) are trained up to turn the override off again :-)

[Ian Jackson]

In message , dave writes

I wonder if there's an off-the-shelf device which will provide a one-shot override, ie one where the override will stop overriding either when the new thermostat cuts out (when the bath water is hot enough), or on a timed basis?

[Dave Liquorice]

I beg your pardon! B-)

(including

Series doesn't sound right you need both to be calling for heat for the immersion to be on. When the lower set one becomes satisfied it turns the heater off...

Gut feeling is that a momentary action switch and a relay could be wired to do that.

[ARWadsworth]

But you would have no safety backup if the strap on stat was knocked off the cylinder. By putting them in series the immersion stat will act as a high limit stat.

Or an immersion booster eg

[Dave Liquorice]

Good point but don't immersions have two stats these days one adjustable to set the temp and a non-adjustable, safety, high limit one?

[ARWadsworth]

They do, but the high limit safety stat is built into the stats head and is in series with the adjustable stat and you cannot bypass it.

I swapped one last week. The condensate was frozen on a boiler so the customers had switched the immersion on overnight. The stat had failed in a closed position and boiled the water. Hot water went up into the tank in the loft and over filled the tank. Due to a bad a badly placed suitcase the overflow had been pulled out of the tank and the water then poured onto the ceiling. I don't know how much the new stat was as the customer nipped to the shop to get it whilst I de-iced the condensate. It took my about 2 minutes to swap (and probably 30 minutes for them to put all the clothes, blankets etc back into the airing cupboard). It could have been much worse.

[ARWadsworth]

It could even be the wrong length stat.

[Andrew Gabriel]

but bear in mind the copper is a lot thinner than you think on a modern cylinder. e.g. don't push hard against it with a stanley knife.