Immersion heater thermostat

[matt1976]

Due to issues with the boiler I've had to use the immersion heater for the first time since I moved into the house. But it got far too hot. When I took the cover off the power cable was wired directly to the element and bypassed the thermostat. There is still a metal link from the thermostat to the element but both wires just go to the element.

I don't know if this is a bodge because the thermostat doesn't work or just someone messed up, the previous owner wasn't the type to do it herself so someone must have done it for her. Can I test the thermostat with a multimeter for continuity? When I adjust the dial it clicks so something seems to be working.

Plus what size wire would I need to replace the cable? The current one is quite tight and if the thermostat is different to the one in there now the solid metal link won't fit so I'll need replace it with some wire and there is no spare.

 

[Hugh Jaleak]

Do not run the immersion without stat connected correctly, it will boil the contents of the cylinder, possibly leading to a deluge of boiling water through the ceiling from the storage cistern above! This has happened, sadly causing the death of a young child sleeping in a cot below.

Maybe a wise idea to replace the stat, newer stats have a cutout to prevent the water overheating. Wire, you'll need something capable of carrying 3kW, anything smaller could melt, possibly causing a fire. If in doubt you really need to consult an electrician.

 

[Charnwood]

Thermostats are available both with AND without integral cutout.

 

[Agile]

Regardless of whats available only the kind whith o/h stat can be made now and thats the only type which should be used now!

Cable should really be 2.5 mm2 and heat resisting.

 

[CBF]

Thermostats are available both with AND without integral cutout.

what a stupid thing to say, a thermostat without a safety cutout should NEVER EVER be fitted

 

[Hugh Jaleak]

I was of the impression the newer type stats with a cutout were the required norm now, purely to prevent any possibility of another serious accident or fatality, should the stat fail and the cylinder boil. Whilst there is no doubt there remain plenty of the 'old' type stats still in service, surely any effort to reduce the risk by replacing with a new stat c/w cutout when chance arises can only be for the better!

Whilst both types may be available, would any of us want it on our conscience, having fitted or changed an immersion which later went on to develop a fault, resulting in a serious injury or death from a plastic cold storage cistern full of boiling water collapsing?

 

[Agile]

My understanding is that it was made a requirement that all new manufacturing would need to have the o/h stat.

That prevented any need to pay to buy up obsolete types.

The expectation is that apart from a few old ones offered on Ebay all those available from shops have been the new kind for the last few years!

Tony

 

[matt1e]

I fitted a 9kw immersion heater on xmas eve
the stat supplied with it did not have a combined O/H trip
so some do still come supplied as such

Matt

 

[Charnwood]

Some immersion heaters have their cutout/reset button independant of the stat; Backer and Redring, for example, are on the brass casting of the IH, that's why stats are available with and without reset buttons.

My understanding is that it was made a requirement that all new manufacturing would need to have the o/h stat.

See above. There are two methods of facilitating the OH/cutout/reset.

Backer stats with the referrence starting BT don't have a reset, stats with the code starting BMST do have a reset. The BMST range should be retrofitted to older IHs to facilitate reset.

.

I would not advocate fitting a non-reset stat into an older, non-reset IH.

 

[Agile]

Charnwood, do you know of a source of elements with a temp adjustment going up to about 85 C ?

To be used for thermal store uses?

Tony

 

[Charnwood]

Domestic stats come factory set (set with a blob of silicon) at 60 C.
From memory most will allow a setting up to 90 C.
I say from memory as I have retired early and do not have access to info like I used to have.

Backer Secondary Cut Out stats go up to 98 C IIRC.

Yup: http://www.backerelectric.com/Data/Product_Downloads/BackermaticLeaflet.pdf

 

[Agile]

All the current stats with a built in o/h stat seem to only go up to 70 C.

Hence I was asking if you knew of one which went higher.

Sorry to hear you have left and no longer have access to all that useful information you have become known for.

Perhaps you should go and find somewhere else to work?

Tony

 

[Charnwood]

Perhaps you should go and find somewhere else to work?

Noy ckufing likely! Retirement (at 57) is suiting me fine. I've got a little pension which, along with she-who-thinks-she-ought-to-be-obeyed's contribution gives a livable budget. I have a local authority pension that kicks in in 3 years which gives me a lump sum plus anoter pensionable amount.

I'm now throwing myself into voluntary work. Over the past 2 days I've hardly been off the phone dealing with it. Bored in retirement? I should cocoa!

Back to the subject in hand, Backer stats, factory set at 60 C, IIRC have 3 more increments of 10 C each, which would be 70, 80 and 90 C.