Emersion Heater Thermostat

[Radio Fixer]

Does anyone know of one that lasts?  Bought different brands, including ones with the Brit symbol, but they all seem to fail in a relatively short time.

thanks Gary

[Nick]

Decent ones seen to last 10+ years.

They typically fail due to burnout on the contacts - if you put a heavier load on than its designed for... they fail quickly... 

One one of our buildings we've used an external SSR to switch the load. I needed an electrically quiet environment and there were these occasional short bursts of broad spectrum noise which turned out to be the thermostat.

Simply using a suitable zero-crossing SSR and running the thermostat at 12V @ almost zero current solved the issue.

[boater sam]

I thought Emerson radio or TV at first till I realised you mean immersion as in water.

The long brass thermostats are more reliable than the fat tin ones in a short pocket. New elements have 2 stats, one for temperature other is high limit safety stat.
Frequent failures could be an element going down.

[Radio Fixer]

Well it made you look Sam... Yes!  Immersion heater thermostat.  
Last time I changed the heater as well but only got about 6 months from what we can remember.
Will get another and this time note the date and keep the receipt.

thanks Gary

[boater sam]

Its your water!

Get up north on real clean water fresh from the Pennines and your elements last for ever.

You can buy stainless and incoloy elements for nasty water areas but strangely not thermostats.

[Cleggy]

You used to be able to buy external stats which are held on the side of the tank with a strap, but only if you have an old tank which wasn't encased in foam at the time of manufacture. We had one and it worked very well....and for a long time   .

[ppppenguin]

No problem fitting a 'stat to a foam clad cylinder. You just cut a pocket for it. I don't know about 'stats for use with immersion heaters but that's how I fitted one to use with a boiler.

[boater sam]

Strap on cylinder and pipe stats are usually single pole change over for central heating valve control, I know of no domestic double pole one one rated at 3kW for immersion heater element.

There is the danger of it falling off and leaving the element with no control to consider and how do you satisfy the regulation that there must be a high limit stat as well?

[chriswood]

With any thermostat just add a heavy duty relay or contactor to switch large loads either conventional mechanical or solid state will do.

[boater sam]

We are talking about a normal sized domestic installation  here not a factory I think.