Unvented cylinder Immersion heater thermostat

[ProDave]

My Telford UVC came fitted with a Thermowatt immersion heater.  It is the type where the immersion element has 2 spade terminals, and when you slide the thermostat into the pocket, it has 2 matching connectors that plug onto the immersion element pins.

 

The "problem" with it, is even at it's maximum setting, the thermostat switches off at 55 degrees.  I would like it to be able to heat a bit hotter than that, say to 70 degrees?

 

So I am looking for replacements.

 

There is this one that looks like it will fit but no min and max temperature quoted. https://www.ebay.co.uk/itm/323292091126

 

I have found this one, that states it is adjustable up to 70 degrees (with the safety cut out fixed at 80 degrees) https://www.ebay.co.uk/itm/202623763800?ViewItem=&item=202623763800

 

But that one is more expensive 

 

Questions:

 

Are this type all the same, i.e will one make of "plug on" thermostat fit another make of immersion heater?  If not neither of these will do as neither are Thermowatt.

 

Is it imperative that I stick to this type of immersion heater?  I guess the answer is yes as these have a 2 pole safety cut out presumably that extra safety is a requirement for an UVC?  If not I might be just as well changing the whole immersion heater for one with a "normal" single pole thermostat and cut out?

 

To summarise what I want is to change the thermostat for one that will work to a higher temperature, for minimum cost.

[Nickfromwales]

42 minutes ago, ProDave said:

But that one is more expensive 

Send me your PayPal address and we’ll crowdfund the £7 ok  

[ProDave]

So I sent a question to the ebay seller of the cheap one,  asking what is the quoted range of temperature setting.

 

His answer was "The temperature range is from 0C-105C."   I won't be buying from him.

 

I have for the time being, taken the "pragmatic" solution.  The little adjusting screw on the existing thermostat comes to rest on a "pip" that limits it's travel.  That pip is no more so it is free to rotate a bit further.  Yesterday it got up to 57 degrees without tripping before the sun went behind the clouds.

 

 

[ProDave]

Well I opted for the "pragmatic" solution.

 

The original thermostat has an adjustment that you turn with a screwdriver. As already noted at it's maximum setting, it switches off at 55 degrees.

 

That adjustment has a "pip" that comes to rest against part of the moulding of the case to limit it's travel.  Well not any more it doesn't. 

 

Now with it's new found freedom to rotate a little further, I have been watching how it performs.  Today the tank got to 63 degrees before SWMBO decided to have a shower and run off some hot water.  My aim is to get it so it cuts off at 70 degrees, alas I will have to wait for another sunny day for that, which seem in short supply here at the moment.

 

P.S this might not be the recommended way of "solving" limited thermostat range.

[Ed Davies]

Speculating wildly, I wonder if they originally made the thermostat for a wider range then limited it to 55 °C because of rules about TMVs or whatever. So maybe it is, sort of, the recommended way of solving the problem.

[ProDave]

I can't find anything about what the temperature range should be, only that the safety cut out is set at a fixed 80 degrees. Hence deciding 70 would be a good max temperature for the normal stat.