I need a hot water tank thermostat for hotter than normal temperatures

[mpooley]

I have a need for for a thermostat for a copper cylinder connected to solar power so I'm looking for an accurate thermostat which will allow me to store water at up to 90c ?
I have tried a bog standard Honeywell and a couple of cheaper stats but none of them even work up to the advertised 80c.
Can anyone advise me of perhaps a speciality thermostat for this purpose please?

Thanks

Mike

 

[John.g]

I have a few EPH cylinder/pipestats that go up to 90C, so can't see a problem if that't the type of stat you mean, how are you heating the cylinder to 90C?., solar thermal?.

 

[mpooley]

Basically it's an immersion heater power from solar panels.
I think I have used the EPH thermostat before! It looks very similar .
It always turned off at a lower temp though. Maybe I was just unlucky .

thanks

 

[Gasmk1]

Is the cylinder storage vessel rated for 90 degree water

 

[mpooley]

I'm not sure ? but I know I it's been like this for a few years.

 

[Gasmk1]

I'm not sure ? but I know I it's been like this for a few years.

https://www.heatrodshop.com/product/cotherm-tsdh0701can you use something like this

 

[mpooley]

Yes That looks perfect !
Thankyou

BTW I didn't know tanks Had to be rated! I'll have to look into it but don't know how to check my tank.

 

[ShaunCorbs]

Do you have a blending valve straight off the top of the cylinder to reduce the temp down ?

 

[mpooley]

Yes I do - it blends it down to 46c if I remember correctly

 

[ShaunCorbs]

I guess your cylinder is a tad on the small side hence the question to up the temp ?

 

[John.g]

Yes That looks perfect !
Thankyou

BTW I didn't know tanks Had to be rated! I'll have to look into it but don't know how to check my tank.

Which stat are you looking at in the attachment? is the electromechanical rod stat?, also have you a top mounted dual immersion with a pocket for the stat or is it a single element with a stat pocket?.
Where, if on the cylinder are you attaching the cylinder stat.

I just attached my 90C EPH stat to the side of a kettle and it operated spot on 90C with a reset hysteresis of ~ 6 to 8C.

 

[mpooley]

Yes cylinder is a Bit small.
I am looking at the Cotherm TSDH0701
It's a dual element with rod stat pocket
Boiler stat has been tried at several positions but is a third from the bottom at the moment
thanks

 

[John.g]

That high temp rod stat looks good.

Assuming a top mounted dual immersion,
Can/do you divert the excess power to the Immersion in a way that you can select sink/bath or is it dedicated to one element?

 

[mpooley]

That high temp rod stat looks good.

Assuming a top mounted dual immersion,
Can/do you divert the excess power to the Immersion in a way that you can select sink/bath or is it dedicated to one element?

No I'm afraid not. I have a device that can switch up to 2 devices but it's not easy and I haven't got anything that I could switch it too.
If I ever get an electric Car I 'd definitely do that.

 

[John.g]

I was thinking along the lines that its connected to the immersion supply and that you switch it between one element and the other manually as required, the (rod) thermostat normally switches the common neutral for both elements, like the majority of top mounted dual immersions.

 

[mpooley]

I was thinking along the lines that its connected to the immersion supply and that you switch it between one element and the other manually as required, the (rod) thermostat normally switches the common neutral for both elements, like the majority of top mounted dual immersions.

I always want the solar power into the longest element. I do have it wired so that it can be switched to the normal mains supply though and the tank is indirect so boiler can heat it as well. I have built all this myself and have a computer running the whole house. The thermostat on/in the tank is only used as a failsafe really.