Correct thermostat for Steel hot water cylinder

[Bifta]

Hi all,

Hoping this is just a small one. Last year we had our HWC replaced with a steel one as the size it came in was best for the space we had available.

At the time I refitted the previous surface mounted thermostat from the old cylinder and found that the temperature control wasn’t as good as with the previous copper cylinder. I’m guessing this is because of the excellent heat conductive properties of copper vs steel.

The thermostat we have is like this one:

https://www.screwfix.com/p/honeywel...id=KINASEKPID&cm_mmc=Google-_-TOKEN1-_-TOKEN2

My question is, are there any thermostats available for steel cylinders? I’ve searched but nothing obvious is coming up.

Thanks

 

[ianmcd]

post a pic of your cylinder, most steel cylinders come with their own thermostat

 

[Deleted member 267285]

If it’s foam lagged, then you need to remove a little bit of it to work properly. A photo may help.

 

[Bifta]

Hi guys,

Thanks for the replies.

It is foam lagged and I've removed a chunk of it so that the thermostat is touching the surface of the cylinder. Sorry you can't make out much in this pic but it's buried behind 3 layers of insulation.

When it arrived I gave it a good look over and there wasn't an integrated thermostat. There was a sizeable hole in the top where you could fit an immersion heater but we didn't want one of those so just got a cap for the hole like this one:

https://www.screwfix.com/p/tesla-im...VR4BQBh0lpgL1EAQYASABEgL3d_D_BwE&gclsrc=aw.ds

This is the cylinder:

https://www.tradingdepot.co.uk/rm-aquastel-1050-x-450-indirect-stainless-steel-vented-cylinder

 

[Nige F]

Hi guys,

Thanks for the replies.

It is foam lagged and I've removed a chunk of it so that the thermostat is touching the surface of the cylinder. Sorry you can't make out much in this pic but it's buried behind 3 layers of insulation.

]

All that insulation is unnecessary - the cylinder is fine with it's factory sprayed foam and the stat cut in as you've done

 

[ianmcd]

All that insulataion is doing absolutely nothing

 

[Bifta]

Hmm, I don’t think it is fine because there are long periods when the pump is still circulating due to not receiving the off signal from the thermostat even though the water inside the cylinder is all heated up.

Are there thermostats available that would more accurately monitor the internal water temperature rather than the surface temperature of the cylinder?

 

[Exedon]

Assuming your cylinder stat is working properly have a look for heat transference paste you will get full contact with cylinder.
.

 

[Bifta]

That’s a good shout thank you, I’ll try that.

It also works the other way in that the water inside can be going cool which leads to a lukewarm shower because there is still latent heat within the casing causing the stat to think it’s up to temp.

 

[flameport]

Have you considered that the thermostat may be faulty?

 

[Bifta]

Have you considered that the thermostat may be faulty?

I did yes so I replaced the stat not long after we had the new cylinder hoping that would sort it, alas

 

[Bifta]

I’ve now refitted the stat with thermal paste and it seems slightly better but still not right I don’t think

 

[Deleted member 267285]

Post a photo of how it’s attached to the cylinder

 

[Bifta]

Post a photo of how it’s attached to the cylinder

Here it is

 

[stem]

Difficult to see from that photo, but I wonder how high up the cylinder it is mounted. The bottom of the cylinder is where the cold water comes in and is below the heating coil, so tends to stay cool. As heat rises, the temperature will increase further up the cylinder and the water at the top can be 40 degrees or more warmer than the water at the bottom. With such a varying range, it can be difficult to regulate the temperature precisely when measuring it at just one point.

Manufacturers tend to recommend that the thermostat be located between one quarter and one third of the way up the cylinder, by which time the water is no longer cold, but not as hot as it is at the top.