Enclosing hot water cylinder stat in insulation?

[andyscotland]

Short version: can I safely enclose a surface-mounted cylinder stat in insulation?

 

Backstory: we have an ancient essentially uninsulated hot water cylinder that leaks heat at an alarming rate. Annoyingly, it is installed in a very confined space - there are (uninsulated) pipes coming out at inaccessible corners, and one side nearly flush to the wall. So it's not feasible to fit a normal tank jacket.

 

Long term plan is to fully replace the heating system.

 

However with costs as they are I'm looking at a short term solution. I have a bunch of waste PIR and mineral wool. So I'm thinking of quickly boxing across the front with PIR, stuffing/pouring wool into the gaps from above, then putting a PIR lid on it.

 

But it has a surface-mounted (and metal cased 😞) stat on the front. I obviously need to keep occasional access. But I can't decide whether to box round & keep it permanently exposed, or put a "hatch" of PIR in front of it and fully enclose it which would obviously be better thermally.

 

My gut says enclosing will be fine, electrically it's very low current and expected to be in contact with the cylinder anyway so overheating seems unlikely, the sensor is electro-mechanical, and it won't go above ~60°.

 

I'm just having a bit of a wobble & can't work out if that's genuine or my brain procrastinating again 🤣

[dpmiller]

the temperature calibration will alter a wee bit, but as the cylinder isn't running too hot and there's no big current being switched there's no safety implication IMHO

[andyscotland]

@dpmiller thanks good point on the calibration, I can work around that as I also have an electronic probe hooked up to a data logger. I've been using that to monitor the heating cycle/heat loss but will also allow me to tweak the stat set point if required.

 

Tbh my other soonish plan is to use that probe to give better control of the temp so I can boost it up ahead of morning showers (it's quite a small tank) but keep it lower the rest of the day. But would still want to keep the actual stat as an upper limit stop for safety/in case the automation packs in. So calibration isn't too important overall.

[SteamyTea]

I boxed my cylinder in with a combination of PU sheet and mineral wool.

Apart from making sure the cables to the immersion heaters are in free air, I did not worry about the thermostats.

My thermostats are part of the element boss anyway.

 

Insulation saves me about 2 kWh/day in standing losses.