Unusual Hot Water Cylinder Thermostat

[anta]

I need a replacement hot water thermostat but I appear to have an unusual one. Anyone know where to get one of these from? Here's a photo:

View media item 22793

 

[DP]

I take it the heater is bolted onto the side of the cylinder. If that is the case, you have a rare beast that can be located but you will need to search far and wide.

Better option would be to change the cylinder as replacement will be better lagged and provide faster heating. I am assuming the water is heated by a boiler with immersion heater being the backup.

 

[Agile]

I will make some assumptions and based on them give you an answer.

IF its used to control the boiler hot water provision and sits in a pocket in the cylinder then the following will apply.

Any standard liquid filled phial type of themostat as used on old floor standing boilers could be used to do the job.

The head would ned to be housed in a suitable box.

OR there is a thermostat with a sensing thube about that size. The one I am thinking of might be Satchwell and usually has two elements, one a variable control and the second an overheat trip with manual reset.

Tony

 

[anta]

Thanks for the help so far. I think it's Aglie's 2nd option, but let me clarify the setup.

It's a 1973 installation domestic indirect hot water cylinder. Header tank in the loft. The boiler heats the water via the indirect coil (three way valve between boiler, CH and HW). An immersion flange is on the curved section just away from the top takeoff connection to the tank. It had a plastic cover over it and under that there's two terminals for the element, and this lift out tubular part which is the thermostat. Ideally I was going to change the element and stat together - it works as is but I've heard horror stories of when a thermostat fails in the on position so I want to change it. I couldn't get the element out and the tank started to deform so I've given up on that. Seeing how the element works I need only change the thermostat to a more modern type with fail-safe default-off behaviour. Trouble is that the ones in plumbers merchants are 7", 11" and 18". This one is closer to 5" and is a fatter tube rather than a thinner probe.

Does that clarify it? What do I need to replace it?

 

[crumplypork]

what tank is it out of?
i will be able to get one

 

[Terrywookfit]

what tank is it out of?
i will be able to get one

It's out of a very old immersion heater.

 

[anta]

what tank is it out of?

The tank is a Hercal grade 4 indirect tank.

It's out of a very old immersion heater.

So is a modern replacement part available?

Any suggestions as to what I should do?

 

[Terrywookfit]

Fit a replacement Immersion heater.

There are ways to remove even the most stubborn.

It's been covered on here plenty of times.

It would be cheaper to pay someone to do it ,rather than kn@cker the cyl.

 

[DP]

I take it the heater is bolted onto the side of the cylinder

Yes or no answer would help!!

 

[Terrywookfit]

I take it the heater is bolted onto the side of the cylinder

Yes or no answer would help!!

It's a 1973 installation domestic indirect hot water cylinder. Header tank in the loft. The boiler heats the water via the indirect coil (three way valve between boiler, CH and HW). An immersion flange is on the curved section just away from the top takeoff connection to the tank. It had a plastic cover over it and under that there's two terminals for the element, and this lift out tubular part which is the thermostat.

Is this a clue.

 

[oilhead]

This is an old Maclaren TBH (?) I think, well obsolete. There is no reason why you should not use a clamp on thermostat, installed in accordance with current regs and good practice. Just make sure it has sufficient switching capacity, 16 Amps or thereabouts.

 

[Onetap]

There is no reason why you should not use a clamp on thermostat, installed in accordance with current regs and good practice.

There is; the thermostat is liable to fall off, leaving the immersion heater permanently on and a clamp-on would have no manual-reset overheat thermostat. Search the archives for details of two fatal accidents in recent years involving old immersion heater thermostats.

It would be sensible to replace the cylinder, if it is an indirect cylinder heated from a boiler. Many cylinders of that era were 'short-coil' types, to reduce the cost. They take far longer to heat up than cylinders manufactured to the current British Standard and are inefficient. It is probably heavily scaled up, if you're in a hard water areas.

 

[anta]

Onetap and oilhead - thank you very much for the help. I'm glad it's finally been dientified, even if it is obsolete.

I can see that no protection is built into an external thermostat - the boiler has it's own protection if the HW/CH controls thermostat failed, but the immersion wouldn't have.

We only use the immersion if there's a problem with the boiler. In the last 3 years it hasn't happened once. I'm about to drain down some radiators and do some work around the house so I want to use the immersion as a temporary measure for a few weeks at most. I didn't want to trust the old thermostat, but I would trust a brand new one on the side of the tank for that period of time.

We need to refit our kitchen and utility in the next couple of years so a new cylinder will be fitted at that time (we want to move the boiler and relocate the cylinder as part of that work). Until then I'd trust a new thermostat for the odd times when we want the immersion. And we'd switch it off after about 30 minutes anyhow. Just want the thermostat in case we forget.

Thanks again for the help.
Ant