Connect an immersion boiler cylinder stat to a back boiler

[Bluesparks89]

Hi, Ive just started out as an electrician and ive got a job to connect a a new immersion cylinder stat to a back boiler behind fire place.
Is this job easy to carry out and are the connection easy to wire up??? I know i have to use heat resistant flex but how many cores would i need?
Thanks for your help

 

[flameport]

Probably 3 core (earth, line, switched line), but the thermostat would not normally be connected directly to the boiler. Surely there are some other controls already such as a timer?

 

[holmslaw]

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[Bluesparks89]

A customer has had a new immersion heater put in but previous heater has no controls and the plumber said to put a new stat on the immersion cylinder and connect it to the back boiler because at the moment the immersion cylinder is permantly heating the water and he said its going to get to hot espically as warm weather is coming so i was wondering if its a fairly simple job to carry out.

 

[bernardgreen]

I think you need to find out EXACTLY what this thermostat is going to control.

If it is JUST controlling the electrical supply to the immersion heater then probably there is no major problem.

BUT if it is anything to do with shutting down the fire / flames / fuel in the back boiler then be very wary of the pitfalls. The safety implications and financial and / or legal risks for you if anything later goes wrong with the system can be very serious.

It is not unknown for a solid fuel back boiler to over heat the water and create a hazard from boiling water in the system. This can happen before anyone notices and the fire can be put out. In the worst case the water in a plastic header tank for cold water can become so hot as to soften the plastic enough for the tank to collapse and dump hot water through the ceiling below.

If the thermostat is to control the back boiler then my advice would be to walk away from the job.

 

[holmslaw]

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[1550]

I've been around a long time now and never have seen an immersion heater in a back boiler.Boilers usually only heat the primary pipes to the storage cylinder and the flow pipes to the heating systems. Are you sure you have understood the requirements?

 

[Bluesparks89]

Thanks for the replies everyone i think i will probably walk away from the job and say ive never come across this before but the lady phoned me this afternoon saying she has no hot water and the plumber told her i have to connect the stat to the cylinder immersion heater...

The immersion heater is up stairs next to the chimney breast and the back boiler is down stairs and the plumber said to drop the wire down next to the pipes through the chimney breast surely the pipes become really hot and would not be suitable to drop the wire down next to the pipes.

Thanks for all the comments and suggestions much appreciated.

 

[1550]

In that case a simple water heater timer will satisfy your problem. If the call for hot water is normally satisfied by the boiler during the timed period the immersion heater will not switch on .(providing the temp set is lower than the boiler limit) The immersion will satisfy hot water call during timed periods or on customer override when the boiler is off. A well lagged tank would be beneficial in keeping the cycle of the immersion heater to a minimum.

The element will also require an over limit stat.

Edit. But on further reflection ,I agree with those who think you should leave it alone. A decent plumber would have had that sorted from day one.

 

[EFLImpudence]

connect a a new immersion cylinder stat to a back boiler behind fire place.

Blond day? What am I missing here?
Do boilers not always have tank stats to switch them off when the water is hot enough and do immersion heaters not have integral stats so that they won't come on if the water is hot enough?

 

[holmslaw]

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[EFLImpudence]

What's that Skippy? You don't know either?

 

[1550]

Lol . What they've got and what they should have is not always the way it is.