Problem Low voltage boiler mains cable

joe kane · Mar 27, 2011

Hello everyone.This is the 2nd time ive had this problem.
I have a 240v supply to the boiler,but it needs a 24v supply(call for heat)Someone said to me an external relay is needed.
But I don,t know what sort,and don,t know how to connect it,Please help.
Thanks

IQ Electrical · Mar 27, 2011

joe kane said:
Hello everyone.This is the 2nd time ive had this problem.
I have a 240v supply to the boiler,but it needs a 24v supply(call for heat)Someone said to me an external relay is needed.
But I don,t know what sort,and don,t know how to connect it,Please help.
Thanks

How did you overcome the problem the first time?

Is it not a link in the boiler control panel to be removed if a thermostat is used?

RWJ · Mar 27, 2011

IQ Electrical said:
How did you overcome the problem the first time?

Is it not a link in the boiler control panel to be removed if a thermostat is used?

I agree with IQ there's normally a terminal for a thermostat which is linked out if not used

joe kane · Mar 28, 2011

it is for underfloor heating,first time wiring it and given wrong instructions by plumber.A wire was left out from manifold to boiler call so i need to turn it on only have a mains supply of 240v but need to turn boiler on 24v in.

joe kane · Mar 28, 2011

if the link is taken out the boiler turns off.
Although the boiler has a 24v supply at link,can i return this call to other side of link via relay with a 240v coil and 0v contact

IQ Electrical · Mar 28, 2011

joe kane said:
if the link is taken out the boiler turns off.
Although the boiler has a 24v supply at link,can i return this call to other side of link via relay with a 240v coil and 0v contact

I would make a quick call to the boiler manufacturer's technical department and just double check what you're proposing, better safe than sorry.

Dunc · Mar 28, 2011

Sounds similar to a boiler I recently did. Sent a 3 core to the boiler as normal from the system controls only to find the boiler had a volt free call circuit. Due to the system having multiple zone valves and pumps the only option was to fit a relay in line with the volt free contacts with the coil powered by the switch live I had already installed. Should work in this case too but it might help to let us know what boiler has been fitted to advise better.