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I wish to have an 'hours meter' connected to a hot water cylinder that has an immersion heater. I do not know at present if I can get at the temperature switch.

Did think of wiring in a relay so that when heat was called for it would operate and via a set of contacts operate the meter and another set of contacts to power the actual heater but then thought one connection taking power to the coil and contacts and the other side of the coil with a connection to the switch and from the contacts providing the power to the heater so effectively zero potential across the coil causing the relay to drop out and then on again, then off so just chattering.

Anyone any ideas?

Mmm. First you don't ever want the relay chattering, as it will create interference and burn out the contacts very quickly.

I'm not sure what kind of hours meter you are thinking of. Presumably a mains one? So long as you use 16A heatproof flex then in theory you could just connect in parallel with the heating element. You might struggle to get two sets of wires into the terminals though.

Any relay would need to have big contacts to power the heater. Because of the big currents involved and the potential for lots of heat and smoke if anything failed I'd leave well alone.

Got to ask why, though. What are you trying to measure? There may be other solutions.

Duncan

Thanks for the reply.

One of the reasons for the question because at the moment I do not know if I can get access to the heating element / wires to it.

Yes, a mains hour meter.

The reason a little investigation into the most economic way to power the heater, i.e. 24 hours a day, x number of hours am, y number of hours pm etc.