Zone Valve Isolation

NozSpark · Feb 20, 2015

Are you allowed to use a relay/contactor for isolation purposes?

Personally I'd stick with a rotary isolator,,, the valve must be somewhere relatively hidden so why not put it with it

buzzlightyear2014 · Feb 20, 2015

Rob_the_rich said:
I would be wary of installing a user-operated manual over-ride of a heating control without checking with Vaillant.

Can the user just turn down the thermostat?

Has all been checked with Vaillant. Its only for isolation and maintenance on the valve, no power through valve, circuit won't fire and boiler doesn't run

steptoe · Feb 20, 2015

Lurch said:
Problem is that's a bit fail dangerous. You are relying on the relay energising to isolate the supply, unless I have misunderstood what you are intending?

Im thinking fail safe,

power failure valve is dead anyway,

the other way is ensuring the relay will fall back and has not arc'd,

tbh, as Noz says, either way is probably not permitted for isolation purposes.

Lurch · Feb 20, 2015

steptoe said:
Im thinking fail safe,

power failure valve is dead anyway

Wouldn't work like that, powering up a relay to isolate a switched live is not fail safe. If the relay failed then you have no isolation. General powercut in the area is not allowable as a safe means of isolation!

steptoe · Feb 20, 2015

Lurch said:
Wouldn't work like that, powering up a relay to isolate a switched live is not fail safe. If the relay failed then you have no isolation. General powercut in the area is not allowable as a safe means of isolation!

Im not talking general powercut,

if you energised the relay it would isolate the valve, if you then lost power to the boiler then the valve would remain isolated,

having the relay permanently energised relies on it not 'growing' in the same way that RCDs often grow if they are never tested.

as pointed out though, this is probably one of the reasons that contactors/relays, are NOT permitted as isolation.