Wiring for boiler timer/thermostat

planemad · 3 Mar 2010

I'm going install a wirefree room thermostat tomorrow in my house.

The unit consist of a relay switching box that connects to the boiler and the wireless receiver which is mounted in the living area.

Is there a regulation on cable thickness that runs from the boiler board to the relay box?

Many Thanks

ban-all-sheds · 3 Mar 2010

The instructions should tell you what to use, but it won't need to be very heavy.

And shouldn't the receiver go next to the boiler, not in the living room?

(Note this is assuming that you don't have the boiler in the lving room.)

planemad · 3 Mar 2010

HI BAS

Sorry I meant the sender (thermostat) unit in the living area.

The instruction are sparce with regards to the cable size.

I'm thinking of using 0.5 mm but I seem to remember someone telling me that all boiler controls are to be wired in 0.75 due to the mechanical strenght.

Taylortwocities · 3 Mar 2010

It all depends on teh size of the fuse protecting the heating circuitry.

I would use at least 0.75mm².

Personally, I have never used 0.5mm² for anything other than lighting pendant drops.

darren17 · 4 Mar 2010

the heating circuit should be on a 3 amp fused spur switch
you should use 1.5 core cable

Monkeh · 4 Mar 2010

darren17 said:
the heating circuit should be on a 3 amp fused spur switch
you should use 1.5 core cable

One and a half core cable? This I must see.

1john · 4 Mar 2010

perhaps he means 1.5mm flex, as due to the 3 amp fuse the cable needs to be able to carry 16 amps

.

Go with the 0.75 suggestion,

flameport · 4 Mar 2010

If the thermostat connects directly to the boiler, they are probably volt free contacts, so even the smallest size cable would be fine.

No need to have anything over 1mm.

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Wiring for boiler timer/thermostat

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