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[Spare Tool]

That helps a lot thanks, so what's the purpose of the contact box does it just protect the thermostat or does it drop the amps entering it...sure my electrician will sort it, just so I've got it straight in my head

 

[Old Mod]

Yeah pretty much. It deals with extra load. That's all I know.

 

[Spare Tool]

Thanks for your help..
Cheers Andy

 

[Uheat - Keith]

Agree with Tile Seller & 3-fall & timeless John above.

if it is 200w/m2 system at 18m2 = 3600w = 15.65amp.
Your electrical engineer will need to install a contactor or relay at 20 amp.
Hope that helps, warm regards,