Old for new thermostat grey wire???

[Craig00100]

Old for new thermostat however new thermostat only has 3 connections live sl earth

Old thermo has a grey wire what is this for and what terminal should it go too ?

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• Craig00100
• 28 Aug 2016

 

[ianmcd]

you would be better posting models of old and new thermostats for the correct advice very few modern thermostats will have an earth, just because it is a green and yellow wire on a heating system does not mean it is an earth

 

[Craig00100]

Hi the old thermo is
Myson
Thermostat MRT1
230v 50hz

New 1

Salus
Digital electronic
Thermostat
Model RT300

Regards

 

[ianmcd]

OK the wires on your old thermostat the two wires you need are between terminals 1 and 3 the other wire is a neutral as your old room thermostat has what is called a heat anticipator , you do not have an earth , your new receiver needs a live and neutral to power the unit then the two existing wires are your switch

 

[Craig00100]

Sorry so what wires do i use ie colour?
Regards

 

[Craig00100]

New back plate

 

[ianmcd]

The old wires are on terminals 1 and 3 and they go to L and SL on that back plate doesnt matter which way round and isolate the other wire cut and tape it up

 

[D_Hailsham]

Red/Brown wire (T4 from left): connect to L
Black wire (T2 from left): connect to SL
Grey wire (T1 from left): not used. Make it safe in a small terminal block behind the thermostat.

 

[Craig00100]

Thanks ianmcd & dhailsham thats it fixed and working now

Regards

Craig