Thermostat wiring

[oldspark]

Hi> Helping out my brother in law doing up his house a, his central heating system is installed and I finished installing the controls late last night ( s Plan oil boiler) everything seems ok but the plumber has left an SCtd Dual Thermostat that i was unsure about. I have a grey from the wiring center to C on the limiter there is a link from terminal 2 on it over to terminal C on the stat Then I have an Orange from terminal 1 back to the wiring center, on the stat there is a terminal 2 so just wanted to check if this is ok with this model or would i need a connection from terrminal 2 to the wiring centre.
no paper work with it and cant find anything on the net

Thanks

 

[ericmark]

Interesting, just looked at the instructions which would make sense with an immersion heater, the problem is the use of thermal plastic header tanks, which can't stand boiling water, so the thermostats have a cut out, to prevent if the thermostat contacts weld together the water being boiler, however with a boiler there are two things which means this does not really make sense.

1) The boiler has its own over temperature cut out.
2) The most likely fault causing the boiler to over heat is the V3 micro switch sticking in the motorised valve, which the duel thermostat would not protect against.

The S plan grey and orange are the colours normally used on the V3 micro switch, grey feed in, orange to the boiler, the central heating side has a by-pass valve. So should the V3 switch stick, it would allow the pump to still circulate.

 

[Johnmdc]

I take it you are talking about a cylinder thermostat, if so then terminal 2 will be the satisfied connection which is only required on a Y plan system and not needed on a S plan.

 

[oldspark]

Yes cylinder stat it is Thanks for the replies and assistance. now I know I have it wired correctly. as they say its best to measure twice and cut once