Room thermostat replacement

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Original Poster:

189 posts

170 months

Wednesday 21st September 2011
quotequote all
I'm wanting to replace a vintage (80's?) sunvic tlx room stat as it is rather tired and dated .
I popped the cover off to look at the connections and this is where I'm a bit confused .
I was expecting a three wire and earth install . What I have is red and blue connected , an isolated (badly) yellow wire and an unsleeved earth that I presume goes to the back box . Is this going to be a nightmare to replace ?
System functions well at present if a little old fashioned . Help !

Rickyy

6,618 posts

220 months

Wednesday 21st September 2011
quotequote all
Its quite a simple task, especially if you understand how a thermostat works.

It is an adjustable heat sensitive switch. When calling for heat the switch is closed and when satisfied its an open circuit.

The two wires that are connected will be the switch wires. One will be live going in to the stat the other will be live out, going to the pump/zone valve/boiler depending on what setup you have.

Make sure you buy a stat that does not require a neutral to work. Some will have a neutral terminal for an anticipator, but will work without a neutral, others will not work without a neutral.

When you get your new stat, identify the common and demand/normally open terminals. These are the two your switch wires need connecting to. The earth will not be needed as the new stat will most likely be all plastic. Good luck!

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Original Poster:

189 posts

170 months

Wednesday 21st September 2011
quotequote all
Thanks Ricky , guess I was getting hung up on coloured wires . Most stats seem to be 2 wire now so should be ok if I can identify switch live and live !