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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> Electrical Thermostat wiring https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1315389414 Message started by Ewan on Sep 7^th, 2011, 10:56am

Title: Electrical Thermostat wiring
Post by Ewan on Sep 7^th, 2011, 10:56am

A mains operated thermostat has three conductors to enable it operate correctly. Is it possible to connect to an existing 2 core plus cpc cable, and if so, why :-??

For info, I'm reading theory on basics with an intention of qualifying eventually as a domestic electrical installer, but books are books and I've hit a wall; any help would be very much a bonus.

Sincerely, John

Title: Re: Electrical Thermostat wiring
Post by thescruff on Sep 7^th, 2011, 4:12pm

Assuming you're thinking boilers electrics, the first lesson is to find out how the controls work and how the system are designed to work.

There's a hundred and one stats, some require a neutral for the anticipator, while others may be 240v 24v or volts free.

Can you run a single cable, yes if it's the right cable, I would use it as the switched live keeping the pair as L&N.

Title: Re: Electrical Thermostat wiring
Post by CWatters on Sep 7^th, 2011, 8:49pm

Are you really asking if the earth wire in a T&E cable can be used to run neutral if the stat doesn't need an earth?

Title: Re: Electrical Thermostat wiring
Post by Lectrician on Sep 7^th, 2011, 9:01pm

If you are asking if you can use a twin and earth cable, using the earth as the third core, then NO! You must not do this.

Yep, it may well work but would be hugely non-compliant.

No inner insulation on the earth, no way of safely terminating it, no earth provision at accessory (required even if not used).

Title: Re: Electrical Thermostat wiring
Post by Ewan on Sep 8^th, 2011, 3:48pm

Thanks eveyone; The question I've been asked is as I thought a tad ambiguous, when I can get hold of a tutor to speak to I will get him to clarify...thanks again.

Title: Re: Electrical Thermostat wiring
Post by CWatters on Sep 8^th, 2011, 4:27pm

Some stats like this one can be used with three+earth or twin+earth (the latter needs a battery to power the stat).

http://www.screwfix.com/p/danfoss-tp4000-24hr-programmable-room-thermostat/90659