Thermostat wire colour query - should yellow be switched ?

[jamesb72]

I want to change the mechanical thermostat for a programmable room stat, both to have a 'night temp' and better programming.

The current mechanical thermostat has 3 wires which I've tested and found:
red/orange - live
yellow - neutral
blue - switches live as thermostat is moved, ie live for demand

My only concern is why blue is switched and yellow is live, I'd expect the other way round, but as I've checked this with a meter I am just going to use them as is.

 

[denso13]

If you get a two wire stat you won't need the neutral connection.

 

[Agile]

There is no standard way to use different colour wires.

Different installers do what they choose and sometimes you would think its intended to confuse people.

Thats why it should always be carefully tested.

You only need to use the live and switched live wires!

Tony

 

[jamesb72]

Thanks for replies, puts my mind at rest that it isn't a bodge job and this is normal

I chose a mains room thermostat as I figured it will be easier than having to change batteries (Horstmann AS1 as I like the simplicity of its display), so will use all three wires, and set the original timer to always on for heating so this room thermostat will control temperature all the time.