Help required wiring in digital thermostat

[MirfDiver]

Hi,

Was wondering if anyone could help. Recently moved into a new house (there will no doubt be more Q's coming!) and decided to replace the central heating thermostat (common system set-up, normal boiler - Potterton, dual timer, hot water tank, rads etc).

Thermostat was hanging off the wall. Bought a new digital one and wired (on second attempt following web research) per the photo below. It appeared to work at first but then was evident that it hadn't as central heating kept firing up constantly despite the timer being in the off position.

Wiring diagram is also shown below too. Can anybody assist with indicating which of the coloured wires should go wire within the thermostat?

Thanks

New Thermostat wiring pic 1

• MirfDiver
• 21 Jul 2011
• 1

New Thermostat wiring pic 2

• MirfDiver
• 21 Jul 2011
• 1

 

[seco services]

You only want 2 wires.
L from heating programmer on to A
SW/L to motorised valve on to B

 

[picasso]

unfortunately the colours dont mean anything, most installers when using these wires would use the red as common, the blue as neutral and the yellow as switched live, IF your wires follow this convention then you would remove the blue and tape it up out of the way, the red would go into A and the yellow would go in B, you would need to go into the wiring centre to be confident of what went where.

 

[MirfDiver]

Brilliant, thanks. I'll give it a go tonight.

 

[D_Hailsham]

New Thermostat wiring pic 2

• MirfDiver
• 21 Jul 2011
• 1

This diagram shows two wires connected to the thermostat.

What made you think you needed three? (Ignoring the earth, which isn't needed either and should be made safe.)

 

[bengasman]

(Ignoring the earth, which isn't needed either and should be made safe.)

Another bit of wondeful advice from our resident arm chair specialist.

The only wire in the picture that is actually connected correctly, is the......... "earthwire".
How do you suggest to make an "earthwire" safe that is already connected correctly?

 

[D_Hailsham]

The only wire in the picture that is actually connected correctly, is the......... "earthwire".
How do you suggest to make an "earthwire" safe that is already connected correctly?

The thermostat is a Class 2 device, which does not need an earth wire and should not have one.

The wire wrapped round the screw is not eathing the thermostat, just the screw, which would be safer if it was not "earthed".

 

[bengasman]

The wire wrapped round the screw is not eathing the thermostat, just the screw, which would be safer if it was not "earthed".

So what should be done with this wire?

 

[matt1e]

The wire wrapped round the screw is not eathing the thermostat, just the screw, which would be safer if it was not "earthed".

So what should be done with this wire?

terminated into a connector,the same with the neutral (made safe as per D hailsham's previous post)
He (the op) has actually been lucky he didn't connect the live on the common

Matt