Help replacing a Stone Age stat

[CFR]

The front was on properly. I'm pretty sure because it took me 5 mins to take it apart so that I could remove the whole stat from the wall.

 

[CFR]

Do I have to program the new stat in any way? I'm asking because I didn't do anything like that. Just popped it on the wall and turned it on.

 

[Johnmdc]

No you don't need to.
Check that the 3 pins on the back haven't been bent.
You wouldn't blow anything by connecting it wrong. You just have a live wire and a switch wire.

 

[CFR]

The pins are not bent. Anyway, I'll give it a try again tomorrow. Thank you for your help @Johnmdc

 

[CBW]

I’d say it’s possibly a faulty thermostat, or the wiring could have been different on the old stat, as in the blue wire is switched as opposed to the yellow? I’ve had a few faulty new Honeywell thermostats fail out of the box.

 

[CFR]

I forgot to mention that I don't have a combi boiler. I have a really old boiler. Is it possible that it uses the mains voltage switching? This is the tank in the airing cupboard.

 

[CBW]

Is it possible that it uses the mains voltage switching?

The old one used 240vac switching. Your new one supports 24 - 240vac switching, so doesn’t matter.

 

[CBW]

Do you have any test equipment? A multimeter or 2 pole voltage tester?

 

[CFR]

The old one used 240vac switching. Your new one supports 24 - 240vac switching, so doesn’t matter.

I see. Thanks Chris!

 

[CFR]

Do you have any testing equipment? Multimeter, or 2 pole voltage tester?

I think I have a multimeter somewhere in the shed.

 

[D_Hailsham]

View attachment 209167

Is it a straightforward process (Like getting a 2 wired Honeywell and connect the red and the yellow wire only) as shown below?

Terminal 2 of the old stat is switched live. So it's the blue which has to be connected to A on the new stat.

I don't understand why the yellow wire is there - unless there is a cooling system or MOMO (motor on/motor off) valves. If the system still doesn't work, connect the yellow to terminal C, which is the equivalent of 3 on the old stat.

 

[ianmcd]

Terminal 2 of the old stat is switched live. So it's the blue which has to be connected to A on the new stat.

I don't understand why the yellow wire is there - unless there is a cooling system or MOMO (motor on/motor off) valves. If the system still doesn't work, connect the yellow to terminal C, which is the equivalent of 3 on the old stat.

really ? the blue is not connected to anything ?

 

[CBW]

really ? the blue is not connected to anything ?

It wasn’t the best photo (very 1st post) where there’s 3 wires poking through. So could it be that the blue wire is the switch?

 

[CFR]

Hope these photos are better.

 

[CFR]

So, the way I connect the wires to the new stat is: red to A, blue to B and if boiler still doesn't fire up try yellow to C?