New thermostat wires

[enz]

Hi, trying to replace an old thermostat and can't figure out the correct wiring. I've tried different combinations but I always seem to trigger the mains switch! I've attached a picture i took of the old one before removing it! Any help would be appreciated! Thanks

 

[333rocky333]

It's likely the red and yellow pair do the switching whilst the blue is a neutral , if so you need to be carefull where you connect the blue

 

[CountryFan]

whilst the blue is a neutral

Usually on those Honeywell dial stats are 2 neutral, so makes sense. @enz - new stat only needs the red and yellow (to A and B) as above as new stat is battery powered. Safely isolate the neutral wire (we’re thinking the blue)

 

[333rocky333]

Honeywell

 

[enz]

Cheers rocky, I've tried that but still it still triggers the mains for some reason! Can't get any power on the boiler or the main thermostat next to it!

 

[CountryFan]

Cheers rocky, I've tried that but still it still triggers the mains for some reason! Can't get any power on the boiler or the main thermostat next to it!

Are you connecting the blue wire?

 

[enz]

Did initially, also tried without connecting, same result!

 

[CountryFan]

Did initially, also tried without connecting, same result!

Ok, it’s one of a few possibilities: your new thermostat is faulty, the existing thermostat was wired up incorrectly, you have a short via touching copper wires or have created a short by introduction, for example driving a nail into the wiring on the thermostat route (I’ve encountered this once)

 

[enz]

Possible, might have to get someone in to test it! Tho can't get the boiler to turn on at all!

 

[CountryFan]

Possible, might have to get someone in to test it! Tho can't get the boiler to turn on at all!

Possibly blew the 3 amp fuse. Have you tried reconnecting the old one?

 

[enz]

Cut the wires too short to fit the old one back! Thanks for your help anyway!

 

[AndyPRK]

Just join red and yellow together to see if at least you can get some heating

 

[enz]

Cheers Andy, tried but problem Is i can't get any power to the boiler as mains switch keeps tripping

 

[Harry Bloomfield]

Cheers Andy, tried but problem Is i can't get any power to the boiler as mains switch keeps tripping

Separate, and insulate, the three wires, and the earth. Now try switching on - does it still trip?

 

[AndyPRK]

well I think you have done some damage to the boiler, or something. Very difficult to tell from here. You will probably have to get a profesional out. But if you post some pictures of the boiler, timer, switch by boiler, consumer unit someone may have some bright idea's or things you can try.

First things:

1) You have mounted that new stat, have you drilled through a cable?
2) Have you tried switching off the switch/FCU by the boiler and seeing if the 'thing' no longer trips? Give us a picture of the thing that trips in the CU. Does it have a test button?