Replacing this thermostat

jr1985

Well I swapped it and nothing blew up but I'm still not convinced it's working. I set it for 22C and once my room thermometer read 20C, I turned the thermostat down to 18C and the boiler continued firing, even after several minutes.

I'm thinking of trying a new thermostat - Honeywell THR870C. Would it be possible with the wiring already in place? If so, where do they go (the instructions for that have A B C instead of numbers).

bridgedino

its unlikely that your room thermostat and the central heating thermostat will be a 100% match. Don't use them as comparisons unless they are side by side and even then they won't be a perfect match

Try it again without looking at your room thermometer constantly

My central heating thermostat is in my hallway. If I set it to 20 then every room in the hose would be at a different temperature. Only the exact spot where the thermostat is located would eventually reach 20 and shut off the boiler

chappers

Ignore the numbers, turn it down until it clicks, wait a few minutes some boilers are so quiet you cant really hear the gas burning, but the fan will run on for a while. After a few minutes is the boiler off, there may be an indicator light when the boiler is fired up. If it is off, turn the stat up until it clicks, does the boiler fire up, may take a few seconds.
Make sure any timers are set to on obviously.

macman

Why are you spending your money on this in a rented property? Contact the LL or LA and get them to sort the problem.

jr1985

Well because I wasn't sure if the thermostat was malfunctioning, or I was just being stupid. Also, I want to fit my own digital one and I'm guessing the LL isn't going to want to fork out for one himself since he installed a cheap manual one.

Anyway, I managed to fit a Honeywell THR870C. I put the brown wire into A and the green/yellow wire into B, wrapped the blue wire in electrical tape and tucked it away. The switch on the boiler has 3 positions - off, timer and on. I assume I just leave it to on and let the thermostat take control.

The digital thermostat says the room temp is 20C and the target is 18C. The boiler goes off but comes on every so often and the radiators are warm.

jr1985

Ok something still isn't right. I turned off the thermostat but the boiler keeps cycling on and off for 5 minutes at a time. Is there something I could look at myself, like the wires on the boiler, or is it time to call the landlord?

EDIT: I completely disconnected the the thermostat, made sure no wires were touching, and turned the central heating back on. Boiler fired up and cycled every 5 minutes again. :-/

TheCyclingProgrammer

What sort of boiler and heating system do you have? Do you have a separate water tank or is it a combi? What boiler is it?

jr1985

It's a combi boiler - Vokera Compact HE.

bridgedino

http://imgur.com/RCIaTxX

jr1985

Thanks! It turns out only the neutral (blue) wire was attached to the boiler! The other two were just hanging there. I've attached the Live (brown) based on the image you linked, but I wasn't 100% about where to put the green/yellow. Does it go in the far left socket, if blue is in the far right (or "top" if blue is in the "bottom")?

http://imgur.com/a/uw8Bs

I know the photos aren't the best, it's in an awkward position.