DIY Doctor UK DIY Forums

hi,

i have fitted a heatmiser prt-ts today to replace a 16 year old honeywell thermostat. It is being used on a combi-boiler.

I wired the red wire to L, blue to N, yellow to A2 and bridged A1 to L as per the installation instructions.

However when i switched the power back on the heatmiser shows no signs of life.

I was wondering if anyone has encountered the same problem and whether I have to do something to switch it on? The old thermostat was working fine, but I did have a new boiler fitted 3 years ago and I am now wondering whether the wiring may have been mixed up then?

Thanks

Phil

Hi Phil1,
had a look at the wiring diagram and it seems to be correct as you have it.
try connecting red to yellow in a connector block to prove circuit to boiler, better still use a standard one way light switch then you should be able to turn boiler on/off.
Check neutral is still connected at boiler since old stat would work without one just have a large temp. 'swing' or 'deadband' of several degrees.

one other thing is to check the ribbon cable is correctly plugged in the right way round,
regards Sparx

hi sparx, thanks for the replies.

i checked out the ribbon cable and that is the right way round, but i think i've found the problem out with the wiring at the boiler.

When i had the new boiler fitted 3 years ago, it was relocated across my kitchen, so the thermostat wires going into the boiler are of the new colour standard, the brown is going into terminal 1 and grey (switched live i think) is going into terminal 2, but the black (neutral i think) has been cut for some reason so not connected.

Now you mention it, that was the problem with the old thermostat, seemed to have a dead spot for a few degrees.

I guess i can just connect the black to the neutral terminal on the 230v input? but the other problem is where the junction box conncecting the new wire to the old wiring to the thermostat is located....as i guess that the neutral will not have been connected there!

At least i seem to have found the issue i think

thanks

phil