I bought a heatmiser Prt digital thermostat unit to upgrade from the previous owners old honeywell T40...
First of all i wired it up with out fitting it to the wall to make sure all was good and in working order from the existing wiring and tried it with the boiler all good !!
I turned off the heating disconected the wiring so i could open up the unit to mount it on the wall,connected it up as it was when i pre tested it put the heating back on then nothing what so ever no display nothing all on the unit.
Can anyone give me any info as to what could of poss happened,thanks