Room thermostat wiring and damage to boiler programmer

[lee_m]

I have recently replaced my analogue, dial, room stat (Potterton PRT2) with a battery powered Siemens RDD10.1 (not 10). However, I accidentally connected the neutral wire to the Q12 connection when wiring the RDD10. Result; 3A fuse at the boiler/programmer (Potterton PRT2002 controlling Suprima 50) blew. Replaced fuse and disconnected incorrectly connected neutral (now unused). RDD10 stat works well but now when it switches on to call for heat the boiler will fire even though the programmer says it is 'off' and therefore the boiler shouldn't come on even though the stat is switched on. Any advice please very, very gratefully received.

One plan I thought, to save programmer replacement, was to change the stat for a programmable one and therefore get around the lack of timer control at the programmer. Any safety issue with this? I assume that the switch in the programmer was damaged and is now permanently in the 'on' position. Hot water does not appear to be affected in the same way, i.e. if the cylinder stat calls for heat and the programmer is 'off' then the boiler does not fire up.

Many thanks in advance for any help.

Mike

 

[stem]

Sounds to me like the contacts in the programmer welded together by the current drawn when the fuse blew.

If so, what you suggest would work, but it would be better to replace the programmer. The "weld" may, or may not be permanent and it could introduce a resistance into the circuit.