Replaced CH programmer, but heating doesn't work

diybob · Jan 21, 2022

I have got a 25 year old Potterton Profile boiler, quite basic and very reliable, on a fully pumped system. It has worked happily with a Glow-worm Mastermind RWB2 programmer, but just recently the programmer occasionally misses a switch-off. So I thought I’d replace the programmer and bought a Siemens RWB29Si programmer. It’s meant to be a direct replacement, re-using the existing base plate, with no wiring connection changes necessary. However, when I fitted it, it did not work. The backlit panel illuminates, the digital clock works, but I can only get the CH & HW to work by pressing the +hrs buttons. It will not come on automatically when it’s programmed to, nor will it come on when pressing the advance button. So I’ve had to refit the old RWB2 and it’s working fine. (I am a retired electrician, and the wiring is okay and not been changed since the boiler was installed, so I don’t think it’s that.) Either the new programmer is faulty, or there is something simple I’m missing in the set up. Any ideas?

ShaunCorbs · Jan 21, 2022

The old wiring matched up with the new wiring set up eg on the back of the old clocks ?

diybob · Jan 21, 2022

ShaunCorbs said:
The old wiring matched up with the new wiring set up eg on the back of the old clocks ?

Yes I think so Shaun.

steadyon · Jan 21, 2022

Have you set the DIP switches on the back of the new programmer, particularly switch 5?

diybob · Jan 21, 2022

steadyon said:
Have you set the DIP switches on the back of the new programmer, particularly switch 5?

Yes, I've set the DIP switches correctly (they were already correct). I'll give it another go tomorrow, in case there's a 'set' or 'start' button I've missed! It's permanently off as far as I can see.