Boiler controls - blown fuse

[Shed Steve]

The power failed to my Wickes RWB 200 CW boiler programmer this afternoon. I replaced the blown fuse in the supply outlet, that promptly blew on switching power back on.
I would like to know, if it is likely to be a failure inside the programmer itself, or is it likely to b elsewhere. The programmer is about 20 years old. The boiler is 1991 Glowworm Hideaway 60CF, so not many electrics in that, no PCB's. The pilot light is still on, and the CH pump is not in use this time of year either.
Any advice would be much appreciated, thank you.

 

[twgas]

Was HW or CH turned on at the prog when you reinstated the power?

 

[Shed Steve]

twgas, thankyou for reply. HW only was on when turned power back on.

 

[mickthegas]

pump or gas valve

 

[Boilerman2]

A 20 year old system is probably "Fully Pumped" i.e. the circulating pump operates for HW as well as CH.
The fuse can blow for a variety of reasons and a methodic investigation will be required but in order of likelyhood I would suggest:
1) Circ Pump
2 Motorised valve actuator/s
3) damaged wiring within the system
4) gas valve on boiler

happy hunting!

 

[Shed Steve]

The system is actually 49 years old, with boiler, pump and controller replaced around 20+ years ago. The HW is gravity, not pumped. Therefore, as the fuse blew in HW mode, I believe the pump would not have been connected. Following my last post here, I put another fuse in, disconnected the boiler power supply, switched on and fuse blew. Yet another fuse went in, disconnected the programmer off its back-plate, switched on and fuse did not blow. I reckon, there may be a fault in the controller. However, I would appreciate and value the views and opinions of others.

 

[Aquaheat]

Ensure that ALL power is of to the central heating system!!

Remove the programmer and disconnect the wires for heating on/off and hot water on/off. Ensure that these are safe from touching any live services!!!

Leave only the live, neutral and earth connected to the programmer.

Replace programmer on wiring assembly and power up. If the fuse still blows its definitely that. If not then you need to start looking elsewhere.

 

[Shed Steve]

jonjb, that is a good idea. I'll try that tomorrow, need to buy some more fuses!

 

[Aquaheat]

jonjb, that is a good idea. I'll try that tomorrow, need to buy some more fuses!

Make sure they are 3A!!

 

[Boilerman2]

fitting a "nail" instead would cause the faulty component to show its self by blowing to smythereens !

 

[Shed Steve]

Just fitted a replacement programmer, Siemens RWB-29, direct to original back-plate, seems all OK again now. I should have known the old one was faulty, as a few weeks back, I was walking past it about midday when the boiler fired, and it's timed off between 07.30 and 17.00hrs this time of year!