fuse in spur that feeds central heating keeps blowing

[pb21]

I have been on holiday for a month and so to avert flooding problems with frozen pipes drained the system and turned everything off.

On my return I refilled the rads and bled them. then ran the water for a little while.

the boiler pilot light is on (baxi bermuda 552). I put the control to water and heating (landis & gyr) and the boiler ignited and then a few seconds after heard the fuse blow that supplies everything (3 amp in a fixed fused spur).

I replaced the fuse and it blew again immediately.

1) is it possible to disengage the pump and see if that stops the problem, so at least i can get hot water by bypassing the programmer.

2) do you think this is the programmer or the pump? I cannot see anything else that it could be as there is no midway vale fitted.

Regards in advance

Peter

 

[breezer]

switch mains off dissconect wires from pump (and isolate them) switch mains back on

 

[oilman]

You should be diagnosing this with the power off as it blows fuses straight away. You should check wire shorts and component (pump etc) values before switching the power on.

 

[pb21]

It still blows with the pump disconnected, so I assume its the programmer type RWB2 by Landis and Gyr which looks very old. there are 3 cables one mains supply, one for the pump and one to the boiler which showed no evidence of shorting although I am not a plumber but am competent with electrics.

can I hard wire this to start? just to get hot water and the rads warm?

regards

 

[marios_kin]

The controller/timer is simply an automatic switch, therefore you could theoretically hard wire it and operate the boiler and pump manually, with the mains switch. At least that way if it blows again you will know it aint the controller.

 

[pb21]

I have bought a new controller and connected it up as it is a direct replacement to the old unit. I have left the boiler unconnected and connected the supply and the pump.

The fuse doesnt blow under that condition ie the pump starts up and the programmer functions, so logic dictates that its the boiler.

As its gravity fed there is no 3 way valve so I assume the only part left having read another similar message is the gas valve on the boiler?

I assume now that this is the end of the road for it and its not an easy fix as its a back boiler and I cannot see for the life of me any control circuitry to look at.

regards in advance of a speedy reply.

Peter

 

[galwag]

Peter do not carry out any further work it is unlikely to be gas valve
What I have seen on a number of occassions is the supply cable to the back boiler scorched & burnt thus causing fuses to blow. This is caused by boiler sooting up and blocking heat exchanger and therefore flames will lick out front of boiler instead of going up flue.
This will have potentially fatal consequences
Get corgi guy to carry out a service.

 

[pb21]

Galwag & others

Thank you for your assistance, I only just read the posting and in fact subsequently discovered that Galwag was correct the supply cable was burnt out completely scorched.

I have replaced it and rerouted the cable and all functions well. The boiler was serviced last june which is strange that it is causing problems, I have checked it on firing up and it seems ok with no external flames seen.

I will keep on eye on it regularly.

once again a big to you ALL the help you all gave, gave me the confidence to check logically and trace the fault plus thank you to those behind the scenes on the forum.

Regards
Peter