Electrical Problem?

[foxhole]

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See pics, Danfoss controller has blown, this was after a series of blown fuses in the supply to the controller, not sure if there is a problem with wiring or the contoller itself was faulty, have replaced with a spare unit but now when selecting heating or hot water the three port valve opens and the pump runs but the boiler does not fire up.[pilot light is lit]There is a live supply to the boiler [potterton kingfisher floor standing model] even when no hotwater/heating is selected.Is this correct?
Should this post be in the electricians forum?

 

[simond]

See pics, Danfoss controller has blown, this was after a series of blown fuses in the supply to the controller, not sure if there is a problem with wiring or the contoller itself was faulty, have replaced with a spare unit but now when selecting heating or hot water the three port valve opens and the pump runs but the boiler does not fire up.[pilot light is lit]

Pump on Kingfisher is linked to boiler live...... assumings its not a Kingfisher MFL

There is a live supply to the boiler [potterton kingfisher floor standing model] even when no hotwater/heating is selected.

Shouldn't be a perm live, if there was the pump would be on 24/7.....

Is this correct?
Should this post be in the electricians forum?

Many electricians can't wire boiler controls, strange but true.
Did you change the Danfoss for another Danfoss? This is the £6million dollar question.

 

[Goldberg]

Danfoss controller has blown, this was after a series of blown fuses in the supply to the controller

Could you be more specific - how many fuses, and what was the rating of each one?

have replaced with a spare unit but now when selecting heating or hot water the three port valve opens and the pump runs but the boiler does not fire up.

What's the rating of the latest fuse?

 

[foxhole]

Thanks for reply, the danfoss replacement was identical model, the fuse was 3 amp replaced about 5 times before controller blew, current fuse also 3amp.Not the MFL model , over 15 years old and not new when installed.
So live to boiler without pump running suggests a wirings problem?

 

[DP]

I would have to say the problem is size of fuse fitted. This kind of damage often caused by fitting a 13 amp fuse. Result is fuse does not blow but the track in the timer does. Seen this often

 

[foxhole]

3 amp fuse????

 

[bengasman]

Stating the obvious: repeatedly blowing fuses indicate a problem. At this stage I would say the whole wiring needs checking/measuring if you don't want to risk blowing the timer again.
Part of the problem is that just about every wiring job I see is botched. At the very least the wires are not colourcoded correctly which makes the chance of mistakes a lot bigger. Maybe not a lot for the chap that stuck the lot in originally, but for whoever works on afterwards.
Most common faults:
Sleeves not entering wiring centre or other connections.
Earth used for live.
Wires in terminal strips screwed too tight or not tight enough.
Considerable visible copper outside connections.
All of these things can cause problems in the long run.

 

[Goldberg]

the fuse was 3 amp replaced about 5 times before controller blew

I think you need to adapt your fault-findng methods, because a fuse rarely blows for no reason.

If you don't already have a working multimeter with a new battery in it, then please go and buy/borrow one before you do anything else.

 

[foxhole]

No doubt you are always right, but how does that help me?
Boiler installed 15 years ago by a relative, corgi registered with about 20 years experience, no been worked on or altered since apart from boiler service which was little more than a vacuum and replacement thermocouple.

 

[foxhole]

Have a working multi meter, open to suggestions.

 

[bengasman]

Check the whole thing out, cable by cable. Mark and colour code (sleeve) as and when.
Make sure the sheath goes in everywhere, and connections are neat.
Good chance this will cure it.

 

[Goldberg]

Do some basic checks with both thermostats on minimum

CH and DHW deselected at the programmer - verify no output from programmer, or 240V at 'CH off' and 'DHW off'.

CH only selected - verify 240V at 'CH on', and supply reaches roomstat.

DHW only slected - verify 240V at 'DHW on', and supply reaches cylinder stat.

 

[foxhole]

With both CH and DHW off at programer there is live at pump, valve, boiler and supply to DHW stat.?

 

[Goldberg]

With both CH and DHW off at programer there is live at pump, valve, boiler and supply to DHW stat.?

Can you trace where those are being supplied from?

Also, did you verify that you have 0V at 'CH on' at the programmer?

 

[foxhole]

Thanks, but will have to check out tomorrow, need a lay down at the moment, have slipped disc in my neck and with most of the wiring connections up in a ceiling void it's become a real pain in the neck to look up for too long.