Fused Switch On Boiler Circuit

[dnh]

Hi,

I have a 5A fused switch mounted just alongside my Grant oil-fired central heating boiler with two programmers (one for the hot water/central heating and the other for the underfloor heating). When I turn ON the fused switch, the 5A fuse will always "blow" immediately and the RCD circuit trips.

In looking to isolate the cause of the problem, I have checked that the fuse will still "blow" even after having done the following ...

- turned the boiler itself OFF
- disconnected (i.e. physically removed from wall) the TWO programmers
- disconnected the room thermostat (in kitchen)

I have also just had the boiler serviced so, hopefully that should all be working fine.

Could I possibly ask whether anyone has any thoughts as to the reason for the circuit tripping, or any follow-up checks that I could perform to make some progress ?

Thanks again.

Regards,
David

[BLAKEY1963]

[quote="dnh"]Hi,

I have a 5A fused switch mounted just alongside my Grant oil-fired central heating boiler with two programmers (one for the hot water/central heating and the other for the underfloor heating). When I turn ON the fused switch, the 5A fuse will always "blow" immediately and the RCD circuit trips.

In looking to isolate the cause of the problem, I have checked that the fuse will still "blow" even after having done the following ...

- turned the boiler itself OFF
- disconnected (i.e. physically removed from wall) the TWO programmers
- disconnected the room thermostat (in kitchen)

I have also just had the boiler serviced so, hopefully that should all be working fine.

Could I possibly ask whether anyone has any thoughts as to the reason for the circuit tripping, or any follow-up checks that I could perform to make some progress ?

Thanks again.

Regards,
David[/quote]

DAVID

Check in the manual power rating of appliance , and see what
size fuse is recommended.
If as u state , u have swictched off boiler and asscociated
programmers and stat , and boiler has been serviced by
an OFTEC registered engineer , conversant in oil boilers ,
THEN some sort of fault is present.
Other than turning off POWER at THE MAINS BOARD ,
MAKING SURE POWER IS OFF , AND CHECKING spur 4
loose or faulty connections , and melted flex feeding
boiler from spur , then u need 2 get in an electrician.

BLAKEY1963

[dnh]

BLAKEY, Thanks for this advice.

I should have mentioned that the boiler had been working (for years) up until the circuit "tripped" and now every time the fused switch is turned on the 5A fuse "blows" ... I am assuming the fuse rating is correct since it has been working for all that time.

Given that the circuit only "trips" when the fused switch is turned on, would I be correct in thinking that the fault (as you have suggested, perhaps, a loose or faulty connection) is likely to be "downstream" of the switch i.e. on the boiler/programmer side (even though the boiler is turned off and the programmers disconnected) ?

Is there a possibility that the fused switch itself is faulty ? ... would it be worth my while just changing the switch and seeing if that makes any difference ?

You have certainly given me some ideas.

Thanks for all your help.

David

[sparx]

Hi it may be worth a look inside boiler as it is possible the guy doing the service trapped a wire when refitting cover, it could have taken a while to fret through,
regards SPARX

[TOPSPARK]

You have'nt said if the underfloor heating is off the boiler or is electric and connected into the same circuit for convenience.if the under floor heating is electric then you need a 13 amp fuse for this but you will need the circuit altering as you only need 3amp for the boiler circuit .As I can only summise what you need done best to get in a local registered electrician to have a look
regards
Topspark

[dnh]

Thanks to sparx and TOPSPARK, for sharing their ideas. I will take another look later today.

The boiler service (obviously not yet fully completed) was performed AFTER the fuse problem had developed. I suppose there is a possibility the cable had been trapped from last year's service (after which everything was then running just fine for around 9 months). Something else for me to check javascript:emoticon(':wink:')

The underfloor heating is coming off the boiler also and everything has been working fine for several years.

From the comments here, it seems as though the problem (faulty wiring ?) is on the boiler side of the fused switch. I will investigate a little more before calling out my local electrician.

Thanks again for all your ideas, they have certainly given me "food for thought".

Cheers,
David