rcd tripping

[i=p/u]

i got call today saying rcd tripping one side of the board, he called when i was passing , so i popped in and tuned all switches off and turned on one by one and leads me to the fused spur for the gas heating... anyway left to monday now ...... what would you logical approcah be to this, i will start from scratch, has anyone anytips to speed me up as i am slow as a donkey when comes to this fasult finding.... thanks

 

[telectrix]

so, what led you to the heatinf FCU.?was it that the RCD tripped when you turned the FCU on?

 

[cagedanimal2010]

disconnect the boiler out of the spur, test from spur to db,

 

[i=p/u]

yh trpped soon as you turn on switch

 

[i=p/u]

left her with no heating now, so want to fi x first thing monday and im ment to be starting another job monday morning so want to be quick and away if i can....

 

[i=p/u]

im in with few rich dudes and they offering me more work than i csan chew.... so trying not to pannic and trying not to say no, cant do it

 

[telectrix]

so, go round and turn everything off. then switch the FCU on first. if it trips, you've found the fault. if not it's probably cumulative leakage. i.e. a bit here , a bit there till it adds up to the RCD threshold. i would suspect the boiler and it's associated garbage as a plumber has been there.

 

[i=p/u]

well she said plumber came out and fittered about with it and says the problem lys with in the fcu or thermostat on other wall.... would acumlitive leakage build up over time.... cause has only happened

 

[cjp1]

I have had similar problems on conventional systems and has turned out to be the heating pump or motorised valve knackered.

 

[tical]

There are a number of things associated with the boiler that can cause the RCD to trip. If you have proved that only the boiler FCU trips the RCD then disconnect the outgoing boiler supply and test the cable back to the CU. If that checks out fine then the fault lies within the boiler/boiler control wiring, ie, roomstat, pump, motorised valve, cylinder stat on tank (which often get damp when the sleeve they sit in fail), trapped cable when the plumber put the boiler cover back on etc. So this could take 10 mins or 2 hours !

 

[i=p/u]

so if i do my R1 and R2 and insulation resistance between cu and fcu and thermostat. it has to be problem with bolier... or as telectx said earth leakage between 4 circuits on rcd.. has any of you evr turned upto a job where you couldnt do nothing as was fault with gas boiler... did you still ask for payment???

 

[telectrix]

i'd go for the pump first.

 

[i=p/u]

aint easy being half a spark, quarter

 

[cjp1]

i'd go for the pump first.

I second that,

 

[cjp1]

so if i do my R1 and R2 and insulation resistance between cu and fcu and thermostat. it has to be problem with bolier... or as telectx said earth leakage between 4 circuits on rcd.. has any of you evr turned upto a job where you couldnt do nothing as was fault with gas boiler... did you still ask for payment???

Is it a combi or condensing boiler?

 

[i=p/u]

its a condensing boiler and apparently its pretty new......

 

[i=p/u]

could i just swap to non rcd side,, what is the risk factors with this???

 

[cjp1]

could i just swap to non rcd side,, what is the risk factors with this???

This is something I would never recomend doing because you only hide the problem and could possibly be the cause of a fire .
There is nothing to say that you dont have a low resistance fault between live and earth that will trip a mcb anyway.
at present the RCD could be tripping first because it is more sentive to live/earth & neural/earth faults.
If you think it could be a problem with the rcd then test the rcd as normal you could also ramp test the rcd to see what current it actually trips at.
If the rcd test is good you could Isolate supply and try removing the feed to the pump first and see if this makes a difference.

 

[Deleted member 9648]

You should IR test all circuits.....even if turning something off/on appears to stop/cause the tripping.... RCD's are funny things and the problem may lie elsewhere. Only a full IR test on circuits connected to the tripping RCD can truly eliminate other causes.

 

[malcolmsanford]

could i just swap to non rcd side,, what is the risk factors with this???

Are you telling us that you have left someone without heating and if it's a combi most likely without hot water over the weekend, and there is a non protected side of the CU available?