just done a board change on a domestic property and i have got faults on 2 32 socket circuits nitemare is there any quick way other than obvious of starting from the first socket then all around the ring, can i measure the fault out with my megger please helppppppppppppppppppppppppppppppp
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RCD tripping on circuits after new board change nitemare
Discuss RCD tripping on circuits after new board change nitemare in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net
P
PC Electrics
Come on, throw the dog a bone!! We need more info.
What test results did you get on the circuits?
Have you checked you have connected the neutrals up to the correct bars?
Have you checked for cross connection between circuits?
Have you tested the RCD?
What test results did you get on the circuits?
Have you checked you have connected the neutrals up to the correct bars?
Have you checked for cross connection between circuits?
Have you tested the RCD?
O
Octopus
What type of "faults" have you got?
How many CU changes have you done before?
Have you tried asking your scheme's technical support?
How many CU changes have you done before?
Have you tried asking your scheme's technical support?
O
Octopus
May be your lack of proper testing has bitten you on the bottom!
M
Megavolt
Try find middle fo ring split it and then test both legs at board then at least you will know which half to consentrate
O
Octopus
I think an IR test would be my first step, but I'd have done one as part of the dead tests.
E
Edd
reading this, it looks like the IR tester's gota be dug out the bottom of the van.... 2 rings down,, either two seprate faults or the rings have got mixed up.. pretty unlucky ... you gota start with the basics, witch would be as soon as the trip went dig out the tester,, should take a sparks less than an hour to narrow it down to at least an area, and get some power on at worst on radials...
yeh yer rite mad murdock
V
vernam616
I suggest calling a electrician mate
E
Edd
ok too be more helpfull,,, disconect the neutrals,, leave the earths conected, they give a good refrance point.switch the mcbs off to the faulty circuits. IR test between N-E and L-E if yoo see a reading less than hmmm lets say 5 Mohm then yoo need to start splitting the ring... you really should be looking at greater than 999M ohm or at worst on a normal T and E instalaton at least greater than 100... if you do get greater than 999 then theres a crossed neutral or somthing... but start with one ring and split it. test both legs the one thats good reconect.. see whats working.. mega bad leg. split again.. and keep going..and breath...
Last edited by a moderator:
V
vernam616
My reluctant suggestion would have been to check the rings aren't crossed, however ive got a good reckoning that you havnt split the circuits properly on the new dual RCD board, otherwise this easy to rule out method would have been acheived straight away
- Reaction score
- 1,168
As you say Vernam,
My first move would have been to make sure the circuit was split properly (ring continuity).
Then do as Edd suggested, but first test across the now disconnected Neutrals to the other sides Neutrals @250V (to rule out any interconnections), before following on with the rest of edds recommendation but again @ 250V first, for the reasons I have already given.
But then again I would have tested for this even before, or at least during the CU change.
My first move would have been to make sure the circuit was split properly (ring continuity).
Then do as Edd suggested, but first test across the now disconnected Neutrals to the other sides Neutrals @250V (to rule out any interconnections), before following on with the rest of edds recommendation but again @ 250V first, for the reasons I have already given.
But then again I would have tested for this even before, or at least during the CU change.
I think mixed up the two rings might be a good call so try end to ends first as u should have done already but if not that might be the culprit....as its unlikely to be both rings that have faults on but not impossible, especially if u have put one ring on one side and one on another and both rcds trip, u may have them mixed up as I say
- Reaction score
- 303
I think some more info is required as to what dead tests were performed.
If you say the neutrals are on the correct bars is that because you carried out the 3 step dead tests on the ring finals.
If they are correct and everything is disconnected and both RCD 's are tripping its down to IR testing.
With a 30 mA RCD it should hold above 7666 ohms so once you start IR testing if you get a 0.00 M ohms reading its time to switch over to low ohms and start to work out where the fault /faults are by spliting the ring etc as has already been mentioned!
Is there any quick test with your Megger???
If you get a low ohms reading when testing as a guide to get nearer the fault you can use a bit of maths to give you a rough distance to the fault as you will know the resistance of the cables you are testing.
Once you have completed the dead IR tests let us know the readings !!
If you say the neutrals are on the correct bars is that because you carried out the 3 step dead tests on the ring finals.
If they are correct and everything is disconnected and both RCD 's are tripping its down to IR testing.
With a 30 mA RCD it should hold above 7666 ohms so once you start IR testing if you get a 0.00 M ohms reading its time to switch over to low ohms and start to work out where the fault /faults are by spliting the ring etc as has already been mentioned!
Is there any quick test with your Megger???
If you get a low ohms reading when testing as a guide to get nearer the fault you can use a bit of maths to give you a rough distance to the fault as you will know the resistance of the cables you are testing.
Once you have completed the dead IR tests let us know the readings !!
E
Engineer54
Yep!! At the very least it will tell you if any problems are found, it's not from any mistakes that you have made at the CU on completion... I mean how long will it take to carry out a few brief tests prior to changing the CU anyway??
E
ezzzekiel
Never understood why after a cu change people start having problems due to existing faults, if you aren't prepared to address them then should you really be changing the board in the first place?
- Reaction score
- 520
Always do eicr on installation before you change board slow down do the tests properly once there ok you can change board in few hours it's easy knowing in advance your board is not going to trip learnt the hard way myself when I was younger lol
V
vernam616
Testing before or afterwards dont suppose really matters does it, its still a fault
A better thing when quoting would be to inform the client of the price and then notify them that you have a hourly charge for finding faults on on completion of the new board
Ironically i changed a board this morning, never tested before hand and powered it up, from experience i had already pre determined that they maybe a borrowed neutral from landing light, and there certainly was, so lighting circuits went onto the same mcb, not conventional maybe but not really breaking any rules
A better thing when quoting would be to inform the client of the price and then notify them that you have a hourly charge for finding faults on on completion of the new board
Ironically i changed a board this morning, never tested before hand and powered it up, from experience i had already pre determined that they maybe a borrowed neutral from landing light, and there certainly was, so lighting circuits went onto the same mcb, not conventional maybe but not really breaking any rules
The only rule it is breaking is that a potentially dangerous situation exists for any electrician working on the circuits who assumes that the wiring was done correctly in the first place.
Seen an electrician thrown off steps due to a borrowed neutral.
V
vernam616
Well whats he doing working live then?
The lighting circuits are on the same MCB, so if anyone needs to work on this circuit they should be isolating
I could understand your point if i had put them on seperate mcbs on the same side
The lighting circuits are on the same MCB, so if anyone needs to work on this circuit they should be isolating
I could understand your point if i had put them on seperate mcbs on the same side
V
vernam616
Have a little think about what you post before hitting "post reply" button Mick
Agree Tel.
I did.
V
vernam616
Nobody said they condoned it, but if the client doesnt want damage or cannot afford to have the circuit altered the alternative is putting them onto the same mcb, yes not conventional but practical and still safely protected by mcb and rcd. Do you understand that if someone isolates that mcb that the neutral wont be live?
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