RCD tripping overnight with nothing connected

[leew85]

Good evening. Had a new consumer unit fitted a week ago, Paid over £500+vat for a proteus 5+5 board to replace an old non-rcd board. Ever since it was fitted the right hand RCD has tripped in the middle of the night, between around 11pm and 7am, every night. This powers a socket circuit, an oven, hob and an alarm. The oven and hob were isolated at the control switches and the ring had nothing plugged in. In order to attempt to figure out what was causing the tripping I switched off the oven, hob and ring MCBs, leaving just the alarm on, it still tripped. I then disconnected the 3 neutrals for those circuits from the neutral bar and taped them up, it still tripped. I then disconnected the alarm, leaving nothing connected to the load side of the RCD, it still tripped. So I called the guy to report my findings that I suspect the RCD is a dud, as cannot see why else it would trip with no load connected. He turned up, used an RCD tester to make sure that the RCD tripped within range, which it did, said the RCD was fine and left. Guy who fitted it claimed there was a borrowed neutral somewhere, but really struggling to understand how the hell that could cause an RCD with no connection to the load side to trip. Can anyone here explain to me how the hell an RCD with no load connection can trip overnight like this?
Thanks, Lee.

 

[littlespark]

The guy who fitted it should have done a quick test on all existing circuits to make sure there wasn't any underlying faults before changing the unit.
A borrowed neutral would trip immediately, not randomly through the night.

Which RCD test did they do? One measures how fast it trips... has to be under 40 ms. The other, named a ramp test, measures how much fault it takes to trip it. Even though they are rated at 30mA, it could be lower. You may just have a very sensitive RCD.

Swapping the left and right RCDs over may rule out the RCD itself or the associated circuits. Please let a professional try this.... not for DIYer

If you have been into the box already, then i don't know how the installer will feel about honoring any warranty he may have given.

 

[leew85]

The guy who fitted it should have done a quick test on all existing circuits to make sure there wasn't any underlying faults before changing the unit.
A borrowed neutral would trip immediately, not randomly through the night.

Which RCD test did they do? One measures how fast it trips... has to be under 40 ms. The other, named a ramp test, measures how much fault it takes to trip it. Even though they are rated at 30mA, it could be lower. You may just have a very sensitive RCD.

Swapping the left and right RCDs over may rule out the RCD itself or the associated circuits. Please let a professional try this.... not for DIYer

If you have been into the box already, then i don't know how the installer will feel about honoring any warranty he may have given.

It was a ramp test, one RCD tripped at 24ma and other at 25ma, so both upper end of the range which I believe is between 15ma and 30ma for a 30ma rated RCD. I reported the nusance tripping after the first two nights and also the fact the consumer unit was not properly fixed to the wall, the guy had spaced it off the wall about 20mm with bits of wood but had not used longer screws so there is very little screw in the wall. I could wobble it on the wall! The guy came back to fix the wobbly consumer unit but moaned that he was not being paid for this (despite being paid £448+vat for 6 hours work to do the initial job). Also maybe worth noting when he first fixed the unit to the wall, it was tight into a corner, and the cover was a few mm larger than the box so in order to get the cover on, he must have had to put pressure on bank of mcbs in order to fit the cover off-centred and now wondering if this could have damaged them?
The guy said he would not investigate the nusance tripping unless I paid an extra £30+vat per hour and that it could take some time so decided to go down the route of disconnecting stuff until such time it stopped tripping, expecting to narrow it down to the defective circuit however ended up disconnecting the whole lot and it still trips. Would disconnecting the neutrals be cause for voiding of the warranty on the board? many thanks, Lee.

 

[westward10]

Can you show a pic of the consumer unit, we like pics.

 

[leew85]

Can you show a pic of the consumer unit, we like pics.

sure thing, outside and inside.
On an unrelated note, are there any regs concerning how far back the insulation is stripped on the incoming tails? I don't like the fact there is a few mm of live tail showing and would have thought the tail insulation should touch the main switch body? I was told by a mate years ago when wiring sockets etc to never leave bare cable showing outside the terminals. This is how it was when fitted with the exception of the disconnected neutrals in the top right and also a groove I cut in the wall to the left in order to get the cover back on without stressing the breakers. I took care to cover the electrics with some plastic sheeting and masking take to avoid any debris getting inside.

 

[DPG]

Did you take the cover off the bus bar?

 

[leew85]

Did you take the cover off the bus bar?

Nope there never was one

 

[westward10]

Those connections are pretty rough to be honest. There should be a plastic cover over the busbar which would have come with the unit.
If you have disconnected the neutrals and turned off the protective devices it shouldn't really be tripping.

 

[littlespark]

I’d like to say something positive about how he’s used a proper tails gland rather than just a hole.....

@westward10 , the tape is where the OP disconnected neutrals to try and find the fault.... read earlier in the thread.

Dog rough on the copper showing, and lack of busbar shield.

was your electrician a member of a CPS such as NICEIC?

 

[westward10]

I’d like to say something positive about how he’s used a proper tails gland rather than just a hole.....

@westward10 , the tape is where the OP disconnected neutrals to try and find the fault.... read earlier in the thread.

Dog rough on the copper showing, and lack of busbar shield.

was your electrician a member of a CPS such as NICEIC?

Yeah I reread the first post and edited it.

 

[leew85]

was your electrician a member of a CPS such as NICEIC?

Yep, NICEIC, although I have yet to receive the paperwork.

 

[littlespark]

Yep, NICEIC, although I have yet to receive the paperwork.

And you’ve already paid him?

Sounds like he’s not going to come back unless he gets more money, which is bad crack.

Did you disconnect the neutral link from the right hand rcd to the neutral bar? I can’t see it.

What was there before? As the brown/blue colours came in about 2005, and rcd’s would have been around then.
Did he have to joint new cables onto old to fit this new board, or has the property been rewired? I’m just wondering why it’s been changed

 

[westward10]

63A rcds I wonder what size the protective device is.

 

[leew85]

And you’ve already paid him?

Sounds like he’s not going to come back unless he gets more money, which is bad crack.

Did you disconnect the neutral link from the right hand rcd to the neutral bar? I can’t see it.

What was there before? As the brown/blue colours came in about 2005, and rcd’s would have been around then.
Did he have to joint new cables onto old to fit this new board, or has the property been rewired? I’m just wondering why it’s been changed

Yep paid after the board was fitted and everything appeared to be working and fine, it was only the next morning I realised there was a problem. I paid by PayPal so there maybe potential comeback there if needed.
The neutral link is still there between the RCD and the right hand neutral bar, probs just the angle of the picture. No need to join new cables, there was enough slack, there was an old non-rcd board with mcbs there before, cannot remember make but it was not a common one. The property had been partly re-wired by the previous owner, although there was still bits of the original 1950's wire left in place, like most of the downstairs sockets were on spurs from the upstairs sockets (solid floors) with bits of original wiring, I presume to avoid chasing out the walls. A few months ago, while I was doing some re-plasring, I took the opportunity to replace what was left of the original wiring (twin only, with a separate bare earth) and chased in new socket drops, so there is now no red&black with separate unslevved earths left, it is all new colours.

 

[brianmoooore]

An independent and properly done EICR would be useful ammunition for legal action against this character.