Protocol on RCD trip problems after new CU install

[SW1970]

Hi folks, did PIR. No issues with cabling etc but outcome was replacement CU due to no RCD. Installed replacement CU but due to some faulty components from the supplier and faff over getting replacements didn't energise until 5pm. Going through a few tests and discovered RCD tripping on a kitchen ring (including freezer). Problem didn't appear until circuit was put under load with an electric kettle. Took ages fault finding and hadn't found it at 10pm. Client (senior citizen) was getting edgy and wanted to go to bed. CU is high integrity, had to leave the installation with kitchen ring on non-RCD slot, and cover off CU. CU is in downstairs loo. Explained situation to client, shut door to downstairs loo and told client not to open it at all and call me if any electrical problems arise, would go back early in am to continue fault finding. Went back in the am and then found fault within half an hour (micro cut in N cable touching metal back box behind socket).

Questions are:

1. Did I do the right thing leaving installation as I did overnight? Wasn't comfortable at all but client understood situation and agreed not to go into downstairs loo. One of those tricky situations where didn't really have a choice.

2. Is it worth having a temporary board set up with an RCD and prior to taking off old CU connecting each circuit up one at a time on temporary board to see if RCD holds? Haven't done this so far but after this job feel it could save a right load of hassle at least form the point of understanding where problems might crop up. Does anyone do this?

Many thanks, SW

 

[Spudnik]

1. NEVER leave a CU with the cover off, especially if it is energised. You will fail your assessment over this.

2. All your IR tests that you did in your pre install would have picked this up which, if they were not clear, meant there was a problem.

 

[Des 56]

First question from me, I am just curious

Why leave the cover off the consumer unit and thereby ban the old gent from the Loo ?

He had no Rcd before the consumer unit was changed,I cant see that would have been too big an issue not having one for another night

Why a temporary board ? you have a board that can do exactly the same as a temporary board

Was there no indication of neutral-earth faults during testing ?the applied load taking out the Rcd indicates it would be evident on test

 

[telectrix]

just wondering why CU cover had to be left off. agrre with Jason here. but have had good IR readings occasionally but RCD still tripping due to intermittent leakage fault due to nicked cables.

 

[Geoffsd]

, and cover off CU.

Why could you not put on the cover?

2. Is it worth having a temporary board set up with an RCD and prior to taking off old CU connecting each circuit up one at a time on temporary board to see if RCD holds?

Not really, you could do this with new CU.

 

[SW1970]

Thanks Jason - I get that. IR test were fine. Problem only appeared with circuit under higher load.

Des - 2 other loo's so old gent ok. No N-E faults during testing. Did it all again when fault appeared and still nothing came up. Temp connection to temp board on floor idea - just thinking about how to avoid this again in the future.

 

[SW1970]

Yep ok - should have put cover on.

 

[Spudnik]

A 500V IR test should have picked this up.

And i think you have got the message about the cover?

 

[Spudnik]

He found the fault which was a trapped N in a backbox.

A bit like the one i had a few weeks back

 

[telectrix]

Earth leakege from freezer which when combined with the kettle just tips it over the edge maybe.........

no

.i think he found a niked neutral

 

[SW1970]

No nicked neutral, did IR test between the neutrals and high IR so ok. Micro slice in cable was about a quarter of the size in Jasons photo & wasn't done by screw.

 

[Spudnik]

So what was it in contact with?

Just a slice in a floating cable would not normally trip an RCD.

 

[Des 56]

He found the fault which was a trapped N in a backbox.

A bit like the one i had a few weeks back

Folks,dont think for a moment that was an inspection job
That was on Jasons latest new install
He had a few coils of red and black hanging around

The neutral fault was his punishment for being shoddy

Only joking, honest,its not worth a ban,really it isn't

 

[SW1970]

In contact with the metal back box.

 

[SW1970]

Cable on a tight angle, suspect it had split.

 

[Spudnik]

Folks,dont think for a moment that was an inspection job
That was on Jasons latest new install
He had a few coils of red and black hanging around

The neutral fault was his punishment for being shoddy

Only joking, honest,its not worth a ban,really it isn't