Hager split load board - 1 RCD tripping but not the other.

[Peepshow]

Hi folks,

My first post so hello! I’ve just put in a Hager 10 way split load CU at my in-laws and a new main isolator switch. They previously had an old rewireable fuse board, supply is via a 60A fuse and TT earth arrangement. No issues previously that I’m aware of.

I didn’t get time to do any proper testing as it was getting late and I’m going to do these and tidy up the installation on Monday but I connected all their old circuits - 2 x ring mains, 2 x lighting circuit, 1 boiler circuit and 1 cooker circuit, 1 of each type of circuit split across each RCD.

Upon energising, the first RCD tripped with anything more than a 6a lighting circuit turned on, so the boiler and a ring main. However if I moved these two larger circuits to the other RCD, then it wouldn’t trip.

Equally, if I swapped a circuit over from the working RCD side to the tripping RCD side, it would trip.

The only circuits I haven’t tried swapping sides are the two lighting circuits.

So the issue doesn’t seem to be with any of the circuits as far as I can tell (though I’ve not tested anything yet) and I’m wondering if one of the RCDs could be faulty - either one is tripping and shouldn’t be, or the other one isn’t tripping and should be!

Any ideas, please?

Thanks!

 

[Peepshow]

Apparently the lighting circuit tripped that RCD too, whereas there were no issues with anything on the other one overnight or this morning.

Surely this indicates an issue with the RCD or its installation from the factory? Trying to think what I might have done wrong!

 

[Andy78]

Where you've gone wrong is not performing any testing.
Have you considered mixed conductors on the lighting circuits ?
It won't be the RCD At fault. Hager are the most reliable brand I know. You could try changing the RCD over but I think that will be fruitless.
It won't be tripping because of "larger" circuits. You have a fault somewhere that needs finding.

 

[telectrix]

1. a "borrowed N" on landing light, where L is from downstairs circuit anf N is from upstairs circuit.
2. a N-E fault that manifests itself when a load is applied to either RCD side.
3. you have a N in the wrong busbar.

4. you should have tested circuits before energising.

5. good luck.

 

[TJ Anderson]

Hi folks,

My first post so hello! I’ve just put in a Hager 10 way split load CU at my in-laws and a new main isolator switch.

No issues previously that I’m aware of.

I didn’t get time to do any proper testing as it was getting late

Upon energising, the first RCD tripped with anything more than a 6a lighting circuit turned on, so the boiler and a ring main. However if I moved these two larger circuits to the other RCD, then it wouldn’t trip.

Equally, if I swapped a circuit over from the working RCD side to the tripping RCD side, it would trip.


So the issue doesn’t seem to be with any of the circuits as far as I can tell (though I’ve not tested anything yet)

Any ideas, please?

All points to one thing.......... lack of testing.
The amount of times you hear this same thing is amazing.

What tests were you going to carry out if it was not getting late??

 

[Peepshow]

Cheers folks. Yep, totally appreciate the testing issue - I know I know I know I should have tested everything first, it just wasn’t going to happen last night and it’s the first thing I’ll be doing on Monday when I’m able to, and as it’s a board change it’ll be the full works on the testing front.

Was just a bit baffled why the same circuits worked with one RCD but not the other. As the only ones I hadn’t swapped over were the 2 lighting circuits I’ll wager it’s those and there’s a borrowed neutral somewhere, I’m pretty sure everything is where it should be on the board anyway.

Thanks for the helpful advice and apologies for posting having not tested first, and indeed for not testing first, terrible practice I know!

 

[Taylortwocities]

Sorry, I have no sympathy. This is exactly why larger electrical work, such as changing a consumer unit is NOTIFIABLE. How do you plan to notify this work to the local authority? You are obviously not a registered electrician and certainly not a competent one.

This is not like swopping a light switch, it is a heart and lung transplant for your parents house. Are they now safer than they were before you started??

There’s some advice above that may help you, but you’ll still be left with the notification issue, not to mention the need to fully test this work and certify it to BS7671.

 

[buzzlightyear]

The job must be plug and play job, start stripping down and find your culprit if you have got the correct test gear.

 

[ChrisElectrical88]

Who the hell leaves after a board change with no testing. How do you know you left the installation safe?!? Even more so a relative.
id be on my way back there right now if I was you to make sure there not without lights for another night. Reason our trades on its arse.
[automerge]1595787005[/automerge]
And just to add, it won’t be the RCD, Hager is the Rolls Royce of domestic boards.

 

[Flanders]

Sounds to me as a guess that you have all the neutrals in the same bus bar or there is a link between to the two neutral bars that requires removing. As others have said testing is the answer.

 

[Vortigern]

There was one occasion I commissioned before testing, never again the new ahole I got ripped indicated to me that it is never never ok to do that. I was under a lot of pressure by the manager of a large commercial unit and thought I know it is all good as we did a EICR on the building just a month prior and all the circuits I had connected were tested already. I had to have the whole thing on by the morning and thought it was excusable in the circ. You can't believe the roasting I got even though it was recently tested!, you're getting it mild on here, just in case you feel you're having a hard time. In fact after the roasting I had to go back and switch off all the units communal power until it was tested and the manager was fuming. I had to keep the key from him so he could not switch on. Bit of a disaster really. Although to be honest it was ok in the end as he understood it must be tested which I did in a day and got back on, and we are still talking.

 

[littlespark]

The more you play around with the circuits, the more you get confused.

as above, neutral in the wrong bar or borrowed neutral across light circuits.

I had one recently that an rcd wasn’t on but there was power to it’s MCBs. The socket rings were mixed up, down to not being tested when the board was changed. (Several years ago.... customer just lived with it)
one side of the split board was being powered through one leg of an rfc. Feeding backwards through the mcb

 

[radiohead]

I note the earthing system is TT. What additional measures have you taken with your metal cased DB to prevent potential danger.... given that you have used a dual RCD board where linking conductors have only basic insulation?
There should be a time delay RCD protecting the DB if you have installed a dual RCD unit, is that not tripping as well?