17th edition Split board issues.

[SafetyFirst]

Hi guys n gals, i've fitted another general electric 17th edition split board. It's the 3rd one i've fitted and the 3rd one that i've had problems with.
Haven't changed many boards over, only ever done so for friends or family who've needed/wanted too, i still have my rewireble box taking care of things in my bungalow without any probs

The first board change i did after much head scratching i found a borrowed neutral with the lighting from down/upstairs after grouping lighting circuits onto one RCD. Also the two way switch was dodgy, all fixed and no problems reported six months down the line-all good.

Second board change, everything worked bar upstairs lighting, megga tested and found a very low reading between E-N so needed further investigating. Haven't had the time to sort that one yet but there's no rush as buildings going to be redundant for sometime yet.

Both jobs for my sis and bro in law.

Moving onto todays, for a friend of mine, currently living there. Moved in just before christmas, have changed all the lights over to new shiney one's. Changed all light switches to chrome and awaiting to do the same with all sockets.

Anyways the building is fairly modern, built in '98, old hrc fuses with 2 30A MCB's protected by a 30mA RCD. They served a ring for upstairs/downstairs general bedroom/living room sockets.
The other ring serves kitchen/utility/garage sockets.

The way i setup new 17th edition board was to split the rings onto either RCD's and what this results in is having just upstairs lights and kitchen sockets on one RCD that trips when powered. The other RCD (1) has downstairs lights/smoke detectors/genereal sockets/cooker (only oven 10Amps)/water heater (13Amp). Doesn't trip and all working fine.

After much head tearing the RCD (2) doesn't like the kitchen ring or the upstairs lights individually.

Have used old boards copper to create a temporary by-pass for the two circuits that are not liked by the RCD till i have time next weekend to megga those cables and further investigate this problem. Whats baffling me is the fact there wasn't a problem with the old RCD protecting the kitchen ring.

Imbalance issue?

What a mare eh!

These fully loaded RCD boards can be a blessing in disguise as there has to be a few issues with the wiring on the kitchen ring and upstairs lights. I just wish i could have one that goes straight forward for once!!

 

[Engineer54]

I taped each leg up, it's as was wired before. If i'd have mixed the rings up surely the other RCD would spot the imbalance on the other side and that too would trip?

The sockets stay on till there's load getting pulled, ie the fridge is swithched on or kettle or owt else, they run a few seconds and trip. As for the upstairs lights, it just doesn't go on full stop. Yet without the RCD no issues.

Well, ....There's a clue for you , Surely??

 

[SafetyFirst]

I would be looking at this bit, as this bit you did change.

Why were they split ?

Well there had been obvious DIY parts to the downstairs lights. Looked like to me that the kitchen/utility had been extended/altered in the past. The old fittings were badly overheated but i have replaced and made good all lights including well before old terminations.


The downstairs cct's aren't causing the issue, which i've joined into one 6Amp breaker. It's the upstairs, gonna place that on same RCD before i test next week see if its a borrowed neutral.

 

[SafetyFirst]

Sounds like you've got an interconnection between circuits - possibly two interconnections. Have you tried taking out all conductors from the kitchen ring and checking for continuity between each of those conductors and all earth and neutral bars? And the same with the upstairs lighting circuit? Have you checked for continuity between those two circuits as well?
Are you sure the RCD is connected to the main switch properly and RCD(2) busbar is isolated from all other busbars in the board?
Did you remove the link between neutral bars?
Have you tried isolating RCD(1) to see if RCD(2) will then hold in? Perhaps RCD(1) only holds in because RCD(2) always trips first?
Have you done all RCD tests x1, x5, < with RCD(2) live but mcbs off?
What order are the RCDs from the mainswitch?
A picture paints a thousand words - how about a photo of the board?

I'm a bit surprised that you didn't IR the circuits in question before now. There are lots of things you could/should be testing. Perhaps you just need time to sit back and assess what is going on. Sometimes with faults like this it is easy to get overloaded with ideas. Think back to basics, and work out a test strategy that covers all bases - and stick to it - do not go off on tangents because you will lose track of what you have and haven't tried. I'm sure you'll suss it out in the end - just be methodical.

And get back to it before next weekend if you can - leaving those circuits without additional protection is not good!

All connections were checked and tightened inc factory terminations. I've re-arranged board to suit temporarily. Will test during daylight when i'm off on saturday.

 

[spark 68]

Is it possible that part of the downstairs lighting is on with the upstairs lighting (hallway maybe) ?, and this is why it was split, rather than anything to do with current rating.

It is still possible that you have an incorrectly placed/borrowed neutral,

The sockets stay on till there's load getting pulled, ie the fridge is swithched on or kettle or owt else, they run a few seconds and trip.

I have seen this before, usually on a TNC-S system, as the imbalance is not always great enough to trip until a certain amount of loading takes place.

 

[Engineer54]

Well there had been obvious DIY parts to the downstairs lights. Looked like to me that the kitchen/utility had been extended/altered in the past. The old fittings were badly overheated but i have replaced and made good all lights including well before old terminations.


The downstairs cct's aren't causing the issue, which i've joined into one 6Amp breaker. It's the upstairs, gonna place that on same RCD before i test next week see if its a borrowed neutral.

That would have been my First check i would have made, with the conditions you have described... even to if it was only eliminate the borrowed neutral senerio. So, what are you going to do, if the lights upstairs suddenly start working again, when you combine all the lighting circuits??

 

[SafetyFirst]

That would have been my First check i would have made, with the conditions you have described... even to if it was only eliminate the borrowed neutral senerio. So, what are you going to do, if the lights upstairs suddenly start working again, when you combine all the lighting circuits??

I'm not going down the road of rewiring mate. I'll just keep it that side, further investigating would mean in all probability after testing ripping upstairs flooring up, guess what it's chipboard and they've carpeted now also.

I had a right chew on installing the kitchen spots, me mate's friend volunteered to make access to floor above ceiling and made a mess of the chipboard floor.

If it is a BN i'll explain this to my mate. This is a home he'll have for years anyways, he's already said he's not moving ever again!Lol. He knows not to touch electrics, he's not a diy person. It'll need rewiring before i have to find where/if its borrowed.

It's one of these jobs that nowt's went straight forward.

 

[SafetyFirst]

Is it possible that part of the downstairs lighting is on with the upstairs lighting (hallway maybe) ?, and this is why it was split, rather than anything to do with current rating.

It is still possible that you have an incorrectly placed/borrowed neutral,

I have seen this before, usually on a TNC-S system, as the imbalance is not always great enough to trip until a certain amount of loading takes place.

So if i run tests and find no low/abnormal readings, what then?

 

[spark 68]

Well what I would do,
and what others have already said, is to switch off all of the MCB's, lift all of the neutrals for each circuit out of the board, and then IR test between the circuits, that way you may only end up with two out of the three lighting circuits on one side (which you probably would have done anyway), but more importantly the correct two.

This is a good lesson as to why you should at least carry out a quick test before changing the board, as this then highlights any issues you may face, and you can decide on the corrective action to take beforehand.


You should always know what you are going to do, as there is nothing worse than the situation you now face, especially when you are faced with a whingey customer who says 'it was alright before, it worked for X amount of years' and refuses to pay you for the extra work.

I made this very sort of mistake very early on, and then vowed it would never happen again.

 

[SPARTYKUS]

I reckon clue is in your posts 9 & 17 as pointed out the light are a hot favourite for jobs like this, esp if you start mixing them up.


Nowt to add really except you'll only do it this way once ) i did like spark68. Long time ago.

 

[Octopus]

What test equipment do you have at your disposal? What tests have you actually done?

 

[Hawk81]

I just think its ironic that the op's name is safteyfirst yet he has left a house with sockets with no RCD protection. The kitchen too!

 

[perrymetcalf]

hey really sorry to cut your conversation but can anyone tell me how to write a new thread please ?

 

[telectrix]

hey really sorry to cut your conversation but can anyone tell me how to write a new thread please ? choose an appropriate forum....... click on the "post new thread" tab....... enter title...... then post.

 

[malcolmsanford]

Outside light installed and DIY installer found he was missing a neutral so borrowed it from the ring?

 

[telectrix]

only way is to dis. all cables from CU. test them individually, test for any cross connections. then connect up and power up each circuit 1 at a time.