17th edition Split board issues.

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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!!
 
Personally i don't like the modern split CU's or the philosophy behind them.

Where you have 2 X RCDs looking after multi MCB protected circuits, is always going to lead to problems, when one circuit develops any kind of fault that will trip the RCD device. It's basically a cheaper alternative to how a CU should be configured. Which to my mind should consist of all circuits being protected by RCBOs. On CUs for TT derived systems the RCBOs being backed up by an upfront S type RCD device, incorporated in the main CU switch...

Yes quite a bit more expensive than these split CUs, but oh so much better all round, and totally adaptable to various and future needs...
 
My advice is that you do all your tests like insulation resistance (megga?) etc before starting your board change. Rectify any issues then change the board. When you say you used copper from old board to get it working tempory do you mean some circuits are not RCD protected at the moment?
 
Hawk81 said:
My advice is that you do all your tests like insulation resistance (megga?) etc before starting your board change. Rectify any issues then change the board. When you say you used copper from old board to get it working tempory do you mean some circuits are not RCD protected at the moment?
Click to expand...

Yes but my mates aware there's a problem somewhere and have told him don't overload the ring for now, ie just do one thing at a time, kettle, microwave etc. I know it's not ideal but i can only try again next wknd. The thing thats baffling me is as i say, the old board had the kitchen ring protected by an old RCD with no tripping issues.

Tbh the job has taken quite a while upto now, changed all lights, added new spots in kitchen (lighting cct), changed all switches and now board, would have been done sooner if i'd have rewired the place but moneys tight for this young couple and tbh the wiring's only as old as the house (13yrs) so thought it'd be fine just to straight swap stuff. Obviously not!
 
ringer said:
Did you try swapping the RCDs to see if one is faulty?
Click to expand...

Yep i did and it made no difference thanks anyways! Oh on that note, i also tried the old RCD which was originally protecting the kitchen ring before which never had a tripping issue whilst in the old board. Guess what, it tripped in the new board which really confuses me!!!
 
Btw just for info's sake, the system is PME, luckily the good guys at the REC installed an isolator at the mains incomer so didn't need to cut the tag for the fuse and it's much easier to switch off/on than pull in/out ....ohhh errrr!lol. Go REC guys!!!

Bonding to gas and water.

Cables into board are clipped direct and i've not caught any insulation replacing the board, installed pretty much like for like position wise, aint modified any circuits barring changed setup inside board. Ie downstairs lights were for some reason split into two seperate cct's i tallied up wattage load and found 6A breaker was more than enough to combine them as one downstairs cct.

Earthing to cct's fine, however as said before haven't megga'd owt yet so i'll see where i go next week with this.


Any helpful advice from you guys is always appreciated thanks very much.
 
I agree with Hawk 81, in that any future CU changes you undertake, you use your test equipment ''Before'' you start undertaking any changes. Knowing of the existing faults you will face first and getting them sorted, will save all the problems your now facing.

Now your trying to trace faults with the RCDs in place and hindering your progress.
 
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!
 
Aye don't i just know it. Still doesn't answer the fact that why all of a sudden would there be an issue with the kichen ring when there wasn't before when it was protected by an older version RCD??

Any idea's?

Bare in mind now that i also tried that said RCD in the new board and it now trips!
 
Ie downstairs lights were for some reason split into two seperate cct's i tallied up wattage load and found 6A breaker was more than enough to combine them as one downstairs cct
Click to expand...

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

Why were they split ?
 
1shortcircuit said:
It would seem that you have made an error somewhere. Rip it all out separate each circuit and start again :thumbsup
Click to expand...

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.
 
SafetyFirst said:
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.
Click to expand...

Well, ....There's a clue for you , Surely??
 
spark 68 said:
I would be looking at this bit, as this bit you did change.

Why were they split ?
Click to expand...

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.
 
ringer said:
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!
Click to expand...

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.
 
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.
Click to expand...
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.
 
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SafetyFirst said:
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.
Click to expand...

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??
 
Engineer54 said:
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??
Click to expand...

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.
 
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spark 68 said:
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.
Click to expand...

So if i run tests and find no low/abnormal readings, what then?
 
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.
 
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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.
 
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.
 
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.
 
Hawk81 said:
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!
Click to expand...

Well i was waiting for someone smarmy to bring that up. I best change my username then eh?

What you guys must remember is this aint a client i've left in a pickle, it's a friend who was with me whilst i had the problem and i've fully explained it to him and his wife. What everyone must realise is that nothing can be more dangerous as it was before, i have not re-wired the place so if there's a borrowed neutral then thats existed long before they bought the house.

I've improved the safety of the house as now all but two cct's are protected by an RCD, unlike just two as before!


Btw there was a time before RCD's infact even before earthing in lighting design so did everything stop in those days?

If daylight never ran out and had more time i'd have ran tests but my mate just wanted everything on for the time being so TEMPORARILY i've by passed RCD for two cct's.

Arrest me, lock me up and throw away the key.

I work during the week and next time i'll have a chance with daylight is sat morning!
 
Thanks everyone for your help especially spark68. I hold my hands up on this i should have ran tests proir but have went gung ho hoping all would be ok. If i had my own business i'd have been at this place for a few days but with working mon-fri and popping over every now and then the time isn't there to get things done as i would like.

I know this is dragging it out now, i'll make sure i at least IR test everything before i undertake another board change.

Thing is i really never expected a problem on any of the rings as they originally were RCD protected. *confused*
 
Right guys, i'm going first thing in the morn to run some tests ie IR (megga) tests etc. I'm going to unplug all sockets proir to testing ring mains. As for the lighting cct's, there's some fancy lights i've now installed including spots with transformers so to save on time rather than disconnecting each lamp and connections to transformers i'm going to avoid testing between L-N, just run IR tests between L-E and N-E.

This is the norm in this situation guys?

I'll flick two way landing light sw also and re-test.

Anything else you guys recommend?
 
Update:- Have been today and did some testing.

No borrowed neutrals exist.

Tried all lighting on same neutral side upstairs lights still weren't happy fed via the RCD, cct tripped straight away as before. Still works with MCB with no RCD protection.

Tested Kitchen ring, wirings sound good IR results and went round with martindales, all skts wired correctly. Transferred ring onto RCD protected side, powered up and plugged and tested each appliance one at a time. Had no problems. (It was very cold last week during board change), possibly had lower IR back then with damp, or there may still be an issue when i come to place 2nd RCD back into board and have rings on seperate RCD's (imbalance issue?) as ideally i want upstairs lighting with downstairs kitchen ring and downstairs lighting with upstairs + (rest of house) ring.

Downstairs lights wiring sound.

Upstairs lights, very low reading between E-N (short), L-E not so clever either of just 28Mohms. Wonder if i have a dodgy JB/light fitting somewhere. Have investigated on suite upstairs inc shaver socket, light fitting connections weren't great but wasn't that. Left in connector block as they need a new light fitting.

Had to leave job earlier than would have liked, back there tomorrow. Normally i'd split the cct in half but as i don't know how it's been wired i'm just checking existing points of interest that i never ammended. Have yet to check spotlights in toilet, loft light and outside lights so there will hopefully be something within them. If not it's a mistake i've made somewhere in fitting the new lights upstairs. Failing that.......which i'm dreading is that all lights are wired soundly and fault exists somewhere i can't get at ie within walls or under floors. Eeeek what's the score if thats the case then? Rewire? I'd love to but thats the last thing the homeowners would want. Surely if tested this would be an instant fail? If left on normal MCB way unprotected by an RCD working but with a fault somewhere? Potentially dangerous and something i'd not like left.

Oh and the smoke detector cct has a very low reading between L-N. Hopefully thats just a dodgy smoke head, otherwise i'll just advise them getting battery fitted one's. Not good but only option if wirings dodgy.

Never again am i not going to test existing wiring before even changing a single socket or switch!!!

I've learnt my lesson........ the hard way!

Anymore advice forthcoming would be much appreciated cheers.
 
Yes i haven't took into consideration that they can give false readings have i, thanks Des. Should have disconnected them. I did have it set on 250v from the previous lighting testing hopefully haven't buggered the detectors, thats all i need now!
 
You might have wanted to have dropped those heads out mate, you say outside lighting is on the circuit that keeps tripping? Have a look around these, had one the other day where guttering had been over flowing and filled the terminal box up wit water, customer failed to mention that they had had gutters repaired cos of this= me walking round testing for 2hrs to find the fault
 
Dan the spark said:
You might have wanted to have dropped those heads out mate, you say outside lighting is on the circuit that keeps tripping? Have a look around these, had one the other day where guttering had been over flowing and filled the terminal box up wit water, customer failed to mention that they had had gutters repaired cos of this= me walking round testing for 2hrs to find the fault
Click to expand...

Cheers Dan, like i say those are the point's i want to concentrate on, there's 3 lights outside the back garden, they even have their own trunking run, will give it a gander tomorrow. How will i know if those detectors are fried now? :(
 
SafetyFirst said:
Cheers Dan, like i say those are the point's i want to concentrate on, there's 3 lights outside the back garden, they even have their own trunking run, will give it a gander tomorrow. How will i know if those detectors are fried now? :(
Click to expand...


Try the test button and see what happens!
 
Buy a can of smoke
Read my own post and it sounds sarcastic

Buy a can of smoke alarm test spray for the suspect alarms
icon14.png
 
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