Hi there. I have recently installed a new consumer unit in a domestic property. The wiring is all old and hasn’t been updated for a good few years. Client doesn’t want to spend the money on a rewire. I fitted a new CU and the lighting circuit will not allow the rcd to stay on. I know there must be a fault on the cable somewhere have done a continuity test and all fine so I’m thinking must be a insulation problem. Any one else have any ideas?
Lighting circuit
- Thread starter Joe89
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If you have dual RCDs its probably a "Borrowed" neutral on the upstairs lts . Put both circuits in the same circuit to avoid any back feeds.
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It is a ground floor flat so there are no upstairs lights. I’ve split the two circuits. One is a supply for a cupboard light and the other supply’s the five lights in the flat. The cupboard light is fine and on a six amp breaker. All neutrals are correct in consumer unit but will not let rcd stay on.
Sharpend
"It Just Is"
Have you tested between all conductors between all circuits?
Doc Hudson
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Well I can't believe you didn't test the cables before re-energising the circuit? I always thought that was the basic principle for all electrical alterations, as per Part 6 of BS7671; Dead tests come before reconnecting the power. What values were you going to write on your electrical certificate for the insulation test readings for each circuit? They may give you a big clue.
Doc H.
Back to it being a Dual board ... have you put the circuit neutrals into to main ( non RCD ) Neutral bar ?
If the lights were working before I'd guess theres not a dead short but there may be a Neutral to Earth fault that wouldn't affect an old fuseboard .
If the lights were working before I'd guess theres not a dead short but there may be a Neutral to Earth fault that wouldn't affect an old fuseboard .
phil d
Well-known member
Oh dear, this has the potential to end badly, before embarking on anything like that you MUST do insulation resistance tests, and that's before you even agree to doing a board change. There are so many potential problems that can come back to bite you, as this job appears to have done.
Potentially if the original board had no RCD protection then you could be looking at any, or a combination of the following
something connected across 2 circuits, I've seen it where a light has taken it's live from the lighting circuit and it's neutral from the ring circuit. there are any number of problems that could cause the situation you have, if you are lucky it will be something you can locate and rectify fairly quickly and easily, if not then you could be heading for a world of hurt.
Don't take this the wrong way, but I'm thinking you don't have much experience, and believe it or not, there are people who'll take advantage of you, "well, it was working before you touched it" is the usual one, then they expect you to repair a fault that was actually there before you started, however, you didn't do the proper tests, so you can't prove it was there.
If I come across a job like this, the first thing I do before even agreeing to do the job is a series of tests, if any come back wrong then I tell the potential client what the problem is and try and give them an idea as to what it may cost, although this isn't always easy. If they are not prepared to pay for the corrective work done, before doing a board change, then I'll walk away, it's just not worth the hassle in the long run.
Potentially if the original board had no RCD protection then you could be looking at any, or a combination of the following
- low IR value between live and earth
- low IR value between neutral and earth
- a dead short between neutral and earth
- damp inside a fitting
something connected across 2 circuits, I've seen it where a light has taken it's live from the lighting circuit and it's neutral from the ring circuit. there are any number of problems that could cause the situation you have, if you are lucky it will be something you can locate and rectify fairly quickly and easily, if not then you could be heading for a world of hurt.
Don't take this the wrong way, but I'm thinking you don't have much experience, and believe it or not, there are people who'll take advantage of you, "well, it was working before you touched it" is the usual one, then they expect you to repair a fault that was actually there before you started, however, you didn't do the proper tests, so you can't prove it was there.
If I come across a job like this, the first thing I do before even agreeing to do the job is a series of tests, if any come back wrong then I tell the potential client what the problem is and try and give them an idea as to what it may cost, although this isn't always easy. If they are not prepared to pay for the corrective work done, before doing a board change, then I'll walk away, it's just not worth the hassle in the long run.
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Good post!
Would you care to elaborate on the series of tests you usually perform upfront?
phil d
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I like to start with a visual of the obvious stuff, size/ condition of tails and earths, are there bonds to gas and water, assuming they are required, then an earth loop, I've had a few jobs where the DNO has had to be called due to external earth faults. worryingly I usually find these on installations that other people have worked on, so obviously they aren't being thorough.
IR test on each circuit, phase to earth, phase to neutral and neutral to earth, I very often just do a global IR on neutral to earth, if that comes clear then ok, if not then it's testing individual circuits, since you have mainswitch off there's no issue with neutral/ earth being connected externally, e.g PME system. Continuity of conductors on ring circuits, after that, I'm usually fairly happy to carry out a board change, you could go further if you wanted but usually, by looking at the general state I have a good idea if there's likely to be any other issues
I've been caught out once or twice when I was younger so you need to cover your own backside.
I never move anything big and expensive either, one firm I worked for gave out about a dozen very expensive flat screen tv's that our lads had "broken" while working on an estate in Manchester. I did a bit of digging and one tenant had got this tv out of a skip at a pub, told our boss that it had been damaged when one of our lads had moved it during work and we'd bought him a new one, unfortunately, the boss hadn't removed the old one, he'd been bragging about it down the pub and given the duff set to someone else, by the time I'd worked out what was going on, our boss must have laid out a good few grand on new tv's.
Sharpend
"It Just Is"
is it not standard to do the visual and subsequent dead tests/ live tests prior to quoting for a job such as a board change? how can you quote on something that you havent had a good reccy of? thats plain stupid imo walking in blind is asking to get fingers burnt.
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Surely if its a ground floor flat you would be fitting individual RCBO's?
AFAIK most flats don't have a fat lot of fuse box space, so a dual RCD board probably physically to big...?
Small 8-module enclosure, half dozen or so RCBO's, (Cooker/Shower/2xSocket/2xLight) …..
can't be that many circuits in a flat.... Can there?
:C
By the sounds of it No testing done..?
So bang in a bit of random pot luck.. could be all sorts....
Knackered Florrie light fitting in the kitchen possibly???
Mouse in the back of the hall light....
Wire squashed and damaged in the back of a light switch...
DIY light fitting wired wrong, directly between Live & Earth….
Faulty RCD.... As that may not have been tested either....
5WW CU change???
just guessing
:shakehead
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Lots of old existing CU's that have 'never been tested/not been tested for a long time' are logistically impractical to do many tests on without pretty much full dismantling.....
AND if you already know the CU needs changing....
Can be best to just bite the bullet...
Start systematically dismantling....
Test as you remove...
Very rare for 100% of circuits to be faulty.. So rebuild all proven good ones back onto new board...
Then carry out whatever investigations/remedial work is needed to fix any faulty circuits...
You just make sure that you build the costs and limitations into the contract you agree with your customer...
e.g. Your quoted price is to remove old board, test circuits, fit new board and reconnect all circuits that Test Satisfactorily.
You do NOT just state a fixed cost to replace the fuse box without building in how you can test and verify to your own satisfaction so you can sign your certificate...
That is just leaving yourself open to hassle and agro.
Any circuits that fail to test ok will be either; Not connected/Partially connected/De-rated or whatever action is appropriate.....
until additional costs/timescales are agreed to get the dodgy circuits working.
If customer doesn't want remaining bits fixed you just certify and test the first good bits as per your agreed schedule of work!
Guinness
The big problem in these situations is not the condition of the installation, or its wiring, or the customer...
It is the electrician doing the work failing to build in sufficient buffer of time/costs to allow for the very common problems that arise during a CU change...
If you just go in with a fixed low price, (trying to win the work), and tell the customer it will only take half a day....
You are just leaving a noose round your neck..
Its not hard to write a contract with costs for the known bits covered, but some additional clauses to allow for unknows that will only become evident once the bonnet is up!
The garage that services our car is able to do that ok... fixed price service/MOT but any extras found they ring me and have to re-negotiate...
Can't see why electricians haven't managed to master this skill?
:C
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+1 to warning the customer there may be faults encountered that need correcting so you can only give an estimate, not a quote.
And even modern, good looking installs can throw up issues, e.g first EICR I did on our village hall had a N-E fault on a lighting circuit. I had to dismantle and inspect about 10 sodium uplighters until I found the one with N and E reversed. It had been working like that for 10 years and was missed on the initial certification by the installer.
And even modern, good looking installs can throw up issues, e.g first EICR I did on our village hall had a N-E fault on a lighting circuit. I had to dismantle and inspect about 10 sodium uplighters until I found the one with N and E reversed. It had been working like that for 10 years and was missed on the initial certification by the installer.
Agree entirely with that . Most of us must have tried testing on an old Wylex crammed with cables , unable to identify corresponding earths & neutrals without ripping the lot out , earth bar with only four terminals and fifteen earth wires rammed in it and two bonding cables .
Sharpend
"It Just Is"
My bad, I thought you were talking about the old boards not the ancient boards.
Old- 16th edition
ancient - 3036.
:C
phil d
Well-known member
These days I only do board changes for people I either know or are friends of people I know, as others have said, you have to do tests before starting or else you're leaving yourself wide open, I have a friend now who had a board change last year, they had a bit of work done (didn't know me at the time) and the guy said they needed a board swap, because, "you have fuses not mcb's" it was an old Wylex unit. Anyway, he's changed the board alright, for a plastic one with mcb's and a main isolator switch, no RCD protection whatsoever!
He's no longer contactable, well there's a surprise, and now they want me to fit a proper board, I have no idea whether this guy was just after making a quick buck, or whether there were issues on the tests, assuming he did any, and that's why it isn't RCD.
I did find a few faults, mostly on what he'd done, taped joint in a wall, 3 twin sockets on a spur, and a diagonally run cable.
The upshot is that these people want me to do the work, they've called me after a mutual friend recommended me to them and they want to be sure it's done properly. I've explained about having to do tests first and then depending on what we find, this will define the cost, fortunately, they both understand about safety and insist it comes before cost, although I'm not going to take advantage of that.
I think these days there are generally three types of electrician, 1, the chancer, little knowledge, just wants to make a quick buck and run. 2 the genuine guy with little experience who needs the money, quite often he'll either be taken advantage of, or potentially end up taking a hit somewhere down the line, and finally 3, the older more experienced guy, he isn't going to do it at a stupid price just to get the work, but if he does do it, it will be right.
As I said, I don't do much these days, but what I do generally involves straightening out other peoples messes, and educating people on how best to avoid being ripped off, I like to think of it as trying to restore the image of an industry which has been good to me over the years, and if someone has had a bad experience, it goes a long way to restoring their faith in us, just because you've met one bad spark, it doesn't mean we're all like that.
He's no longer contactable, well there's a surprise, and now they want me to fit a proper board, I have no idea whether this guy was just after making a quick buck, or whether there were issues on the tests, assuming he did any, and that's why it isn't RCD.
I did find a few faults, mostly on what he'd done, taped joint in a wall, 3 twin sockets on a spur, and a diagonally run cable.
The upshot is that these people want me to do the work, they've called me after a mutual friend recommended me to them and they want to be sure it's done properly. I've explained about having to do tests first and then depending on what we find, this will define the cost, fortunately, they both understand about safety and insist it comes before cost, although I'm not going to take advantage of that.
I think these days there are generally three types of electrician, 1, the chancer, little knowledge, just wants to make a quick buck and run. 2 the genuine guy with little experience who needs the money, quite often he'll either be taken advantage of, or potentially end up taking a hit somewhere down the line, and finally 3, the older more experienced guy, he isn't going to do it at a stupid price just to get the work, but if he does do it, it will be right.
As I said, I don't do much these days, but what I do generally involves straightening out other peoples messes, and educating people on how best to avoid being ripped off, I like to think of it as trying to restore the image of an industry which has been good to me over the years, and if someone has had a bad experience, it goes a long way to restoring their faith in us, just because you've met one bad spark, it doesn't mean we're all like that.
Naw mate , you missed the fact that it was Specs talking ....so it would be .."Ancient" not just "Old" You're looking at Bakelite , wood & porcelain here .
phil d
Well-known member
Ah, you mean one of those proper non- combustible boards, cue a barrage of posts from older electricians who've unsuccessfully tried to incinerate an old Wylex, lol
Sharpend
"It Just Is"
Jeez I really am slipping, perhaps it’s time to see the doc about the old memory. I really should know better.
