230v neutral to earth ? row of lights gone out mcb not tripped

[marlon89]

Hello all,

I have recently attended a job where a row of lights have gone out and was advised and seen for myself when i got there that no breakers have tripped.

First i took the cover off of the panel with the mcb's that feed all lighting circuits in open office area , and checked i have 230v on load side on mcb , which i did have on all mcbs to rule out a faulty breaker. I next went to the nearest light fitting to the riser where dbs where and found 230v at fittings with lights not working (all on sensors ) and ballast units also had 230v.

I then was advised (by site engineer) that sometime in the past these lights had lost power and had been rewired by someone ?? not sure if they were qualified or not ... i then went to a room at the end of the office area where he advised me they repowered this lighting circuit which has now gone out but power still there couldn't see any polarity faults but didn't get a chance to check all fittings as was in working hours of a office.

At the end fitting i was getting 230v between N-E and i haven't come across this before would appreciate any help

 

[Darkwood]

Welcome to the forum marlon89

 

[Deleted member 72666]

What voltage did you measure between L & N at the fittings?

 

[marlon89]

230v N-E and L-E at fitting with lamps not working

 

[Simonslimline]

Line+Neutral voltage?

 

[Barry White]

230v between neutral and earth usually means a lost neutral or polarity reversed did you test between L and N on the same fitting? and L and earth

 

[HandySparks]

Post removed

 

[marlon89]

Yes on the same fitting one of the furthest away from dB's , what I don't get is why are none of the lights working if ballasts and main connections in fitting have 230v ?

 

[Octopus]

Time to do some basic tests

 

[marlon89]

Time to do some basic tests

Haha yes I'm going back on Monday out of hours as couldn't conduct further tests due to being a very busy office floor .

Thanks for your input murdoc. ..

 

[conrad]

What tester are you using? Did you check which breaker was isolating the supply to prove where the circuit is fed from?

 

[Lucien Nunes]

i was getting 230v between N-E

230v N-E and L-E at fitting with lamps not working

what I don't get is why are none of the lights working if ballasts and main connections in fitting have 230v

Crikey. It's a circuit with a supply, a switch and a lamp, and it's broken somewhere. Ask yourself where. It doesn't seem to be the line...

 

[snowhead]

Crikey. It's a circuit with a supply, a switch and a lamp, and it's broken somewhere. Ask yourself where. It doesn't seem to be the line...

I can't think of a more common fault that gets people stumped.

 

[HandySparks]

Crikey. It's a circuit with a supply, a switch and a lamp, and it's broken somewhere. Ask yourself where. It doesn't seem to be the line...

I wrote something similar at post 7, but then thought "why bother"!

 

[Besoeker]

230v between neutral and earth usually means a lost neutral or polarity reversed did you test between L and N on the same fitting? and L and earth

Yes, that would be the most obvious thing to check I would have thought.

 

[marlon89]

But these lights were working fine up until Friday no one has touched wiring recently , but thanks guys . So it may have come out one of the fittings or sensor's ? Can't think of any other options that could have happened ? as no one has touched circuit recently to my knowledge.

 

[marlon89]

Crikey. It's a circuit with a supply, a switch and a lamp, and it's broken somewhere. Ask yourself where. It doesn't seem to be the line...

I was getting 230v N- L at fitting as well .. so how can it be broken ?

230v L - N 230v N-L and 230v N-E row of lights out mcb not tripped .

 

[Lucien Nunes]

230v L - N 230v N-L and 230v N-E

Re-read what you typed and confirm whether it is what you meant to type!

 

[Marvo]

Lol, I guess it might be possible with the right (read 'wrong') digital tester and no 'low-z' range

 

[marlon89]

Re-read what you typed and confirm whether it is what you meant to type!

Yes this was what I was getting !! 230v N-L 230v N - E and 230v E to N .

If I was getting not 230v between L and N then obvious it's a broken neutral but this is what iv been writing and people are saying it's a broken neutral when it can't be !!

 

[Lucien Nunes]

230v N-L 230v N - E and 230v E to N

That's not what you typed in post 18 and I think it's not what you mean. Or you're making it up as you go along...

 

[Marvo]

Maybe check the continuity of the cpc through the entire circuit as well.

 

[Barry White]

Watch the "sensors" they are often wired in 3 core flex and the earths not sheathed brown.

 

[marlon89]

That's not what you typed in post 18 and I think it's not what you mean. Or you're making it up as you go along...

What do you mean . I typed the same thing in post 17 . Post 18 was your post

 

[marlon89]

Thanks Marvo and mykey . Appreciate the constructive replys . :smug:

 

[Lucien Nunes]

Post 18 was your post

My bad, I meant the bit of your post 17 that I quoted in post 18.

230v N-L 230v N - E and 230v E to N

230v L - N 230v N-L and 230v N-E

See the difference? If you meant:
230V L-N, 230V L-E and 230V N-E that's different, and also impossible unless L and 'N' happen to be two lines from a 3-phase corner grounded delta supply which I somehow doubt. Test and report accurately or any help you might get will be meaningless.

 

[telectrix]

you can have a bad connection on the N which shows 230V to L untill loaded.

 

[Lucien Nunes]

But it won't also show 230V N-E under the same conditions, which is what he seems to be getting at. In any case if he has 230V L-N at a fitting (which was not mentioned at first) and it's not alight, that fitting is faulty. In which case there are two faults. Methinks the reported findings are inconsistent.

 

[marlon89]

My bad, I meant the bit of your post 17 that I quoted in post 18.




See the difference? If you meant:
230V L-N, 230V L-E and 230V N-E that's different, and also impossible unless L and 'N' happen to be two lines from a 3-phase corner grounded delta supply which I somehow doubt. Test and report accurately or any help you might get will be meaningless.

Ok yes my bad just for clarity one more time the voltage I was reading at fitting was 230v L-N 230v L-E 230v N-E

And yes it is a 3 phase supply as I stated it's commercial offices so of course it's 3 phase Lucien ....

My guess is they have took a feed off another lighting circuit on a different phase but somehow lost a N to the circuit feeding both row of lights cos when I looked at db supply lighting in office area it looks like each phase done a different row of lights .

It seemed like the row of lights I was looking at , the ones that were not on but had power and the other half along the same row still was working . But couldn't turn more breakers off to prove what kills feed to it as was in hours busy open space.

But I have never come across 230v between all 3 voltage tests . Hence why I thought someone may have come across this before and have some fault finding advice . I'm still to do my test and inspect but planning to this year . For more fault finding knowledge. As knowledge is power !! Haha

 

[Lucien Nunes]

My reference to three-phase supply was tongue-in-cheek and does not relate to normal UK 230/400V supplies. If you lose a common neutral to two circuits on two different phases, the voltage across the two circuits in series will be 400V and something will probably have gone bang.

With a single-phase circuit from a 3-phase 230/400V supply it is almost impossible to have the readings you describe. If one connection is floating you might see ghost voltages at it as Tel points out, but they won't all be 230V at the same time. Either something was changing between readings (e.g. sensor operating) in which case it's not a true description, or your measurement was in error.

Try drawing an equivalent circuit to the fault, that will read 230V L-N, L-E and N-E at the same time on an MFT or DMM.

 

[PEG]

I bet testing out with a device which put a decent load on,would give you different results,and,probably point to exactly what your fault is :winkiss:

 

[snowhead]

I was getting 230v N- L at fitting as well .. so how can it be broken ?

230v L - N 230v N-L and 230v N-E row of lights out mcb not tripped .

If they were the readings either all the lamps have failed, all the ballasts have failed or a combination of the 2.

If you truly have; "At the end fitting i was getting 230v between N-E and i haven't come across this before would appreciate any help"

You potentially have a dangerous situation, particularly to yourself when fault finding.

The only way you can get your readings is if E or N are a different phase to L.

Don't be distracted by the comment, they were previously working OK and no-one else has touched them,
ASSUME NOTHING.

 

[marlon89]

If they were the readings either all the lamps have failed, all the ballasts have failed or a combination of the 2.

If you truly have; "At the end fitting i was getting 230v between N-E and i haven't come across this before would appreciate any help"

You potentially have a dangerous situation, particularly to yourself when fault finding.

The only way you can get your readings is if E or N are a different phase to L.

Don't be distracted by the comment, they were previously working OK and no-one else has touched them,
ASSUME NOTHING.[/QUOTEt

thanks , but what do you mean when u say "The only way you can get your readings is if E or N are a different phase to L. "

do u mean if a N or a E is touching a Live somewhere ?

 

[UKMeterman]

Ok,
1. Stop.
2. Sketch out a simple circuit showing a bulb L N and E including the substation transformer, with the N-E link.
3. Now have a look where breakis in the circuit could cause 230V N to E....

 

[snowhead]

but what do you mean when u say "The only way you can get your readings is if E or N are a different phase to L. "

do u mean if a N or a E is touching a Live somewhere ?

More likely been deliberately connected to another phase and not serving the purpose of N or E.
Hence caution, assuming your readings are correct as the body of the fittings may be Live and not earth.

 

[davesparks]

More likely been deliberately connected to another phase and not serving the purpose of N or E.
Hence caution, assuming your readings are correct as the body of the fittings may be Live and not earth.

How did you draw that conclusion? There is 240 N - E and 240 L - E with the L - N voltage unknown.
The logical conclusion is that the N has risen to the same potential as the L with respect to E

 

[marconi]

Hello all,

I have recently attended a job where a row of lights have gone out and was advised and seen for myself when i got there that no breakers have tripped.

First i took the cover off of the panel with the mcb's that feed all lighting circuits in open office area , and checked i have 230v on load side on mcb , which i did have on all mcbs to rule out a faulty breaker. I next went to the nearest light fitting to the riser where dbs where and found 230v at fittings with lights not working (all on sensors ) and ballast units also had 230v.

I then was advised (by site engineer) that sometime in the past these lights had lost power and had been rewired by someone ?? not sure if they were qualified or not ... i then went to a room at the end of the office area where he advised me they repowered this lighting circuit which has now gone out but power still there couldn't see any polarity faults but didn't get a chance to check all fittings as was in working hours of a office.

At the end fitting i was getting 230v between N-E and i haven't come across this before would appreciate any help

Is the MCB protecting the lighting circuit double pole? Is it an RCBO which is double pole? If it is double pole, did you check for 0 Volts between Lin and Lout and then for 0 Volts between Nin and Nout, both measured when the mcb is closed to confirm the closure of the pair of contacts?

 

[marlon89]

How did you draw that conclusion? There is 240 N - E and 240 L - E with the L - N voltage unknown.
The logical conclusion is that the N has risen to the same potential as the L with respect to E

L-N voltage was 230v as well and thanks guys . Will have more info after the morning getting there for half 5am . :0 .

 

[davesparks]

L-N voltage was 230v as well and thanks guys . Will have more info after the morning getting there for half 5am . :0 .

So that's 230V L - N, 230V L - E and 230V N - E ?

Are you sure you've measured that correctly?

 

[snowhead]

How did you draw that conclusion? There is 240 N - E and 240 L - E with the L - N voltage unknown.
The logical conclusion is that the N has risen to the same potential as the L with respect to E

Stated as 230v. Post 17

Personally I believe the test results are confused and it's a simple lost neutral.

 

[Hellmooth]

Concur.

 

[Deleted member 72666]

Concur.

Me too!

 

[Deleted member 72666]

L-N voltage was 230v as well and thanks guys . Will have more info after the morning getting there for half 5am . :0 .

What were your findings, do tell?

 

[Deleted member 72666]

Could be in for a long wait I fear!

 

[marlon89]

Hmm ok well my day started off got there at half 5 to give myself some time to inspect as much as poss before people started coming in

Security wouldnt let me in without presence of the site engineer who turned up at half 6 bcos the trains couldn't get him in any sonner even tho we agreed half 5 at the weekend .. lol so my day started well and got better ...

Eventually got in the office and past security , first started taking fittings apart and sensors down and also the circuits have lighting control modules that control all sensors and lights .. but a different company look after them have advised they also come in to check there equipment

Anyway just to clarify for the final time my readings I was getting the first time were 100% correct and at all fittings in was getting 230v L-N L-E N-E

But then I went back to the db to check between earth and neutral bar and was reading around 2v . Also at the mcb that feeds this circuit it has two feeds going in and only one neutral returning . So straight away doesn't look good . When taking one phase out the mcb and testing between earth bar and phase taken out of mcb I was still getting 230v !! So circuit was still live when taken out of mcb but only when that same mcb was re energizer it become live . When switching phases in mcb and turned back on the other phase was reading 120v from cable taken out of mcb to earth bar .

All the fittings have 230v and ballast side and emergency packs ( not all are emergency ) changed lamps but not ballasts and still not working .

Checked all wiring to fittings and couldn't see any cross polarity between switch lives and neutrals between sensors and t5 fittings or any lost neutrals

After further searching for jbs and speaking with site engineer who's been looking after the place for years ! He pointed me to a lighting control module fed from a fuse spur behind a wall in the office corner . Sorry forgot to mention also all fittings have a d1 and d2 connection for lighting control module to be able to dim lights. All connections in module fed from spur seemed to be ok but by this time keen office people started coming in around half 8 and need to start putting everything back together

But I also haven't got the equipment as company won't pay out yet for a fluke tester or multi megger as they are around £€5-600 haha but 1 pr two other engineers have got these testers and 2391 or 2395 as it's called now which I have not yet obtained. Plan to as it's so important for fault finding and hopefully company will agree and help us out abit haha . Doubt it tho .

But yes stil very confused have left circuit isolated as can't be leaving dangerous things like that on without test and inspecting throughout.

Thanks guys . Any ideas what these readings could mean ? As I have never come across this in my 7 years of being a electrician .

 

[davesparks]

You weren't using an approved voltage indicator or test lamp of any kind were you?

You might want to do a little bit if research on capacitive coupling and the associated/resultant phantom voltages before you go much further.

And you might want to advise your customer to call an electrician.

 

[davesparks]

Anyway just to clarify for the final time my readings I was getting the first time were 100% correct and at all fittings in was getting 230v L-N L-E N-E

.

Was that with a multimeter by any chance?

 

[Lucien Nunes]

all fittings in was getting 230v L-N L-E N-E

Any ideas what these readings could mean ?

Yes - your testing method is suspect. SP supply is 230V L-N and L-E, and approximately zero N-E (a volt or two makes no odds.). If the circuit neutral is high-resistance, then the N-E voltage at the load will be higher when under load, but the L-N voltage will be lower, the total always being 230V (but might read less, if the resistance is approaching the input resistance of the meter if unloaded), it's simple physics and not the subject of any mystery. You need to do dead tests to prove the continuity of the conductors. R1, Rn, R2, find the air gap if there is one.

couldn't see.... any lost neutrals

In the land of the blind, the man with a continuity tester is king.

Sorry forgot to mention also all fittings have a d1 and d2 connection for lighting control module to be able to dim lights.

I wonder what other useful bits of information we're missing. I give up.

 

[clubba]

Did you ever get to the source of the problem?

 

[DPG]

Did you ever get to the source of the problem?

Doesn't look like he's been on here for nearly 8 years.