Tell us about your faults!

[kung]

Hi ALL
Just thought id put this one up for all those faults we find.
heres one to kick it off !
Domestic RCD tripped and wouldnt reset cause was a blown low energy light bulb.
There you go now for yours !

 

[rossco96]

Door entry system seemed to work ok but now getting lots of feedback from one plot it's ok when disconnected from phone and have checked phone in different plot seems ok cables test out ok not sure where to go next

- - - Updated - - -

Door entry system seemed to work ok but now getting lots of feedback from one plot it's ok when disconnected from phone and have checked phone in different plot seems ok cables test out ok not sure where to go next

 

[44ALLAN]

Apologies in advance if this has been brought up earlier but I'm not trolling through god knows how many previous posts
I thought I'd mention a 3 phase fault I had recently for the benefit of a lot of guys on here who are learning or are not familiar with working on 3 phase systems.
See if you can work out the fault. ( if you know it please give the guys a chance to try and work it out first.......ta).

The factory where I work has its own 500kva transformer.
Built in the early 60's this supplied both the factory and the remote office block.
I recently had the DNO run a 3 phase/N SWA cable into the office block so I now have 2 separate supplies.
I then installed a 3 phase board and ran several single phase sub mains to various c/units around the office block.
From the main board I then ran a 3 phase 'dedicated supply' to the server room for the IT dept ( this is the only 3 phase board in the building apart from the incomer).

I was called to the IT dept because the main server had 'crashed'. UPS had kicked in but lots of things not working.
Main thing I noticed on my way there was ALL the power and lighting in the offices was still on.

Anyway...........work this out if you can
Testing the 3 phase D/B in the server room gave me these results.

L1-N = 230v.
L2-N =230v.
L3-N =230v.
L1-E = 230v.
L2-E = 230v.
L3-E = 230v.
N-E = 0v.
L1-L2 = 432v.
L1-L3 = 432v.
L2-L3 = 0v.

What fault could cause this, bearing in mind, ALL power and lighting was still on !

I'll wait and see if there's much interest before giving any clues if their needed but I'm sure many have come across this problem on here just thought it would be good to share with others that haven't.

 

[Megavolt]

Are L2 and L3 the same phase

 

[44ALLAN]

Are L2 and L3 the same phase

Meaning?
How could this be?

I need to add that the install ( 3 phase etc) has worked ok for many weeks prior to this happening).

 

[electric will]

Short between L2 and L3 but only took one of the phases out?

 

[daiplayer]

Found this in my mates bathroom ceiling.
The cieling is a flat roof with approx 100m space above the plasterboard , which is also PACKED with insulation.

 

[daiplayer]

good access to source.....plus some nice jb's , lol

 

[daiplayer]

Short between L2 and L3 but only took one of the phases out?

All phases still showing 230 - E ........???

 

[KAS1]

was it one phase blown and then back feeds through the neutrals indicting a phase present when testing all phases to earth?

Apologies in advance if this has been brought up earlier but I'm not trolling through god knows how many previous posts
I thought I'd mention a 3 phase fault I had recently for the benefit of a lot of guys on here who are learning or are not familiar with working on 3 phase systems.
See if you can work out the fault. ( if you know it please give the guys a chance to try and work it out first.......ta).

The factory where I work has its own 500kva transformer.
Built in the early 60's this supplied both the factory and the remote office block.
I recently had the DNO run a 3 phase/N SWA cable into the office block so I now have 2 separate supplies.
I then installed a 3 phase board and ran several single phase sub mains to various c/units around the office block.
From the main board I then ran a 3 phase 'dedicated supply' to the server room for the IT dept ( this is the only 3 phase board in the building apart from the incomer).

I was called to the IT dept because the main server had 'crashed'. UPS had kicked in but lots of things not working.
Main thing I noticed on my way there was ALL the power and lighting in the offices was still on.

Anyway...........work this out if you can
Testing the 3 phase D/B in the server room gave me these results.

L1-N = 230v.
L2-N =230v.
L3-N =230v.
L1-E = 230v.
L2-E = 230v.
L3-E = 230v.
N-E = 0v.
L1-L2 = 432v.
L1-L3 = 432v.
L2-L3 = 0v.

What fault could cause this, bearing in mind, ALL power and lighting was still on !

I'll wait and see if there's much interest before giving any clues if their needed but I'm sure many have come across this problem on here just thought it would be good to share with others that haven't.

 

[electric will]

All phases still showing 230 - E ........???

they would do, one phase down but then receiving 230 from other phase via the short?
Don't know why the other 2 phases have a slightly raised voltage though.

 

[daiplayer]

they would do, one phase down but then receiving 230 from other phase via the short?

good shout

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Short between L2 and L3 but only took one of the phases out?

im going with that :-D

 

[daiplayer]

Are L2 and L3 the same phase

which would make this right too

 

[44ALLAN]

Short between L2 and L3 but only took one of the phases out?

That would mean everything fed from that phase would be off..............all the power and lighting was still on!

 

[44ALLAN]

good shout

- - - Updated - - -



im going with that :-D

A short between L2 and L3 would blow the fuses or trip the mcb's surely guys?

 

[Silly Sausage]

Give us numpties a hint Allan!

 

[44ALLAN]

Give us numpties a hint Allan!

LOL.

Well look at the test results again and you'll notice ALL single phase power was still on ALL 3 phases but the 3 phase server wasn't working !
Test results will tell you why.

How could this happen though as non of the Mcb's had tripped.

 

[Bobster8]

Re: Tell us about your faults !

My main fault is I get angry with stupid thick customers when they ask questions like how much is it going to cost and how long is it going to take

 

[daiplayer]

Come on alan dood.....need to know now ....
us thicko's that add extra sockets for grannies extra heater are dumbfounded ...lol

 

[44ALLAN]

Come on alan dood.....need to know now ....
us thicko's that add extra sockets for grannies extra heater are dumbfounded ...lol

ok.

You were close originally mate so here's one last clue to see if you can fathom it out.
Always better if you work it out yourself

The fault caused me to lose a phase.........call it L3.........but all my single phases were testing 230v and non of my circuit breakers on site were tripped?
Twas a head scratcher for a few minutes lol

ok anyone know what the fault was here's your big chance lol

 

[daiplayer]

nope ...still lost :-9

 

[44ALLAN]

nope ...still lost :-9

ok mate no interest elsewhere so here goes........one for your fault archives.

The new 3 phase/N feed into my office block was taken from a joint in the street outside which also feeds street lighting/pump house down the road etc etc.

Turns out the cable/joint/termination ( downstream from us) developed an earth fault on L3/blue phase/grey phase whatever you want to call it.

This earth fault blew the main fuse in their substation but the heat from the blast ( at the location of the fault) 'welded' L2 and L3 together at the same time clearing the earth fault..........if you get my drift ! lol

This meant L1 was still ok and fused.
L2 was still ok and fused.
L3 was now fused to L2 and being fed through L2 back to my main D/B giving me good tests on all single phases.

Moral of the story........if their is one lol
You can have good tests but still be in a fault situation.

Subsidence seemingly causes this problem on underground cables sometimes but not sure how often..........new one on me that's for sure.

Clear as mud mate

 

[Megavolt]

ok mate no interest elsewhere so here goes........one for your fault archives.

The new 3 phase/N feed into my office block was taken from a joint in the street outside which also feeds street lighting/pump house down the road etc etc.

Turns out the cable/joint/termination ( downstream from us) developed an earth fault on L3/blue phase/grey phase whatever you want to call it.

This earth fault blew the main fuse in their substation but the heat from the blast ( at the location of the fault) 'welded' L2 and L3 together at the same time clearing the earth fault..........if you get my drift ! lol

This meant L1 was still ok and fused.
L2 was still ok and fused.
L3 was now fused to L2 and being fed through L2 back to my main D/B giving me good tests on all single phases.

Moral of the story........if their is one lol
You can have good tests but still be in a fault situation.

Subsidence seemingly causes this problem on underground cables sometimes but not sure how often..........new one on me that's for sure.

Clear as mud mate

To be fair that is what I was trying to say that is way you showed 0 volts as they was same phase

 

[Bobster]

Old cable joints cause similar faults, quite common once they are in 30+years.

 

[44ALLAN]

To be fair that is what I was trying to say that is way you showed 0 volts as they was same phase

Originally Posted by Elrick
Are L2 and L3 the same phase



Meaning?
How could this be?



You certainly did mate I was just asking if you knew what fault could have caused it though and the clue was that non of 'my' breakers had tripped.

 

[44ALLAN]

Old cable joints cause similar faults, quite common once they are in 30+years.

Hi Rob,
I've seen a few 'strange' faults in my time and for a few moments this one had me bamboozled to say the least.
Then training kicked in...........think easy/think logically.
So I walked down to the main incomer and my new dazzling meter showed L3 was lost lol. (on the incoming side I hasten to add).
Fault finding at it's best.... quick phone call and someone elses problem

 

[electric will]

Short between L2 and L3 but only took one of the phases out?

a bit like what I said here then?

 

[Megavolt]

To be fair that is what I was trying to say that is way you showed 0 volts as they was same phase

Originally Posted by Elrick
Are L2 and L3 the same phase



Meaning?
How could this be?



You certainly did mate I was just asking if you knew what fault could have caused it though and the clue was that non of 'my' breakers had tripped.

I wouldn't of guessed what it was never came across this one before thanks for sharing got my grey matter going. What tester did you use to confirm it.

Thanks

 

[44ALLAN]

I wouldn't of guessed what it was never came across this one before thanks for sharing got my grey matter going. What tester did you use to confirm it.

Hi mate.
It might help a few to 'show-off' with their fault finding skills if they come across it in the future lol
It was a bit tongue in cheek about mine because our 3 phase meter has 'phase indication' on it and it showed L3 was missing
Confirmed it with my Fluke 1653 on the main incomer.
Local DNO guy was blowing 500amp fuses trying to clear the fault ffs !!!

 

[Stroppy]

Here's a good one: two two-core SWA's of differing csa's and a length of flex feeding some outside lights, connected with connector blocks, and made 'safe' (ish) by covering with silicone sealant, and buried between zero and three inches across a gravel drive! The doubled-back earth wire of the flex is taped to the swa plastic sheath, but the swa's armours are touching, so sort of achieving earth continuity.

Oh yes, protected by a 50A MCB. And as far as I can find (so far) no earthing to the installation whatsoever - definitely not PME in the 1930's cast iron head, and no conductor in the board that could end in an earth stake, unless the stake is connected to one of the final circuits somewhere.

 

[Stroppy]

Same house as above: noticed that every time you shut the front door the lights flicker. Found why, they are using these p1ssy little electronic 5 amp fuses in both lighting circuits which are considerably smaller than their correct BS1361 equivalents.