3 phase problem after spark did 5 year safety inspection

[jimthegent]

Hi lads 5 year safety inspection the spark put the tails back and later line 2 of the 3 phase blew blowing the box off the wall and taking out the main fuse on the same line into the building can you all just say quickly what you think the spark may have done wrong ?
Cheers

 

[suffolkspark]

Hi lads 5 year safety inspection the spark put the tails back and later line 2 of the 3 phase blew blowing the box off the wall and taking out the main fuse on the same line into the building can you all just say quickly what you think the spark may have done wrong ?
Cheers

Why did the spark have the tails out for an inspection?

 

[jimthegent]

Why did the spark have the tails out for an inspection?

No idea but it's a local council job so I assume because they can bill them for more dough

 

[suffolkspark]

No idea but it's a local council job so I assume because they can bill them for more dough

Are you sure he actually did remove them? He should have spotted a loose connection when checking all the terminals though, thats if it was that and not faulty contacts in the switch.

 

[jimthegent]

Are you sure he actually did remove them? He should have spotted a loose connection when checking all the terminals though, thats if it was that and not faulty contacts in the switch.

Yes 100% he took them out and put them back in again

 

[westward10]

I would say a dead short has occurred there.

 

[jimthegent]

I would say a dead short has occurred there.

Yeah and what do you think caused it

 

[westward10]

There is molten metal albeit it doesn't look like copper, the remains of something else?

 

[snowhead]

Looks like the Red clamp has squashed the cable and split the insulation.
That's allowed the copper core to touch the earthed metal backplate and or the screw holding the clamp.

If it was the cable lose in the terminal or wrong side of termianl clamp it would have fizzled and overheated for a while before ultimately failing.

As Westwood, it looks like a dead short, especially with the ball of copper

 

[jimthegent]

There is molten metal albeit it doesn't look like copper, the remains of something else?

Yes the cover of the board was blown off and there's a lot of black soot all over the switches so clearly a lot of heat was generated

 

[plugsandsparks]

Cable clamp look suspicious....

 

[jimthegent]

Looks like the Red clamp has squashed the cable and split the insulation.
That's allowed the copper core to touch the earthed metal backplate and or the screw holding the clamp.

If it was the cable lose in the terminal or wrong side of termianl clamp it would have fizzled and overheated for a while before ultimately failing.

As Westwood, it looks like a dead short, especially with the ball of copper

Yep now bear in mind all other tails and switches are pristine is there any votes for system overload the main fuse that blew into the building is also on phase 2

 

[westward10]

It is a dead short. Can you show a more direct pic below the red clamp.

 

[plugsandsparks]

Not overload, short cct fault as WW states

 

[jimthegent]

It is a dead short. Can you show a more direct pic below the red clamp.

 

[plugsandsparks]

Needs to be powered down and clamp removed, i can see it is already pinching the RHS cable sheath.

Once clamp removed photograph the back side of it, remove the LHS cable and photographc the back plain of board, should tell you everything you need to know, Merry Xmas

 

[jimthegent]

It is a dead short. Can you show a more direct pic below the red clamp.

Hi no they can back and replaced the switch and tail and removed the offending bits

 

[suffolkspark]

Ah so its all sorted....

 

[jimthegent]

Ah so its all sorted....

Seems the wire being nipped seems to be winning the vote can any of you guys see a situation were a nicely balanced 3 phase which was always well well under max amps would see just one phase go up like this

 

[jimthegent]

Ah so its all sorted....

Yeah but the upshot was that we were running on 2 phases for a a good few hours the fans failed the temp in the building rocketed and a load of other problems as a result

 

[jimthegent]

Needs to be powered down and clamp removed, i can see it is already pinching the RHS cable sheath.

Once clamp removed photograph the back side of it, remove the LHS cable and photographc the back plain of board, should tell you everything you need to know, Merry Xmas

Hi can't thank you enough for the advice what would photos of the back of the clamp and board show or what should I look for ?

 

[westward10]

What did they say caused it.

 

[jimthegent]

What did they say caused it.

An overloaded board but it's run fine for 5 years and it just happend to blow a few hours after they wiggled the wires plus each phase is perfectly balanced with 9 feeds

 

[jimthegent]

What did they say caused it.

I've attached a picture of were the feeds are they are the ones on the rhs blue ones

 

[westward10]

An overloaded board but it's run fine for 5 years and it just happend to blow a few hours after they wiggled the wires plus each phase is perfectly balanced with 9 feeds

That wasn't an overload that was a dead short, a short they created.

 

[snowhead]

An overloaded board but it's run fine for 5 years

So is it still "overloaded" or has that been corrected?

 

[jimthegent]

That wasn't an overload that was a dead short, a short they created.

Thanks again pal really appreciate it

 

[jimthegent]

So is it still "overloaded" or has that been corrected?

Never was plus there's breakers on the pdus there's 9 sockets and we are always on about 50% of max amps the units cooling runs on a separate board and there's no other power pulls plus it's winter so the system isn't stressed due to high temps

 

[pc1966]

Cable clamp look suspicious....

It looks too small for that wire size, or is it just fitted strangely?

 

[jimthegent]

It looks too small for that wire size, or is it just fitted strangely?

You getting warm mate not as warm as that tail got the consensus seems to be the outer casing got nipped when refitting but I'm seeing if any sparks have another take on it

 

[jimthegent]

......but if any other people want to chip in I'd like to get as much feedback as possible on this feel free to join in

 

[plugsandsparks]

Hi can't thank you enough for the advice what would photos of the back of the clamp and board show or what should I look for ?

Perhaps should have mentioned it. You are looking for - what looks like a poor attempt at welding.. You should see black burn marks either at the back of the red clamp or black burn marks on the backplane, the melted - either copper or steel is plain to see in the pic.
Its no big deal, *hit happens, whoever repaired it will know the real reason.
If you have an overload that blows the doors off you may wish to consider the efficacy of your overload devices, lol
Anyway, you can hardly expect to be told that the electrician who disturbed the cable clamp and cable made a total *ollocks, i may admit to it, if it was me, depends on how i feel on the day.
Its possible it was previously fitted to an inch of its life and the EICR guy just fitted it back without "being fully alert"

(generous hat off)

 

[jimthegent]

Perhaps should have mentioned it. You are looking for - what looks like a poor attempt at welding.. You should see black burn marks either at the back of the red clamp or black burn marks on the backplane, the melted - either copper or steel is plain to see in the pic.
Its no big deal, *hit happens, whoever repaired it will know the real reason.
If you have an overload that blows the doors off you may wish to consider the efficacy of your overload devices, lol
Anyway, you can hardly expect to be told that the electrician who disturbed the cable clamp and cable made a total *ollocks, i may admit to it, if it was me, depends on how i feel on the day.
Its possible it was previously fitted to an inch of its life and the EICR guy just fitted it back without "being fully alert"

(generous hat off)

Yeah cheers you've been a mine of info really appreciate it ....the contractors are claiming we overloaded the board but there's plenty of spare leads and sockets and the others bits look like they have been fitted yesterday after 5 years use and given what they say if it was dodgy they should have noted it in their inspection report they didn't because it wasn't.....that only happend after they left

 

[Diddy]

Im getting the feeling that the contractors are trying to get you/company to pay for them to come out and "fix" the result in the 1st picture?
I would say that the 1st picture should throw any opinions out the water with the evidence of a dead short.
What has puzzled me is how did it not happen while the contractor was on site and when they re-energised the offending board? Did they not re-energise ?
Even if it did happen after several hours use then id still say dead short and cause being poorly terminated cables including but not limited to the cable clamp itself. Pretty ironic that if they had been "rough" and missed out the cable clamp this wouldn't have happened....unless the tails were super loose even a few hours under a decent load would do the job of melting the insulation leading to a dead short fault.
It shouldn't be a problem if they have rectified free of charge...but if there is other costs such as down time and damage then im sure their public liability will do what it's intended for.

 

[jimthegent]

Im getting the feeling that the contractors are trying to get you/company to pay for them to come out and "fix" the result in the 1st picture?
I would say that the 1st picture should throw any opinions out the water with the evidence of a dead short.
What has puzzled me is how did it not happen while the contractor was on site and when they re-energised the offending board? Did they not re-energise ?
Even if it did happen after several hours use then id still say dead short and cause being poorly terminated cables including but not limited to the cable clamp itself. Pretty ironic that if they had been "rough" and missed out the cable clamp this wouldn't have happened....unless the tails were super loose even a few hours under a decent load would do the job of melting the insulation leading to a dead short fault.
It shouldn't be a problem if they have rectified free of charge...but if there is other costs such as down time and damage then im sure their public liability will do what it's intended for.

Hi thanks for you thorough reply no we didn't power back until later that day, the firm are trying to say we over load the whole system and the melted outer casing is as a result of the tails getting warm it's taken a year to get to this point and they are hiding behind a loss adjuster who isn't even using a qualified electrician to produce reports that are laughable

 

[suffolkspark]

Looks to me like it was loose, got hot, popped out (maybe it was under tension but the clamp wasnt on properly, clamp doesnt look right to be honest but ive never fitted that brand) and then shorted like the others spotted, and bang. All hard to prove, but as you say, if it was an overload why wasnt it mentioned in the report. Thats because it wasnt.

 

[marconi]

Please tell me what loads were connected to the blue and brown c form sockets. Were they 3 phase motors or transformers connected to the brown sockets?
If they were three phase were they 3 phase 3 wire ie neutral not used?
Is the L1cable at the bottom of the 3 phase dis board - 2nd from left- showing signs of overheating - it is discoloured.
What other site loads were powered during the few hours after the L2 Incomer fuse ruptured and the site was left powered just by L1 And L3 - your #20 refers. Amongst these other loads were there 3 phase 3 wire motors energised by L1 and L3 ?

 

[jimthegent]

Please tell me what loads were connected to the blue and brown c form sockets. Were they 3 phase motors or transformers connected to the brown sockets?
If they were three phase were they 3 phase 3 wire ie neutral not used?
Is the L2 cable at the bottom of the 3 phase board showing signs of overheating - it is discoloured.
What other site loads were powered during the few hours after the L2 Incomer fuse ruptured and the site was left powered just by L1 And L3 - your #20 refers. Amongst these other loads were there 3 phase 3 wire motors energised by L1 and L3 ?

Hi the red / brown are not used and haven't been for 3 years the only board in use was the smaller board to the right with the blue sockets . In short our servrrs and cooling system abd ventilation systems all ran on the L2 but was balance with the others It's only the unit cooling system that ran off that board so when phase 2 blew the fans ran on 2 phases for a short period then stopped the temp in the unit would have rocketed a number of pdu's also blew up and there's evidence of molten copper and plastic on these also the surge protection wasn't enough to take the surge and we suffered catastrophic data loss and most of our hardware has been comprised it did look like a house fire when we got in

 

[suffolkspark]

L2 in that three phase board looks like its got hot too?

 

[DefyG]

is there any votes for system overload the main fuse that blew into the building is also on phase 2

No, definitely not.

An overloaded board but it's run fine for 5 years and it just happend to blow a few hours after they wiggled the wires plus each phase is perfectly balanced with 9 feeds

The fault you show is of the top (input) of a single phase consumer unit. A 3phased balance load would not have any bearing on the fault IMHO.
The damaged cable is a 'red herring', I believe as the clamp being insulating material there would nothing to make a circuit and cause a 'short'.
I would think the DP Isolator has failed and there has been a L-N 'short' within the isolator, or maybe a stray strand!

 

[jimthegent]

L2 in that three phase board loo from the electrical

No, definitely not.


The fault you show is of the top (input) of a single phase consumer unit. A 3phased balance load would not have any bearing on the fault IMHO.
The damaged cable is a 'red herring', I believe as the clamp being insulating material there would nothing to make a circuit and cause a 'short'.
I would think the DP Isolator has failed and there has been a L-N 'short' within the isolator, or maybe a stray strand!

The clamp is mild steel

 

[plugsandsparks]

Only going to know for sure with photos of the back of the clamp and back plate, if there are no marks i would agree and internal failure of the isolator comes into play, then was it caused by a loose connection or an internal failure of the DP Isolator. I saw the split in the tail on L2 supply and blamed the clamp (until proven otherwise) - it possible the heat generated by a loose connection compromised the tail insulation, hence you would need to see the components to work out what went first.
However i think we all agree unless the CB in the TP board is welded shut, then ADS should have saved it from this mess if it was indeed overload. (assuming the SP board is fed from the TP board) - i cannot tell from pic

 

[jimthegent]

L2 in that three phase board looks like its got hot too?

Could that have come from the electrical fire in the box we had it was cleaned up but initially there was a load of soot and detritus all over the box

 

[plugsandsparks]

I cannot see a SP breaker in the TP board to feed the SP board, so do the tails go to the Henleys and then straight to the incoming fuse? - If so i assume (again) this is either a 80A or 100A TP supply?

 

[jimthegent]

Only going to know for sure with photos of the back of the clamp and back plate, if there are no marks i would agree and internal failure of the isolator comes into play, then was it caused by a loose connection or an internal failure of the DP Isolator. I saw the split in the tail on L2 supply and blamed the clamp (until proven otherwise) - it possible the heat generated by a loose connection compromised the tail insulation, hence you would need to see the components to work out what went first.
However i think we all agree unless the CB in the TP board is welded shut, then ADS should have saved it from this mess if it was indeed overload. (assuming the SP board is fed from the TP board) - i cannot tell from pic

Only going to know for sure with photos of the back of the clamp and back plate, if there are no marks i would agree and internal failure of the isolator comes into play, then was it caused by a loose connection or an internal failure of the DP Isolator. I saw the split in the tail on L2 supply and blamed the clamp (until proven otherwise) - it possible the heat generated by a loose connection compromised the tail insulation, hence you would need to see the components to work out what went first.
However i think we all agree unless the CB in the TP board is welded shut, then ADS should have saved it from this mess if it was indeed overload. (assuming the SP board is fed from the TP board) - i cannot tell from pic

We are never going to know that the contractor returned the next day replaced the breaker replaced the burnt out tail and clean the crime scene up they also removed the items which technically still belong to us

 

[plugsandsparks]

OK, but your loads presumably have not changed prior to now, so just measure the load now.
A pic of the SP board breakers may give a clue to whether overloading the board is even possible.

It was rather naughty to not leave the isolator with you, however you still have the board and clamp. ;-)

 

[jimthegent]

OK, but your loads presumably have not changed prior to now, so just measure the load now.
A pic of the SP board breakers may give a clue to whether overloading the board is even possible.

It was rather naughty to not leave the isolator with you, however you still have the board and clamp. ;-)

They probably

 

[MJPD29]

Yes the cover of the board was blown off and there's a lot of black soot all over the switches so clearly a lot of heat was generated

The cover was blown off? Really?

 

[MFS Electrical]

Yes 100% he took them out and put them back in again

Certainly not a standard thing to do on an inspection.

When you do the 2391 (inspection and testing) you are told to disturb as little connections as possible to ensure you don’t create faults.

It’s highly unlikely that the electrician would have removed the tails and reterminated them on an EICR (inspection)

Also, the picture you’ve posted looks like a single phase main switch?

 

[MFS Electrical]

An overloaded board but it's run fine for 5 years and it just happend to blow a few hours after they wiggled the wires plus each phase is perfectly balanced with 9 feeds

So he didn’t remove the tails? But wiggled them?
Sounds more likely that there’s been a problem hiding there for a while either from a loose connection causing the cable to overheat and eventually melt into the clamp or the wiggle has exacerbated a defect already there and with a little load on the cable the cable moves and boom.

Also re the overload; It is certainly possible that an overload has occurred even if it has been running fine for years. An overload of a small magnitude can be enough to heat the cable past its operating temperature and cause it to significantly expand, then upon cooling and contracting loosen the connection. Rinse and repeat for 5 years and you certainly could have a situation like this.

I see it all the time where a shower installed on a 6mm cable ran through insulation in a wall and then under loft insulation is used to power a 9.5kW shower and due to the overloading of the cable (which should have been derated due to the insulation) burns out at the terminations of the switch or the MCB or the shower.
Genuinely, funnily enough it usually takes around 5 or so years of normal use for the problem to come to light by which time the spark that put it in is long gone.