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3 phase problem after spark did 5 year safety inspection

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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
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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)
 
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
 
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.
 
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
 
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.
 
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 ?
 
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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
 
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!
 
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
 
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

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
 
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. ;-)
 
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?
 
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.
 
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I don’t think the clamp is the source of the problem it would of been in a dam sight worse condition if it was

I’d say a loose connection that has eventually caused the internals to short

To be honest the whole design of l2 to be loaded up like that is a sh!t show
Another 3 phase db instead and sockets spread across the phases

It’s easy to sit there blaming the spark who could easily of been anyone one here with ought knowing the full circumstances

The biggest thing that stands out to me is he used the tail clamp what puts him/her above 60/70 %of the butchers that get away with it week in week out
 
Good morning. If the cooling system fed by the 3P db did indeed have three phase 3 wire motors, then even though the main L2 fuse ruptured the site‘s L2 conductors would remain energised because it is connected by the motor windings to L1 and L3. The voltage of L2 with respect to N will depend on the L2 load impedances and that of the motors. The current in L1 and L3 will increase as the 3 phase motors run in single phase mode. The motors would not start with only L1 and L3 but they can continue to spin if they were already and a phase was lost.

What happens to the 3-Phase Motor When 1 Out of 3 Phases is Lost? - https://www.electricaltechnology.org/2021/11/what-happens-to-the-3-phase-motor-when-1-out-of-3-phases-is-lost.html

Thus even though L2 fuse ruptured further damage to equipment loads may have happened using current drawn from L1 and L3. What if anything happened to isolate all electricity ie disconnect L1 and L3?

Where the servers fed by UPS and/or voltage regulators?

I concur that the original short circuit was caused by a failure of the termination and squashing of the cable by the clamp. But can see how L2 may have remained energised and significant current might still flow causing further damage.
 
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They probably
They probably
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.
Sorry I was being flipent there he did remove the tails and put them back in the day before the outage
 
MFS makes an interesting point, i cannot recall needing to remove tails from an isolator to do an EICR, plus if they are connected to the Henley rather than a CB off the TP board, they would have been live unless the main fuse was pulled or there is another TP isolator for the whole supply. If you have the ECIR report it will tell us how the board is connected to the supply. I am wondering if he was getting poor readings when testing to the isolator terminals and removed the cables to work out why ?

Anyway, plenty of theories, which do not appear to have a way forward without some evidence to rule in or out various possible causes
 
MFS makes an interesting point, i cannot recall needing to remove tails from an isolator to do an EICR, plus if they are connected to the Henley rather than a CB off the TP board, they would have been live unless the main fuse was pulled or there is another TP isolator for the whole supply. If you have the ECIR report it will tell us how the board is connected to the supply. I am wondering if he was getting poor readings when testing to the isolator terminals and removed the cables to work out why ?

Anyway, plenty of theories, which do not appear to have a way forward without some evidence to rule in or out various possible causes
Morning the best evidence I can produce is that we had perfect balanced system un stressed working well and a few hours after someone did work on it the system failed I do have a video of the electrician who came the next day to rectify on the phone to the office saying "it looks like we've nipped the outer casing when we put it back" and her boss saying is the main fuse that blew on the same line as the breaker......they know they've balls'up but that'd why I so great full to you guys as I'm not an electrical engineer and they are trying to lead me by the nose to bankruptcy
 
That single phase board doesnt appear to be fed by the three phase board, so at some point L2 looks to have been loaded up, or loose, with the visible heat damage there, but is possibly un related, theres just so many unknows here for us, which board are you saying blew off the wall? If you could post the report on here with the inspectors details redacted that may help, but im not so sure. You mention data loss, was there no off site backups? Or ups? Or anything to alert you to the supposed high temperatures in that area by the fans not working? I may have detsils mixed this threads getting a bit long now
 
How do you know your system is perfectly balanced? Why is that board fed in tails? Generally heavily loaded single phase boards would indicate the system is unbalanced in my experience. I can’t really see why the spark had the tails out for testing either, just doesn’t really make sense.

Edit- no answer to my previous question either, did the cover actually blow off? How did that happen with threaded screws on the cover, did they break? Do you have a picture?
 
Morning the best evidence I can produce is that we had perfect balanced system un stressed working well and a few hours after someone did work on it the system failed I do have a video of the electrician who came the next day to rectify on the phone to the office saying "it looks like we've nipped the outer casing when we put it back" and her boss saying is the main fuse that blew on the same line as the breaker......they know they've balls'up but that'd why I so great full to you guys as I'm not an electrical engineer and they are trying to lead me by the nose to bankruptcy

How do you know your system is perfectly balanced? Why is that board fed in tails? Generally heavily loaded single phase boards would indicate the system is unbalanced in my experience. I can’t really see why the spark had the tails out for testing either, just doesn’t really make sense.

Edit- no answer to my previous question either, did the cover actually blow off? How did that happen with threaded screws on the cover, did they break? Do you have a picture?
Hi its our job to have precise amps distributed to our servers so we take a great deal of effort to get it bang on the lid was on the floor and covered in black soot when we went in as was the entire board with heat marks all over
 

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How do you know your system is perfectly balanced? Why is that board fed in tails? Generally heavily loaded single phase boards would indicate the system is unbalanced in my experience. I can’t really see why the spark had the tails out for testing either, just doesn’t really make sense.

Edit- no answer to my previous question either, did the cover actually blow off? How did that happen with threaded screws on the cover, did they break? Do you have a picture?
Also this is a local authority building so the electricians are paid in a way that anyone who's got a local authority contract will understand its in their interest to have everything undone and redone and they also then get the gig to do any remedials and this is done on the nod a couple of photos to the Borough electrician and help yourselves lads look forward to your invoice
 

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