3 phase problem after spark did 5 year safety inspection

[jimthegent]

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?

There's a pic of inside the box there's black all up the rhs and inside it's black and scorched

 

[jimthegent]

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?

 

[jimthegent]

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?

There's the best I can get of the burnt tail after it has been taken our

 

[suffolkspark]

View attachment 112423

But thats all hanging off that single phase board, so i dont get why you keep talking about phase balancing? How many amps are each of those servers drawing? If the full or near to the 16A that is mighty loaded, With that board connected straight off the henleys i wonder what the upfront main fuses are. Are they greater than 100A?

 

[jimthegent]

But thats all hanging off that single phase board, so i dont get why you keep talking about phase balancing? How many amps are each of those servers drawing? If the full or near to the 16A that is mighty loaded, With that board connected straight off the henleys i wonder what the upfront main fuses are. Are they greater than 100A?

Hi 5 amps a unit and yes the fuses are 100amp per phase there's a small drawn through the main board to run the fans but it's tiny

 

[jimthegent]

Hi 5 amps a unit and yes the fuses are 100amp per phase there's a small drawn through the main board to run the fans but it's tiny

They servers all run on low power setting

 

[suffolkspark]

They servers all run on low power setting

How many amps each?

 

[jimthegent]

How many amps each?

Hi I can't promise this is dead right but each units is 1500 w

 

[suffolkspark]

Hi I can't promise this is dead right but each units is 1500 w

One on each socket?

 

[jimthegent]

One on each socket?

Yeah and we'd have 5 to 8 running at any one time

 

[jimthegent]

Yeah and we'd have 5 to 8 running at any one time

We are talking 12kw at the top end no more than that a 1kw for other bumfluffery fans main server lights etc

 

[jimthegent]

One on each socket?

I'm not ruining your Christmas here am I mate ? More than happy to leave this till mid week if your dinners going cold

 

[suffolkspark]

I'm not ruining your Christmas here am I mate ? More than happy to leave this till mid week if your dinners going cold

I just dip in and out of here when i get a sec, i really have no further ideas, thats not a massive load if all is well, but hefty if there was a poor main switch or loose wire

 

[jimthegent]

I just dip in and out of here when i get a sec, i really have no further ideas, thats not a massive load if all is well, but hefty if there was a poor main switch or loose wire

True there is a higher draw at start up as we need to get the building down to optimum temp and the fans on the machines work harder until we reach equilibrium but a loose wire is a disaster no matter what the load is isn't it

 

[DefyG]

True there is a higher draw at start up as we need to get the building down to optimum temp and the fans on the machines work harder until we reach equilibrium but a loose wire is a disaster no matter what the load is isn't it

I still maintain its nothing to do with a balanced or unbalanced 3phase load.
I do not think it is an overload (you dont get flash/bangs like that and molten copper from an overload)
IMHO Its a L - E or N 'Dead Short'

 

[suffolkspark]

I still maintain its nothing to do with a balanced or unbalanced 3phase load.
I do not think it is an overload (you dont get flash/bangs like that and molten copper from an overload)
IMHO Its a L - E or N 'Dead Short'

I think we all agree on that, but as it was running when the inspector left, something happened in between, the live side of the main switch has a significantly larger hole in the top compared to the neutral, so id say its sat there loose with 50A running through it getting mighty hot followed by a bit of arcy action first before it truly ---- itself

 

[jimthegent]

I still maintain its nothing to do with a balanced or unbalanced 3phase load.
I do not think it is an overload (you dont get flash/bangs like that and molten copper from an overload)
IMHO Its a L - E or N 'Dead Short'

Yeah and there's a lot of breakers on our system theres breakers in the pdu there are breakers on the main board surely it would just stop working with too much power drawn

 

[DefyG]

This was what is left of a RCD that had been in service for years without being touched (even during an EICR a few months prior).
It was from an installation in a community hall which would have been drawing less than 20A at the time.
The 'Dead Short' caused the cutout fuse (100A) to 'blow'.
We concluded it was an internal failure of the RCD and not caused by recent activity (as there wasn't any) but why? Who knows, one of those things!

 

[HappyHippyDad]

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

Good spot! It looks exactly that.

 

[freddo]

There have been several reports of Hager RCCBs detonating when the test button is pushed which then blows the cutout fuse, it also happened to me a few years back, really loud.