Mains on 3-phase DB

[Martin Flint]

Hi I am working in a hotel and I found that a 3-phase DB was fed by 2 seperate swa cables one containing the 3 phases and the other a seperate neutral and earth I know this is bad practice but can someone tell me why the NIC firm have picked this ad a fault I would not have done this myself it has been installed for over 20 years can any one help thanks

 

[Jibapproved]

Eddy currents

 

[Richard Burns]

Ferro magnetic (steel) enclosures are required to enclose all live conductors including the neutral. Chapter 52 at the beginning somewhere.

 

[Pete999]

Are the two SWAs terminated in a metal enclosure??

 

[Martin Flint]

Are the two SWAs terminated in a metal enclosure??

Yes both terminated in metal case fuse board and into mains switch room

 

[Pete999]

Then take note of Richards reply eddy currents, and chapter 52 BGB

 

[Engineer54]

Hi I am working in a hotel and I found that a 3-phase DB was fed by 2 seperate swa cables one containing the 3 phases and the other a seperate neutral and earth I know this is bad practice but can someone tell me why the NIC firm have picked this ad a fault I would not have done this myself it has been installed for over 20 years can any one help thanks

What i'm concerned about, is that the OP had no idea about this fundemental rule, and put it down to just bad practice!!!

 

[Pete999]

My lad was asked to finish off a PV job, just a few connections mate couple of hours at the most, when he arrived 4 25mm singles all neatly entering a dirty great metal box all neatly installed with stuffing glands the guy that gave him the job wouldn't believe it had been installed incorrectly, and he had been doing it this way for years, makes you wonder doesn't it?

 

[Engineer54]

My lad was asked to finish off a PV job, just a few connections mate couple of hours at the most, when he arrived 4 25mm singles all neatly entering a dirty great metal box all neatly installed with stuffing glands the guy that gave him the job wouldn't believe it had been installed incorrectly, and he had been doing it this way for years, makes you wonder doesn't it?

It certainly DOES!! ...lol!!

 

[Risteard]

Ferro magnetic (steel) enclosures are required to enclose all live conductors including the neutral. Chapter 52 at the beginning somewhere.

Not only the live conductors - but the protective conductor too. Although for SWA that might be the armouring, and the Regulation does oddly allow a separate protective conductor to be run outside the ferromagnetic enclosure in the case of SWA only!

 

[Risteard]

Are the two SWAs terminated in a metal enclosure??

Hardly relevant. The armouring is already a ferromagnetic enclosure!

 

[Engineer54]

Hardly relevant. The armouring is already a ferromagnetic enclosure!

Perhaps you need to think a little more about that statement!! lol!!

 

[benji]

Are you sure its 20yrs , is there any sign of anything getting hot

 

[Knobhead]

Having had a transformer fail due to a contractor using steel locknuts I’ll confirm it is a major problem.

 

[Hawkmoon]

What i'm concerned about, is that the OP had no idea about this fundemental rule, and put it down to just bad practice!!!

His quals are 17th and 2392....what do you expect