4 pole main switch on pme supply

[rujebogdy]

Hello guys,I have a question that I hope you may be able to help me with. The installation is a 3 phase PME supply but all the distribution boards in the installation are supplied from the main panel by TNS. All these db's have the main switch 4pole 60947-3 Schneider. Do you think is aceptable? Sorry for the obvious question but I don't have the regs book with me. Appreciate all answers,cheers

 

[Andy™]

a TNCS supply cannot be made into TNS.

are you saying that the installation uses TNC and the earth is switched at each board?

but then you say its distributed as 'TNS' which scraps above.

are you sure your competent to be playing with three phase?

 

[Sidewinder]

I would guess a 4 wire 3ph sub main to each db from the origin db?

If the sub mains are TN-C then there may be a few issues, unless the building has a "special" dispensation.

 

[SparkyMarky]

This sounds fairly standard doesn't it? PME at the main DB. Sub mains to other DB's using 4 core SWA and depending on cable sizing using the armour or a separate 16mm + earthing conductor. 4 pole isolator for 3 x line and neutral.

 

[rujebogdy]

Maybe I haven't been clear enough with my explanation,sorry if I created any confusion. The arrangement is how sparkyMark said,just wanted to know if is acceptable for the main switches of the db's to be a 4 pole.thanx

 

[Sidewinder]

As I said 4 wire 3ph sub mains, no issue with isolating all live conductors.

Could be preferred as long as the polarity is correct.

No need to have a separate earth though, if could be the 5th core, the SWA or an additional, as long as suitable.

 

[rujebogdy]

Thank you for you're answers,i was curious as I saw in different places same arrangement but with the 3pole main switch,neutral not switchable

 

[Sidewinder]

On TN OK, on TT not acceptable, mate, you should really know this if you are doing PIR's else you could end up in trouble.

Is that what you are doing?

Else why the questions?

 

[rujebogdy]

Now you made me feel bad about asking the question,lol...

But I had a look in the regs at 537.1.2 and537.2.1.1

 

[Technician]

Is PME now one of the earthing arrangements and would it have been advisable to refer this to a body like NAPIT or similar?

 

[Zeespark]

Nope, PME is all to do with the local DNO, nothing to do with us.

AndyGuinness

 

[Technician]

I said that with tongue in cheek, Zee.

 

[Zeespark]

I apologise then Tech, I don't do subtle a lot of the time.

AndyGuinness