PME install, no CPC

[silentboarder69]

Hi guys,
I've been called to look at a flat in north London. The flat is in a converted piano factory. Looking at the CU, perhaps installed in the 70's or 80's, it has a CPC. All good.
Under the CU is a termination box of some description. The tails come up, through metal conduit, into this box. There's no CPC at this point. The positive runs through the box and into the CU. The negative however, runs into a small Henley block. Coming out of the Henley block, is a negative, and the CPC.
The flat is located on the top floor of this factory conversion. Investigating the electrical riser, it's clearly marked up as a PME install, and I presume the other flats are similarly wired.

I've never seen this before, is it OK? I haven't checked the continuity of the conduit.


Thanks

Rick

 

[telectrix]

measure your pssc and pefc. if virtually identical readings, then it's PME. what was the Ze?

 

[Guitarist]

Positive and negative?

 

[Silly Sausage]

Positive and negative?

Red & Black wires...

With the horrible thought that the conduit isn't earthed at the intake(!) (which isn't proved in the OP), that would make this sub main a TNC within the building? A complete No No.
Wouldn't it best for the conduit to earthed at the intake and the flat earth taken off the other end and lose the N E separation at the flat?

 

[Guitarist]

Red & Black wires...

With the horrible thought that the conduit isn't earthed at the intake(!) (which isn't proved in the OP), that would make this sub main a TNC within the building? A complete No No.
Wouldn't it best for the conduit to earthed at the intake and the flat earth taken off the other end and lose the N E separation at the flat?

It concerns me that a qualified electrician would refer to the Line and neutral as positive and negative in this situation....

 

[Des 56]

It concerns me that a qualified electrician would refer to the Line and neutral as positive and negative in this situation....

Who knows? There could be a bank of batteries in the basement :smartass2:

 

[Knobhead]

Can we see some photo's of this terminal block and the service head. We can go on guessing for ever.

 

[Engineer54]

Red & Black wires...

With the horrible thought that the conduit isn't earthed at the intake(!) (which isn't proved in the OP), that would make this sub main a TNC within the building? A complete No No.
Wouldn't it best for the conduit to earthed at the intake and the flat earth taken off the other end and lose the N E separation at the flat?

We need to see how the incoming mains have been distributed. It is more than likely that the N-E connection has been made here and that this conduit is earthed via that arrangement. What i can't understand, is why they are then making separate N-E connections at each flat. You only need to make that connection Once, so as you suggest, the correct method would be to take each flats earthing from the conduits carrying the sub-main cables with a suitable and solid means connection to the conduit.