Bonding Size for Old Incoming Supply

[IAmSparkytus!]

Incoming supply on our job comes into the building and then the tails from which go into a switched isolator with 200A fuses fitted.

No idea what size the incoming fuses are or incoming conductor sizes. Would have to contact the DNO but not sure whether they would give that info to anyone or how long it would take for that matter?

The 200A fuses feed a busbar chamber which we are tapping off with 70mm tails and 35mm earth to feed our DB.

Can our bonding be sized from that - 25mm?

Would 16mm suffice?

 

[davesparks]

What is the earthing system and what is the size of the earthing conductor?

 

[westward10]

What relevance would knowing the incoming fuse size make.

 

[IAmSparkytus!]

What is the earthing system and what is the size of the earthing conductor?

Can’t really tell as the cable goes straight into the cabinet. Doesn’t look to be TT as there are no overhead lines in the area.

What relevance would knowing the incoming fuse size make.

Just trying to give as much info as I know as possible, apologies if that troubled you

 

[timhoward]

Can’t really tell as the cable goes straight into the cabinet.

Can you really not see it anywhere?
Nothing to lose by asking DNO what their records say.
Seeing if PEFC and PSCC (phase to N) are similar or wildly different might give you a further clue.

As you probably gathered you need to know whether you are aiming at half the earthing conductor if not PME or according to the table in the regs if PME.

 

[IAmSparkytus!]

investigated a little bit more today and noticed a piece of metal connected externally to the incoming head which was bolted to some copper earth tape going up into the cabinet. The earth tape has a sticker on advising “Earthing Terminal PMS System”

Still couldn’t decipher what size the incoming conductors are as the cabinet is sealed. The armoured feeding the incoming head doesn’t have any conductor sizes marked on it.