Changes are coming, what do you all think

[Wilko]

Potential Customer has asked me to put a power socket on the outside wall of his garage, what's it for I ask conversationally "its to charge up my hybrid"... PME, so IET Code of practice recommends min 2 by 2.4m rods. Plus get it back to MET. I wish I'd just shut up.

 

[1Justin]

Potential Customer has asked me to put a power socket on the outside wall of his garage, what's it for I ask conversationally "its to charge up my hybrid"... PME, so IET Code of practice recommends min 2 by 2.4m rods. Plus get it back to MET. I wish I'd just shut up.

I more or less had to refuse exactly that request recently. It's going to get more common, and especially with hybrids which only need small charge off 13A socket, hard to draw a line against the regs.

 

[Deleted member 26818]

There’s a number of issues I have with this particular proposal.
1, This proposal is supposedly in case of a supply Neutral fault, which the DNO’s have a Statutory requirement to maintain and protect consumers if such faults do occur.
Why is the IET proposing another Non Statutory Regulation to offset a breach of Statutory requirements?
2, In the event of any such fault occurring, the installation Earth will effectively become the Neutral.
Is this acceptable?
Are the present Installation Earthing and bonding CSA requirements sufficient?
3, In situations where it is not practicable to install Earth electrodes and perhaps even in situations where it is practicable, should upfront RCD protection also be provided so as to disconnect the supply in the event of a supply Neutral fault?

 

[telectrix]

 

[1Justin]

3, In situations where it is not practicable to install Earth electrodes and perhaps even in situations where it is practicable, should upfront RCD protection also be provided so as to disconnect the supply in the event of a supply Neutral fault?

.
& This would need to be before MET then wouldn't it? - Thus the property of DNO ?

 

[Deleted member 26818]

.
& This would need to be before MET then wouldn't it? - Thus the property of DNO ?

No it would not be the property of the DNO, just as an upfront RCD for a TT Installation would not be the property of the DNO.

 

[Wilko]

Agree - If the neutral is lost surely we should isolate the installation not add rods so it can carry on in a busted condition ?

 

[telectrix]

IETLTP.that is translated...
IET lost the plot.

 

[Deleted member 26818]

Agree - If the neutral is lost surely we should isolate the installation not add rods so it can carry on in a busted condition ?

At present if there were a supply Neutral fault, the bonding and extraneous metal pipework would become the Neutral.
This proposal has been introduced as so much of the gas and water supply network has been changed to plastic.

 

[1Justin]

No it would not be the property of the DNO, just as an upfront RCD for a TT Installation would not be the property of the DNO.

.
I don't see that. Image attached. Surely in PME case, an RCD would need to be before the head so as to be able to pick up on return N current not running in PME N ? - It could still look balanced in the tails.

 

[Wilko]

Hi J, IIUC with an upfront RCD (same position as TT case) the RCD would sense current in L and not N as it's now going back through the rod. And so it'd trip. We would still need a rod (at the PME terminals in your pic) but now we just use it to disconnect the installation rather than put in many rods and try to keep touch voltages down.

 

[1Justin]

But it's not fault current, it's any residual installation neutral return current which is able to lift the MET and all exposed conductive parts. The neutral current is surely still balanced in the tails since it's got to be the same as any live current. (There is no earth fault in the installation during this condition to make it otherwise)

 

[Wilko]

I think I get you now - the "upfront RCD" would have to be on the DNO side of the PME connection to work.

 

[Deleted member 26818]

I think I get you now - the "upfront RCD" would have to be on the DNO side of the PME connection to work.

The RCD would be best placed after the DNO PME connection. It would then also operate in the event of an installation Earth fault.

 

[Sparkingmad]

I can see the logic in it to be honest IET have produced guidance notes on this before but NICEIC inspectors would give you a berating for having 2 different earthing arrangements . So when you are asked for earthing arrangement at origin what would you put down TNCS, TT or will there be a new classification code TNCS/TT?
Would you have to install a rcd on tails from the meter before they enter an AMD 3 board rated at 30mA, or would you be able to install an rcd with upto 1A tripping current as it is for a dribution circuit on a TT system? Could you decide to ignore the TT side of it and continue as for TNCS as the TT part would only come into play when DNO lose neutral on their network. I don’t mind as I am on a trusty old TNS supply at the moment lol.