Exterior socket on PME system

Midwest · Jun 16, 2017

soulman said:
Apologies, I was just surprised at that comment.

Which one?

soulman · Jun 16, 2017

Achieving an Ra of 3.35

happysteve · Jun 16, 2017

Rob said:
Draw it out Steve, the N>E link is before the RCD, so current flowing down the PE will not go through the RCD causing an imbalance.

Okey dokey

The squiggles inside the circle are meant to represent an RCD. In the event of a broken PEN (and no other fault), the same current passes through both poles of the RCD and there is no imbalance. The current then flows through the CPC, through the person, and to earth.

[ElectriciansForums.net] Exterior socket on PME system

The picture below just shows that the formula A722.3 is correct.

So I still maintain that an RCD will not help in this situation.

Midwest · Jun 16, 2017

I'm cooking 'tea' at the mo, so not following the thread, but this vid (Pete's copyright) is often used;

South Spark · Jun 16, 2017

Ok long day so bear with me. Informative video but it seems to me that it only applies if there is no other path to earth than the affected person.

If the PEN is broken then would the current not flow back through the bonding to true earth especially if I introduce earth rods into the system?

Could I introduce an earth rod connected to the earth terminal in the socket?

Midwest · Jun 16, 2017

It's a matter of timing

Des 56 · Jun 16, 2017

Utilise the Pme for the socket,add a rod

Don't employ any Horses,Donkeys or Cows to operate the sound system and every ones happy

happysteve · Jun 16, 2017

South Spark said:
Ok long day so bear with me. Informative video but it seems to me that it only applies if there is no other path to earth than the affected person.

If the PEN is broken then would the current not flow back through the bonding to true earth especially if I introduce earth rods into the system?

Could I introduce an earth rod connected to the earth terminal in the socket?

Sorry South Spark for meandering off a bit...

Re your first question... yes it would. There has been some to-ing and fro-ing about the numbers, but essentially yes, having an earth rod would make the situation safer.

Re your second question... If you mean, "connect the earth rod to the socket and still retain the CPC from the TN-C-S" I would advise against this, unless you have 10mm earthing conductor all the way back to the MET (for the same reason that bonding needs to be 10mm). If you mean, "Run the CPC to the socket but don't connect it to the earth pin (or anything exposed) and connect the earth pin to a local rod," then this sounds like "TT-ing your shed" without a sub-board. The protective device (and additional protection) would be on one earthing system, and the socket-outlet on another. I don't know if this is relevant or not, and I've reached the limit of my knowledge about whether this would be permitted or advisable.

I suppose the way of complying to keep everyone (incluing your CPS advisors) happy would be to treat this 32A socket as a separate board and TT it. So install an RCD garage subboard with the socket nearby, put this sub-board on the earth rod, and follow the usual procedure for making sure exposed conductive parts from the two different earthing systems are not simultaneously accessible (411.3.1.1).

South Spark · Jun 16, 2017

Des 56 said:
Utilise the Pme for the socket,add a rod

Don't employ any Horses,Donkeys or Cows to operate the sound system and every ones happy

Where are you talking about adding a rod? To the socket (disconnect PME earth) or to the MET?

davesparks · Jun 16, 2017

If it is to be used for outdoor events then you'd do well to read up on the requirements of BS7909 'code of practice for temporary electrical systems for entertainment and related purposes'
This is becoming more commonly recognised in the industry, and councils are increasingly requiring compliance as part of event licensing.

As it stands you may find you have a grumpy customer on the phone when the event electrician comes along and refuses to use the socket as it is non-compliant.

Midwest · Jun 17, 2017

Rob said:
Draw it out Steve, the N>E link is before the RCD, so current flowing down the PE will not go through the RCD causing an imbalance.

Just checking, that you agree an RCD will not afford additional protection, in the case of a broken PEN conduct?

static zap · Jun 20, 2017

Midwest said:
.... in the case of a broken PEN conduct?

Is there a way forward with this situation .
Detecting under voltage at the supplied load ,
Supply voltage being shared between Load, and unfortunate Human earth connection .
(remebering some old RCD technology ran warm
and needed a suppy to stay latched ON )

Bobster · Jun 20, 2017

Midwest said:
Just checking, that you agree an RCD will not afford additional protection, in the case of a broken PEN conduct?

Not without the addition of a local earth rod connected to the met.

Midwest · Jun 20, 2017

Rob said:
Not without the addition of a local earth rod connected to the met.

Arrgh I see, your recommending installation of earth rod with every PME supply. I was reading your #22.

Exterior socket on PME system

Midwest

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soulman

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happysteve

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Midwest

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South Spark

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Midwest

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Des 56

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happysteve

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South Spark

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davesparks

Midwest

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static zap

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Bobster

Midwest

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