PME Earth & DP Isolator

[Adam_151]

You need to be able to isolate the supply to do the consumer unit, central networks (who have taken over from east mids electricity) like to handle this by comming down and fitting you an isolator to save two visits (to isolate and re-engergise)

Many sparks however will just cut the seals on the main fuse (and the meter if they need to change the tails), generally this is frowned upon though and some DNOs will threaten to have you over the barell for criminal damage, this area I'm not sure although I get the impression from the my mate who is a trainee central networks jointer that they don't really care too much (although the meter operating company may care about the meter ones)

So many different companies involved these days and I've only just got my head around it myself.

You have one company you pay the bill too, the DNO (distribution network operator) looks after the infrastructure, and the meter opperting company takes care of the meters (its as bad as the bloody trains!)

If you don't get an isolator now, just ask central networks at a later date

 

[JohnD]

I have one of those white MEMs in my own house, so has my old mum. No idea when it was fitted, must have been before I moved in

 

[Cartboy52]

That is the sort of isolator I was looking at getting

I'll see what reply I get from ecotricity.


Thanks everyone for all your help. It amazes me that you all reply so quickly and are willing to share your knowledge for free! I'll make you all a virtual coffee for your time and trouble!

 

[securespark]

I don't know if anyone's said it yet, but the earth supply is not coming from the DP isolator (the Voltage Operated Earth Leakage Circuit Breaker), rather that is an earth connection for the unit.

The problem with these is that unless the fault current is running down a cpc, they won't trip... So the fault current could be running through you to ground, and the VO ELCB will not trip.

In my experience, TT heads that say PME on them are ready to go. You just need to get the DNO to put an earth into the cut-out. Unless the terminal screws are accessible- they are on some.

Another point - all DNO's I know will not connect to PME without MEB's being done.

 

[Cartboy52]

I don't know if anyone's said it yet, but the earth supply is not coming from the DP isolator (the Voltage Operated Earth Leakage Circuit Breaker), rather that is an earth connection for the unit.

So are you saying there is no earth on any of my circuits at present? All the earth cables only run between isolator and the four fuse boxes.

 

[Cartboy52]

Another point - all DNO's I know will not connect to PME without MEB's being done.

What's a MEB?

 

[davy_owen_88]

Main Equipotential Bonding - the bonding of all metal services (gas, water etc.) to the main earthing terminal.

 

[Cartboy52]

Main Equipotential Bonding - the bonding of all metal services (gas, water etc.) to the main earthing terminal.

Oh yes, of course.

Still a bit concerned I may have no earth.

As far as I understand it, PME is where the earth is linked to the Neutral? If that is the case, then I'm sure I have a PME system already, where the earth currently splits from the neutral at the isolator. The reason I think this is that I had a fault in the garage recently. When I screwed a socket to the back box, the isolator tripped. I thought there was a short somewhere and got the trusty multimeter out. Earth and neutral were linked, even back at the isolator (I traced it back this far until I discovered the PME existed!), therefore I must have an earth (hopefully)

 

[JohnD]

doesn't follow, you didn't continuity-check N to the PME terminal on your suppliers cut out. Doing that will tell you if they have remembered to connect the link inside. As they have stuck a label on, I expect it is connected.

A N-E connection downstream of the cutout is not now allowd (It might have been permitted when your voltage-operated ELCB was installed, but I don't know).

Who knows what year that ELCB might have been instaled?

 

[Adam_151]

Just to clarify, that ELCB will have two earth terminals, in and out, I'm assuming that bundle of earths is connected to the out one, the in connection should have a connection to an earth electrode in the ground outside

ELCBs are going to be pre mid-80's AFAIK

Its possible there exists a N->E short in the installation as well

 

[Adam_151]

A N-E connection downstream of the cutout is not now allowd (It might have been permitted when your voltage-operated ELCB was installed, but I don't know).

AFAIK, you always needed special permission from the secretary of state for this!

 

[securespark]

VO ELCB's were outlawed in 1985.

 

[Cartboy52]

I've done a bit of searching in the rain and have found an earth rod outside that links back to the Henley block.

I have also checked continuity between a neutral going into one of the fuse boxes and the earthing terminal on the cutout and can confirm a link.

This would appear the indicate that PME is available for me to link to instead of the earth rod.

If however, the earth rod outside is the current earth rather than the PME terminal, how come I have neutral to earth continuity in my circuits at the moment? Does that indicate I have a neutral to earth short somewhere in one of my circuits?

 

[Taylortwocities]

If you have PME then neutral = earth. If you are doing the earth-neutral test with the supply still connected then u will see the impedance from your existing earth rod to the nearest lekky board earth rod (which is connected to neutral).

You need to do this test with all supplies isolated otherwise you'll be chasing your tail.

 

[seasickstevie]

How come the cutout in Cartboy's job has got two cables feeding?
Or is the second going to next door or something?