Any opinions about my Main Earth Bonding? (with pic)

[ThrumptonPerriwhistle]

Hi chaps.
Something doesn’t seem quite right with my MEB, and I'd like to get an opinion more professional than mine about it. I’m pretty sure my earth is a TN-S system, although a couple of things puzzle me:

One, the main earth bond only seems to be in about 4mm2 wire. And it’s the old silver-coloured stuff, not copper. After having a dig in these forums, I think it should be at least 16mm2 to be safe.

Two, I was under the impression that a TN-S earth connected to the neutral conductor. The earth that’s on it now splits and connects to both the phase and neutral sleeves. Is this right?

There’s a picture below if any bits of that don’t make sense.

Cheers for your help,

P


View media item 12915

 

[oharaf]

It certainly looks to be TN-S. The MEB is undersize for the current regs, 16mm being the norm now.

I have come across acouple of installations where both the phase and neutral are used as an earth, it is actually the cable armouring that is used rather than the cable itself, this would be a VERY dangerous situation.

Yours is attached to the armouring from what I can see.

The clamps are the incorrect type.

If you are worried then contact your DNO and ask them to carryout a survey it is their responsibility to main tain this part of the installation, we/you are only responsible for everything after the meter.

 

[stem]

It looks to me like TN-S (Earth & Neutral Separate) The earth is the armour of the cable. There is no link between the earth conductor and the neutral that would make it TN-C-S.

The earth cable size is old, the size of earthing conductors has increased over the years. It was probably fine when it was installed.

The earth that’s on it now splits and connects to both the phase and neutral sleeves. Is this right?

The two cables entering your service head probaby both contain phase and neutral conductors. One is the incomming supply and the other feeds a somewhere else (another property or detached outbuilding with a separate meter)

 

[aptsys]

I have come across acouple of installations where both the phase and neutral are used as an earth, it is actually the cable armouring that is used rather than the cable itself, this would be a VERY dangerous situation.

ummm? One cable will be a feed to the next property.

 

[oharaf]

#Sorry aptsys, been up early this a.m. without coffee!!!!

Never considered feed to another point

 

[aptsys]

I know what you mean. I got to work this morning and the coffee jar was empty

 

[ColJack]

I know what you mean. I got to work this morning and the coffee jar was empty

that's it, down tools until the situation is remedied brother..
it's a safety issue..
hard hats save your head, coffee saves the customers lives..
the more awake you are, the more clearly you think and less mistakes are made ( or more are caught and rectified anyway.. )

 

[ThrumptonPerriwhistle]

Hi.
Thanks for the quick reply oharaf.
I was hoping that I wouldn't be breaking any rules if I swapped the wire
for a piece of 16mm2 myself, to save taking a day off work waiting in
for the DNO bloke.
But if the clamps are the wrong type, that's scuppered that plan.
Again, cheers for your help.
P.

 

[Spark123]

You also need a "Safety Electrical Connection Do Not Remove" notice adjacent to the MET

 

[oharaf]

Yes unfortunately the DNO are useless at turning up, you could put a piece of 16mm in and use a BS951 clamp, thou it really is their responsibility and then tend to get a bit upity if you tinker with their kit.

 

[RF Lighting]

You shouldn't fit BS951 clamps to PILC cables.

They are not designed for it, and you are at risk of crushing the cable, and that would go with one almighty big bang

Also I don't like the idea of someone who is not specifically trained to do so messing about with an incomming earth which could also affect the quality of next doors supply, not to mention any unexpected currents / voltages which could suddenly become apparent as you break the earth supply to the outgoing cable.

This really is something best left to the DNO, although, they will more than likely turn up and say there is nothing wrong with the existing earth.

 

[oharaf]

Your right BS951 shouldn't be used, but, whilst in Manc. the other week the lovely chaps from UU used just that to attach the 16mm earth to the armour!!!!!

 

[VanSolo]

Your right BS951 shouldn't be used, but, whilst in Manc. the other week the lovely chaps from UU used just that to attach the 16mm earth to the armour!!!!!

I've seen it done plenty of times.

View media item 12928
This was probably done by a contractor rather than a DNO.

 

[RF Lighting]

I had a supply moved in Guiseley a few weeks back, and they stuck a BS951 on the sheath

Doesn't make it right though

 

[oharaf]

No it doesn't!!! But goose and the gander.

Wish I had taken a pic of the incomer on my job in Manc. for to take my camera.

DNO board was so rotten it had turned to powder, service head was hanging out into the room supporting a very large old meter.

The MEB was about 2.5mm unsheathed clamped between 2 pieces of brass!!!!

Called MANWEB raised it as an emergency, I would be suprised if anyone would argue the difference.

Anyway, 3 hours later UU show up, fella takes a look.

"It's not really an emergency, but we'll come and deal with it today"

7 O'Clock comes, no one has been. I go off to the pub for the evening, get back card through door

Ring them next morning, another fella comes out takes a look

"It's not serious, but we'll send some one out today"

8 O'Clock sod it off to pub, get back no card.

In the entire next day getting finished still no one, phone them again.

We'll send some one out.

Anyway I get cleared up and packed away a set off back to gods own, in traffic for 6 hours.

That evening the customer phones to tell me still no one had been and the service head was making crackling noises. I phone MANWEB tell them that as they had failed to do the work that I had told them was an Emergency, the service head had been under so much tension that it was now crackling, and that their no Emergency was now a real danger to life and that the customer had been advised to evacuate the property until they arrived.

1:20a.m. they arrived to carryout the repair!!!!!!!!!!!

Privatisation for you!!!!!!!