Supplier earth terminal on intake

SJD · May 7, 2021

The attached photo shows the suppliers head that includes an earth terminal.
The incoming supply cable is a single phase plastic sheathed cable containing L & N.
The earth terminal is not actually connected to anything (not internally linked).
The DNO is SSE.

A previous contractor was under the impression this was the suppliers earth and used it for earthing.
However, they did leave a comment that the earth impedance was "a little high"!

Historically the property was TT, but there is no longer any sign of an earth rod etc.
This is a fairly old property, now with a number of somewhat less-old properties nearby.
Likely the original supply was overhead, before the area got developed a few decades ago.

Question:
With this head fitted, with an accessible earth terminal, would it be correct to say the DNO has supplied an earth?
And in which case they should maintain it?
Or are there circumstances when this head would fitted but with the earth terminal not connected?

Ideally one would simply ask SSE what type of supply is available, but this seems to be proving difficult.
If it is reasonable to say this should be a supplier's earth, I'm tempted to log a call to say the earth appears to have failed.

timhoward · May 7, 2021

I'm sure I've seen that type of head on a TNS setup, obviously without a link inside, exactly as you have but with a TNS earth coming from the suppliers cable. So I don't think the head style can be used as proof and there is apparently no evidence (like a PME sticker) that they ever supplied one.
But equally you also aren't really supposed to know there is no link inside so maybe playing a little dumb might get a visit sooner rather than later and if PME is available it might simply get sorted there and then.

Is there still an up front RCD? If for whatever reason SSE don't treat it as urgent this is a bit tricky isn't it.

westward10 · May 7, 2021

Have you looped direct to it with that earth disconnected.

Lucien Nunes · May 7, 2021

Haha that's a good one. Will be interesting to hear their response. 'No, not an earth terminal, wherever did you get that idea? It's a decorative accessory.' Perhaps you should put an earth symbol sticker on before sending them a pic.

SJD · May 7, 2021

timhoward said:
Is there still an up front RCD? If for whatever reason SSE don't treat it as urgent this is a bit tricky isn't it.

There is no up-front RCD, but a reasonably modern consumer unit with RCD protection for all circuits (2-pole RCDs, in a dual RCD plastic housing).

westward10 said:
Have you looped direct to it with that earth disconnected.

I have carried out a number of loop tests, there is some earthing from bonding to gas & water pipework, with a value of around 55 Ohm when all connected. There is no earthing at all from the terminal (meter won't actually execute a loop test), and it is open circuit to N.

timhoward · May 7, 2021

To my thinking it would not be unreasonable to report a failed earth as there is no present evidence of TT, or TNS, and at first glance it looks like TNCS. If they agree to investigate without delay fine, otherwise I'd feel I couldn't really walk away without bashing a rod in.
Of course the fact the property has a working neutral destroys the argument, but they might not ask that on the phone!

brianmoooore · May 7, 2021

The presence of an earthing terminal on the side of a DNO service head is NOT proof that an earth terminal is provided. This is a mistake I made many years ago, and was told this in no uncertain terms by the engineer that attended when we complained.

timhoward · May 7, 2021

Isn't it around £150 to provide PME at an existing suitable cut-out as long as the supply is suitable?
Might be best to provide a temporary electrode so earthing isn't via services and recommend the customer gets this done asap (which will probably mean a 3+ week wait)?

Samhhh · May 8, 2021

SJD said:
The attached photo shows the suppliers head that includes an earth terminal.
The incoming supply cable is a single phase plastic sheathed cable containing L & N.
The earth terminal is not actually connected to anything (not internally linked).
The DNO is SSE.

A previous contractor was under the impression this was the suppliers earth and used it for earthing.
However, they did leave a comment that the earth impedance was "a little high"!

Historically the property was TT, but there is no longer any sign of an earth rod etc.
This is a fairly old property, now with a number of somewhat less-old properties nearby.
Likely the original supply was overhead, before the area got developed a few decades ago.

Question:
With this head fitted, with an accessible earth terminal, would it be correct to say the DNO has supplied an earth?
And in which case they should maintain it?
Or are there circumstances when this head would fitted but with the earth terminal not connected?

Ideally one would simply ask SSE what type of supply is available, but this seems to be proving difficult.
If it is reasonable to say this should be a supplier's earth, I'm tempted to log a call to say the earth appears to have failed.

Wether the incoming supply is PME or not that earth terminal should still be earthed via the DNO. If its a split service then you should be getting an eli reading to it, even if the earth is broken outside you would still get >1. If there's no reading at all I would say that it's a PME system and the PME link was either not installed or has been removed, the only sure way to find out is for the DNO to attend site and check what the feed in is. If its a CNE cable then it's as simple as a link being installed and that terminal is now a usable earthing point.

UNG · May 8, 2021

SJD said:
I have carried out a number of loop tests, there is some earthing from bonding to gas & water pipework, with a value of around 55 Ohm when all connected. There is no earthing at all from the terminal (meter won't actually execute a loop test), and it is open circuit to N.

Had a job a while back where it was a TNS supply did a neutral - earth loop test and got no reading called the DNO guy attended site and then called for reinforcements as a large part of the street had no earth after some digging and repairs I believe they finally finished at around midnight after about 10 hours onsite

Wilko · May 8, 2021

timhoward said:
Isn't it around £150 to provide PME at an existing suitable cut-out as long as the supply is suitable?

Hi - fwiw @SJD a Customer in our world recently got a free PME connection from SSE, which saved me redoing the ”long lost rod”. I had her ring for a safety check and the good SSE Operative did it on the spot.

Dartlec · May 8, 2021

timhoward said:
Isn't it around £150 to provide PME at an existing suitable cut-out as long as the supply is suitable?
Might be best to provide a temporary electrode so earthing isn't via services and recommend the customer gets this done asap (which will probably mean a 3+ week wait)?

UKPN seem to do it for free every time I've needed one (assuming that supply is suitable, but pretty much all of them are around here now it seems)

I've run into a similar setup (block was on the side, not top) and made the same assumption before - seen the earth block on the side and assumed, then discovered no internal connection. In that one, they'd upgraded the head to TN-C-S while moving it anyway, so didn't matter.

My guess is that it was part of the design to allow the TN-S earth something to connect into when first installed on a new build? In this case it was a 70s Council House....

Samhhh · May 8, 2021

Dartlec said:
UKPN seem to do it for free every time I've needed one (assuming that supply is suitable, but pretty much all of them are around here now it seems)

I've run into a similar setup (block was on the side, not top) and made the same assumption before - seen the earth block on the side and assumed, then discovered no internal connection. In that one, they'd upgraded the head to TN-C-S while moving it anyway, so didn't matter.

My guess is that it was part of the design to allow the TN-S earth something to connect into when first installed on a new build? In this case it was a 70s Council House....

I've never known a DNO charge for such work either as it should be done during the installation process or when the cut out has been changed. In all fairness the DNO should fit a seperate earth block away from the cut out with 16mm earth for any further connections to be made

Dartlec · May 8, 2021

Samhhh said:
I've never known a DNO charge for such work either as it should be done during the installation process or when the cut out has been changed. In all fairness the DNO should fit a seperate earth block away from the cut out with 16mm earth for any further connections to be made

UKPN seem to now fit the earth into a single through terminal block of their own supply, rather than connecting into an earth bar, even if I've provided one. Maybe to make it obvious when they've done it, or some internal rule of their own....

SJD · May 9, 2021

Thanks for all the replies.

Opinion seems to vary, and I'm veering towards the customer just asking for the earth to be checked, perhaps giving enough reason to get this done urgently (rather than in 6 weeks), and see if it can just be internally linked there and then (I suspect it can).

If SSE won't provide the earth, then I'm going to have to fit an earth rod, and the front outside (everywhere near the intake) is all block paving, so rather hoping I don't have to!

Supplier earth terminal on intake

SJD

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