Earthing Cable Sticking Out Of Neutral Henry Block?

HappyHippyDad · Aug 16, 2016

As I was being ushered out of the door after a brief pre-work visit I saw that the incoming neutral goes into a Henly block with an Earthing cable sticking out of it. The earthing cable was 10mm and it was just snipped off and had been left there. The CU was changed in 2012.

I have 2 questions, I have never seen a TNCS where the main earth is just attached to the neutral through a Henly block, would this have been ok as it is not in one of the recognised DNO cut outs as I have always seen before?

Also, the incoming line and neutral cables are seperate. The line goes through the cut out and the neutral into a Henly block. There is no sign of any other earthing cable , does this mean that it HAS to be a TT? I'm sure I'll be getting the work so will be investigating but was interested!

HappyHippyDad · Aug 16, 2016

From now on I'm going to give all junction boxes their own name as a sign of respect to JB's!

Richard Burns · Aug 16, 2016

Some (older) service heads only had a fuse block for the line and the neutral is in a connector block like a Henly block.
If it is TNCS then this is where the earth would come be generated.
as per picture below.

Taylortwocities · Aug 16, 2016

Nice to see the main fuse properly sealed

BTW, what is teh sealed fuse in teh bottom of the picture for?

HappyHippyDad · Aug 16, 2016

Richard Burns said:
Some (older) service heads only had a fuse block for the line and the neutral is in a connector block like a Henly block.
If it is TNCS then this is where the earth would come be generated.
as per picture below.
View attachment 32972

Many thanks Richard.
That's pretty much exactly what it looks like apart from the earthing cable has been cut off. I can't understand this? Why would it have been made into a TT? Thats assumung there is any main earthing.

westward10 · Aug 16, 2016

happyhippydad said:
Many thanks Richard.
That's pretty much exactly what it looks like apart from the earthing cable has been cut off. I can't understand this? Why would it have been made into a TT? Thats assumung there is any main earthing.

Sounds to me like it may have been TT in the first place and the 10.0 coming from the neutral service terminal block was added later to give a TN-C-S system often called PNB ( Protective Neutral Bonding ) when a TT system is altered. Is it possible when the CU was changed in 2012 that this earth was cut off and never reinstated, posing the question what is now earthing the installation the original TT system or nowt.

snowhead · Aug 16, 2016

Taylortwocities said:
BTW, what is teh sealed fuse in teh bottom of the picture for?

Unmetered fused supply for a DNO supplied E7 Timeswitch?

netblindpaul · Aug 16, 2016

westward10 said:
Sounds to me like it may have been TT in the first place and the 10.0 coming from the neutral service terminal block was added later to give a TN-C-S system often called PNB ( Protective Neutral Bonding ) when a TT system is altered. Is it possible when the CU was changed in 2012 that this earth was cut off and never reinstated, posing the question what is now earthing the installation the original TT system or nowt.

Don't see how it can be PNB, as PNB requires a single N-E link, and this cannot be guaranteed on a public supply Tx.
It will be PME, if you have TN-C-S in a domestic dwelling, unless they have a dedicated on site HV/LV Tx.

Gnasher · Aug 16, 2016

The only way to be 100% sure Is an enquirey to the DNO company if TNCS is available at the property or meter number as the photograph is inconclusive. It is not only a case of sticking an earthing conductor in the neural block. This may have been done incorrectly by some unqualified person or persons unknown for some unknown reason.
Quite often you will see an old PME label close by if it is TNCS.

mhar · Aug 17, 2016

PNB is exceptionally rare in a domestic situation and has nothing to do with converted TT systems. It has more to do with the earthing off a transformer supplying a single property in a remote location.
The photo could either be a 'homemade pme' connection or it could be dno supplied. Whenever I see this, if there is a dno pme label nearby then I accept this at face value, if there is not then I will enquire of the dno

Midwest · Aug 17, 2016

steveberry said:
The only way to be 100% sure Is an enquirey to the DNO company if TNCS is available at the property or meter number as the photograph is inconclusive. It is not only a case of sticking an earthing conductor in the neural block. This may have been done incorrectly by some unqualified person or persons unknown for some unknown reason.
Quite often you will see an old PME label close by if it is TNCS.

Bizarrely, that was exactly what I was told to do by a DNO at a domestic property recently.

The service head had a lead sheathed cable, with an earth clamped to the lead sheath. However there was also an earth rod with cable to the MET. I queried with the DNO if there was a problem with their earthing facility, as the supply looked a TN-S. Engineer visited the property and suggested I could convert it to PME. I said what you mean you convert the supply to TNC-S, he said ' what's that in English, do you mean PME?'. He said it would take weeks for one of their engineers to be booked to do it, he said I should just put new earth into service head neutral terminal and then into MET, reasoning that the supply cable in the road had probably been replaced with new cable, somewhere, which will have been changed to PME.

7029 dave · Aug 17, 2016

Midwest said:
Bizarrely, that was exactly what I was told to do by a DNO at a domestic property recently.

The service head had a lead sheathed cable, with an earth clamped to the lead sheath. However there was also an earth rod with cable to the MET. I queried with the DNO if there was a problem with their earthing facility, as the supply looked a TN-S. Engineer visited the property and suggested I could convert it to PME. I said what you mean you convert the supply to TNC-S, he said ' what's that in English, do you mean PME?'. He said it would take weeks for one of their engineers to be booked to do it, he said I should just put new earth into service head neutral terminal and then into MET, reasoning that the supply cable in the road had probably been replaced with new cable, somewhere, which will have been changed to PME.

Well I hope you did not do that, it needs to be verified by the DNO , under no circumstance should you connect you main earth conductor into the N unless it is TNCS.

Midwest · Aug 17, 2016

7029 dave said:
Well I hope you did not do that, it needs to be verified by the DNO , under no circumstance should you connect you main earth conductor into the N unless it is TNCS.

Nope posted before about it. Removed the earth rod earth and just used the TN-S. Found it quite peculiar!

Gnasher · Aug 17, 2016

Why

What was your Earth on a TNS system

Midwest · Aug 18, 2016

steveberry said:
Why

What was your Earth on a TNS system

? Was that reply to mine above, in that case DNO earth clamp around lead sheath.

Gnasher · Aug 18, 2016

Sorry I was looking at the photograph from Richard.

Midwest · Aug 18, 2016

steveberry said:
Sorry I was looking at the photograph from Richard.

No probs

Mablec · Aug 20, 2016

Taylortwocities said:
Nice to see the main fuse properly sealed
BTW, what is teh sealed fuse in teh bottom of the picture for?

HSE say you do not work on live so in order to comply you remove the main fuse, after all you are fully qualified certificated electrician and if you need to cut the seal to maintain your safety what court of law is going to convict you?
In the past for meters we had gas board, electric board and water board now days you have Eon, Edf etc etc none of whom give the slightest interest all they want is the money from the sale,