Earthing and supply in Hartlepool

[oharaf]

Hear are a few (poor) pics of a job in Hartlepool, didn't get any of the before NEDL arrived and only a few when I returned as the cameras batteries failed

Any way here we go

Untitled

• oharaf
• 17 Sep 2008
• 1

This is after I had Called NEDL out to replace the service head which 'wobbled' when you touched it!!!!!!!!!!!!!

Clearly they didn't bother he stuck chewing gum in to steady it!!

What he did do was remove the isolator that was 'hanging' in mid air (not theirs by the way, fix it side on using the 2 RED tails that were there and leaving inplace the 2 grey tails of different csa!!

Anyway after calling them every name i could think of I began to investigate the bonding which they had refused to provide any information about

After much removal of woodwork and digging around I found this

Untitled

• oharaf
• 17 Sep 2008
• 1

A little earth rod under the front porch


and then this

Untitled

• oharaf
• 17 Sep 2008
• 1

The Water bonding was connect to the LEAD pipe that was not even in service any more (more on this one later

I found the gas bonding near here as well, totally unaccessible and no BS951 to be seen anywhere!!!

To top it of the CU

Untitled

• oharaf
• 17 Sep 2008
• 1

spaghetti junction, and every single screw was loose and wobbling from the incomer, to the MCB's to the terminations of Line, neutral and Earths


of and a few of these as well

Untitled

• oharaf
• 17 Sep 2008
• 1

Needless to say all bonding was replaced and a tidy up of the CU.

Gas now bonded with BS951 in an accessible place

The water however is a different kettle of fish!!!

The old Lead pipe enters the house from the front, however the 'new' supply is from the rear (no problem you think) under concrete into the kitchen where ther is access to 1.5cm of copper pipe, no stop cock anywhere!!! and then poly pipe, there is absolutely no way of attaching a clamp to the water without some serious plumbing!!!!


So as a VERY VERY VERY temporary measure I have had to use a Radiator pipe , the house owner is calling in a plumber to install a stop cock and some copper pipe so I can return and correct the situation.

Even then I will have to find a route to it as the entire house apart from the hall way is concrete floors!!!!!!!!!!!!!!!!!!

Oh service head replacement is 12 -16 weeks (yeah right) and they will install PME then[/img]

 

[FingRinal]

NEDL wouldn't give any bonding info as to them it's TT. Though they should have given you their requirements if they are going to TNCS it.

Interested to hear what Zs readings you got.

The bond to the old lead water is probably a better earth than the earth rod. Though strictly naughty, it should do until NEDL provide a means of earthing.

Did you connect the earth rod or just leave it?

Is the new water supply metallic or plastic. You mentioned that it is plastic in the house, so if the supply is plastic, no bond is required. It sounds like metallic in and then plastic which requires bonding.

The spaghetti junction is par for the course and I've yet to find a neglected board, socket or accessory that didn't require some nipping up of screws (hidden JBs be warned!!).

Not a lot you can do with disconnected cables. I usually crimp them and tape them.

 

[Spark123]

What about the lack of RCD protection on the incomer? I take it that the board is split load?

 

[FingRinal]

Depends on the Zs readings. Which is why I asked.

I wouldn't be worried about short term perfection, if Zs readings were good from just the lead and without the rod connected.

(I wouldn't be surprised if the lead bond had a 'Ze' of 0.1 to 0.3 ohms. Interested to know though.)

Assuming a max. B40, Zs of 1.15ohm or less would preclude the need for RCD protection. If it's just lights on the non-RCD side, there's 7.6ohms to play with.

 

[Spark123]

How would you guarentee the Ze readings (or Ra) don't go up and down outside the specified range?
I take it there is no EIC for this consumer unit? No expense spent with the choice of brands

 

[oharaf]

Hi Fellas, water supply in is metal then plastic thats why I need some useable copper!!!

I did use the earth rod again!! NEDL wouldn't say if it was TNS TNCS or TT they point blank refused to tell me anything!!!

The board is split load, with shower and ring finals on RCD side.

I considerdd changing the main incomer but as I will be going back any way when PME is installed it seemed an expense not worth going to.

Zs was 0.34 so very happy with that its next to the sea so loads of good damp salty ground!!!!

Spark123 good point about fluctuation

 

[FingRinal]

What the earthing system should be and what it is can be two different things.

In the absence of a means of earthing, you assume TT and install an earth electrode. NEDL are only obliged to put it in writing and NEDL will put it in writing to the owner or resident of the addess - posted to that address.

As for the Ra values fluctuating - well they do with TT anyhow. The point about Ra being less than 200ohms is mainly to do with the increased risk of varying of Ra values.

With Zs being so low and plans afoot for an upgrade, you've done as much as is practicable and cost effective so far.

With such Zs values, an RCD isn't needed as the mcbs perform all functions - certainly for the next couple of months.

 

[oharaf]

Thanks FR, i'm glad others think I have done the best so far, I was alittle concerned but it certainly is better than it was

 

[Spark123]

What the earthing system should be and what it is can be two different things.

In the absence of a means of earthing, you assume TT and install an earth electrode. NEDL are only obliged to put it in writing and NEDL will put it in writing to the owner or resident of the addess - posted to that address.

In the absence of a means of earthing from the supplier and an electrode in place it smells of a TT system.

With such Zs values, an RCD isn't needed as the mcbs perform all functions - certainly for the next couple of months.

But who is to say something doesn't happen in the next couple of months to say that isn't permanent? My guess is the main protective bonding is causing the Zs to be low via a neighbouring property - what if next week next door replaces their pipework with plastic?
I'd be tempted to stick a 100mA RCD on the incomer to protect your botty!

 

[FingRinal]

And how would the 100mA RCD discrimminate with the other RCD on the left of the board?

The assumptions of the future are often based on the assumption that the customer can/will pay for everything that takes the electricians fancy.

I doubt the huge lump of lead will be excavated from the property in the next two months.

 

[oharaf]

No you're right that is staying in place until NEDL have been and done their work.

THEN it IS coming out and straight in to the back of my van, it is a good 15m long

 

[Spark123]

And how would the 100mA RCD discrimminate with the other RCD on the left of the board?

The assumptions of the future are often based on the assumption that the customer can/will pay for everything that takes the electricians fancy.

I doubt the huge lump of lead will be excavated from the property in the next two months.

How is this lump of lead providing a low Zs? Will you get 0.3 ish through the general mass of earth?
A 100mA may not fully discriminate but weighing up the risks posed by a too high impedance resulting in non disconnection vs the risks posed by RCD discrimination I'd take the 2nd option.
If you wanted to you could fit a high integrity board.

 

[GaryMo]

My guess is the main protective bonding is causing the Zs to be low via a neighbouring property - what if next week next door replaces their pipework with plastic?
I'd be tempted to stick a 100mA RCD on the incomer to protect your botty!

My thoughts exactly.

 

[FingRinal]

How is this lump of lead providing a low Zs? Will you get 0.3 ish through the general mass of earth?
A 100mA may not fully discriminate but weighing up the risks posed by a too high impedance resulting in non disconnection vs the risks posed by RCD discrimination I'd take the 2nd option.
If you wanted to you could fit a high integrity board.

Well, you seem to suggest that the low Zs is as a result of next door's bonding connected via the general mass of earth.

It is a TT installation remember?

100ma might not fully discrimminate? It won't discriminate at all.

Weighing up the risks? Too high impedance...where from? Are you suggesting that the TT installation has a low Zs only because of its general mass of earth connection to next door's gas and water? If next door replace their pipework with plastic - so what? Are you suggesting that the 'TT' connection to next doors metallic services will be any less just because they have gone plastic inside?

If the water or gas board intend to dig up the whole road to install plastic, they will put a letter through the door weeks or months in advance. Even so, the branches to properties will remain metallic, the lump of lead will remain.

The TT earth path is shown on diagrams as a single line only for illustration purposes. The 'general mass of earth' is a very complex myriad of paths, parallel paths etc. which take into account all such connections to the numerous PME earth rods.

RCDs have an expected in service failure rate of 3% according to research by ERA (commisioned by the ESC). How you propose to eliminate that 'possible' risk. The failure rate sky rockets depending on environmental conditions such as warm, dry and dusty. How will you prevent the home owners from being slobs with dust everywhere?

The OP has done a commendable job so far on a cost/risk basis. With a NAPIT assessment looming, I don't see the point in worring him with such fairly trivial concerns.

In fact, were he to mention his actions to date, I'm sure the NAPIT assessor would be delighted.

 

[GaryMo]

Well, you seem to suggest that the low Zs is as a result of next door's bonding connected via the general mass of earth.

Or a supply converted to PME, maybe this house is currently getting a low Ze due to next doors PEB.