What would you do?

[RMS]

Question for the electrically competent.

You are working in a property and establish a high Ze reading. 180 ohms. The earthing arrangement is TN-C-S. The seals are missing from the cut out and out of interest you remove the cover and find the link between the incoming neutral and installation earth is missing.

All circuits are protected by a 30mA RCD apart from lighting circuits. The customer is very elderly and it is the end of the day / early evening.

Would you:

1/ Isolate supply and advise customer to contact electricity supplier?

2/ Leave power on and advise customer to contact electricity supplier?

3/ Provide a temporary PME link and advise customer to contact electricity supplier?

All other solutions welcome.

 

[Electrifying]

Why have you only found this out at the end of the day?

How do you know it's TN-C-S if there is no link between the neutral and earth?

You cannot just insert a link between neutral and earth (creating TN-C-S) without confirming that the supply neutral is actually a PEN conductor and part of a PME, (or PNB), system.

If your working on the installation, then I assume it is isolated - you cannot re-energise the installation without confirming the earthing arrangements are satisfactory.

In the real world, this is the first thing I would have checked and tested - probably at 'estimate' stage - you need to know what earthing system you are dealing with.... a lot of your other decisions would depend on this information.

 

[Spark123]

Upon discovering the high Ze I'd contact the electric company. They have 24/7 people on call.

 

[flameport]

4) Contact electricity supplier and get problem fixed.

 

[333rocky333]

Why advise her to contact them in all cases and not contact them yourself on her behalf.

 

[westie101]

4) Contact electricity supplier and get problem fixed.

Contact the DNO NOT the supplier as suppliers do not do this work as they have no details of the system which the DNO does.

Also as the electrician you would be the best person to make contact rather than the customer as, invariably, they don't get all the information correct which often means the wrong staff get dispatched to the job.

I have never seen contact with us with an issue like this at the beginning of a job, only ever at the end. Read into that what you will

 

[RMS]

Why have you only found this out at the end of the day?

I was not the person present on the job. The start of a job is not necessarily at the start of the day.

How do you know it's TN-C-S if there is no link between the neutral and earth?

Because there is a PME sticker present on the cut out.

You cannot just insert a link between neutral and earth (creating TN-C-S) without confirming that the supply neutral is actually a PEN conductor and part of a PME, (or PNB), system.

I know that and clearly you do. However I have experienced a DNO advise myself to reconnect a link that was hanging out (A bit of insulated stranded conductor was used)

 

[Electrifying]

However I have experienced a DNO advise myself to reconnect a link that was hanging out (A bit of insulated stranded conductor was used)

The problem with this is, if it all goes pear-shaped and you say "The DNO advised me to do it" - They're going to say "No, we never"....so I'd want it writing.

Doesn't help your question, though.

Like the others said, you have to contact the DNO regardless and see what they offer as a solution - they'd probably send someone out soon as.

 

[westie101]

In the DNO I work in this would be attended as an emergency job up to 22:00 hrs

 

[RMS]

In the DNO I work in this would be attended as an emergency job up to 22:00 hrs

Obviously the DNO were contacted, they promised to attend by 20:00 hours.

 

[RMS]

The problem with this is, if it all goes pear-shaped and you say "The DNO advised me to do it" - They're going to say "No, we never"....so I'd want it writing. :

This is so true and something I have have learned form in the past with manufacturers technical advice over the phone. There is often conflicting advice given so like you say it's always safer to revieve confirmation by letter or email.

 

[ricicle]

If the Ze reading was a constant 180 Ω then as you have a 30mA RCD protecting the power circuits I wouldn;t be isolating the supply. I also wouldn't worry too much about the lighting circuits if all plastic accessories. It would need urgent attention from the DNO but not immediate isolation.

 

[RMS]

Why advise her to contact them in all cases and not contact them yourself on her behalf.

Well the customer needs to make the call initially as it is their property the DNO is supplying. Then they can pass the phone over to the electrician to explain or the electrician can write down the information so the customer can explain. Thats down the electrician I suppose.

When you think about it it's no different to a gas supplier changing a gas meter and advising the customer to contact an electrician to have the protective bonding re connected. I don't know how they get away with this

 

[westie101]

Well the customer needs to make the call initially as it is their property the DNO is supplying.

No reason why the electrician could not make the call with customer's agreement.

Then they can pass the phone over to the electrician to explain or the electrician can write down the information so the customer can explain. That's down the electrician I suppose.

Very rarely happens, (B Gas are the worse for this)
As I said we in most cases get the wrong info, panicked customers and the like.

f the Ze reading was a constant 180 Ω then as you have a 30mA RCD protecting the power circuits I wouldn;t be isolating the supply

We would as anything between the cutout and the meter is unprotected as the main fuse would not operate for a fault in that area

Our rules

When ELI is above 1.6 ohm.
Action: - The supply is classified as dangerous and shall be immediately disconnected by withdrawal of the cut -out fuse, pending investigation and corrective action by the Response Section.

If the ELI is less than 20 ohm, temporary installation of an approved RCD, in accordance with Appendix A can be considered.

Also within the document

On receipt of a report from a customer’s qualified electrician of High ELI,

So again the electrician should report it!

 

[ricicle]

We would as anything between the cutout and the meter is unprotected as the main fuse would not operate for a fault in that area

What about a L-E fault then between cut-out and first RCD on a TT supply with a Ze of 180 Ω. Would the fuse operate