Distribution board question

[leebut]

hi guys

Question for the knowledgeable on here, I went to look at a possible board change last night after the couple had experienced the ring final circuit going down when the fuse wire burnt out due to s faulty socket outlet had burnt out

The socket face had been replaced by the customers insurance companies emergency electrician, my question is why would the distribution head unit have overheated and melted quite a bit of black tar out the bottom edges

See the photo i have enclosed




Regards


Lee

 

[dmxtothemax]

It is not unusual for the tar to ooze out of those types of cables over time.
Did you point this out to the electrician ?
They can test it for you and determine if there are any problems.
But just because it is coming out doesn't mean it is a problem.
A megger type test will soon tell you.

 

[Jim_e_Jib]

If there is tar coming from the service head, it would be worth getting the DNO out to check there isn't an issue - an loose connection overheating perhaps.

As @dmxtothemax says, it's not unusual but it would be worth getting it looked at. The whole lot looks like it might be due an upgrade anyway (cast iron service head?), plus they could fit an isolator for that board change.

 

[Bobster]

It's bitumen, an from the looks of that I wouldn't say it's an issue.

It cold flows naturally, but the DNO will come out an check it for you. They'll come a bit faster if you tell them it feels hot....

I'd be more concerned why the G/Y bond has been disconnected and is just hanging in free air.

Also the proximity to the gas meter, far to close.

 

[Wilko]

Hi - looks a bit like its dripping from the cutout (?) which may've had it to seal it up years ago.
As above, have it checked out by DNO.

 

[telectrix]

get that cuot-out replaced and an isolator fitted by DNO. then sort the CU out.

 

[leebut]

Hi All

Thanks for the replies


ROB

The earth/gas bonding is connected in the Wyler board to the right whoever did the last install had looped it through the MET as you can see, but somehow the brass bolt had come out and got lost not sure if that happed when emergency spark came out to the customers house on Saturday.

My concern with the earthing arrangements is the size of the original earth it must only be 4 or 6mm


The tar has poured out recently so it must have warmed up at some point, there has been a smart meter installed recently too, but nothing said to DNO About the condition of the head at that point going to advise customer to get the local DNO our ready for me to carry out board change.


Cheers

Everyone

 

[Dustydazzler]

Dear oh dear , that lot is a sorry state ....

As above get the cut out replaced and a new isolation switch installed just before the old fuse box ,

Then do a full Eicr on the property and later down the line a new consumers unit

 

[leebut]

I’m doing a board change in April for them

 

[Bobster]

My concern with the earthing arrangements is the size of the original earth it must only be 4 or 6mm

Does it show signs of overheating or thermal damage?

Is the Ze compliant.

If so it's still ok for service.

Edit: If you are having the head replaced it would be upgraded at the same time.

 

[leebut]

I’m going to advise customer to have the head replaced upgrade the MET and new isolator fitted


LEE

 

[davesparks]

.

My concern with the earthing arrangements is the size of the original earth it must only be 4 or 6mm

What size is it required to be for this particular installation? 4 or 6 is often all that is required when you calculate it.

 

[leebut]

16mm earth on any installation where the tails are up to 35mm so being either 4 or 6mm is way undersized

 

[Bobster]

16mm earth on any installation where the tails are up to 35mm so being either 4 or 6mm is way undersized

You are wrong, an if you find me the regulation you believe you are quoting you will know why.

4mm is the minimum but not due to current carrying capacity.

 

[The Ghost]

As a matter of urgency I would have called out the DNO on the spot. I am astonished the "emergency electrician" did not do so or that he would blithely connect a new socket without addressing the earthing and checking that is ok before doing any remedial work. I think I would offer to talk to the insurers for the client to discuss the matter. I am concerned the insurance company is allowing such a cavalier approach to electrical safety. If as you say tar had melted out of the main supply cable then DNO immediately!

 

[davesparks]

16mm earth on any installation where the tails are up to 35mm so being either 4 or 6mm is way undersized

Nonsense, where did you get that from? The size required is calculated using the adiabatic equation and subject to a minimum of 4mm if I remember correctly.
16mm would be the size you install if you choose to select the conductor size rather than calculate, but you cannot use this method to assess an existing installation as undersized.

 

[Bobster]

As a matter of urgency I would have called out the DNO on the spot. I am astonished the "emergency electrician" did not do so or that he would blithely connect a new socket without addressing the earthing and checking that is ok before doing any remedial work. I think I would offer to talk to the insurers for the client to discuss the matter. I am concerned the insurance company is allowing such a cavalier approach to electrical safety. If as you say tar had melted out of the main supply cable then DNO immediately!

What is wrong with the earthing to prevail an emergency?

Also a small amount of bitumen is quite common to leak from these heads, so again what would you reasoning behind the emergency?

There is not enough information provided to say the emergency electrician has acted inappropriately.

 

[leebut]

This is what regulations I work to

 

[leebut]

The homeowner has phoned Electricity North West who are their DNO they’re going today to look at the head unit, customer is getting back to me once they’ve been today

 

[davesparks]

This is what regulations I work to

View attachment 48533

That is not the regulations, that is a guide to to the regulations. Also if you read it properly you will see that it says quite clearly that the adiabatic equation can be used to calculate the size of earthing conductor required. If you carry out this calculation you will find that 6mm I slamost always sufficient for domestic supplies.

 

[Bobster]

This is what regulations I work to

An now that you have read them I'm sure you see where your blanket statement is incorrect.

 

[leebut]

Customer has just had DNO at his house, they’re changing the Head unit tomorrow afternoon and changing the earth connection

 

[leebut]

So is there anything wrong with fitting larger earth cables than a calculation says rule of thumb better to be safe than sorry

 

[Bobster]

So is there anything wrong with fitting larger earth cables than a calculation says rule of thumb better to be safe than sorry

Absolutely nothing wrong with fitting larger than necessary.

I don't like blanket statements though, and following these "rules of thumbs" dumbs down the trade. There are rare instances where following that table will provide the wrong size. An so it is always better understanding the theory behind it to confirm.

 

[leebut]

The latest from the customer electricity north west have already changed the head unit this afternoon

Now that’s quick service he only rang them at 10.30 this morning

 

[davesparks]

So is there anything wrong with fitting larger earth cables than a calculation says rule of thumb better to be safe than sorry

There is nothing wrong with fitting a larger earth than required. What is wrong is stating that an installation is incorrect because it has a correctly sized earthing conductor rather than the oversized one you normally fit.

 

[The Ghost]

What is wrong with the earthing to prevail an emergency?

It is not the earthing I was on about it was the bitumen leaking as the OP stated

distribution head unit have overheated and melted quite a bit of black tar out the bottom edges

If that is the case I would definitely phone the DNO. In any event the cut out would not pass muster for me. I do not like the earth and if I did an adiabatic on that I have doubts it would pass. That is the earth on the TNS outer armouring. The earth floating looking like it should have a home is also somewhat suspect as I am not there I cannot say for sure but it looks like it has come off of the MET above it. In the state the picture shows the installation/cut out to be in I would be doubtful about replacing anything until I had satisfied myself that the earthing/bonding was as it should be. NOT as a matter of emergency just diligent application of regs and best practice

 

[leebut]

Hi Voltigern


I wasn’t happy with the size and condition of the earth on the armour, the bonding was disconnected from the MET when I went to view the job but was connected to the gas pipe and connected securely in the consumer unit so not a worry for the minute, the brass retaining bolt was missing or I would have reconnected.

My main worry was the amount of fresh tar that had oozed out of the joint hence the post, as per my message earlier the DNO must have had concerns over its safety as they initially said it would be replaced in the week, then it was being replaced by the end of this week and eventually they came back and replaced it today.


All now ready for me to go in and replace the consumer unit with an rcbo board after initial testing the installation


Regards


Lee

 

[leebut]

This is my take on why I was saying the earth cable wasn’t up to spec I was meaning the earth to the incoming sheathing shows in all parts of the on-site guide to be 16mm plus in table 4.4 (i) and 4.4(ii) all say minimum cross section of earthing conduct should be 16mm

 

[Andy78]

This is my take on why I was saying the earth cable wasn’t up to spec I was meaning the earth to the incoming sheathing shows in all parts of the on-site guide to be 16mm plus in table 4.4 (i) and 4.4(ii) all say minimum cross section of earthing conduct should be 16mm

View attachment 48543

View attachment 48544

As stated previously, that table shows one way of calculating the size of a protective conductor, the method that errs on the side of caution and simplicity of instruction. That's why this method is shown in the on site guide.

The table references 543.1 next to it which you should read to understand why the information in the guide is just that, a guide.