Earthing/bonding advice - TN-C-S

[jakesm20]

Hello everyone, I'm in need of some advice
First I'll explain why I'm in the situation that is concerning me..

About a year ago I became unemployed. This was due to a lot of issues with personel life, it had became so distracting that it was effecting my work so my boss had to let me go, it was on good terms he just couldnt risk my falling concentration effecting our work anymore, fair enough.

This led to me taking almost a year of to work on my problems and get to a healthy stage in my life again. Obviously a year off drives you crazy and I had become so desperate for work. Finally I found what appeared to be a good job.

I recently became employed by a emergency call out company. We getcalled out to fix emergencies, fault find, remedials and recommend upgrades. All our work is sub contracted through insurance companies. On my third day I'm asked to change a damaged fuse board.

It's TN-C-S system on a 60amp cutout.
So myproblem is, the insurance company issues board changes without issuing any check on earthing, infact they don't even cover earthing. I get there and the earthing and bonding is all in 6mm. I raise my concerns to my boss basically explaining I don't want to do it without the earthing being up to scratch. He tells me because the insurance company only issues the board change that that's all we do and recommend upgrading it on the insurance job sheet, signed by me me.

I belive it's my duty to have it upgraded as the installing electrician. My boss tells me theyve been doing it like this for 7 years.
Because of this I'm going there behind my bosses back to upgrade it because I'm so worried about it coming back on me, even though he signs off the testing etc. I just sign off the job sheet from the insurance company

I can upgrade the main earth to 16mm but the bonding is just not doable. Can someone give me advice on what to do? I'm loosing sleep over this, worrying about what could happen. All I wanted was a good job and now am forced into this at the fear of loosing my job. the 6mm bonding is in good shape. Can I leave it As it is guilt free?

Sorry for the lengthy post, I just wanted you to understand the awkward position I'm in.
Any advice that could help me feel better abou tthis would be very grateful. I hate cutting corners and it frustrates me to have been put in these situations over and over again. It's just not how I work

Thanks in advance guys

 

[Jay Sparks]

Check for any signs of over heating, then do the adiabatic equation to see what size bonding you need.

Jay

 

[HappyHippyDad]

Hi Jake,

You are right regulation 544.1.1 does state that the minimum CSA for a bonding conductor should be 10mm. However, Best practice Guide Number 6 (issue 2), page 5, section 6.1 (see notes 2 and 3) states that :

"A 6mm bonding conductor could be deemed adequate if the bonding conductors have been in place for a significant time and show no signs of thermal damage."

See this link for the full note View attachment 6.Consumer unit replacement in domestic and similar premises.ESC Best Practice Guide No.6.pdf

The same section also states that 6mm or 10mm earthing conductor could be ok if it meets regulation 543.1.3 (i.e the adiabatic equation).

I'm sure you're aware this work is notifiable so you will need to be registered with one of the schemes. Perhaps your company is registered with them though, although I am unsure how this would work as I am a sole trader.

I hope you get some sleep :smiley2:

 

[Leesparkykent]

Hello everyone, I'm in need of some advice
First I'll explain why I'm in the situation that is concerning me..

About a year ago I became unemployed. This was due to a lot of issues with personel life, it had became so distracting that it was effecting my work so my boss had to let me go, it was on good terms he just couldnt risk my falling concentration effecting our work anymore, fair enough.

This led to me taking almost a year of to work on my problems and get to a healthy stage in my life again. Obviously a year off drives you crazy and I had become so desperate for work. Finally I found what appeared to be a good job.

I recently became employed by a emergency call out company. We getcalled out to fix emergencies, fault find, remedials and recommend upgrades. All our work is sub contracted through insurance companies. On my third day I'm asked to change a damaged fuse board.

It's TN-C-S system on a 60amp cutout.
So myproblem is, the insurance company issues board changes without issuing any check on earthing, infact they don't even cover earthing. I get there and the earthing and bonding is all in 6mm. I raise my concerns to my boss basically explaining I don't want to do it without the earthing being up to scratch. He tells me because the insurance company only issues the board change that that's all we do and recommend upgrading it on the insurance job sheet, signed by me me.

I belive it's my duty to have it upgraded as the installing electrician. My boss tells me theyve been doing it like this for 7 years.
Because of this I'm going there behind my bosses back to upgrade it because I'm so worried about it coming back on me, even though he signs off the testing etc. I just sign off the job sheet from the insurance company

I can upgrade the main earth to 16mm but the bonding is just not doable. Can someone give me advice on what to do? I'm loosing sleep over this, worrying about what could happen. All I wanted was a good job and now am forced into this at the fear of loosing my job. the 6mm bonding is in good shape. Can I leave it As it is guilt free?

Sorry for the lengthy post, I just wanted you to understand the awkward position I'm in.
Any advice that could help me feel better abou tthis would be very grateful. I hate cutting corners and it frustrates me to have been put in these situations over and over again. It's just not how I work

Thanks in advance guys

This could be handy to read, especially section 6 what I've put below

http://www.----------------------------/mediafile/100126672/Best-Practice-Guide-6.pdf

6. Main earthing and bonding and meter tails

6.1. The installer must verify, as a minimum, that:
Notes.
a) the main earthing terminal of the installation is connected to an adequate means of earthing via a suitably sized earthing conductor, (see notes 1, 2 and 5),
b) the main protective bonding is adequate, (see notes 3 and 5), and
c) the meter tails and the distributor’s equipment have adequate current-carrying capacity (see notes 4 and 5).
1. A measurement of the external earth fault loop impedance, Ze, should be carried out at this stage if practicable.
2. A 6 mm2 or 10 mm2 earthing conductor used with an associated line conductor of 25 mm2 could be considered adequate if the requirements of Regulation 543.1.3 are met.
3. A 6 mm2 main protective bonding conductor size could be deemed adequate where the minimum size required by Regulation 544.1.1 of BS 7671 is 10 mm2, if the bonding conductors have been in place for a significant time and show no signs of thermal damage.
4. 16mm2 meter tails with a 100A cut-out fuse could be adequate if the maximum demand of the installation (taking into account diversity and load profile) does not exceed the current-carrying capacity of the tails, and also provided that the requirements of Regulation 434.5.2 for protection of the tails against fault current are met.
5. Some electricity distributors have requirements regarding the earthing conductor, main bonding conductors and meter tails that exceed the requirements of BS 7671.
6.2. If any of conditions 6.1 (a), (b) or (c) is not met, the customer should be informed that upgrading is required. If the customer refuses, the installer should not proceed with the replacement of the consumer unit.

Edit: didn't see happyhippydads post when I posted.

 

[HappyHippyDad]

I don't usually manage to post before you Lee! ;-)

 

[Midwest]

The regs etc are as said, but also your Boss is correct. I've done a few CU changes where the bonding, invariably the water (opposite side of house to the CU) is 6mm. Explain regs/recommendations to the customer and they don't want they lovely flooring taken up or new cable run round side of house etc. Some customers see sense, but a few do not. You can't make them have the upgrade and I certainly would pay to do it myself. Some on this forum will argue that you should walk away and not do the job in the first place. As long as you've bought it to your boss's attention and noted it on the cert', its his problem to worry about, NOT yours.

 

[davesparks]

Check for any signs of over heating, then do the adiabatic equation to see what size bonding you need.

Jay

The adiabatic equation cannot be used for bonding conductors

 

[Andy78]

Some great advice above !
If existing earthing and bonding are adequate, and you can prove they are adequate via the adiabatic equation and testing, then make a note on the cert and crack on.
If however your boss is telling you to change consumer units where there is less than adequate or even non existent earthing or bonding, then that's where I would draw the line. You should have a word with him about this potential situation before it arises and then you can be clear with each other.

 

[Deleted member 26818]

Just make a note of the under size bonding conductors under 'comments on the existing installation'.

 

[jakesm20]

Thanks for the great responses guys, really handmade me feel a lot better. I did the job today and replaceable main earth with 16mm, I then R2 tested the bonding with a result of 0.05. So this has helped feel better too. I've stated issues on the sheet. Myboss is doing the test sheets so as far as I'm concerned it's his problem now.

I hate that I'm in this position again, I've been working hard for years with no real pay off. Is finding a firm with knowledge and enough of a moral concern about there work impossible? Or am I just that damn unlucky?

I know it may seem I worry a bit obsessively but I don't think that's too bad a thing in this industry
Anyway thank you for helping everyone it's a very appreciated.

....if anyone ever wants an experienced hard working, honest employee that desperately wants to build a strong career, then please let me know. I'll even move to your location.That's how desperate I am

 

[Midwest]

Yep, you've done all you can. All this is good experience for you. Have a look in the Electricians Unite, might find someone in there looking for an employee.

 

[Jay Sparks]

The adiabatic equation cannot be used for bonding conductors

I didn't say it could. If the size of the main earth worked out to be 6mm2 or even 10mm2 then the 6mm2 bonding would be OK if it shows no sign of thermal damage.

 

[davesparks]

I didn't say it could. If the size of the main earth worked out to be 6mm2 or even 10mm2 then the 6mm2 bonding would be OK if it shows no sign of thermal damage.

Your post said 'do the adiabatic equation to see what size bonding you need'
Which implies that the adiabatic equation can be used to work out the size of the main bonding, which it does not do directly.
On some earthing systems the bonding size is relative to the size of the earthing conductor, which is selected based on the result of the adiabatic calculation. In other earthing systems the main bonding size is not based on the earthing conductor size. And some times the size of the earthing conductor has to be selected based on the size of the bonding required.

 

[Jay Sparks]

My post didn't imply that at all. That is how you read it. No one else mentioned it. They all said the same but with more detail.
Oa