Main earth and bonding issues

[leep82]

So today i go to a job to remove 3 x dual sockets, 1 x light switch and 1 x light fitting from a bedroom that the customer is converting into a bathroom, so that the plasterer can get in and make a start.

As i will be returning to do the job i took a look at the mains and checked out the bonding to both incoming gas and water. It is a TT system and after a little bit investigating it became clear that there is no main bond to the incoming gas.

What i could see were two 10mm2 earth cables leaving the DB. One i traced and it appears to be the main water bond the other dissapears after being clipped along the top of a piece of skirting board where it meets the arcitrave of a door. I checked with the customer and had a thourough walk around the property hoping to find an inspection point for an en earth rod, but couldnt.

When i performed a Ze at the mains ( with the main switch off ) i got a reading of around 4ohms. I then disconnected the 10mm2 water bond and performed the test again getting a reading of around 20ohms.

For anyone who has read any of my recent posts i have recently gone into self employment, and whilst i have my inspection and testing certificate, my previous experience of testing has largely been on new installations/circuits. I feel that it is still very much a learning curve and so i suppose im looking for a little guidance even reassurance that what im doing is along the right lines.

I am aware of the need to install a main bond to the gas supply, but are the tests ive done today enough to suggest that there is a reliable earth, even if it is not visible. And when it comes to filling out my test sheet should i note this down?

Any advice mich appreciated

 

[Pete999]

My advice for what it's worth, you should have checked and tested for main bonding before starting work, what was the Zs at the sockets and lights?

 

[leep82]

My advice for what it's worth, you should have checked and tested for main bonding before starting work, what was the Zs at the sockets and lights?

Even though i have only removed items and not actually installed anything yet?

 

[Wilko]

Like you, I would like to see the means of earthing (rod). Seeing it you can confirm it's mechanical condition, its label etc. Without seeing it you can't confirm it meets 542.1.2.3 which will be part of your cert. So, I'd have another real good look

 

[Pete999]

Even though i have only removed items and not actually installed anything yet?

Right OK, but presumably you have submitted a price for the work, and now you have to explain to your customer that there may be extra costs to install an earth bond to the Gas intake.
Main earth and bonding issues - http://www.electriciansforums.co.uk/threads/main-earth-and-bonding-issues.119229/#post-1246120

 

[The Ghost]

Oh yes @Pete999 is right check out the installation you are working on before starting any work as installing later you will find the problems you missed and be crying. It is a bit strange your Ze changed when you disconnected the water bond. As the Ze is disconnected from the installation so no chance of parallel earths. You did disconnect the main earth in from MET yeah?

 

[leep82]

Right OK, but presumably you have submitted a price for the work, and now you have to explain to your customer that there may be extra costs to install an earth bond to the Gas intake.
Main earth and bonding issues - http://www.electriciansforums.co.uk/threads/main-earth-and-bonding-issues.119229/#post-1246120

I had already paid a visit to the property albeit late one evening, and with no test equipment in tow. Its for a friend and i did make them aware that the price may differ if the main earthing and bonding werent upto scratch

 

[westward10]

Is it a terrace because I have found them below the ground floor floorboards. You need to physically verify the water bond continuity to eliminate it as the source of earth.

 

[Des 56]

Even though i have only removed items and not actually installed anything yet?

The earthing and bonding will only be an issue when you come to installation,the safety reasons and the regulations can or should have been explained when pricing the new works

As far as determining what needs doing

I would have disconnected the two 10mms and identified the visible water bond
Do a loop impedance on the now disconnected other 10mm and noted the reading
Shoved a temporary stake(screwdriver) in the ground and measured the resistance between that stake and the 10mm with a trailing lead,if good continuity was found it could be assumed the 10mm is connected via a (usual Builder) buried electrode,explained the requirement for it to be visible and agreed for a new rod (using that existing cable)

If the customer does not want a new rod and the loop reading is adequate,note the deviation of the lack of visibility for inspection on the certification and that the customer declined improvement

 

[marc8]

Hello Leep82
ok as you have only removed stuff not that much of a problem as long as you have made them safe.
if TT system is 4ohms with everything connected then you are not going to get a reading below this at the sockets or the lights your better of with an r1+r2 & IR test.
but I would start with the following myself.
ZE test first with switch off across L/N then PFC.
get these results & then do the loop test on what you suspect to be the earth rod.
look at the incoming supply is it a concentric cable or a pair of cables.
explain to customer about the TT system & you strongly recommend to bond the water if Metal incoming or even plastic before I get my head bitten off, check readings first if plastic to see if it needs bonding.
gas bonding or oil if they have it.
explain these will need to be done before you can do any electrical work on the bathroom.
install 100ma trip s type on mains & new earth rod or alternatively if readings are good & you can bond water & gas install a 16mm tail from consumer unit into a MET block ring up board & ask for an earth upgrade to PME.
normally free of charge I have done this years ago for customer but check readings first mainly ZE.
if not then go with new rod bonding & 100ma trip before you start the bathroom.
also so you don't have to test the whole house if you can run a new circuit for bathroom lights & install on own RCD unit then do this & issue an electrical certificate for your works.
if you can't run new feed then check IR, r1+r2 of old circuit run to a RCD fused spur above door or other location outside bathroom & treat the bathroom lights, shaver & fan as a new install from the rcd unit outside the door & then issue a new certificate.

 

[Midwest]

Some good advice offered to OP, although I feel its a bit harsh to suggest you should verify earthing & bonding at quotation stage, I do free quotations not free electrical work I look to see if everything's in place, but I ain't spending time testing it, when they are just asking for a price.

That said, I'm always cautious with TT supplies, like to see something resembling an earth rod.

Edit: have some reference in your T&C's on the subject.

 

[leep82]

Hello Leep82
ok as you have only removed stuff not that much of a problem as long as you have made them safe.
if TT system is 4ohms with everything connected then you are not going to get a reading below this at the sockets or the lights your better of with an r1+r2 & IR test.
but I would start with the following myself.
ZE test first with switch off across L/N then PFC.
get these results & then do the loop test on what you suspect to be the earth rod.
look at the incoming supply is it a concentric cable or a pair of cables.
explain to customer about the TT system & you strongly recommend to bond the water if Metal incoming or even plastic before I get my head bitten off, check readings first if plastic to see if it needs bonding.
gas bonding or oil if they have it.
explain these will need to be done before you can do any electrical work on the bathroom.
install 100ma trip s type on mains & new earth rod or alternatively if readings are good & you can bond water & gas install a 16mm tail from consumer unit into a MET block ring up board & ask for an earth upgrade to PME.
normally free of charge I have done this years ago for customer but check readings first mainly ZE.
if not then go with new rod bonding & 100ma trip before you start the bathroom.
also so you don't have to test the whole house if you can run a new circuit for bathroom lights & install on own RCD unit then do this & issue an electrical certificate for your works.
if you can't run new feed then check IR, r1+r2 of old circuit run to a RCD fused spur above door or other location outside bathroom & treat the bathroom lights, shaver & fan as a new install from the rcd unit outside the door & then issue a new certificate.

Wow lot to take in but thanks. The current DB has a 30ma RCD already in place. I performed an RCD test on this today to ensure tripping times were met and all was ok.

The customer has plans in place to have an extension built this will mean the current DB, meter and cut out will require moving. He has already informed Western Power of this, and after speaking to myself asked if he can be upgraded to a PME system. This extra work may not go ahead for a few months so in the mean time i just want to ensure the work i do is up to standard

 

[Midwest]

OP are you with a scheme?

 

[leep82]

OP are you with a scheme?

Not yet but registered with LABC as a competant person

 

[marc8]

Wow lot to take in but thanks. The current DB has a 30ma RCD already in place. I performed an RCD test on this today to ensure tripping times were met and all was ok.

The customer has plans in place to have an extension built this will mean the current DB, meter and cut out will require moving. He has already informed Western Power of this, and after speaking to myself asked if he can be upgraded to a PME system. This extra work may not go ahead for a few months so in the mean time i just want to ensure the work i do is up to standard

the first bit I have sent you will take about 30mins to determine, I would not always listen to the client about short term stuff. the day you do the work is the day it needs to conform not at a later date. get the PME before you do works & the bonding.
just suppose they don't go ahead with extension or you fall out with them & they don't want you back.
you could end up doing that work for nothing when if they use someone else because you have undertaken electrical work & left unsafe. I have been in the game a while now & I have been fooled & heard a lot of stories of this nature.

 

[Midwest]

Not yet but registered with LABC as a competant person

Cool how does that work? Interested cos I'm paying 500 squids to Elecsa

 

[leep82]

Cool how does that work? Interested cos I'm paying 500 squids to Elecsa

Ive had to send off copies of my relevant certs, 17th edition and 2391 inspection and testing. Once theyre satisifed with these i go on there register. Problem is every time i do any work that is notifiable i have to fill in a building notice form and send it off to them along with a fee of £82. The fee is payable for every notifiable job i do so being in a scheme is probably more cost effective long term. I just didnt want to lose out on any potential work in the short time whilst im not registered with a scheme

 

[Midwest]

Ive had to send off copies of my relevant certs, 17th edition and 2391 inspection and testing. Once theyre satisifed with these i go on there register. Problem is every time i do any work that is notifiable i have to fill in a building notice form and send it off to them along with a fee of £82. The fee is payable for every notifiable job i do so being in a scheme is probably more cost effective long term. I just didnt want to lose out on any potential work in the short time whilst im not registered with a scheme

Not such thing then, as a free lunch. You might wanna try Stroma at £285 (I think), although their on-line software is pants (so I'm told)

 

[Midwest]

explain to customer about the TT system & you strongly recommend to bond the water if Metal incoming or even plastic before I get my head bitten off, check readings first if plastic to see if it needs bonding.
gas bonding or oil if they have it.
explain these will need to be done before you can do any electrical work on the bathroom.
install 100ma trip s type on mains & new earth rod or alternatively if readings are good & you can bond water & gas install a 16mm tail from consumer unit into a MET block ring up board & ask for an earth upgrade to PME.
normally free of charge I have done this years ago for customer but check readings first mainly ZE.
if not then go with new rod bonding & 100ma trip before you start the bathroom.
also so you don't have to test the whole house if you can run a new circuit for bathroom lights & install on own RCD unit then do this & issue an electrical certificate for your works.

Not wishing to dis some of your advice, but struggling a tad with some.

Metal services must be bonded. Plastic services do not need bonding, and wouldn't waste my time checking them. The metal pipe work that runs from the plastic services may need bonding (528.3).

Changing from TT to TN-C-S may have a cost implication to the client which may not be necessary (although I would), and I wonder why installing 100mA S Type in this situation, would be a consideration. And OP doesn't have to test the whole installation, if he is doing an alteration or addition (minor works).

I'm always learning, so I willing to stand corrected.

 

[westward10]

Ive had to send off copies of my relevant certs, 17th edition and 2391 inspection and testing. Once theyre satisifed with these i go on there register. Problem is every time i do any work that is notifiable i have to fill in a building notice form and send it off to them along with a fee of £82. The fee is payable for every notifiable job i do so being in a scheme is probably more cost effective long term. I just didnt want to lose out on any potential work in the short time whilst im not registered with a scheme

Sent my quals off to LABC got a letter back asking if I was any good at road sweeping