Rewire - Equipotential bonding etc...

[TJR]

Hi,

First post here so be kind!

I am intending to do a DIY rewire of my property. I am aware of part P regs and I am going to be doing this under a building notice, where the LBA inspect and test. I am an electronics engineer by trade, and have been reading up 17th reg requirements etc. so I feel I am fairly competent at attempting the rewire.

Currently the house has an old wylex wired fuse box with a 60A main fuse. I am intending to contact my provider (Southern Electric) to ask about a fuse upgrade, and also installing an isololator. Anyone know if they will do this? My DNO is EON I believe (I am in Knowle, near Solihull, west midlands).

Also another question - currently there is no equipotential bonding between the incoming earth, and the service pipes. I assume that the electricity company will not touch anything until. this is done? Is 10mm cable the correct size to use? Also can the cable run from say the water main, to the gas main and then back to an earth block I will have to add near to the meter, or does it need two separate earth cables?

Thanks, Toby.

 

[Spark123]

You'll have to ask your DNO if they can do the upgrade thing.

As for the equipotential bonding, it depends on supply type. If your upgrade ends up with TN-CS then you need to confirm the sizes from table 54.8 in the regs book with your DNO, then ensure that the resistance of it does not exceed 0.05 ohms.
You can use a single length of cable to join the two services to the MET however the conductor should remain unbroken throughout its length so you will need to loop it through at the first service without cutting it.

 

[17thman]

so I feel I am fairly competent at attempting the rewire.

it would be good that you are very competant.


Eon near me and yourself have upgraded service fuses and put in an isolators for free. The troubles locally seem to revolve around upgading main earth conductor to their sheath terminal (if required) on a tns system. They simply wont do it.

You need to assess your supply type to be sure about 10mm but should be ok. You can bond individually or collectively but the latter requires an unbroken conductor.

You can use the brass earth block in your shiny new cu as your earth terminal.

 

[TJR]

Thanks for the replies.

The supply is either a TN-S or TN-CS - how do you tell? - There is a bare metal earth block next to the main fuse on the incomer - not sure if this indicates either?

Is it best to put in the equipotential bonding in before they come out to do anything, or wait until they upgrade (i.e will they do the upgrade without it there)? This is all assuming of course they will do the upgrade/ fit isolator.

 

[bongos]

Thanks for the replies.

The supply is either a TN-S or TN-CS - how do you tell? - There is a bare metal earth block next to the main fuse on the incomer - not sure if this indicates either?

This will help you see which earthing arrangement you have.

Is it best to put in the equipotential bonding in before they come out to do anything, or wait until they upgrade (i.e will they do the upgrade without it there)? This is all assuming of course they will do the upgrade/ fit isolator.

I would ring them and ask. If they will supply an isolator and you have your nice new 25mm tails and 16mm main earth (if TN-C-S and appropriately sized) ready for them to connect it should make things easier. I would expect that they would probably want the protective bonding in place but a phone call will clarify.

 

[TJR]

Thanks for that. I was actually intending to get the service fuse upgrade and isolator fitted before I did the re-wire and CU upgrade so the new CU can be wired in without havng to pull the main fuse and cut seals etc.

Would it be better to get the upgrade done after I have completed the re-wire / new CU? Or just provide new tails for the old CU - assuming they will reconnect the old CU....

 

[17thman]

Eon 2 weeks to attend for an upgraded fuse and isolator. will sub it out to another firm. In my experience the fitter will not check any bonding arrangements. If you need new tails from service head to meter and meter to cu then you will need to pull service fuse and open the meter seals (not the best idea)

When upgrading and providing an isolator they will do the tails for you.

 

[TJR]

Well just off the phone to Southern Electric (my provider). Booked in for the 15th April for a service fuse upgrade and isolator fitting. Surprised it was so easy! Not sure about any charges I did ask, but they didn't know just said he could book me in for an upgrade / isoloator just have to wait and see now I suppose!

Also couldn't ask about the earth bonding cable size requirement as it was not the DNO I was speaking to.... maybe I will try to get in touch direct with them or just use the 10mm for the time being.

 

[ColJack]

for my own curiosity, where does it say in the regs that the bonding wire must be unbroken or looped through at the earth clamps?

 

[Click-Sure]

Nowehere anybody on here was able to find the last time it was debated (around 3 moths ago).

 

[Spark123]

It doesn't say that in black and white in the regs, as far as I know it is a take on 528.3.3.

 

[sparkyspike]

Depending on the interpretation, 543.2.8 and 543.3.4 could mean that joins in the earth cable are or are not permitted. I don't think either of these directly refer to main bonding cables though.

It is obvious that if a water main is removed or moved for any reason, this will compromise the direct connection to the gas main (or vice versa) which is the reason for an unbreakable connection. Therefore, to put a join in which relies on a non-electrical service being present, is a general shortfall with regard to BS7671, in particular to 526.1 etc.

 

[TJR]

Regarding the supply fuse upgrade, and isolator fitting - I have just had confirmation that this will be free of charge

 

[17thman]

great news

Ericmark recently reminded another poster of a discussionhere is the link. look at the advice given about getting something in writing from them about inspection and testing being included in the fee as you may incurr unexpected charges.

 

[TJR]

Yes, I already queried this as the building notice application form said on the back that if the installation was done by a non-qualified person or DIY then there may be an additional charge to pay for an electrical subcontractor to inspect the work. (My LABC is Solihull by the way)

I sent them an email asking the following:



Hi,

I am looking at doing a DIY rewire of my house (in Knowle). I am aware of the Part P regulations, and that the work will need to be inspected by a qualified person. I see that the fee for the building notice is currently £212.77 + VAT.

However on downloading the application form point number 4 in the notes, says that if the work is carried out by an unregistered electrician or DIY, then SMBC will arrange for a competent electrician to supervise the work and verify that it complies with Part P, and there will be a charge for this.
Doesn't the building notice fee cover this cost? I was under the impression that is what this fee is for as it is called "Supervision by Solihull MBC of Electrical installation Work carried out by unregistered electrician"?


Best regards, Toby


The reply I got from building control said:

"You are correct, the fee covers the cost of checking by Solihull SMBC"


I hope I am correct in assuming that 'checking' means inspection and test...