Main Bonding question?

chrisgc · Sep 9, 2011

Just a question on main bonding to the main incoming gas pipe.

Where the location of the gas pipe is to be laid and where it is in relation to the MET in the CU, I was wondering if it is allowed to bond (with 10mm earth) the main gas pipe directly to the earth rod? (TT system).

I am guessing not but am simply asking just due to the access for running the earth cable to the CU.

Chris

telectrix · Sep 9, 2011

but the main earthing conductor goes from the rod to the CU, you could break that and fit a MET in a convenient place to bond you gas to. then you've got a readily accessible MET.

chrisgc · Sep 9, 2011

What then happens to all the other earth cables which are currently connected to the met in the exusting cu?

Richard Burns · Sep 10, 2011

The MET would now be the one by the gas pipe and this would be connected to the earth bar in the CU (now no longer MET) by the main earthing conductor. This is just having an MET outside the CU. You have probably seen supplies set up with an earth block mounted on the back board connected to the incoming earth and the main earth conductor going into the CU, where all the CPCs are connected. This is the same but a longer distance away.

chrisgc · Sep 10, 2011

Update......
just updating in that the main incoming gas pipe is going in a service channel (filled in and then expensive floor tiles will be put on top for finish.
i know your meant to main bond within 600mm etc so where would I main bond gas pipe if its not visible?

Engineer54 · Sep 10, 2011

Richard Burns said:
The MET would now be the one by the gas pipe and this would be connected to the earth bar in the CU (now no longer MET) by the main earthing conductor. This is just having an MET outside the CU. You have probably seen supplies set up with an earth block mounted on the back board connected to the incoming earth and the main earth conductor going into the CU, where all the CPCs are connected. This is the same but a longer distance away.

And that is exactly where it should be, in the same local location as the cut-out and CU, ''Not'' in some remote corner of the house!!

Richard Burns · Sep 10, 2011

As near to the point of entry to the building as possible (presumably here, where it exits the service channel) and before any branch, so long as it is accessible.
What do you mean by the service channel being filled in?

Engineer54 · Sep 10, 2011

chrisgc said:
Update......
just updating in that the main incoming gas pipe is going in a service channel (filled in and then expensive floor tiles will be put on top for finish.
i know your meant to main bond within 600mm etc so where would I main bond gas pipe if its not visible?

That is not then a service channel if it's going to be filled in, it's just a chase!!

You would bond the gas pipe at the nearest accessible location, hopefully before any splitting of the gas main, as in the same way you would for a water main... Where is the gas meter located then??

spark 68 · Sep 10, 2011

The Bonding should also be done on the consumer side of the meter (within 600mm) before any branch work, and not on or before any flexi pipes, not on the supply side

chrisgc · Sep 10, 2011

Bear with me on this then.

Main gas pipe enters house underneath front door. Into ex service channel (but this is being back filled).
immediately to left of front door understairs cupboard is cu.
the main gas will then head off and go upstairs to where boiler location is going to be.
location of boiler is maximum of 15 metres away from met of existing cu.

spark 68 · Sep 10, 2011

Where is the gas meter ?, and stop tap for the gas ?

telectrix · Sep 10, 2011

so where's the bloody gas meter then? outside the house, under the floor, below the CU?

Deleted member 26818 · Sep 10, 2011

Your point of bonding should be where the pipe becomes an extraneous-conductive-part.
In otherwords, where it can be touched.
The connection should also be accessible for inspection and maintenance.

Octopus · Sep 10, 2011

Within 600mm is a recommendation, you can be outside this dimension if it makes the point more logical/accessible etc.

spark 68 · Sep 10, 2011

Within 600mm is a recommendation

Yeah Murdoch, I should have said or as near as practicable

chrisgc · Sep 10, 2011

telectrix said:
so where's the bloody gas meter then? outside the house, under the floor, below the CU?

Believe the gas meter is outside house.
also I do understand 600mm rule but where it comes into house its to be buried so not accessable where it comes in to property.
so guessing will have to find out route of main gas pipe and then when it becomes extraneous bond there then to met.

Silly Sausage · Sep 10, 2011

chrisgc said:
Believe the gas meter is outside house.
also I do understand 600mm rule but where it comes into house its to be buried so not accessable where it comes in to property.
so guessing will have to find out route of main gas pipe and then when it becomes extraneous bond there then to met.

Bond the consumer side of the gas pipe at the meter and pass the cable through the wall to your MET.
I've seen one those guides (by ESC or the like) which shows this. I'll post it up if I can find it.

GN8, where else?!
It should be made mandatory that every electrician should own a copy.

Deleted member 26818 · Sep 10, 2011

Well Archey, shouldn't you get a new version of GN8.
The only problem that I have with your suggestion, is that the pipe work will then be buried after the bond, and I'm not certain that it would be possible to confirm that the part of the pipe that enters the property will be at the same poential as where the bond is made at the meter.

Silly Sausage · Sep 10, 2011

spinlondon said:
Well Archey, shouldn't you get a new version of GN8.
The only problem that I have with your suggestion, is that the pipe work will then be buried after the bond, and I'm not certain that it would be possible to confirm that the part of the pipe that enters the property will be at the same poential as where the bond is made at the meter.

Spin, I will when it gets released, that is the latest version, next one will be a while yet.

You could easily confirm continuity with your meter and a wander lead.

I wish people would post pictures or at least a drawing of the areas they're looking at, it'd make it so much easier to give advice, hard work doing it blind.