Gas supply earth connection

[magill]

After a bit of advice please. I need to earth the gas supply. The only query i have though is that a pipe branches off to supply the gas hob, prior to entering the building.
Do i need to connect the earth prior to this branch on the outside or is it ok to connect as the main supply pipe enters the building, which is after the branch?

 

[malcolmsanford]

The regulations do allow you to connect up at the point of entry into the building on an external meter.

The one thing that regulation 544.1.2 is clear about is that you must connect before the branch, so connect as close to entry as you can

 

[magill]

Thanks for quick response. The branch "T" joint is approx two metres away from where the main supply enters the building, so running the earth cable through the wall down to it then clamping on the other side of the T join is the way to do it i take it?

 

[High Tower]

Magil,

I think you need to seek professional help, Earthing to services is a serious task and for the sake of safety requires the job to be done correctly. if you are not sure of the requirements then leave well alone. The safety of you family and yourself could depend on it.

 

[magill]

I fully understand concern. I completed the Domestic Installers course, but there are certain elements they do not go into great detail which is where i find myself at present. I am confident enough with the connections at the MET and the safety involved. I did cover bonding in great detail but the part where i have an external branch was never covered. It was a case of within 600mm of entering the building and before any branches. So it was more confirmation i was after really.

Magil,

I think you need to seek professional help, Earthing to services is a serious task and for the sake of safety requires the job to be done correctly. if you are not sure of the requirements then leave well alone. The safety of you family and yourself could depend on it.

 

[SimpleSimon]

Again what Malcolm said. You have to bond as close as possible to the entry of the pipe into the building before any branch work. The fact it has branched before it enters the building is not your fault.
The wording of reg 544.1.2 is premises be what you make of that but IMO if you can get to before the branchwork this should be done.
However at the end of the reg it does state point of entry into building for external meter.
IMO (and I'm happy to be corrected) I would do it as close to the entry point as possible and fill out a letter detailing the deviation from the reg.

 

[magill]

Totally happy with your opinion. I will bond at entry into building and record appropriately. Many thanks.

 

[sjm]

I think this is right, but fully expect to be corrected.
Test the resistance between where you bond at the point of entry and before the branch, if you get a reading of less than 0.05 ohms then you can assume that the point you should have bonded at is effectively bonded. Fill out a minor works cert and record the altered point of bonding as a departure from BS7671, job done IMO.

 

[Deleted member 26818]

You should bond at both points of entry to the building.

 

[magill]

Hi mate
Back again. Value your opinion. I have found time to test resistance and gained a reading of 0 ohms. I remember having the same reading on my test board and was told it was because it was such a short distance. I know the book says 0.05 or less, so is 0 ohms ok? (Cable run is approx 15 metres).

 

[terminator]

No - 15m of 10mm should give you 0.027. Either your meter is faulty or you didn't disconnect first?

 

[Deleted member 26818]

I'm assuming he's measuring the pipe, and using some cable to lengthen his probes.
I'm also assuming he nulled his meter with the cable attached to the probes.

 

[smartspark]

As close to the stopcock as possible in my eyes, and on the consumers side, main reason for the bonding is that the new supply pipes are now run in blue plastic pipe or yellow for the gas, the old pipes used to be a ferrous metal and gave a good ground to earth, so was never a problem. For those that are unsure why we do it.

 

[magill]

Hi
I used a wander lead and nulled all. Disconnected the cable from MET and placed one probe on end. Placed other probe on pipe as it entered building. Cant think of anything i am doing wrong, so it could possibly be the meter!

 

[Deleted member 26818]

I wouldn't worry about your meter the resistance is probablly so low that most meters won't read it.
You could try not nulling the meter and then subtract the figure for the wander lead from the figure for the pipe and wander lead.
Might actually give you a figure to play with, whether it would be accurate though is anybodies guess.

 

[terminator]

What meter are you using magill? Most modern low ohm meters should be capable of a resolution of 0.01

Edit: Thinking about it (I'm trying to work on my laptop as well as desktop, multitasking is not my strongest point) - Most meters have an intrinsic accuracy of about +/-0.05 ohms. So go with spinlondon's advice. We're trying to split the atom here. If shows zero you may have found the mythical superconductor.

It's good enough how do you get smilies on here?

 

[terminator]

Actually, thinking about it again (sorry to be boring) I have used my trusty Megger BMM503 to calculate the lenght of cable left on a reel, and it's pretty bloody accurate within a couple of metres.

 

[Deleted member 26818]

Try measuring a length of 15mm copper pipe.

 

[terminator]

I use a tape for that spin!

 

[Deleted member 26818]

Is your tape in Ohms or Meters?

 

[terminator]

Ha ha - goodnight.

 

[magill]

Right, i've now changed one of the leads and am now getting a reading of 0.5 ohms. (Using a Fluke multimeter).!!!

 

[High Tower]

thats why! multimeters are no where near accurate enough!

 

[magill]

Apologies, i meant to put multifunction - 1651. (Its been a long day!!)

 

[terminator]

Right, i've now changed one of the leads and am now getting a reading of 0.5 ohms. (Using a Fluke multimeter).!!!

What 'lead' have you changed? It's now reading 10 times higher than maximum allowable?

Beg or borrow a recently calibrated meter from a mate or test yours on a known resistance!