Gas pipe bonding

[Roger]

Evening All,
Another bit of advice please.

Doing a property at the moment and it has no bonding on the gas pipe.The problem is I have
electric meter box one side of house and Gas meter box the other.I know I have to bond with 10mm and within 600mm of gas meter on consumer side.But this means i have to run an unsightly cable around half of the whole house !.The boiler is within a couple of feet of the dual RCD protected CU and the gas feed to that comes down from the roof in a loft which has no access.Bonding to water services measures 0.02 as it so close ,so that good.
Its a TN -C -S and measured Ze is 0.36 and apart from some crazy IR readings as a result of additions over the years with bits in cupboards and still looking and not being able to isolate things the house seems ok.All my Zs readings will come within spec.
Could I not bond at the nearest available point ie where the gas pipe comes down from the ceiling near the CU and close to the bolier,althought it has branched off to feed a gas fire before that point.
I guess my Zs will drop when bonded but how much do I gain ?

Whats the opinions of the wise forum ? I am sure I am not the only one to have come across this one.I know what the OSG says and the BRB does say 'practicable' but come judgement day.

Thank you

 

[waitees]

Hello Mate

I just had my niceic assesment and the bonding for the water was hidden behind loads of built in cupboards all the floors were solid. it was a old victorian house and running trunking all around the house is not a option and not nice looking.

The inspector did say that if it was not for the earth cable that was already there, i would have had to put a cable in where "most practable".

So i think if there are solid floors and other things and you really cannot get it to the intake put it where best, but as close as you can get it.

Dont forget to write on the cert ! ​

 

[Guest123]

Its a TN -C -S and measured Ze is 0.36 and apart from some crazy IR readings as a result of additions over the years with bits in cupboards and still looking and not being able to isolate things the house seems ok.All my Zs readings will come within spec. 0.36 is high for a TN-C-S, indeed above (although only just) the max quoted of 0.35.
Could I not bond at the nearest available point ie where the gas pipe comes down from the ceiling near the CU and close to the bolier,althought it has branched off to feed a gas fire before that point. It MUST be earthed before any branchwork, and where practicable within 600mm of the meter.Thank you

Be worth double checking the Ze, loose terminals, corrosion etc and re-test.

 

[Roger]

Thanks Lenny,

So i have to do and get a unsightly cable round the property.
The Ze value of .35 where is it stated ,i know its there as i have seen it,give us a clue please.

I guess i would struggle to better what i have as i was only about 1 meter of 16mm from meter head.So that as good as its gets.I guess the addition to the gas will help with the Zs.

Would it be worth contacting the Electricity company ? I have another meter (not calibrated )which i could use to validate the original measurement.

Thank you

 

[Spudnik]

I wouldnt worry too much about .36




As long as your Zs's are good.

 

[lloyd1980]

agree with the 'most practical' option

on the NICEIC test cert it has a section on bonding and a box which says ' where bonded if not obvious'
Ideally it would be 600mm from point of entry you will get continuity if you bond the pipework at the boiler, and as long as all pipework is at same potential youve done your job

hope this helps

 

[SirKit Breaker]

I bond as close to the point of entry as is practically possible. Did both Gas and Water on Monday in bungalow. There was no way of getting to either service within 15feet of the point of entry unless i was about 4 inch tall when on my back under the floor. I dont think it will make much difference to how fast the fault current will get away if it has to travel an extra 15 feet, maybe it will take an extra tenth of a millionth of a nano second to go the extra 15 feet.

 

[Roger]

All done 10mm running round the whole back of the house,very unsightly but no choice.She has 5 dogs so how long will it last god only knows.
Took a Zs from ring feed socket outlet and its 0.57.
PFC 638A @0.38
PSC 645A @0.37
Ze still to high for a TN-C-S but that will be ok though ? should I note that on the cert as well although the value is stated on there.Likeley to be queried ?

Have another problem one ring is not complete,which i did know about before doing the CU change.I have found where the break is and it effects 4 sockets.It is a bodged extension by the looks of it.I was going to make it into 2 radials each protected with a mcb of either 10 or 16amps.They do not want me chasing walls or doing surface trunking to correct it so i thought that was a good workaround.I will make a note on the cert so its clear and mark the CU accordingley.It all in 2.5 so should handle 16amps ok being buried in plaster

Have others found this a practical solution ?

 

[ezzzekiel]

youre just ensuring that under fault conditions all metalwork rises to the same potential, providing you can confirm that then mark it up on the test sheet.

would always try to get as near as poss but there will always be times when you just cant. as long as its not just used as an excuse not to put full run in then cant see the problem.

 

[pushrod]

The Ze value of .35 where is it stated ,i know its there as i have seen it,give us a clue please.

OSG 1.1 note iv (page 11) gives all the values

(but i must admit i couldn't find it either in the BRB)

 

[Roger]

Bloody hell man ,I must have spent ages going through it but never found it.Of course in the introduction.
Thank you.

Any pointers on the ring main issue ? might start a new thread.
Cheers

 

[pushrod]

Bloody hell man ,I must have spent ages going through it but never found it.Of course in the introduction.
Thank you.

Any pointers on the ring main issue ? might start a new thread.
Cheers

Assuming the 2.5 mm is in the plaster behind capping ie not totally insulated i reckon you are good for 18.5 amps (ref method A table 4D2A) so can't see anything wrong at all with two radials on 16A breakers.