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Testing Extraneous Council Block?


Blue Duck

Question

Usual story: gas man's been in and declared a national disaster as there is no bond within 600mm of the gas meter!

The property is near the top of a 10 storie block, old 3036's in a mantel with 1960s UFH all wired in pyro.

Normally I would replace what's there but there is nothing existing for the gas other than some 2.5mm supplementaries.

I didn't take my meter when I first went to have a look as it wasn't clear what the customer wanted.

I did however notice that none of the blocks in the area have "main" bonding on the incoming gas suppies, usually a 25mm bond in steel conduit close to the point of distribution.

TBH I'm anxious about pumping 1000v dc into a communal gas supply!

Any help on this as always will be gratefully received.

:)

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Is it just one flat or the block  you are dealing with ?

Where are the meters in relation to each flat.  The normal argument will probably occur if you bond correctly at the point of entry to the flat when the gas dude wants it done 10 floors down at the meter position.

 

Slightly OT i am doing a 90% rewire on a 70'S flat at the mo. Good Ze before i started and only just noticed the main earth is a 4mm link to a rusty non galvo 2x2 trunking riser. I think the 10mm bond to the gas (plastic water supply)  i did 6 months ago when central heating was fitted is linking out to all the other flats in the block. The gas supply is all barrel up the block but yellow plastic feed at the base.

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...TBH I'm anxious about pumping 1000v dc into a communal gas supply!

Any help on this as always will be gratefully received...

 

Don't use 1kV for a start, no need, and no reason to on any domestic or commercial, including 3ph.

Ref: GN3 Table 2.2, been the same since the 16th bar the change in minimum requirements.

You should only be using 500V, and this would be limited to 10mV anyway.

However, I do appreciate your concern about the energy going into the communal gas supply.

 

Be back later.

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Is it just one flat or the block you are dealing with ?

Where are the meters in relation to each flat. The normal argument will probably occur if you bond correctly at the point of entry to the flat when the gas dude wants it done 10 floors down at the meter position.

Slightly OT i am doing a 90% rewire on a 70'S flat at the mo. Good Ze before i started and only just noticed the main earth is a 4mm link to a rusty non galvo 2x2 trunking riser. I think the 10mm bond to the gas (plastic water supply) i did 6 months ago when central heating was fitted is linking out to all the other flats in the block. The gas supply is all barrel up the block but yellow plastic feed at the base.

Just the one flat slapper, the meter is on the kitchen floor and the gas pipework is external.

I imagine that this was an all electric building at some point and the gas was later installed due to the issues involved in rectifying faults on UFH buried in concrete.

I also suspect that the new gas supply is plastic but someone has kindly painted it black.

:)

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So the reality is that you have to determine if it's extraneous or not... Usually plastic supplied services are often not extraneous and therefore don't have to be bonded..

However determining that with parallel earth paths might proove to be difficult

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Bit of a catch 22 really!

I'm pretty sure that some of the other flats gas pipes will be bonded to the MET and then back to the suppliers earth so where do I go from here?

Earth rod in the lawn?

@sidewinder, thanks! Wasn't sure what the voltage should be for this particular method hence I put it in the OP.

:)

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As Sidey says.....common misconception.

NO NEED for 1000V test.....

Regs says "as far as is reasonably practical within 600mm of point of entry"

Tell the gas/double glazing/PPI/compo sales executive Engineer that you are working to BS7671 as amended and NOT to some Gas Regs. If HE wants it within 600mm then let HIM put it there at HIS expense

Just saying

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Are they trying to say "point of entry" is where the gas enters the block?, i,e 10 floors down?

 

I have always taken it as point of entry to a particular dwelling, i.e entry to your flat.

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I may have added some confusion to the OP by mentioning the bonding of the gas pipes externally. AFAIK most council buildings gas supplies are bonded externally back to the MET in the supply room!?

The gas bod wants the supply bonded within 600mm of the meter on the kitchen floor.

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so why is that so difficult to arrange?

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It's not that it's difficult. Im wondering whether it actually needs doing? I believe that the gas supply pipe is not extraneous but proving this may be difficult.

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I think my point is sometimes it's easier just to fit it, then everyone is happy, rather than spend time proving it is not necessary and you will be arguing that case every time a different gas man comes to visit.

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Many items are easier to just do so you fit in with 'the normal'  rather trying to defend yourself later on as to why  something was or wasn't done.

 

Thinking this over........................

 

Bit of a catch 22 really!

I'm pretty sure that some of the other flats gas pipes will be bonded to the MET and then back to the suppliers earth so where do I go from here?

Earth rod in the lawn?

@sidewinder, thanks! Wasn't sure what the voltage should be for this particular method hence I put it in the OP.

:)

 

This probably is the case, so due to this the pipe  is  extraneous as its bringing in an earth potential ?

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Duck,

 

It's not just the voltage for the extraneous test.

There is no requirement to IR test >500V on any normal 230/400V nominal voltage install.

The 1kV test is just for systems >500V nominal voltage.

This is in the table quoted & the other info in GN3 & associated back to BS7671.

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snake,

this I know but was unsure about the voltage to be applied to the "extraneous" test.

:)

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Ahh OK, now I see, which is not bad for a blind snake! ;)

 

TBH, the 23k "extraneous" test, is not actually documented in GN3 at all.

It is a derived test from "safe" touch voltage and "safe" current flow as it were.

I would do this @ 250V, I can never remember what it should be either.

 

Snakes have small brains too remember.

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The gas man is just covering his back.

If there is no gas bonding "apparent" in the property within 600mm of the meter, then it is "not to current standards" and an advice notice is issued with the words something like "consult a qualified electrician". His job is now done.

Regardless of whether the incoming gas main to the block is plastic, if the internal pipework is metal (and it must be steel in communal areas) and somebody has bonded it in another flat (very likely), then it must be extraneous and needs bonding within the flat, surely?

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no actual requirement to bond anything within 600mm anywhere, it is a recommenedation only, like most of the regs are. I have to say I'm getting fed up with bloddy plumbers who think they know how to do our job. Seem to be getting more and more phonecalls about these sort of issues. Thinky they are in league with Trumpton.

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I used to get a lot of jobs off the back of BG terrorising people they aren't the only ones, had the AA of all people refuse to cover the customers boiler as the bonding wasn't 600mm but 800mm! :o

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Ahh OK, now I see, which is not bad for a blind snake! ;)

TBH, the 23k "extraneous" test, is not actually documented in GN3 at all.

It is a derived test from "safe" touch voltage and "safe" current flow as it were.

I would do this @ 250V, I can never remember what it should be either.

Snakes have small brains too remember.

small brain or not it's not very well documented anywhere!

:)

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They can get a bit pedantic to say the least .... last year I was wiring an extension to a huge property , existing bonding in place .  Customer says  " The gas man wants to see you , he says your electrics are wrong "   He'd just arrived.

 

Now you really need this from the customer .     so , The Gasman cometh and says your bond is in the wrong place at the meter .  As I said , existing, I look up at it , "I can it , it looks fine to me "    Customer looks on , anxiously,  " Its not within 600mm of the meter , I've noted it on my report " 

 

It was about  700mm ..I guess . I say " If it worries you that much you need to report it to somebody ...why didn't you just move it ?  I didn't fit it anyway , how does it become my problem ? 

 

Mon Dieu !!!

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They know little of the wizardry that is involved with electrickery But the assumption that gas is more dangerous therefore must superceed electrical regulations.

WTF difference does it make?

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But this gas bloke is an 'engineer'. We are mere electricians.

Wise words indeed...

Gas engineer

Domestic Appliance Service Engineer

Nail Technician.....FFS count to 10. If you have a nail left at the end then you have missed one. If you are one short at the end then you have stuck two,together. Assuming the normal,number of digits per hand...Norfolk excluded

File,the points off

Paint

Bull up

Take money

Next

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ive got 20 nails. i must be speshul

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ive got 20 nails. i must be speshul

Ah, i had omitted feet

I apologise, i have not got a leg to stand on

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