Clarification on gas bonding please

[MickSmith5824]

Hi. Could someone please clarify bonding requirements for me please. I know requirements are to have a seperate 10mm earth bond conductor for water and gas or that these can be in one cable if looped between each other. I have been working in a couple of properties lately that are in residential blocks. The both have combi boilers installed. I have noticed that they don't have any seperate bonding to gas. Just one 10mm that goes to water. Is this in breach of current regs? Thing i dont quite understand is as far as I am aware all pipe work of combi boiler is interconnected so if the bond the water pipes is in place then in effect the water and gas pipes of boiler are also aren't they? If this isn't adequate and a dedicated gas bond needs to be provide is the any solution to situations where meter is situated outside apartments and can't find where enters property or where access in a near on impossibility. Any advice/clarification be appreciated

 

[Ian1981]

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Best practice (IET Guidances Notes, AM2, Viper gas training, etc) often exceeds what the regulations demand.

To me they are guidance only and do not exceed or overrule the requirements of bs7671

 

[pc1966]

To me they are guidance only and do not exceed or overrule the requirements of bs7671

Exactly.

There are things like the "continuous earth conductor" that are best practice but are not a requirement. So it may be true to say that "The AM2 complies with the regs 100%" but reverse is not necessarily true, for example, a split cable may not meet AM2 practice but it is not then in breach of the regulations.
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There is a regulation that requires good workmanship. So if you are not following "best practice" then you need to be able to justify that it still meets the goals of safety and reliability.

 

[davesparks]

The AM2 complies with the regs 100%

But you can't quote a regulation to support your statement that bonding needs to be an unbroken conductor?
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Best practice (IET Guidances Notes, AM2, Viper gas training, etc) often exceeds what the regulations demand.

AM2 and Viper gas (whatever that is) have no bearing on the regulations.

Guidance notes are worth taking note of of course, but again are not the regulations.

 

[bigspark17]

Because each individual flat has its own installation, and that installation should have its own main bonding to create its own equipotential zone.

why couldn't the whole installation be covered as one?
you dont main equipotential bond off any suboards in large houses or houses with granny flat cu’s..these are fed off one DNO earthing arrangement and any equipotential bonding is wired to the MET.

 

[pc1966]

why couldn't the whole installation be covered as one?

I guess that comes down to who is responsible for it. If it is centrally maintained so all work in all flats (and communal areas) is coordinated that would be fine.

If I don't know who is looking after the outside of my flat I would want my own inside area done on the assumption they might screw up!

 

[Midwest]

The answer is belt and braces. You can use one continuous piece of cable to bond the gas and water. Also it is bonded via the actual boiler when it is working. HOWEVER. if the boiler is changed when it is of the wall you lose the bonding provided by the boiler which is dangerous. When I have taught gas engineers I have instructed them all to use a temporary bond ie it looks a bit like a set of jump leads when you fit a new pump as again the bond is lost when you take the pump out. It has resulted in a plumber being killed when he touched both ends of the pipe at the same time.
also it does not take much time or materials to be sure. live long and prosper.

How was this plumber killed, by touching two pipes? Was there a fault in the electrical installatio?

 

[bigspark17]

I guess that comes down to who is responsible for it. If it is centrally maintained so all work in all flats (and communal areas) is coordinated that would be fine.

If I don't know who is looking after the outside of my flat I would want my own inside area done on the assumption they might screw up!

if your flat was having an eicr done, access to the main intake would be required anyway to test the sub, check fuse rating and main bonding. Lim on these doesnt really cut it for me.
As i said if the contractor wanted to bond additionally internal nothing wrong with that (as i would most likely do myself at least 10mm to boiler) then it is not necessary wrong, if your advising someone who is doing an eicr on such property that it must be done, that is wrong advise.

 

[Ian1981]

The flats and the landlord communal areas if you like are completely separate installations, the supplies to flats are from a BNO arrangement.
Same is said for gas to flats which are separately metered as they are considered separate installations.
Therefore each installation requires separate bonding arrangements etc.

It’s likely that a main gas pipe in say the basement is bonded using a much larger CSA conductor than what is required for an individual flat.
Ive done many many buildings of this nature, we have always been required to bond inside the individual installations (flats) by the local DNO/as their internal set up in the building becomes a BNO

 

[davesparks]

why couldn't the whole installation be covered as one?
you dont main equipotential bond off any suboards in large houses or houses with granny flat cu’s..these are fed off one DNO earthing arrangement and any equipotential bonding is wired to the MET.

You do of they are in a seperate building.

The earthing and bonding guidance note has good diagrams which make this quite clear for blocks of flats and separated buildings if I remeber correctly.

 

[Ian1981]

Regulation 411.3.1.2 requires main protective bonding if applicable to each separate installation, individual flats are considered separate electrical installations

 

[Pete999]

If you get a copy of the Viper gas book it states that bonding must be looped

Please elaborate on your statement

 

[pc1966]

Regulation 411.3.1.2 requires main protective bonding if applicable to each separate installation, individual flats are considered separate electrical installations

This was my original point but put much more precisely.

While you might look at the building as a whole and argue that centrally maintained bonding is sufficient, each flat is a separate installation (with own CU and access/ownership differences).

Even if it were one building as an installation you would be looking at supplementary bonding for "exposed conductive parts" in each areas not totally covered by RCD protection, so basically the same thing (but subtle differences in bond size I guess).
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How was this plumber killed, by touching two pipes? Was there a fault in the electrical installatio?

Probably back to the PME fault debate once more!

Avoiding gas mains being earthing means was mentioned in one of the IET articles (Wiring Matters 61, Summer 2016) just search for:
"Insulation inserts in metallic gas service pipes to consumers’ premises"

 

[davesparks]

If you get a copy of the Viper gas book it states that bonding must be looped

That appears to be a plumbing text book, not exactly a reliable source of information on the wiring regulations.

If you get a copy of D. W. Cockburn's book on earthing and bonding you will find all sorts of incorrect information about the subject.

Just because something is published in a book which claims to be correct it does not mean it is necessarily correct.