Clarification on gas bonding please

[Ed Evans]

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

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.

 

[davesparks]

The answer is belt and braces. You can use one continuous piece of cable to bond the gas and water.

The Cable does not have to be continuous/unbroken it can be a seperate piece of cable linking the two.

 

[Ed Evans]

The Cable does not have to be continuous/unbroken it can be a seperate piece of cable linking the two.

If you link the cable you will fail your AM2. it must be two separate runs or one continuous piece with NO joins.

 

[davesparks]

If you link the cable you will fail your AM2. it must be two separate runs or one continuous piece with NO joins.

Can you support this with a regulation?

As far as I know the AM2 doesn't overrule the wiring regulations, so the rules for the AM2 are largely irrelevant in the real world if they don't fall in line with the wiring regulations.

 

[pc1966]

If you link the cable you will fail your AM2. it must be two separate runs or one continuous piece with NO joins.

Most likely AM2 is following the examples given in the IET Guidance Note 8 (figure 5.5 on page 64 if anyone cares to look it up) but others have pointed out that is not an actual requirement in the regulations.

Best practice for sure, as we probably have all seen wires drop out of supposedly properly fixed screw connections (or some muppet disconnects it), which is a very good reason for teaching it that way.

But not absolutely necessary. There must be bonding of extraneous conductive parts, and it should be reliable and low resistance, but other approaches may be acceptable depending on the practicality of applying it.

 

[Ed Evans]

Can you support this with a regulation?

As far as I know the AM2 doesn't overrule the wiring regulations, so the rules for the AM2 are largely irrelevant in the real world if they don't fall in line with the wiring regulations.

The AM2 complies with the regs 100%

 

[Ian1981]

With all due respect , this is not the AM2 and there’s no requirement in bs7671 that states that a bonding conductor must be continuous.
It’s another myth imbedded into the industry much like the myth of the 0.05 maximum resistance figure which again is incorrect but it’s getting taught in colleges and is not inline with what bs7671 states.
For example if you came across this while conducting an EICR, you can’t code it anything as what regulation would it not comply with?

 

[Ed Evans]

With all due respect , this is not the AM2 and there’s no requirement in bs7671 that states that a bonding conductor must be continuous.
It’s another myth imbedded into the industry much like the myth of the 0.05 maximum resistance figure which again is incorrect but it’s getting taught in colleges and is not inline with what bs7671 states.
For example if you came across this while conducting an EICR, you can’t code it anything as what regulation would it not comply with?

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

 

[Ian1981]

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

But what does that have to do with bs7671?
Do they quote a regulation number?
Is this Viper book an official British standard on the requirements of electrical installations?
Or is it for gas engineers and has no actual factual electrical regulations to support its guidance?

 

[pc1966]

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

 

[Ian1981]

[

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