Bonding Gas Supply in an Outbuilding

[Piratepete]

Hi Guys
Doing an EICR of a property.
The client has an outbuilding with gas and water supplies. It has it's own CU fed from the main CU in the house.
The water is bonded but the gas is not.
The water supply is underground from the house in plastic and then changes to copper which is bonded.

The gas supply comes from the house in an underground copper pipe linked to the gas pipes in the house. So, electrically, it would be subject to the bonding in the house.
But does this negate the need to bond it in the outbuilding?

Looking forward to wise words!

Cheers
Pete

 

[shanky887614]

544.1.2 says "The main protective bonding connection to any gas, water or other service shall be made as near as practicable to the point of entry of that service into the premises."

Since it refers to the point of entry of the service, rather than the point of entry of the pipework, it appears to be saying that, even if the reason that the copper pipework is extraneous is that it feeds out underground in copper, the main bond should still be made at the incoming point.

wrong.

then a block of flats only has bonding on the intake into the building and nothing in the flats?

each seperate building requires bonding in this case the house and outbuilding both need bonding

 

[HandySparks]

wrong.

then a block of flats only has bonding on the intake into the building and nothing in the flats?

each seperate building requires bonding in this case the house and outbuilding both need bonding

You misunderstand my point.

The regs seem to be saying that extraneous pipework have to be bonded where the supply (water/gas) enters, rather than at the point that makes the pipework extraneous, which could be where another building or an outside tap is supplied.

 

[Geordie Spark]

Never found the need to use that particular picture book Dave... lol!!

Here's me thinking you wrote the book!

 

[shanky887614]

You misunderstand my point.

The regs seem to be saying that extraneous pipework have to be bonded where the supply (water/gas) enters, rather than at the point that makes the pipework extraneous, which could be where another building or an outside tap is supplied.

if it is a seperate building its a seperate premises

 

[Simlec]

You misunderstand my point.

The regs seem to be saying that extraneous pipework have to be bonded where the supply (water/gas) enters, rather than at the point that makes the pipework extraneous, which could be where another building or an outside tap is supplied.

You need to drop the supply part, it could be uni-strut with tray that enters the building from outside in contact with ground. Supply service is just an example.

 

[davesparks]

if it is a seperate building its a seperate premises

Not necessarily, but there could be more than one premises within a building.

 

[specs]

Just bond it
, I would

 

[HandySparks]

You need to drop the supply part, it could be uni-strut with tray that enters the building from outside in contact with ground. Supply service is just an example.

I agree that main bonding may be required to extraneous parts other than services. However, where it is a service, 544.1.2 defines where the bonding connection should be made, namely where the service enters the premises.

 

[davesparks]

I agree that main bonding may be required to extraneous parts other than services. However, where it is a service, 544.1.2 defines where the bonding connection should be made, namely where the service enters the premises.

Neither the gas nor the water in the outbuilding in the OP is entering the premises though, yet one certainly needs bonding and the other might.

 

[HandySparks]

Neither the gas nor the water in the outbuilding in the OP is entering the premises though, yet one certainly needs bonding and the other might.

Yes, I've drifted away from the OP and was speaking more generally.

 

[Deleted member 26818]

I take it no one bothered to google the definition then?
BS7671 requires us to bond any conductive part which enters the building from outside, which may introduce a difference in potential.
There is no requirement to bond conductive parts that do not enter the building from outside.
The plastic water pipe is not conductive, so does not require bonding.
The internal copper water pipes are conductive, but as they do not enter the building from outside, they cannot introduce a difference in potential, and therefore also do not require bonding.

 

[TJ Anderson]

I take it no one bothered to google the definition then?
BS7671 requires us to bond any conductive part which enters the building from outside, which may introduce a difference in potential.
There is no requirement to bond conductive parts that do not enter the building from outside.
The plastic water pipe is not conductive, so does not require bonding.
The internal copper water pipes are conductive, but as they do not enter the building from outside, they cannot introduce a difference in potential, and therefore also do not require bonding.

I quoted the definition in previous post. What difference does it make if it becomes extraneous within the building or outside. If conductive pipework was buried in the floor of the house it could become extraneous.

 

[Deleted member 26818]

I quoted the definition in previous post. What difference does it make if it becomes extraneous within the building or outside. If conductive pipework was buried in the floor of the house it could become extraneous.

You quoted the definition of an extraneous-conductive part, not the definition of extraneous.
It doesn't make any difference, as it's physically impossible for something that is entirely inside a building to also be extraneous.
If the copper pipework were buried in the ground, then the part that is in the ground (no longer inside the building) would be extraneous, and where the copper pipework re-entered the building would require bonding.
However as far as I'm aware, the copper pipework does not exit then re-enter the building.

 

[Geordie Spark]

Twenty three HOURS and fifty four posts later and you're all still arguing about this bloody copper pipe!!

How long would it have taken to find out by testing the damned thing with a meter & long bit of wire???

and it's you lot who think plumbers are a bit mentally challenged!! :laugh:

 

[Engineer54]

Staying with the OP's outbuilding installation, if the metal water pipework that's fed/connected to a incoming plastic pipe, enters the slab internally, say to supply something on the other side of the room it would be prudent to test for being extraneous. Which is going to be pretty certain that it will be, especially if it's been tied to the slabs rebar grid, and therefore will require main bonding. If however it's just been visibly clipped internally to the walls, it's unlikely that it will be extraneous and main bonding will not be required.

The incoming gas pipe goes without saying, will be an extraneous conductive part that will require main bonding...

And that just about clears everything up as far as these two services are concerned with this OP's outbuilding query!!!

 

[Knobhead]

Twenty three HOURS and fifty four posts later and you're all still arguing about this bloody copper pipe!!

How long would it have taken to find out by testing the damned thing with a meter & long bit of wire???

and it's you lot who think plumbers are a bit mentally challenged!! :laugh:

This is the tilers forum! What do you expect?

 

[Knobhead]

The IET mandarins must be howling with laughter at the farce they’ve created!

Bring back the 15th.
Non of this is it, isn’t it, slap a bit of wire on it then it isn’t.

From the OED

Irrelevant or unrelated to the subject being dealt with: one is obliged to wade through many pages of extraneous material.

 

[richy3333]

Whoever did this was either confused or trying to make sure 'belt and braces' style. The incomer for the water before the stopcock is plastic. The floor it passes through is chipboard and the pipe drops down into a solem/void (timber building raised up on blocks). After the stopcock and meter it's all copper either clipped to joists or in stud walls.

 

[shanky887614]

View attachment 28056
Whoever did this was either confused or trying to make sure 'belt and braces' style. The incomer for the water before the stopcock is plastic. The floor it passes through is chipboard and the pipe drops down into a solem/void (timber building raised up on blocks). After the stopcock and meter it's all copper either clipped to joists or in stud walls.

nothing wrong with belt and braces, i wear them when its cold (attached to my sellopets)

 

[Geordie Spark]

This is the tilers forum! What do you expect?

I know it is!!

I'm still trying to work that one out!

 

[Piratepete]

Thanks for your entertaining and informative (some) replies. Rather gobsmacked to see this continue for 5 pages!:angel_smile:

Pete

 

[Piratepete]

NO, it doesn't negate main bonding to the outbuildings CU (EMT) especially if the supply is PME, in which case the sub-main earth should be a minimum of 10mm....

Why should the sub-main earth be a minimum of 10mm? Doesn't table 54.7 apply for a PME supply? Also Table 4.4 (clearer) in the On Site Guide. 6mm supply 6mm earth. Or have I missed something?
Cheers
Pete

 

[Leesparkykent]

Why should the sub-main earth be a minimum of 10mm? Doesn't table 54.7 apply for a PME supply? Also Table 4.4 (clearer) in the On Site Guide. 6mm supply 6mm earth. Or have I missed something?
Cheers
Pete

Have a look at Regulation 543.1.1 and 544.1.1

 

[Des 56]

Thanks for your entertaining and informative (some) replies. Rather gobsmacked to see this continue for 5 pages!:angel_smile:

Pete

Sorry Pete but it seems that even after those 5 pages Leespakykent is still providing info you don't seem to twig

 

[davesparks]

Why should the sub-main earth be a minimum of 10mm? Doesn't table 54.7 apply for a PME supply? Also Table 4.4 (clearer) in the On Site Guide. 6mm supply 6mm earth. Or have I missed something?
Cheers
Pete

Minimum size of a main bond on a PME supply is 10mm. Main bonds must be sized according to the incoming service not for the size of any submains.

 

[Piratepete]

Minimum size of a main bond on a PME supply is 10mm. Main bonds must be sized according to the incoming service not for the size of any submains.

Read my text. I'm querying the sub-main earth size, not main bonding.

 

[Piratepete]

Have a look at Regulation 543.1.1 and 544.1.1

I've looked. where does it say min 10mm? As this section of the regs is a nightmare of cross references, please read the whole of section 4.4 in the On Site Guide and table 4.4(i) in particular.
There is a minumum size, 10mm, for main protective bonding but for the Earthing conductor it is 6mm where 'buried and protected against corrosion and mechanical damage'.

 

[spark 68]

Read my text. I'm querying the sub-main earth size, not main bonding.

The point being made is that if bonding is required at the remote end of the sub-main, then that sub-main's CPC will be required to be sized to act as both a CPC and a main bonding conductor, which means the sub-mains CPC will need to be 10mm minimum to satisfy the PME regs.

 

[Leesparkykent]

But the whole purpose of this thread is about bonding the gas supply in an out building.
If you connect your 10mm bond to the EMT in the outbuilding then the CPC in the cable feeding the sub board in the outbuilding will have to be adequate to comply with the minimum CSA of the bond to the gas. For example it's no good having a 6mm 3core SWA feeding the sub board in the outbuilding when you are required to bond the gas in the out building in 10mm (if it's TNC-S), The CPC in the sub main cable would have to Adequately sized for the bond as well.

 

[Leesparkykent]

The point being made is that if bonding is required at the remote end of the sub-main, then that sub-main's CPC will be required to be sized to act as both a CPC and a main bonding conductor, which means the sub-mains CPC will need to be 10mm minimum to satisfy the PME regs.

I was trying to write the same thing but it took me nearly 10mins lol so didn't see your post.

 

[Piratepete]

But the whole purpose of this thread is about bonding the gas supply in an out building.
If you connect your 10mm bond to the EMT in the outbuilding then the CPC in the cable feeding the sub board in the outbuilding will have to be adequate to comply with the minimum CSA of the bond to the gas. For example it's no good having a 6mm 3core SWA feeding the sub board in the outbuilding when you are required to bond the gas in the out building in 10mm (if it's TNC-S), The CPC in the sub main cable would have to Adequately sized for the bond as well.

Ok. I can see where you're coming from, but can you please explain the application of the first 2 columns in table 4.4 On Site Guide?

 

[Leesparkykent]

Ok. I can see where you're coming from, but can you please explain the application of the first 2 columns in table 4.4 On Site Guide?

Sorry mate haven't got the OSG near me, would have to look later unless someone else can point you in the right direction.

 

[spark 68]

Ok. I can see where you're coming from, but can you please explain the application of the first 2 columns in table 4.4 On Site Guide?

What is there to explain ?

As you go down those first two columns in 4.4 (i) it gives the minimum sizes according to function of said conductor, obviously if it is only an EC then the minimum size is given, likewise for a MPB, where it is used as both functions again the minimum size is given, so a combined EC and MPB then the minimum size for the MPB is used (or whichever is the larger minimum size to satisfy that particular requirement/s), the last row in that table refers specifically to PME/TNC-S, as that table covers both TNS an TNC-S systems, table 4.4 (ii) being for TT

 

[telectrix]

Ok. I can see where you're coming from, but can you please explain the application of the first 2 columns in table 4.4 On Site Guide?

you will not see 4mm, 6mm, or even 10mm for supply live conductors in the normal course of your travels.

 

[Piratepete]

What is there to explain ?

As you go down those first two columns in 4.4 (i) it gives the minimum sizes according to function of said conductor, obviously if it is only an EC then the minimum size is given, likewise for a MPB, where it is used as both functions again the minimum size is given, so a combined EC and MPB then the minimum size for the MPB is used (or whichever is the larger minimum size to satisfy that particular requirement/s), the last row in that table refers specifically to PME/TNC-S, as that table covers both TNS an TNC-S systems, table 4.4 (ii) being for TT

Yes, it's obvious. Mea culpa! I assume there is a statement somewhere about a combined EC and MPB, but then if I'd used my brain.... I was thinking technically.

The CU in this outbuilding is from a 32Amp 6kA MCB in the house CU via a 6mm 3core SWA cable. Main Bonding (min 10mm) is required to the gas and water installations in the outbuilding. Technically, a 6mm earth will easily carry the maximum fault current of the installation. The regs would require the main earth to be 10mm, just because the minimum bonding size you are allowed is 10mm. So on an EICR would this count as a C3 or would you not even bother mentioning it? IMHO i don't see this as a C1 or C2. (Shoot me down again!)

 

[Des 56]

The lack of main bonding to a service?
Have a look for guidance (ie the esc or whatever its called lately)as to the code,that is until your experience allows you to answer these questions when you do start carrying out Eicrs in the future

 

[Leesparkykent]

http://www.----------------------------/mediafile/100126678/best-Practice-Guide-4.pdf

Have a read through this but ultimately it's you that decides what code to give to any given situation as you are the inspector and signing the report, this is only a guide.

 

[Piratepete]

The lack of main bonding to a service?
Have a look for guidance (ie the esc or whatever its called lately)as to the code,that is until your experience allows you to answer these questions when you do start carrying out Eicrs in the future

You've misunderstood. The gas and water supplies are now bonded in 10mm. The main earth however is only 6mm. technically this will take any likely fault current (32 amp 6 kA supply). So it doesn't comply with the regs though it's not dangerous IMHO.

 

[Piratepete]

http://www.----------------------------/mediafile/100126678/best-Practice-Guide-4.pdf

Have a read through this but ultimately it's you that decides what code to give to any given situation as you are the inspector and signing the report, this is only a guide.

Ok. Thanks for your patience. I have the guide. not sure if it'll help. It might require a call to NICEIC Technical Help Line. I think my assessor would give it a C3 but everyone always has a different opinion when it comes to fault codes!
Cheers

 

[spark 68]

Can you not utilise the armourings along with the third core to increase your effective CPC csa ?

You might find it complies after all if this has already been done, I will have a look through the various tables later.

Otherwise just note it on the EICR as per the advice given in the links above