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

 

[Engineer54]

Agggggh!! Not that poxy Wirenut table again!! Do yourself a favour spark 68 (and anyone else that still has this table) throw that bloody thing in the bin where it has belonged for years!!

There is very little in that table i would take as correct, the whole thing about this table, is it's inconclusive, misleading and in many respects just plain Wrong!!!

Just get shot of the bloody thing!!

 

[davesparks]

Chaps, I'll just bring your attention to the fact that 543 applies to Protective Conductors only, NOT Protective Bonding Conductors, that's 544.

So what does a section title protective conductors apply to? If it's not protective bonding conductors then it also can't be circuit protective conductors.

 

[spark 68]

Agggggh!! Not that poxy Wirenut table again!! Do yourself a favour spark 68 (and anyone else that still has this table) throw that bloody thing in the bin where it has belonged for years!!

There is very little in that table i would take as correct, the whole thing about this table, is it's inconclusive, misleading and in many respects just plain Wrong!!!

Just get shot of the bloody thing!!

Cheers, E54

TBF I thought that table was a little on the optimistic side ,it is the only one I have that shows the copper equivalent, I have others that show which sizes the SWA are suitable for use as a CPC, I probably got one of those from you.

When I have finished my paperwork I might have a go at the calcs for the hell of it , the OP should really be looking at this, but then again he could just C3 it, if it is not showing any distress etc..etc..

Note to self, do paperwork as and when it comes in, instead of leaving it all to the last minute! lol

 

[GEOFF S]

543.2.1

(I have quoted the relevant sub sections)

A protective conductor may consist of one or more of the following

(ii) A conductor in a cable
(v) A metal covering, for example, the sheath. screen or armouring of a cable

Going by that, you could use the combination of armour sheath and cable conductor as a main protective bonding conductor.

I agree, i see no issues.

Cheers

 

[spark 68]

I agree, i see no issues.

Cheers

I disagree, and there are issues, see 543.2.5

 

[GEOFF S]

I disagree, and there are issues, see 543.2.5

I dont have the regs to hand, could you expand?

Cheers

 

[Leesparkykent]

K1/k2xS=13.5294

k1=115
k2=51
S= 6mm

 

[GEOFF S]

Thanks Lee.

Well i still see no issues.

Cheers

 

[spark 68]

I dont have the regs to hand, could you expand?

Cheers

Then why the blanket statement ?

543.2.5 The metal covering including the sheath (bare or insulated) of a cable, in particular the sheath of a mineral insulated cable, trunking and ducting for electrical purposes and metal conduit, may be used as a protective conductor for the associated circuit, if it satisfies both requirements of items (i) and (ii) of reg 543.2.2

543.2.2 this reg is actually more about switchgear and bus bar trunking etc. but the salient points here are (i) and (ii)

(i) Its electrical continuity shall be assured, by construction or by suitable connection, in such a way as to be protected against mechanical, chemical or electrochemical deterioration.

(ii) Its cross sectional area shall be at least equal to that resulting from 543.1, or verified by test in accordance with the appropriate part of BSEN 61439 series.


What this is basically saying is that if the armouring is of insufficient csa to satisfy its use as a protective conductor, you cannot make up the difference with another undersized protective conductor, either the armouring has to comply on its own for its intended purpose, or the other protective conductor has to comply the same way. as an example of what would not be allowed, consider you need a CPC of say 10mm, and you calculate your armouring works out as a copper equivalent of 6mm, you cannot just add another CPC or core of 4mm to make up the difference, you would need the additional CPC or core to be 10mm on its own.

You can use both where for instance the armouring would comply as a CPC and a core for the MPB purposes, or vice versa.
This is one reason why you sometimes see a 10mm G/Y cable running along side an armoured cable.

 

[Leesparkykent]

SWA, armour equivalent copper - Ted

 

[Leesparkykent]

Reg 542.1.3.3

Where a number of installations have separate earthing arrangements, any protective conductors common to any of these installations shall either be capable of carrying the maximum fault current likely to flow through them or be earthed within one installation only and insulated from the earthing arrangements of any other installation. In the latter circumstances, if the protective conductor forms part of the cable, the protective conductor shall be earthed only in the installation containing the associated protective device.

 

[spark 68]

To be honest this type of situation is one of the few times TT ing the far end is worth considering on economic grounds due to the cable sizes involved, probably not in domestic where the distances are fairly short, but certainly in cases where you may only want say a lamp in an outbuilding containing plant that may be some considerable distance from the main building.

 

[Deleted member 26818]

Has the type of supply been established?

 

[GEOFF S]

Then why the blanket statement ?

543.2.5 The metal covering including the sheath (bare or insulated) of a cable, in particular the sheath of a mineral insulated cable, trunking and ducting for electrical purposes and metal conduit, may be used as a protective conductor for the associated circuit, if it satisfies both requirements of items (i) and (ii) of reg 543.2.2

543.2.2 this reg is actually more about switchgear and bus bar trunking etc. but the salient points here are (i) and (ii)

(i) Its electrical continuity shall be assured, by construction or by suitable connection, in such a way as to be protected against mechanical, chemical or electrochemical deterioration.

(ii) Its cross sectional area shall be at least equal to that resulting from 543.1, or verified by test in accordance with the appropriate part of BSEN 61439 series.


What this is basically saying is that if the armouring is of insufficient csa to satisfy its use as a protective conductor, you cannot make up the difference with another undersized protective conductor, either the armouring has to comply on its own for its intended purpose, or the other protective conductor has to comply the same way. as an example of what would not be allowed, consider you need a CPC of say 10mm, and you calculate your armouring works out as a copper equivalent of 6mm, you cannot just add another CPC or core of 4mm to make up the difference, you would need the additional CPC or core to be 10mm on its own.

You can use both where for instance the armouring would comply as a CPC and a core for the MPB purposes, or vice versa.
This is one reason why you sometimes see a 10mm G/Y cable running along side an armoured cable.

Of course you can, you just need to calculate the current sharing between the two cpc.

Cheers

 

[Deleted member 26818]

Of course you can, you just need to calculate the current sharing between the two cpc.

Cheers

That's fine for determining the CSA of a CPC, but will it be suitable for determining whether the armour and core are acceptable as a bonding conductor?