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

 

[spark 68]

Okay fair enough, I think we are singing from the same hymn sheet here, when designing a sub-main we go through the assessing compliance bit when we are selecting our cables, and no I wouldn't try to make up the csa as a mix.

I was taught that where PME conditions apply that we allow for the worst case, and the CPC should be calculated separate from the MPB, so if the armourings would have been marginal for the MPB (just complying), then either use an extra core for the CPC or if large enough csa the core as the MPB, and use the armourings for the CPC.

I will have to look in the 16th ed and see if there was an actual reg for this, or if my then old boss was just belts and braces.

 

[LeeH]

Arghh! we don't, either the core complies, OR the armourings comply for a "straight" CPC, that is what we have been saying, the armourings are earthed for protective reasons where a core is used as the CPC, NOT to make up the csa.

Sometimes we use a core for a bonding conductor, and the armourings as the CPC, so long as both comply csa wise for their respective functions, ie. as two separate protective conductors, both (in their own right) fulfilling two different roles.

What's the problem with using the core for both?

 

[davesparks]

What's the problem with using the core for both?

Of course you use a core for both if a core is available, if no core is available then you use the armour for both.

I really don't understand how so many people manage to complicate such a simple issue.

If a submain is required to include a main bond you size the cpc accordingly. You cannot install a seperate conductor and then make one conductor operate as a bond and the other as a cpc, they're joined together at both ends!

 

[Engineer54]

Of course you use a core for both if a core is available, if no core is available then you use the armour for both.

I really don't understand how so many people manage to complicate such a simple issue.

If a submain is required to include a main bond you size the cpc accordingly. You cannot install a separate conductor and then make one conductor operate as a bond and the other as a cpc, they're joined together at both ends!

Just one rather big problem with that, you'd need a 2 core 70mm SWA to provide a near suitable CSA of steel wire to give you the minimum 10mm equivalence of a copper main bonding conductor!!

 

[Dan]

I'm just bumping some threads in the Electrical Forum, don't mind me while I do this, you don't have to respond to them. Although if they are still current topics, and you do wish to reply, you're welcome to. Keep the thread on-topic and make sure you stick to the forum rules though.