Proximity of Gas pipe to Electrical cableing

[mrstitt]

I'm looking at this from an electrical perspective, but I am interested in the view of a Gas Safe engineer - hence posting here.

BS6891:2005 8.16.2

Where installation pipes are not separated by electrical insulating material, they shall be spaced as follows: a) at least 150 mm away from electricity meters and associated excess current controls, electrical switches or sockets, distribution boards or consumer units; b) at least 25mm away from electricity supply and distribution cables.

BS7671:2008 (the wireing regulations) dose not have a reciprocal clause, but the on site guide does mention it. "Seperation of at least 25mm to be provided for domestic pipework up to 35mm. For pipework over 35mm then 50mm separation is required. The separation distance can be reduced if the gas pipe is PVC wrapped or a pane of insulating material is interposed."

I'm proposing to run several electrical cables past an existing 22mm copper gas pipe. I obviously don't want to cause the existing gas installation to be non-compliant. Ideally I also don't want to relocate the existing gas pipe.

I think that the sensible thing to do is use PVC conduit. This would bend around the existing gas pipe. PVC is electrically insulating so am I correct in thinking that its okay for PVC conduit carrying electrical cabling to touch a gas pipeline?

If I turned the question on its head. Would any gas safe engineer be comfortable running a 22mm copper gas pipe such that it touched or had minimal clearance from a PVC conduit?

 

[JMGas]

Electrical cable too near a gas pipe was classed as Not to current standards, aka not a safety hazard at this time. Now they've got rid of NTCS...I wouldn't loose sleep over it and I wouldn't class it as At risk.

 

[muggles]

PVC conduit will be fine. You can even split a section of waste pipe, fit it over the gas pipe, then stick it back together again

 

[mrstitt]

Its probably going to be tidier to keep the PVC to the new cable installation.

Just to throw a spanner in the works, if it was a galvanised steel conduit instead of PVC, the conduit is solidly earthed and the gas pipe is also equipotentially bonded. Anybody see a hazard there from a gas perspective?

 

[Aquaheat]

Fine with the plastic conduit.

With galvanised I'd say no regardless of earthing it requires a barrier of insulating material. So galvanised would be a no no.

Jon.

 

[mrstitt]

Hence I just thought I would play devils advocate and throw galvanised in there.

The strict wording in the standards can sometimes bind you in your choice of design. Galvanised conduit that is properly bonded would on the face of it be as good as PVC (ok there is an additional failure mode).

From an electrical perspective there is nothing in the regulations stopping me from installing even bear cabling across a gas pipe - although the OSG advises against it. If a gas engineer was to place a gas pipe across a galvanised conduit then perhaps they would, as JMGas suggests, wrap it in PVC in the area around the electrical circuit. But otherwise they could perhaps risk assess it and document it as a departure - nothing wrong with departing from the standard as long as you've done the due dill and properly risk assessed it - just its normally less expensive to simply comply with the standard verbatim.

I'm not a gas expert, but I would imagine that any significant lengths of PVC encasement may introduce new risks relating to the escape of gas.

Worth noting also that since the 1st January all new enclosures of protective electrical switchgear will be made of a non-combustible material which essentially means steel - not electrically insulating. For legacy reasons many consumer units are installed adjacent to gas meters and there associated pipework. Any replacement of such consumer units will give the gas meter operator an interesting time when they come to periodically replace the gas meter. I am aware of an instance where somebody trying to get a PPM gas meter changed for a credit meter was stuck in limbo due to electrical services all over the meter cupboard.

Just to finish off, and be pedantic, lots of combi boilers have a three core mains flex for their electrical supply, often wrapped around the back of the piping including the boilers gas supply. Perhaps this is done by a non gas safe plumber after the formal installation of the boiler - or by the user who simply wanted the cable tidied away.