Main bond question.

[RF Lighting]

I'm currently working on a commercial project which has involved knocking a mill through to next doors building, making the two effectively one building.

There is a 100A TP&N TN-S supply into the 2 storey building, and a 300A TP&N supply into the mill.

Both buildings have a seperate gas supply, which there is no need / intention to alter, and both buildings have independant electrical installations.

As this is really one building do both gas supplies need bonding to both electrical installations, or should they be left as if it were still two buildings?


I'm not sure I like the idea of connecting together the main earth of two independant supplies, which could possibly be fed from entirely different subs due to the distance between them.

 

[Lectrician]

Last time we had a situation like this was in a shopping mall. Two shops into one.

The NIC clant was to leave the installs as they where, but to run a bonding condductor sized to the largest supply to 'unite' both MET's.

 

[Lectrician]

Or if their is capacity inthe 300 supply, submain the 100, and upgrade any bonding that is required to 25mm.

 

[Lectrician]

had problems in a large solicitors once with three supplies - two PME andone TN-S. The TN-S being from a seperate supply competly - there where occasions when a power cut would kill have the site, but not the rest.

Different earthing systems is a concern.

We eventually managed to convince them to remove two services, and submain everything back to the TN-S supply which was on it's own sub. DNO refused to remove service heads, but metering was removed.

 

[RF Lighting]

It would be a hell of run between the two incommers, and VD would force the cable size up.

Cost is an issue as things are, so I can't see them liking that idea.

Whacking a big earth between the two supplies should be ok, just didn't sound right to me.

 

[JohnD]

looking at it differently, yes, the earths of the two supplies might be at different potentials, and this could have undesirable consequencies if they were not bonded together. Sooner or later pipes or cables from one side will extend into the other side.

If there is any particular current across the bonding cable perhaps you could use iit for underfloor heating (but the DNO designers are sure to know the answer to the problem, they will have seen it before in indstrial sites. I used to work in an REC building in Ipswich which had been deliberately designed to have two internal substations fed from different parts of the network, to improve resilience in the event of a network fault)

 

[bengasman]

As far as I know, you are not allowed to have two gasmeters in one building, at least for domestic. Not sure if the same applies to commercial.

 

[baz1968]

 

[plugwash]

could you stop posting emoticans on thier own in loads of threads it's getting rather annoying