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Hello, can anyone advise on bonding of extraneous conductive parts when supply is from a generator run parallel with distribution network?
There'll b a 200kva generator supplying spray booths that have a gas supply to them.
The metal pipes aren't underground but connect to tanks outside sitting on concrete pads, could be bringing an earth into building so may need Bonding.
If they do can I run suitable bonding conductor back to generator MET independent of mains earth?
 
Looks like they will need Main bonding,sized appropriately,all main bonding back to the generator Earth terminal.
You may also have a main earth terminal too,these can be linked.
 

Ian1981

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They do not necessarily need bonding at all.
 

davesparks

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Presumably you are already in contact with the DNO about this if you are connecting a generator in parallel with their network.
This does raise the question of why you are doing this though?
If its just for the spray booth why not run that from the generator independant of the DNO supply?
 
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  • #5
Hi, should have said the existing supply is not fit to take the added load, cheaper to buy generator than increase supply.
I plan to run 50mm2 to a suitable 3ph high load board, independent from mains supply.
Earth the centre point of the generator with a 5/8 rod to get Ra as low as possible and bond the gas which only serves the spray booths.
That's the plan but I can't find anything in regs to confirm this is ok.
I'm thinking as long as both supplies are kept separate there shouldn't be any problems, there won't be any danger of gas bond rising from earth potential if there's a sound connection at generator, which I obviously intend on doing.
Can anyone else advise specifically on any other possible dangers that this install could create, or is my planned install suitable?
 

James

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Hi, should have said the existing supply is not fit to take the added load, cheaper to buy generator than increase supply.
I plan to run 50mm2 to a suitable 3ph high load board, independent from mains supply.
Earth the centre point of the generator with a 5/8 rod to get Ra as low as possible and bond the gas which only serves the spray booths.
That's the plan but I can't find anything in regs to confirm this is ok.
I'm thinking as long as both supplies are kept separate there shouldn't be any problems, there won't be any danger of gas bond rising from earth potential if there's a sound connection at generator, which I obviously intend on doing.
Can anyone else advise specifically on any other possible dangers that this install could create, or is my planned install suitable?
You will need to be careful regarding notices on main isolator from grid supply.
warning that there is a second supply to the building, idealy with a diagram pointing to where this is isolated. (the fire brigade and other emergency services may have to isolate this when nobody is available to direct them)

my understanding is that this is no longer a generator running in parallel with the grid but seperatley to supply equipment that is not grid powered?

there are lots of regulations about grid tied generation, regarding synchronisation and disconnection etc. but it seems this is not the intention.
this document should help.
 
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  • #7
Yeah bit of confusion by saying the gen and supply are in parallel, my bad.
Good point about labeling, will make it clear there's a generator supplying some of the load.
Can't see anything specific about bonding in the document and there's nothing in regs, can I just size it based on neutral, same as tncs?
 
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  • #9
Hi sorry for delay in reply been busy.

From previous posts and my own research I think the install will be ok set up as a tns, with gas bonded back to generator MET.

My main concern was there could be a danger of bonding the gas to the generator creating a shock path from any other exposed or extraneous parts on the tncs earthing, provided by supply company. Basically any neutral currents in the supply feed part of the building could find there way to earth via generator earth, if someone was incontact with metal work from both supplies.

As the gas is only supplying the spray booths and there are no other extraneous parts entering that area it should be safe. Also the spray booth area only has circuits from generator supply feeding into it so again I see no danger of contact from both supplies.
Maybe worth telling client that no extension leads should be run into spray booths for other equipment, it will have to remain isolated from the rest of building supply.

If anyone else has any more to add please let me know, thanks.
 

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