Generator bonding/ seperate structures..

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sparkydon

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I'm looking at a job that has me a little stumped. There is a MDP located down a driveway about 200' from a pumphouse. The pumphouse has an MCB panel with a few loads and then feeds to a house located 200' from there. There is no metallic connections from the three seperate places. On the pumphouse, the customer wants to add a 12KW Kohler generator. There are only three 4/0 CU from MDP to the MCB panel on the pumphouse and only three 4/0 CU from pumphouse to the panel in ther house.

The installer obviously used 250.32 (B)(2) to avoid the EGC conductor between structures.

My question is, when a generator comes into play, are there any code conflicts with not having a seperate EGC from the GES of the pumphouse the the house, (or from the MDP for that matter)?
 
Make sure that the ATS doesn't switch the grounded conductor.If it does switch the grounded conductor the generator is a SDS.

Careful consideration should be done with this application it can become very complicated.

I would recommend pulling an EGC due to the possible dangers of a lost neutral . Lost neutral= lost effective ground fault current path.


Ibew441dc
 
Thanks, George. As far as melon scratchers go, this one's a honeydoodle. (Flanders) Or maybe it's not at all.

ibew441dc said:
Make sure that the ATS doesn't switch the grounded conductor.If it does switch the grounded conductor the generator is a SDS. Ibew441dc
Click to expand...

The HO has decided on a MTS, since they will be at the property infrequently. Hiking 200' to the pumphouse at 2 AM to pull the switch handle doesn't sound like too much fun to me, but hey.
I will stay clear of switching the grounded conductor to avoid the SDS classification, thanks.


ibew441dc said:
I would recommend pulling an EGC due to the possible dangers of a lost neutral . Lost neutral= lost effective ground fault current path.Ibew441dc
Click to expand...

I know pulling the EGC to all locations would be ideal, but 200' past 3 3/0 wires may not be possible at this point, shy of trenching in a sigle DB wire..

I don't follow what you mean by "lost neutral."
 
In the event of a "lost neutral" (open or resistive neutral) between the loads and the source, all metallic equipment bonded to the system neutral on the load side of the break becomes energized, with the neutral current seeking a path back to the source.

If there is an EGC installed, and the neutral break occurs on the load side of the point where the neutral is connected to the EGC, then the equipment doesn't become energized.

IMO, I wouldn't bother adding an EGC to the feeders between the buildings; I would continue to use 250.32(B)(2) and double-check the neutrals for solid connections.

Bear in mind, new installations under the coming 2008 will not be allowed to use the neutral as the fault-clearing path between structures. (I believe there is going to be some leeway for old work.)
 
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