Generator Main Bonding Jumper

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RUWired

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If i have a transfer switch that has a solid neutral connection, and the generator is not considerd a SDS, does the main bonding jumper have to go in both the generator main breaker compartment and in the load panel.Or is it only required at the load panel per 250.24(C)
Rick
 
For separately derived systems, it is called a System Bonding Jumper, see the 2005 definitions.
If the system is not separately derived, there will be no bonding conductor, Main or System. The panel and generator installation will get treated the same as any subpanel.
 
I was following the ground fault path at the load panel on one of the branch circuits, the fault would have to travel back to the main service panel main jumper and then through the neutral to the generator in order to trip the branch breaker.It seems the fault would trip sooner if any of the two jumpers were installed.The reason i quoted 250.24(C) is because in 250.20(D) fpn no. 2, it referrs me to size at 445.13 and that takes me to 250.24(C) where it says to bond to each enclosure.
Rick
 
Yes the fault current path is quite long in situations such as this, but by installing a bonding jumper on the load side of the service disconnect, you are creating a parallel path for neutral current. If the ground fault current path is the proper size and installed properly, it will function. If you are really concerned, you can increase the size of the groundfault current path and not create a violation in the process.

BTW: typically the fault path is much longer than most imagine, as the fault current will travel to the source, which could be a transformer down the street.
 
I am always concerned and always looking to understand. Recently, i was on a job and came across a branch ground fault that did'nt trip and traced it back to the xfrmr xo not being bonded and thought that the same potential could be with the generator if it was'nt bonded.Thanks for your help.
Rick
 
The transformer would be a separately derived system. A generator is not always a separately derived system, therefore it is not always bonded as you mentioned. The transfer switch determines if the generator is a separately derived system. You have already determined it is not.

We are all learning here. Maybe me the most ;)
 
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