Portable generator question

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goldstar

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
I recently installed one of those Reliance 10 circuit manual generator transfer switches with a remote 30A, 120/240V plug-in port (all customer purchased material including the Honda generator & cord). Everything went smooth and interfaced it into a main breaker panel with considerable ease. However, I was not able to test the operation with the generator for a number of reasons, all of which were the HO's problem.

As luck would have it, there was a power failure while I was away on vacation and I got a call from the HO stating that as soon as he plugged the cord into the genaretor and then the remote port (before transferring any circuits) the breaker on the generator tripped immediately. So, I went out today and discovered that ALL the receptacles on this particular generator were GFCI protected via the portable generator distribution panel, including the 30A, 120/240 receptacle.

My immediate solution was to disconnect the green ground wire between the xfer switch panel and the main breaker panel but the 1 1/4" greenfield connecting between the two panels provided a redundant ground path. So, I disconnected the greenfield from the xfer panel and allowed it to float.

So, now what I have is a properly grounded main breaker panel but the xfer panel is not bonded in any way to the MB panel and does not have a common ground path. The xfer panel will be bonded to the grounded casing of the generator during a power fail condition (with the cord attached) and will be providing power to the 10 circuits in the house without a common ground path to the MB panel in a power fail condition.

Any suggestions on how you would properly correct this would be appreciated. I'm thinking I'm either screwed or I should let the xfer panel float and not worry about it. BTW, until now I've never come across a portable generator that has a GFI protected 120/240V output.

I probably could pull the generator distribution board off and re-wire the 120/240V circuit so it's not GFI protected. I'm not concerned about voiding any warranties at this point. I just want to do this the safest way.

Thanks in advance.

Phil,
Gold Star Electric
New Jersey
 
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Is the generator neutral bonded to the chassis and generator grounding pins? If so, I'd break the bonding of the generator to its ground (hopefully, they provided an easy means to do that). Let the house be the main bonding jumper. However, it may still leak enough current through capacitive or other means to trip the GFCI.

In that case, I think your only alternative is to intercept power from the supply side of the GFCI and install your own 30A breaker box on the generator that isn't GFCI protected.
 
walkerj said:
You need to remove the neutral/ground bond at the generator?
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I agree (as a solution, not a question). Bonding at the generator and the MBJ creates a parallel path for neutral current... resulting in enough neutral current bypassing the GFCI for it to trip.

Removing the bond will not defeat grounding as long as it is plugged into the transfer panel. However, caution the HO that if used as a portable gennie other than this will require the bond reconnected.
 
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suemarkp said:
Is the generator neutral bonded to the chassis and generator grounding pins? If so, I'd break the bonding of the generator to its ground (hopefully, they provided an easy means to do that). Let the house be the main bonding jumper. However, it may still leak enough current through capacitive or other means to trip the GFCI.
Click to expand...
There's a label on the side of the generator indicating that the neutral is bonded to the chassis. However, I would imagine that it is bonded on the line side of the GFI breaker. If it were bonded on the load side it would always trip
In that case, I think your only alternative is to intercept power from the supply side of the GFCI and install your own 30A breaker box on the generator that isn't GFCI protected.
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I believe you are correct but I wouldn't have to install separate breakers or fuses because there are "in-line" breakers installed at each receptacle location on the generator distribution panel.

Thanks for your input. Good suggestion.
 
Well...this is a problem that I wondered about with the new NEC requirement that all portable generators under 15kw have GFCI protection intergral with the generator.

If the 30amp receptacle is GFCI protected on the generator, how are we to backfeed a residential system that has the neutral and grounding conductor bonded in the main service without tripping the GFCI on the generator?

NOT GOING TO HAPPEN!

The HO needs an older generator without GFCI protection.

shortcircuit2
 
Smart $ said:
I agree (as a solution, not a question). Bonding at the generator and the MBJ creates a parallel path for neutral current... resulting in enough neutral current bypassing the GFCI for it to trip.

Removing the bond will not defeat grounding as long as it is plugged into the transfer panel. However, caution the HO that if used as a portable gennie other than this will require the bond reconnected.
Click to expand...


Thank you, Smart.

I knew that but I put a question mark because i was about 90% sure!
 
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