Generac 10000e and flourescent lighitng causing Nuisance tripping

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NjWireMan

Member
Location
New Jersey
I need help here guys. Here is scenario. Customer rents Warehouse space with offices. Customer did not want to connect to Utility with a transfer switch because he does not own the place. So he wanted a portable generator set up that powered some Troffer lights and outlets to network equipement and computers without running extension cords every where when power was out. So basically it is a stand alone system that is only powered when fired up with Generator.

Connection = Generator 50 amp outlet to cord that enters a outlet that feeds a Subpanel with 50 amp breaker inside. Neutral and ground Not bonded. Ground to steel and not using ground from generator.

Problem = Full GFCI protected Power from Generator keeps tripping the GFCI when a flourescent light breaker is turned on whether the Generator ground is bypassed and connected to steel or if I send the ground back to the Generator itself. Trips right away.
Lights work fine with no ground to steel or no ground to Generator. ( I set up 2 of these systems in 2 of warehouses next to each other) ( both have same flourescent lighting issue. 2 different brand new Generators with same result)

Generac xp10000e that has a bonded neutral. I needed this generator for the true power to use on the Network equipement.

No sign of a actual ground fault and tried a light right next to Generator with same tripping result. Outlet powers a shopvac fine. No tripping.


I can understand the tripping if I was using the ground back to the generator. But how does it trip when I wire nut off the ground back to generator and do ground to steel?????


Any help would be deeply appreciated.

Thank You
 

GoldDigger

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Sounds like the GFCI may just be too sensitive.


Any fluorescent light will draw a significant (more than microamps) amount of capacitive current between the arc inside the lamp and the nearby metal reflector. This aids in starting the lamp, especially for long tubes.
But a "reasonable" number of such fixtures should not trip a normal GFCI.
Since the source is a generator and the current path is capacitive any high order harmonics in the generator output will lead to a higher RMS value of the leakage current than when operating off cleaner POCO power.

My first action would be to use a variable resistor or set of resistors between hot and ground to determine the actual sensitivity of the GFCI.
I would also try (carefully) operating the troffer isolated from ground/EGC to see what happens. Then measure the current from one troffer to ground.

As to why this happens even with the generator side ground disconnected, I am not so sure.
Possibly there is just too great a capacitive coupling at the generator end too?
Finally, some GFCIs will trip if they sense a low impedance between ground and neutral wires on the downstream side of the GFCI. Again, measurements might help. AC impedance this time.
 

GoldDigger

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Location
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I can understand the tripping if I was using the ground back to the generator. But how does it trip when I wire nut off the ground back to generator and do ground to steel?????
A GFCI or other Residual Current Detector (RSD) does not directly sense flow of current on the EGC. Instead is senses any difference between the current on the hot and on the neutral. That current is assumed to have left the intended circuit conductors and gotten back to the source by some other path.

EGC or building steel among other possibilities. Even the other hot wire in an MWBC if you try to use a single pole GFCI.
 

NjWireMan

Member
Location
New Jersey
My supply house is not Home Depot.

Thank you golddigger for the response. I understand it is too sensitive. What do I do going forward because replacing the gfci will just cause the same results? I need to finish this job out and get paid but also make this a safe system. This is a critical system so there cannot be nuissance tripping.

1. Disconnect the gfci function so it is the same as a cheaper generator that does not have a full generator GFCI? How does this full generator gfci work??
2. Cant just lose the ground all together.
3. Bond the subpanel and disconnect the ground to steel and back to the panel. ( generator has a bonded neutral)
4. Any ideas??
 

GoldDigger

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Location
Placerville, CA, USA
Occupation
Retired PV System Designer
OK, the very first thing I need to confirm is whether the GFCI you are talking about is built into the generator?
If it is, you musteither disconnect the ground/neutral bond at the generator OR carry both neutral and EGC from the generator to the panel for your separate electrical system and then do NOT bond the neutral to EGC at the panel or anywhere downstream.
You will have to bond the EGC to a ground electrode system, preferably the same one that serves the normal building wiring, but don't connect the neutral to anything but other neutrals in your separate system. Not even (or especially not) any other normal building neutrals since they are bonded to ground at the service.

You have edged your way into the whole painful topic of whether to wire a generator as a separately derived system (SDS). If you leave the ground/neutral bond at the generator you have no choice.
 

Martin B

Member
Location
Nebraska
Sorry about giving you a hard time about the Generac.

But, could there be a problem with the lights??? Will they trip a GFCI that's not associated with the Generac generator?
 

NjWireMan

Member
Location
New Jersey
Yes. The generator has a built in gfci that protects everthing. 120 outlets, 240v 30 amp outlet, and the 240v 50 amp oultet all protected by the gfci.
 

NjWireMan

Member
Location
New Jersey
I have tried using just the 4 wire system from the generator to my subpanel and it trips the gfci. Are you saying disconnect the bond in the generator and try that same hook up again??
 

GoldDigger

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Location
Placerville, CA, USA
Occupation
Retired PV System Designer
I have tried using just the 4 wire system from the generator to my subpanel and it trips the gfci. Are you saying disconnect the bond in the generator and try that same hook up again??
If you do not have any bond (deliberate or accidental) in or after the sub panel and no connection between the subpanel neutral and building neutral, I would try lifting the ground neutral bond at the generator and then measuring current putting the ammeter where the jumper was.

If you unplug the generator completely from the separate system, you should not read continuity between neutral and ground in the subpanel.
If you plug in the generator again while its bond is lifted you should still have no continuity between neutral and ground.
 

NjWireMan

Member
Location
New Jersey
So you have a ideal of how this gfci might be working in the unit itself. I have read that because the neutral is bonded in the generator if you do not have some kind of disconnecting means for the main panel neutral. The gfci will trip because of the closed loop. You will need a neutral switch kit or 3 pole transfer switch.

I wish this was my issue as this would be a easy fix.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
So you have a ideal of how this gfci might be working in the unit itself. I have read that because the neutral is bonded in the generator if you do not have some kind of disconnecting means for the main panel neutral. The gfci will trip because of the closed loop. You will need a neutral switch kit or 3 pole transfer switch.

I wish this was my issue as this would be a easy fix.

You do not need to switch the neutral in this case as long as the separate system is completely separate. But if you connect your lighting system neutral to the building neutral you have created an extra ground/neutral bond affecting your separate system.

Your EGC and the building EGC will be connected. Your neutral and the building neutral must not be.
Or you can connect your neutral to building neutral and remove the bond at the generator.
 

NjWireMan

Member
Location
New Jersey
Right next to my generstor seperste system at both locations is a 480 to 120/208 system. 480 panel to transformee 120 panel. The 120 panel has the neutral and ground bonded together. When I say I am connected to steel, i have split bolted my ground from my system to the ground wire coming from the transformer to steel and both locations.
 

NjWireMan

Member
Location
New Jersey
I used mc so even if i am not using the steel as a ground i think i still am because the mc wire is ran along emt and steel joist. I can only assume this will create a ground back to my panel.
 

GoldDigger

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Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Right next to my generstor seperste system at both locations is a 480 to 120/208 system. 480 panel to transformee 120 panel. The 120 panel has the neutral and ground bonded together. When I say I am connected to steel, i have split bolted my ground from my system to the ground wire coming from the transformer to steel and both locations.
There may be part of your problem. But I still do not understand clearly.
From your first post:
Connection = Generator 50 amp outlet to cord that enters a outlet that feeds a Subpanel with 50 amp breaker inside. Neutral and ground Not bonded.
It is correct that your subpanel does not have a ground/neutral bond.
And it is correct that the 208Y/120 side of your normal building wiring has a ground/neutral bond at the panel since that transformer is creating a separately derived system.
So far, so good.
You also said that this lighting system is ONLY powered from the generator and so is only powered when the generator is running.
Also good to this point.
Now comes the potential explanation for your symptoms:
Did you connect the separate system neutral to the 208Y/120 neutral even though they there are no loads in common between the two panels? If so, that is your problem since you are picking up that ground/neutral bond for your system too.
If the two sets of neutrals are completely isolated, we are back at something mysterious involving capacitive coupling.

What happens when you connect an incandescent light (trouble light) or heater at the separate panel?(i.e. in place of the troffers)?

When you connected the fluorescent locally at the generator was the connection still in place from the generator to the separate panel even though you fed the fluorescent directly from one of the generator receptacles?
 

NjWireMan

Member
Location
New Jersey
I did not connect to the other systems neutral. I took my systems ground and connected to the groind wire that is going from the transformer to a steel beam.

I was also saying that whether i connect a ground wire from my system to the ground wire of the transformer the connection will always be there any way because of my MC cable running along the other sytems conduit, sttel joist/beams??

Can there be current that is coming from that transformer??
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
I did not connect to the other systems neutral. I took my systems ground and connected to the groind wire that is going from the transformer to a steel beam.

I was also saying that whether i connect a ground wire from my system to the ground wire of the transformer the connection will always be there any way because of my MC cable running along the other sytems conduit, sttel joist/beams??

Can there be current that is coming from that transformer??
That should not be a problem. Current flowing through the generator EGC to the generator ground rod or building steel should not be problem either. As long as current going out the generator hot lead(s) to your separate panel has no way to get back to the generator except through the neutral.
So it seems to come down at last to the fact that the fluorescent fixtures have enough leakage current from 120 to ground that they are tripping the EGC.
1. Overly sensitive breaker GFCI. The number of fluorescents that you can put on a normal 15 or 20A lighting circuit should not be enough to trip a properly functioning GFCI.
2. Those fluorescents may have more leakage than normal?
3. There may be something about the generator waveform that is causing more leakage current to flow.

With no other connections to the generator plug one fluorescent into the receptacle through a cheater box that lets you measure the current in the EGC. Or plug the fluorescent into a normal branch circuit GFCI protected branch circuit or into a GFCI receptacle and see what happens.
 
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