Panel GFCI tripping with generator

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  #1  
Old 09-17-04, 12:31 PM
logistico123
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Panel GFCI tripping with generator

Had a gen-tran transfer switch professionally installed in the garage next to the service panel last year. No problems at first. Yesterday, did a generator test and 3 of the breakers tripped in the panel when I switched from line to gen. All three were GFCI breakers. Had no problems with the other breakers. Any ideas? Thanks
 
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  #2  
Old 09-17-04, 12:32 PM
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What happened when you reset the GFCI breakers?
 
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Old 09-17-04, 03:08 PM
logistico123
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They immediately tripped again before I even took my finger off of em. p
 
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Old 09-17-04, 07:39 PM
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The GFCI breakers are measuring to see the same amount of current leaving the hot conductor and returning on the neutral conductor (grounded conductor). If they do not trip when connected to the regular utility power, then they shouldn't trip when connected to the generator, as long and the load sees the same type of source of power.
Make sure no wiring within the panel was changed since the last time it tested ok. The breaker may have had wiring changes, making it think there is a fault.
It is also a good reason to take careful voltage and current measurements on the generator at the transfer panel, to insure the gen is not emitting (and the loads are not drawing) a significant amount of harmonics or poor power quality, and that the voltage is stable.
 
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Old 09-17-04, 09:36 PM
resqcapt19
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I'll bet the generator has the neutral bonded to the equipment grounding condutor and unless you are using a transfer switch that switches the neutral as well as the hots, you can expect that GFCI breakers will trip. The use of a generator with a neutral to grounding bond and a two pole transfer switch is also a violation of the National Elctrical Code.
Don
 
  #6  
Old 09-18-04, 05:03 AM
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I think Don has it. The unbalanced system neutral current attempts to return to its source through the n-g bond at the utility the the n-g bond at the gen. Since you are not switching the neutral within your transfer arrangement, the n-g bond at the gen needs to be open.

Out of curiosity, does this happen when you are on utility power and the gen is still connected in the same fashion to the transfer panel?
 
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Old 09-18-04, 08:49 AM
logistico123
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No, with the gen running and the power supply cord plugged into transfer box, all switches set to line, the gfci breakers will not trip. They only trip when changed to gen. Now, if possible, dummy this down a little and tell me how I can maybe fix the problem. I have some knowledge of the innards and workings of the main panel. I appreciate your help. p
 
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Old 09-18-04, 11:04 AM
logistico123
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I have a four pole manual transfer switch--interlocking 30 amp 240 volt.----Also, could the problem be from the gen not being grounded properly outside? thx p
 
  #9  
Old 09-18-04, 06:33 PM
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Does the four pole switch, switch both hots and the neutral with one pole left unused?
 
  #10  
Old 09-21-04, 11:18 AM
logistico123
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The gen switch has a red wire and a black wire for each breaker --one to the breaker and one to the house circuit. There is only one green wire and one white wire left over after all of the wires have been bonded together. The green wire is connected to the ground post in the panel and the white wire to the neutral post. I pulled the panel cover off and it looks exactly like the instruction manual diagram. thx. p
 
  #11  
Old 09-21-04, 04:28 PM
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You cannot use GFI breakers with a Gen-Tran panel. At all.
The breaker monitors the imbalance between line and neutral. With the neutral hooked up to the breaker and the line coming from the generator you have nothing but imbalance, especially since you have no line voltage at the breaker input.
Fact is even if the breakers trip you still have power from the generator to the circuit (unless the panel is wired wrong). The other problem is you have NO GFI protection while running off the generator.
 
  #12  
Old 09-21-04, 06:20 PM
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You know, I saw in the first post you stated gen-trans panel, but it didn't register. If I understand the gen-tran product, it only transfers the hot conductor from the utility side to the gen source. The neutral remains unswitched.
I don't understand why you mention a four pole switch, unless it is an odd gen-tran panel that is really a manual transfer switch that transfers four conductors from one source to the other. I doubt it, that's why I asked for clarification in the earlier post.
Is the GFCI a three position breaker that you bought with the gen-tran panel? If so, and the neutral from the gen is not electrically isolated from the neutral of the utility, then back to Don's original comment which I agree, you need to unconnect the neutral to ground connection within your generator, as it is not a separately derived source.
Sometimes this connection is within the box that the gen mounted receptacle is in.
 
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Old 09-23-04, 04:38 PM
logistico123
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Forget what I said about the four pole switch.--(brain spasm). The GFCI breakers are in the main service panel and control three different areas of the house. The gen is wired to these breakers just like the non gfci breakers in the panel. I guess the only reason they used gfci breakers in these areas is because there is a bathroom and kitchen associated with them--along with non "wet"areas. (example: one of the gfci circuits controls the sunroom which does not need gfci but it also controls the bathroom next to it) The bathrooms and kitchen also have gfci outlets. Is it overkill to have both gfci breakers and gfci outlets and can I replace the gfci breakers for regular breakers and solve the problem and still be safe.? Also please go over again the part about disconnecting something in the outlet on my gen. Thx p
 
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Old 09-23-04, 07:02 PM
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I'm not following. Is the GFCI breaker in the gen-trans panel or in the main panel?
Since the gen is serving a wired premises, and not things plugged directly into the gen itself, and the transfer only transfers the hot conductor, not the neutrals, then you need to disconnect the neutral and ground connection in the gen. Every gen manuf does it in a different location, you need to look at your owners manual or call the manuf.
 
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Old 09-26-04, 11:08 AM
logistico123
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The gfci is in the main service panel, not the gen-tran panel. As far as I can tell, there are no gfci breakers on the gen tran panel. p
 
  #16  
Old 09-26-04, 07:33 PM
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you will need to post the the manufacturer and model number of the "gen-trans panel" you have. The model I'm familiar with does not feed power to the main panel, but only to those special breakers in the gen-trans panel.
http://www.gen-tran.com/Merchant2/me...egory_Code=MTS
 
  #17  
Old 09-27-04, 08:12 AM
logistico123
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Gen-Tran model 302110. There are installation instructions and diagram available from the web site by pdf file. This model is no longer sold but the info is still there. https://www.gen-tran.com/assets/pdfs/oldinstall.pdf Thanks a bunch. p
 
  #18  
Old 09-27-04, 08:41 AM
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Ok, you will have to find the wiring diagram of your generator, from the manuf. Someplace in the receptacle wiring, they have connected the neutral and ground of that receptacle circuit. This gen neutral to ground connection needs to be disconnected to eliminate the additional path of travel for return current for the branch circuit, partially through the neutral at the main service panel (where the GFCI is mounted and should see all the neutral current) and the neutral to ground connection at the generator. It should only go back to the service panel.
 
  #19  
Old 09-27-04, 05:36 PM
logistico123
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Disconnect the wires and do what with them? Do I leave them loose, cap them off or bond to something else. I have been reading some other literature and I am beginning to understand what is happening. HandyRon, you are the man. I appreciate your assistance greatly.
 
  #20  
Old 09-27-04, 05:59 PM
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Depending on the way the neutral and ground are interconnected in the gen, you would safeoff (or cap or tape off) the neutral. From the few that I've seen, it is a wire that is just disconnected from both ends and the terminal screws remain. The one that comes to mind had the neutral and ground connection on the gen mounted receptacle itself connected with a 4" peice of #12.
As a side note, my theory leads me to think that if the generator is pugged into the gen-trans panel, and not running, where the GFCI circuit gets its power from the utility, the GFCI should trip too. But I know further up the thread you said it didn't, so I'm curious ....
 
  #21  
Old 09-28-04, 06:02 AM
logistico123
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That's right, they do not trip with the gen plugged in and running or not running.---as long as their breaker is in the line position. I guess they are completely isolated from the gen at that point. Ya have to go through the off position to reach line or gen (i'm sure you know that), just thinking out loud, so there are no pathways leading to the gen at that point. I was hoping to have this mess figured out before Hurr. Jeanne came calling but luckily all I got was wet. (I live in NC.) p
 
  #22  
Old 09-28-04, 08:38 AM
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Question:

When you turn on the generator, and then switch the problem circuits over to generator power, the GFCI breakers trip...but have you ever gone into the house at this point to check the power in the areas fed by these GFCI breakers?

If I understand the transfer switch manual correctly, this particular device is actually _several_ transfer switches all in the same enclosure. Each of these small 15A transfer switches gets connected to an _individual_ circuit in your main panel. This connection is made downstream of the main panel circuit breaker for that circuit. If your transfer switch is installed as the manual describes, then when a particular circuit is in generator mode, the state of the circuit breaker in the main panel is irrelevant; power still goes to the circuit.

Now, when this is happening, current is going from the generator into the circuit, then returning via the neutral conductor to the GFCI breaker. The GFCI breaker is seeing return current, but no supply current, and is of course tripping. Speedy Petey described this. But unless your GFCIs are opening the neutral as well as the supply, you should still see power going to your circuits.

I don't think that the GFCI tripping is a symptom of neutral/ground bonding issues (though you may have those as well; simply no evidence)

-Jon
 
  #23  
Old 09-28-04, 07:17 PM
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I've been putting more thought in this. In this installation, the circuits do not get GFCI protection when the gen tran switch is in the Gen position for that circuit. It is interesting to see that the GFCI breaker that is not even in the circuit at the time the gen trans is in the Gen position would trip.
I would begin by making the installation code compliant first, and it may take care of the problem. Find the gen's neutral to ground connection and remove it, as mentioned in the earlier post.
 
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Old 09-29-04, 05:52 AM
logistico123
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I will double check to see if those areas are getting power with the gfci breaker tripped. I follow what you are saying. Now, those areas that have gfci breakers also have gfci outlets which should offer gfci protection. I have asked several friends and none have gfci breakers in their main panel. I suspect that is overkill.?
 
  #25  
Old 09-29-04, 06:27 AM
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If you have GFCI receptacles in the locations, and you test it monthly like we all should, then the breaker is overkill.
The breaker trips the same as an outlet.
 
  #26  
Old 10-02-04, 08:42 AM
logistico123
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Well, I looked at the receptacle wiring on the gen. Oh boy. I used a voltmeter and isolated the neutral and grounds but their are many interconnections between the 240 outlet, the 4 120 outlets and the gen breakers. I have no idea which one to disconnect.

For Winnie, yes the rooms are powered even if the gfci breakers are tripped.

Everything works fine but I still want to be in code. thx. p
 
  #27  
Old 10-02-04, 09:09 AM
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Reviewing the above, I believe that it is very likely that you actually do have a code compliant installation.

The _potential_ problem is that neutral and ground are bonded both in the generator and in your main panel. You are supposed to have only one single bond.

There are almost certainly no ground to neutral interconnections in the transfer switch. The only question would be if you had neutral and ground bonded _in the generator_. If you have isolated these two, then you are golden.

-Jon
 
  #28  
Old 10-02-04, 01:10 PM
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You will find many interconnections between the 120V receptacles and the 240V receptacle. You are only looking for the single interconnection between the neutral and ground. There is generally only one neutral to ground interconnection in the generator.
 
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