GFCI on 240V generator.

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  #1  
Old 03-23-13, 11:05 PM
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GFCI on 240V generator.

I've wired a generator to back feed the house. I can plug 120v cords in and they work fine. I've wired both 30A and 50A 240v four wire to the sub panal from the generator. Both trip the GFCI in the generator. With the plugs attached without the wires both stay on. I can't find anything going to ground. The breakers that back feed are off. The breaker from the main panal that feeds this sub is off. I tried the 50A first and when it failed I wired in the 30A. Could the generator GFCI be bad? I'm at a loss and it's snowing heavy wet stuff. The ground and neutral buss's are seperated with each going back to the main panal. Any and all help is welcomed.
 
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Old 03-23-13, 11:27 PM
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I've wired a generator to back feed the house.
Dangerous and illegal unless you are using a transfer switch or interlock. We will be glad to help as soon as you assure us this is being done in a safe manner.
 
  #3  
Old 03-24-13, 01:22 AM
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The problem is because of the existence of TWO neutral-to-equipment bonds; one in the generator and one in the Service panel. How to alleviate this condition will await confirmation that you are indeed using a legitimate means of connection.
 
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Old 03-24-13, 09:33 AM
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Thanks for the response to Furd and Ray. It was a long night with a few flickers but no complete outages here. This sub does have an interlock that won't allow main feed and back feed breakers to be on at the same time. With the 120v plugins on the generator I knew the frig would be all right.
 
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Old 03-24-13, 10:27 AM
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Just for the record you should not call what you are doing backfeeding. That raises red flags. I'm not an expert but someone should be along to help you soon. Furd though has already given you the basic information you need. There is probably a bonding wire between the neutral of one or more receptacles and the metal frame of the generator. See: http://www.doityourself.com/forum/el...neutral.html#b
 
  #6  
Old 03-24-13, 04:11 PM
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To get the whole picture, you currently have a generator that has a GFCI protected output, and that output is connected to a sub-panel that has an approved interlock device that absolutely precludes the possibility of feeding generator power back to the service panel that is connected to the utility, correct? This means that the ONLY loads served by the generator are the loads connected to the sub-panel. Is this also correct?

Do the instructions for your generator have anything to say about connecting the generator to a premises? Anything about transfer switches or transfer panels? Do you have a four-wire interconnect cable from the generator to the sub-panel, two "hot" leads, a neutral lead and an equipment grounding lead? How are these four wires (assuming they are present) connected to the sub-panel? How are the feeder conductors from the service panel connected to the sub-panel?
 
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Old 03-26-13, 04:32 PM
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Sorry it took so long to reply. Got busy after the storm. You are correct in the first paragraph. I purchased this Honda EB12D used with no manual or instructions. I've looked on line for wireing but have found nothing. I do have a 4 wire interconnect cable from gen. to sub.. Two "hot" lead are connected to the breaker in the sub. from the gen.. The neutral and ground go to their seperate buss bars (not connected). The service panel (with ground and neutral bonded together) feeds the sub with two "hot" leads attached to the sub main with its ground and neutral going to the seperate neutral and ground busses. Also what is the correct term instead of "backfeeding".
 
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Old 03-26-13, 04:41 PM
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In general, backup power should feed the main panel, not a subpanel.

The connection needs to be made in a manner that ensures that the standby power and the utility feed cannot both be connected at the same time, among other requirements. The means of connecting to the standby power must automatically disconnect the supplied loads from the utility feed.
 
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Old 03-26-13, 05:41 PM
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Also what is the correct term instead of "backfeeding".
Often when people come here they use the term backfeeding to mean using a suicide cord to connect to a dryer or stove receptacle. Just say feeding the generator and explain the method. Example: I am feeding my generator to my main panel which is equipped with an interlock.
 
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Old 03-27-13, 01:22 AM
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Just for a test, open (turn off) the circuit breaker in the service (main) panel feeding the sub-panel and then disconnect the incoming neutral lead (from the service panel) in the sub-panel and then try the generator. If it works okay then the second neutral-ground bond in the service panel is the problem.

The only legitimate way to alleviate this problem is to install a three-pole transfer switch between the incoming feeder from the service panel and switch the neutral along with the "hot" conductors between the service panel and the generator. The interlock will NOT work.

If the feeder to the sub-panel is 60 amperes or less this transfer switch will do the trick.
USA, Universal Changeover Switch|Manual Generator|3PDT Center OFF|Rotary Cam| RV Transfer Swith| Pedestal Power Supply | Boat Panel | Power Source| Utility | Line | Shore| Back-up Power| Solar Energy| Battery Charger| Rectifier | Transfer Switch|
(I have no connection to the linked company, never even bought anything from them. Other companies may have a similar switch.)
 
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Old 03-27-13, 11:27 AM
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Thank you Furd. I'll try this. My sub is on a 100 A breaker. Now to find out what a three pole transfer switch costs. Do I look for the same in a larger (100 A.) transfer switch. That is if this works. Please forgive the delays as I now go to the Library to use thier computers.
 
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Old 03-27-13, 11:33 AM
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Thanks Nash,Can I feed my "needed" circuits in the sub from the gen. while allowing the main service to remain on so when power comes back on line those loads will come on in the house? I'll know to transfer back to the service feed from the gen. feed this way.
 
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Old 03-27-13, 11:39 AM
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Thanks Ray. I'm trying to use this terminology now.
 
  #14  
Old 03-27-13, 03:03 PM
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IF your current set-up is as follows:

Utility power > service panel > feeder to sub-panel > sub-panel with interlock device selecting EITHER utility (from service panel) OR generator power to sub-panel circuits.

THEN yes, you may leave the service panel main circuit breaker in the on position and that way any circuit on the service panel will denote a return of utility power.


Do you NEED 100 amperes at the sub-panel under normal conditions? Finding a three-pole, double throw switch will not be all that difficult but you WILL pay handsomely for that switch, in the neighborhood of $1,000 or more. Here is a new switch on E-bay that is a 100 ampere model of the switch I use in my house.

Square D 82353 100 Amp Double Throw Safety Switch New Scratched | eBay

I bought mine, a 60 ampere model (used, but in very good condition) through E-bay several years ago for about $75.
 
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Old 03-27-13, 10:15 PM
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Can I feed my "needed" circuits in the sub from the gen. while allowing the main service to remain on so when power comes back on line those loads will come on in the house?
Yes, so long as the two power supplies cannot be connected at the same time. To add to what Furd said, this should be done with a 3-pole transfer switch that transfers the neutral along with the two hot feeds. Not with an interlock, which only switches the hot feeds.
 
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Old 03-28-13, 12:51 PM
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I think your right. A 60A would probably due. In the case of 800 dollars for a 100A I think it will have to do. But I may not need it because of what was found yesterday. I removed the neutral in the sub panel from the main. I then removed the ground in the main that feeds the sub panal. I found that there is continuity between that disconnected ground and the neutral buss in the sub panal. With the service neutral removed that should not happen right?
 
  #17  
Old 03-28-13, 01:02 PM
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As I told Furd there is a problem with my ground and neutral connections. I removed the neutral from the service panal in the sub panal. So all three (two hots and neutral) were detatched from the sub and the generator gfci still tripped. With all the breakers off in the sub panal I have continuity between the ground buss and neutral buss. I'm looking for that conection now. I hope that when it's found and fixed that a three pole disconnect won't be needed. With the neutral disconnected the gfci stayed closed. Is there an easy way to find this ground problem?
 
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Old 03-28-13, 01:38 PM
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in the sub panal I have continuity between the ground buss and neutral buss.
Was the bonding screw and/or strap removed from the neutral bar?

 
  #19  
Old 03-28-13, 02:20 PM
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As long as you have the neutral-equipment ground bond and the GFCI circuit breaker in the generator you will need the neutral switching transfer switch. I do not advocate any changes to the generator.

Is your sub-panel connected to the service panel with metallic conduit?
 
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