GFCI on generator tripping; home backup

80421 Views 21 Replies 9 Participants Last post by micromind, Jul 3, 2009

MrNeutron

Discussion Starter · Jul 1, 2009

I just had an electrician wire my house with an interlock kit so that I can use my new 6600 watt generator for power backup. Unfortunately, the GFCI in the generator's panel trips as soon as I attach the cable to the house. My electrician says that there is absoultely nothing wrong with the wiring in my house and that the problem is with the GFCI. He says that most generators with built in GFCI's won't work for power backup. He also says that there is no way he'll touch the generator to disable the GFCI for liability reasons. How do I use this brand new $2,200 generator to power my house if the GFCI keeps tripping and can't be disabled? Thanks in advance for the advice!

1 - 20 of 22 Posts

Yoyizit

· #2 · Jul 1, 2009 (Edited)

http://159.105.83.167/Portals/0/WP Safety/Portable Generators qnd OSHA Construction Standards22.pdf

?

BTW, 900' of perfectly good Romex will probably have enough inter-conductor capacitance to give you 4 mA of reactive leakage current and so would validly trip a GFCI.
If it is the Romex the fix would be to have the gen. only run sections or only specific appliances/fixtures in your house.
I suppose you could check this by running the generator with almost all breakers off in your house. Turn them on one by one until you trip the GFCI. If the thing trips with all breakers off the problem almost certainly has to be elsewhere.

You could also check the leakage current of the wiring in your house. Put a 7-1/2w incand. lamp in series with the ground wire that serves the cable downstream of your GFCI. If the voltage across the bulb reads from 0.6 vac to up to 120vac you've found your leakage path to ground. A normal reading would be less than 15 mVac. Disconnect chunks of the cable or appliances until the leakage current goes away.

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kbsparky

· #3 · Jul 1, 2009

The problem of GFCI tripping is that the service panel that you are backfeeding already has its neutral conductor bonded to the grounding conductors.

If these conductors are separately monitored by an integral GFCI device in the generator, it will trip out as soon as you plug it in, even with the interlocking breakers switched off.

Some generators have instructions on how to configure when used as a stand-by power source for a home.

What brand and model number are you dealing with here?

Speedy Petey

· #4 · Jul 1, 2009

Are you saying the 120v GFI is tripping?
If you are trying to connect your panel to the 120v 20A receptacle on a generator this is a VERY flawed plan. You should be using the 120/240v receptacle on your generator which is not GFI protected.
Your electrician should have know this.

micromind

· #5 · Jul 1, 2009

As stated above, almost certainly the generator neutral is bonded to the ground. So is the house. You'll need to remove the bond jumper in the generator.

Also as stated above, it'd be a huge waste of generator capacity to use a 120 volt receptacle to power the house. You can only get 2400 watts through a 20 amp 120 volt receptacle.

Some generators have two pole GFIs though, if the cord that plugs into the generator has 4 prongs on it, then it'll deliver full power to the house. But you'll still need to remove the bonding jumper.

In no case remove the bonding jumper at the house panel. If you do, you'll have no ground-fault protection when on utility.

Rob

Scuba_Dave

· #6 · Jul 1, 2009

Yoyizit said:
http://159.105.83.167/Portals/0/WP Safety/Portable Generators qnd OSHA Construction Standards22.pdf

?

BTW, 900' of perfectly good Romex will probably have enough inter-conductor capacitance to give you 4 mA of reactive leakage current and so would validly trip a GFCI.

Did I miss something?
Where does it say the Gen is 450' away from the house?
That would be 3 houses away for me :laughing:

MrNeutron

Discussion Starter · #7 · Jul 2, 2009

Thanks everyone for the quick replies. The generator is a Wacker Neuson GPS6600A and I'm using the 12/240v receptacle.

I posted here because I wasn't hearing from the manufacturer. Wouldn't you know, they just replied tonight. Looks like bond or ground jumper is the issue. Below (in italics) is the reply I got from Wacker Neuson.

Thanks for the guidance. It looks like I'm on track now.

The neutral - ground jumper wire on the generator will have to be
removed to prevent the nuisance tripping of the GFCI.

Your house should already have its neutral bonded to ground so this
still meets requirements of the National Electric Code (NEC).

Your Wacker Neuson dealer can sell you a kit p/n 0164835 that contains
these instructions and stick-on labels that warn the generator now has a
floating neutral.

NOTE: If you ever disconnect the generator from the house and use it for
other purposes, you MUST re-connect the neutral - ground jumper on the
generator!

If you (or the next owner of the generator) do not intend to re-connect
the generator to the house again... then you may also remove the
floating neutral labels.

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Cow

· #8 · Jul 2, 2009

Exactly how many generators has this guy wired to not know there is a neutral-ground bond that needs to be removed in the generator. I just don't get it.:whistling2:

Yoyizit

· #9 · Jul 2, 2009 (Edited)

Scuba_Dave said:
Did I miss something?
Where does it say the Gen is 450' away from the house?
That would be 3 houses away for me :laughing:

Nah, I think the average house has more than 900' of Romex in it and all that distributed capacitance adds up.
I'm going to fire my ghostwriter!

To the OP: you know, there is an implied warranty of merchantability and an implied warranty of fitness. Your electrician must have known what your intention was in buying this generator. Your State's Attorney may persuade the guy to make this right.

micromind

· #10 · Jul 2, 2009

In my experience, very few electricians know about neutral bonding of generators. This includes small home-style generators all the way up to huge ones that would run half a city.

Neutral bonding is not all that difficult; in the end there can be exactly one. No more, no less.

With a generator, if the transfer switch doesn't transfer the neutral, the generator cannot be neutral bonded. If it does transfer the neutral (rare, but required in some cases, like hospitals), then it must have its neutral bonded.

Very few people, even electricians with lots of experience, and a multitude of electrical engineers, understand this.

Rob

AndrewF

· #11 · Jul 2, 2009

MrNeutron said:
. . . 6600 watt generator for power backup.. . . How do I use this brand new $2,200 generator to power my house. . .

Did you really spend $2200 on a gas 6600 watt generator? Wow, someone made a profit.

Speedy Petey

· #12 · Jul 2, 2009

AndrewF said:
Did you really spend $2200 on a gas 6600 watt generator? Wow, someone made a profit.

Maybe it's not a piece of crap. :whistling2:

kbsparky

· #13 · Jul 2, 2009

If its an 1800 RPM unit, worth every dime. :wink:

AndrewF

· #14 · Jul 2, 2009

kbsparky said:
If its an 1800 RPM unit, worth every dime. :wink:

True, I didnt check the specs and would agree. If it is a 3600 RPM...then no.

KeithM62948

· #15 · Jul 2, 2009

I think it's sweet of the manufacturer to sell you a 'part' that contains nothing but instructions & labels!

MrNeutron

Discussion Starter · #16 · Jul 2, 2009

Thanks for everyone's concern for my financial well being!

I actually found it on craigslist and paid $1200. The guy I bought it from paid $2200, or so he said but my research indicated he probably did. Apparently he was liquidating some assetts. The whole thing seemed sketchy but I checked the serial with the manufacturer and the seller's story checked out. I figured it was a good deal for a quality unit with a Honda motor.

I agree that the kit consisting only of labels is a bit ridiculous. Anyone want to sell me some duct tape and a sharpie? The manufacturer did send me the instructions electronically. So, I'm satisfied. It looks like a pretty easy job.

Thanks again for the feedback everyone!

Scuba_Dave

· #17 · Jul 2, 2009

Yoyizit said:
Nah, I think the average house has more than 900' of Romex in it and all that distributed capacitance adds up.
I'm going to fire my ghostwriter!

Ah, I see - learn something new every day

Yoyizit

· #18 · Jul 2, 2009

MrNeutron said:
The generator is a Wacker Neuson GPS6600A

While I have your attention, does 5.2 gals of gas in this generator give you 60 kwh? More? Less?

MrNeutron

Discussion Starter · #19 · Jul 2, 2009

Yoyizit said:
While I have your attention, does 5.2 gals of gas in this generator give you 60 kwh? More? Less?

Not Sure. Here are the specs. Maybe you can tell me.
http://products.wackerneuson.com/we...ay?storeId=10051&partNumber=0620386&langId=-1

Yoyizit

· #20 · Jul 2, 2009 (Edited)

MrNeutron said:
Not Sure. Here are the specs. Maybe you can tell me.
http://products.wackerneuson.com/we...ay?storeId=10051&partNumber=0620386&langId=-1

I couldn't log in.
At $2.50/gal for gasoline you'd be paying 21 cents per kwh. It's got to cost more than this. . .people in Hawaii pay this much for commercially generated power.

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