GFCI on generator

I was hoping to go to the cemetery today to finish a project, but it's raining a little, and I was going to use my generator. I have been using a GFCI on this generator for some time, but never tested it, not just pushing the test button, but putting a load from hot to ground. That test works well on a wall receptacle but it won't trip on the generator, and I am hesitant to go out and use it in a wet environment. I called a friend and he says to ground the generator and then try it, but that won't be very handy, as I haul it around in the cemetery in a small trailer behind a 4-wheeler. Any ideas? Thanks for looking!

Your generator is only safe if it is grounded to earth. Riding around in the trailer will insulate it from ground. I have seen OSHA inspectors write up fellows for not having a earth ground on a generator. John T. or B&D can tell you the why but I just know it is not safe without it having an earth ground. I have an old BIG screw driver with a wire to the ground terminal on my generator, I drive in the ground while using my generator now. You could do the same thing just use a longer ground wire and leave the generator in the trailer.

It will work as if the same current doesn't flow in the neutral leg as in the hot leg the GFCI will trip.

Russ from MN,

I've never tried this, but may someday. CFCI's are very sensitive to detecting current difference between the power and neutral so small, in the ma range, that we can't even feel it. To prove my point you can use a small power supply, connect a dc ma meter in series, completing the circuit hold the two wires with your right hand, which won't allow current to pass through your heart. Crank up the voltage slowly. You will notice what the threshold current is for you body to detect it. Usually it a few ma. At 10 ma is considered the threshold of pain. Trust me, you will let go before it get to 10 ma. 50-100 ma is considered deadly. Deadly means that it kills half the time. However I think the current needs to pass through your heart. I'm not about to find out. You can try it and post back if you live.

That said, do an experiment and see if putting a wire in either side of the CFCI on your generator will trip when you touch the other side to ground. Good idea if you use insulated gloves and wire. I'm guessing it won't because your generator is isolated form ground. If it did, then there is some current leaking through the insulation of your generator, or there is a little capacitive reaction at play.


I have no clue why OSHA wants you to ground a generator unless it has something to do with lightning. But then what do I know. This information is worth exactly what you are paying for it. geo.

The GFI detects a leak of 5 miliamps approximately. So if you take the neutral wire with a load on it and run it through the ground then it should trip since the difference of load on the hot is imbalanced with the load through the neutral. For an example, if you take an electrical meter and try to test for voltage in a GFCI from the hot to neutral it will show the voltage, however if you try to test from hot to ground it will trip the GFCI since the return path of the neutral is not being used.

Sorry gents, this is all too complex that there's no way I can explain it in a few sentences, especially to non electricians, but I will lay out a few facts and basics and NEC rules at least. DONT FEEL BAD if you still don't get it, it took me a lot of education and experience before it all sunk in lol

1) SOME small portable gensets use a FLOATING NEUTRAL while OTHER small portable gensets BOND NEUTRAL TO THE CASE/FRAME. That's because the way you use it in conjunction with what transfer switch (how many poles) you use makes a difference if the Neutral should be Floated or Bonded.

2) In the RV and camping and construction world when line device monitors are used that will trip out due to an open Neutral and the genny had a floating Neutral, the FIX is to wire up a plug that has Neutral tied to Ground which turns a Floating Neutral Genset over into one with a bonded Neutral, that way the monitor and protection devices will work.

3) CONTRARY TO LAY OPINION AND URBAN LEGENDS AND OLD WIVES TALES (unless NEC has changed) if you use a portable genset to operate cord and plug tools that are fed from onboard mounted receptacle THERE IS NO NEC NOR SAFETY REQUIREMENT OR REASON the genset be connected to a Grounding Electrode!!!!!!!!!!!!!! If your body gets exposed to 120 VAC Line to Neutral you die regardless if the genset was wired to a copper rod driven into mother earth. ALSO AND VERY IMPORTANT a non Neutral earth grounded genset (Floating) has ZERO NONE ZILCH NADA voltage potential with respect to mother earth, so if you touch the hot even barefooted on wet ground theres no shock but you still get shocked if you get across Line and Neutral. HOWEVER your home utility DOES HAVE NEUTRAL BONDED TO EARTH so if you touch a hot wire standing on bare ground you do get shocked.

4) If you think stickling a screwdriver down into the earth is going qualify as a proper NEC "Grounding Electrode" or serve the identical purpose or "protect you and save your life" compared to one or two 8 ft driven copper rods GOOD LUCK WITH THAT ONE LOL.

FIRST OF ALL the earth is a poor conductor subject to iron and minerals and salts and moisture etc etc
which is why the 'ground" is tested to see if a second rod is required in some jurisdictions
SECOND OF ALL the portable genset you think you are "grounding" (yeah right) may or may not even have a bonded Neutral, so how does it save your life by wiring the genset to a screwdriver into the earth?????????????????????????? What good do you think that does anyhow???

5) The way a GFCI works is to pass HOT and NEUTRAL through a Torroidal Coil. If ALLLLL the current flowing out the HOT is returned in the NEUTRAL no voltage is induced so no GFCI trip. HOWEVER if as little as 5 milliamps of current is NOT returned via the Neutral but your body or earth or ground or elsewhere voltage is induced so it trips to save your life. It takes something like 30 to 50 milliamps to fibrillate the heart so 5 ma is the GFCI trip current.

6) AS LONG AS the GFCI passes HOT and NEUTRAL through the torroid it will function
REGARDLESS IF THERES AN EARTH GROUND AT THE GENSET (or screwdriver in ground lol) OR NOT
REGARDLESS IF THERES A GROUNDING ELECTRODE CONDUCTOR (3rd wire in cord out to tool) OR NOT
(still works on a 2 wire plug)
HOWEVER the self test push button feature may not work

7) When using a portable genset if youre worried about being on wet earth YOURE BETTER OFF AND SAFER if theres NO VOLTAGE WITH RESPECT TO EARTH ON ANY OF THE WIRES!!!!!!!!!!!!!!!!!!! 1) It may NOT EVEN HAVE A BONDED NEUTRAL IN THE FIRST PLACE so driving a rod into earth is absolutely NO HELP. 2) If it has a bonded to earth Neutral and you're on wet ground and you touch a hot wire YOU GET SHOCKED. If you accidentally touch a wire and youre barefooted on wet ground WOULDNT YOU PREFER THERES NO VOLTAGE ON THAT WIRE RELATIVE TO EARTH GROUND??????????????????????

NUFF SAID, don't feel bad if you don't understand this, go get some books and read up and study because its still NOT rocket science (maybe to Billy Bob and Bubba lol) and makes sense once you understand the basics.

NOTE don?t get me wrong, there are situations THAT DO REQUIRE A GENSET BE BONDED AND GROUNDED (such as if its configured as a ?Separately Derived Source?) , I just addressed certain limited situations above not alllllllllllllllllllll READ THE NEC

John T Long retired electrical power distribution engineer and rusty so no warranty

NOTE just because some inspectors (many NOT engineers) MAY NOT understand this, that don't mean they still don't rule, you have to do as they say just like the grouchy lady at the license branch lol

Good afternoon JD, hope alls well your way, however with all due respect to help educate the good gents here, I must take issue with some of your post, READ MY DETAILED ANSWER ABOVE FOR MORE INFO

"Your generator is only safe if it is grounded to earth." NOTE YOUR WORD ONLY !!!!!!!!!!!!

NOT NECESSARILY TRUE IN ALL CASES, in fact, read my post above which explains why it can (depends on conditions and wiring) be safer IF ITS NOT GROUNDED. If your grandchild was barefooted on wet ground and touched a wire, WHY WOULD YOU INSIST THAT WIRE TO BE 120 VOLTS ABOVE EARTH GROUND POTENTIAL???????????????? Id rather it have ZERO volts relative to earth if I touched it (IE NO ground rod) BUT if the genest has a bonded Neutral and Neutral is bonded to mother earth THEN THE WIRE YOUR GRANDCHILD TOUCHES IS 120 VOLTS ABOVE GROUND YIKESSSSSSSSSSSSS Why wish that on him????

As a matter of fact, unless its changed, the NEC (they are smarter then me lol) indicates if you use a portable genset to power cord and plug connected tools that are fed from onboard mounted genset receptacles NO CONNECTION TO A GROUNDING ELECTRODE IS REQUIRED

"I have seen OSHA inspectors write up fellows for not having a earth ground on a generator"
THAT MAY WELL BE TRUE because 1) It can depend on if the Genset has a FLOATING or BONDED NEUTRAL (come both ways)
2) The inspector may just be WRONG (or that's his jurisdiction and which code and
which version was adopted)
3) BUT IT MAKES NO DIFFERENCE LOL ITS THEIR TURF DO AS THEY SAY

Also read my post about how good it does or what difference to stick a screwdriver in the ground DONT WANNA BET YOUR LIFE THAT WILL SAVE YO DO YOU??????????????

God Bless and keep safe now BUT AS ALWAYS DO AS YOU PLEASE NOTTTTTTTTTT WHAT I SUGGEST, ITS YOUR LIFE AND YOUR RISK. NOTE there are cases where a Grounding Electrode is indeed required, IT DEPENDS ON FLOATING OR BONDED AND OTHER FACTORS I CANT EXPLAIN IN DETAIL HERE

John T Too long retired Electrical Power Distribution Design Engineer so NO WARRANTY, DO AS YOU LIKE IS FINE BY ME OR DO AS YOUR INSPECTOR OR BILLY BOB OR YOUR BROTHER IN LAW SAYS and I will do as I have studied and learned......To each their own choice when it comes to life safety

Osha does not require portable generators to be grounded.

Well I am almost sorry to have answered. LOL

I just know that the generator I have has a copper ground terminal on the front of the panel that is wired directly to the case/motor/generator. The operators manuals says to ground that lug/terminal.

As for OSHA. At the local ethanol plant they had a full OSHA inspection while they were building it. The general contractor was my brother-in-law. He had several things they wrote him/his company up on. One of these things was the fact that his portable generators where not grounded. That "violation" was a $1750 one. The others dealt with inspections and dating on safety harnesses and such. The total fines where over $7500.

So I saw the written ticket and have heard him complain about it for the five years since then.

I do know he has been inspected since then and always has two copper ground rods driven in and hooked to the portable generators they use.

So maybe I am a Hill Billy dumb butt but I have always ground everything I could. I have not been shocked and really do not know anyone personally that has been seriously injured or killed by electrical grounding issues.

The major issue I would have with the original post is using a generator in wet rainy conditions. I would not do it with or without grounds. Using electric in wet conditions is just asking for trouble in my opinion. Makes no difference if it is line voltage or generated current.

Thanks for all the theories! I think I have a good understanding of how a GFCI works, and I think the reason it does not trip is because the generator has no connection to ground, and the ground terminal on the receptacle is not wired. This is a very old 1500 watt Power-Craft generator and probably built before there were ground prongs. I am pretty sure the receptacle has been replaced. The GFCI is a portable one with pigtail cords, designed for temporary use, and I have verified that it works properly. There is no ground lug on this generator like the newer ones. I put on rubber boots and gloves and went and got the job done, but I would feel more comfortable with GFCI protection.

I never ground mine. It's on a cart with rubber wheels. Used ohmmeter. Infinane resistance between from any wire to metall frame. Totally isolated.

Hey dont feel bad or be sorry JD, it takes time for even an electrical engineer to understand all this !!! When I was a farmer and mechanic type before I studied and practiced electrical engineering I likewise didn't get it all either..

SURE, if a genset is configured as a SEPARATE DERIVED SOURCE IT REQUIRES A GROUNDING ELECTRODE

But if NOT and youre tied to a utility the Neutral MUST BE FLOATING

SURE the NEC says if portable gensets feed plug and cord equipment via onboard receptacles NO GROUNDING IS REQUIRED

SURE a manual always states to ground it BECAUSE THEY HAVE TO BE COVERED if its wired as a separate derived source

SURE OSHA can levy fines if its NOT wired per the NEC

Hey if you are okay with a wire being 120 VAC above ground and let your barefoot grandchild touch on wet ground it that's too bad but I prefer a wire with ZERO volts above ground if I had to touch it

You are NOT A hill billy dumb butt as you called yourself in my opinion, I think youre pretty sharp and can NOT be expected to understand what takes years and years of study and experience and practice to understand

DO NOT FEEL BAD youre a good man and different professions have different expertise, just because youre not an electrician or tech or engineer DOES NOT MAKE YOU BAD OR DUMB

Take care and God Bless and keep you safe

John T

Youre sure welcome, keep safe now

John T

Fellow sparky Dr, you state "Osha does not require portable generators to be grounded"

NOR DOES THE NEC if it feeds cord and plug tools fed via onboard receptacles BUT TRY AND EXPLAIN THAT TO A NON PROFESSIONAL ELECTRICIAN, OR NON ENGINNER OR A LAY PERSON lol or Billy Bob and Bubba and they seem to take offense sometime ??????? WOW

John T Retired Electrical Engineer

You are correct George per the NEC IF it powers cord and plug tools via onboard receptacles but NOT if its configured as a Separate Derived Source (its like the Utility transformer there), unfortunately that's over the head of many non tech or non electricians or other non electrical trained lay persons. By Golly I think you have it though congratulations

John T

JohnT,
I went to the same Redneck Tech University that Bubba attended on the pass fail system. He flunked out because he didn't attend class. geo

JohnT,
Why are ants attracted to GFCI's? Tenant wanted an outside outlet, so I installed a GFCI inside the house, ran a wire out to the outlet outside. After replacing the GFCI two times because ants would short it out, I finally gave up, removed the outside outlet and got rid of the GFCI. No ant problem in house, so sign of ants anyplace. So what's the attraction? geo

You got me there George, my first thought was maybe the heat as it could possibly consume some small degree of energy as opposed to a non GFCI ??? Heck if I know

John T

John T.
I don't know either. Neighbor's AC wouldn't work. Ants were covering the compressor contactor . There was so many dead ants, the poles of the contactor wouldn't make connection. Keep in mind it summer, hot, ants all over the contactor, as if they liked the coil vibrating or something weird. Cool inside GFCI was covered with ants too . George