Question for the experts about generators

This really has nothing to do with home inspection so I hope the mods don’t shut me down, but I had a passing thought today about generators and I was wondering if those who hold the knowledge here can answer me…

Portable generators have no means of getting a reference to ground for providing ground at the attached receptical…nothing I can assume anyway, right? Thus bonding it to neutral (or the frame/etc) could acutally create a situation of voltage relative to ground, right? So, do they get around this by NOT attaching anything to the ground and using a GFCI?

How IS the ground handled on portable generators?



The frame of the Generator takes the place of the " Grounding Electrode " in the case of the portable units. Now if you are not able to MEET that requirement of the frame to earth so to speak…then you must drive a ground rod per say…most portable units sit on the ground and create this bond.

The GFCI’s play an important role in the DEFENSE against shock as well…and we all know how GFCI’s work right…:wink:

The combination of these factors make it safe as a portable…Once the Generator is installed on a pad or become permanent or used in a trasfer setup…the RULES change and the good old NEC takes over.

**NOTE: NEVER plug the generator into a wall outlet. This practice, known as backfeeding, can cause an electrocution risk to utility workers and others served by the same utility transformer. **

Since we know that everyone does plug their generator into outlets it is a good idea to also mention that it is very necessary to turn off the main circuit breaker when doing this. This can make it difficult to know when the power is restored but should be done.

In my area transfer switch is required but most often they are simply back fed with the main breaker off. The back feed connects to the ground to the regular ground of the permant equipment.

Paul A

You sort of started another thread about back feeding. Good Florida subject right as storm season is starting. In the telecom industry plus some others back feeding is done to help the power co out during peak load and also to properly load test large generators. With solar and wind generators back feeding in also done. Yes there are electronic safe guards but it is done.

With a home during a long term power outage by back feeding a stove or dryer outlet and opening up the main disconnect, might be safer that running extension cords all over the place.

Yes, the safety issue of the “male hot” plug does exist. I have never tried it but if the main disconnect were to remain closed I would think that a small generator not designed for load sharing would be overloaded and would trip off line on its own.

Yes improper back feeding is WRONG but other than the “male hot” issue all should work ok.

Your thoughts sir


I have two generators both portable. One has a ground lug on the frame while the other generator does not. I do not have a transfer switch but do have a double pole throw switch which disconnects the breaker panel from the main 200 amp panel. The generator feeds directly into the breaker panel but one must ensure the main throw is disconnected before firing up the generator.

I SURE hope everyone does not do this…it is illegal to do so !

Gosh… what have I started? lol

The only reason that I asked is because I saw a guy on the bus with a generator and I noticed it had some grounded recepticals and I got to thinking about how that ground works.

lol…You did not start anything fella…lol…Just everyone making comments is all…anyway if it is ON a bus lets say…and it is NOT in contact with the earth…it would NEED a grounding source…

Now they may be using the GFCI as the protection which will work…but in truth it is not a proper installation method…but again I could be wrong…generators are NOT my defined area of Expert Testimony…lol

Paul A

The question of legal got me thinking esp for my self. While I have no problem doing something myself, I do not want my wife to do certain thing (electrical when I am not here) also don’t like upsetting the power company so a little internet searching came up with these boys. Sort of makes things legal and safe for not too much $$

Let me log out and get the link

If you saw this on an inspection would you OK it??

Generator Interlock Technologies
3107 Lanvale Ave
Richmond, Virginia 23230

The reason for disconnecting the main either by a transfer switch or manual is so that the generator isn’t feeding juice to the poor line man working up the pole or down the street somewhere.


Based on my CURRENT knowledge of the NEC I would not allow it, however ever AHJ may have a different opinion of it. While the product may be UL listed it most certainly does not mean it has been reviewed by the electrical community.

I certainly don't want to be the one to REVIEW

However let me say that I am not an expert of “Generators” per say…just the concept and theory of operation…but it sure seems to me that the concept of “Automatic Switch Transfer” was to take the HUMAN error factor out of the equation…in that the system automatically shuts down at detection and well avoids the MANUAL need to do so.

I can't tell you in regards to this new device....I will ask around to my buddies who would have much more info on it that I would....the Illegal aspect of the direct PLUG is as someone stated the effects it can have on the POCO people upon re-energizing the system.

Very interesting in that all this device seems to be is a higher cost lockout setup....which in my opinion is not the correct method to use.....but again we are all evolving.

I am not saying anything here…The difference in perception is something wrong or simply unsafe…not what ifs or what could be’s…but what the average consumer MAY do…

Now you may not…and I agree…BUT what a wife or child or brother MAY do is another story so the concept of the back feeding in THIS nature is incorrect…but FAR be it for ME to say what is right or wrong…I am only giving information.

The concern to ANY AHJ is this quote" One must ensure the main throw is disconnected before firing up the generator."…this is where the AHJ never assumes anyone is aware of this need…:slight_smile:

Joe T…is you are lurking…I would LOVE your take on this as well…maybe I am JUST to cautious on this…another SET of eyes always helps but wiring and doing a Generator incorrectly can be very hazardous…

Any Thoughts ?

Truly portable generators like you would use on a job site or camping do not have a grounded connection. They are isolated systems with no fault path to ground. That actually makes them safer since the only way you can get hurt is to get between line and line.
Once you connect them to a grounded system they become a separately derived source and you have rules anout how the ground is handled, probably more complex than we want to discuss here but the intent is we won’t have parallel ground paths.

As for the transfer equipment it protects the generator from grid loads as well as the neighbor who may be screwing with his “dead” service too. Linemen will not be affected if they are following their own rules. They assume everything is hot if they haven’t grounded it. When you think of the inductive coupling they deal with every day it is just a habit for them to assume this. Again this will be seen as a dead short to your generator, as would the grid itself in most cases.
I will say if they traced power back to your drop the effect would probably be a drop cut loose from the pole and left dangling until every other ticket on the truck was finished.