Grounding portable generators? Is it really necessary?

C

Chris B.

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Mar 16, 2003
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I just purchased my first generator, a big Predator 9500W inverter unit. Runs smooth and quiet. I noticed a big warning that says the generator must be grounded to a grounding rod deep in the ground. I'm having a licensed electrician who specializes in generators hook it up to my house. I plan on moving it to different spots all over my property and wont have a grounding rod in these areas. How necessary is grounding the generator? I know people who used these for camping and construction are most likely NOT grounding these out. I'll ask the electrician about this but we already talked about it a bunch and he is including a 100 ft. extension cord for it so he know I plan on moving it and he never mentioned the grounding rod thing....thanks for any advice!
 
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I’ve never understood it. If it is ungrounded and you touch any one wire… nothing happens. Tie to ground and if you touch the hot wire… bad things happen.

The tie to ground comes from years of using earth ground for getting power to us, plus for lightning dissipation. That is my understanding. For a temporary setup it doesn’t seem necessary.

(On an ungrounded generator the “ground” wire should be tied to neutral at the generator, and then you do have that safety still working. Any fault to chassis will still trip the breaker.)

In your setup though you will have a ground rod: the one at your house. bond to that appropriately and forget about it. That is why your electrician isn’t listing one, as it is already there.
 
...how to make the Predator 9500 into a floating neutral so you can connect it to home transfer switches and meet NEC requirements....
-
 
Very vague subject. If using a transfer switch, the only place the neutral and ground should be bonded are at the service entry panel (code) (no ground rod at the generator). But, best practice is to check your local electrical codes.
 
They may want it grounded so that the ground-fault circuit interrupter (GFCI) will work.
 
When you plug your big power cord into the house…. That power cord has 4 wires in it. Two hot wires, a neutral, and a ground wire that connects to your panels ground. So plugging in your power cord grounds the unit. You have to disconnect your neutral wire from your ground wire on your unit to make your generator a floating neutral system. I would say no you don’t need a ground rod pounded into the ground.

Don’t forget to run it out of fuel before storage. AND drain the carburetor using the bowl drain screw. There is still several teaspoons of fuel left in the carburetor if you use the fuel shutoff and run it until the engine dies. That way your engine carb remains clean and ready to start next time you need it.
 
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+1 for ka9mnx's post. Ask your electrician when he is there. Typically the ground goes through the electrical panel in the house.
 
You can read about "separately derived systems" and that will explain it.
(two separate sources attached to one dwelling).
 
if you do install a ground rod, you will need to run a 4 gauge wire seperately to bond the ground rod to the main panel rod, direct-diorect connection. Also if more than one rod, they are only supposed to be so many feet apart, depending on ground conductivity. You want the two rods at equal potental.
 
Vern_in_IL said:
if you do install a ground rod, you will need to run a 4 gauge wire seperately to bond the ground rod to the main panel rod, direct-diorect connection. Also if more than one rod, they are only supposed to be so many feet apart, depending on ground conductivity. You want the two rods at equal potental.
Click to expand...
Not understanding this one--the bonding makes them equipotential.
 
Ground rod issues happen in rocky terrain with a home's main ground. That's why they like 2 separate grounding points now.
4 wire 240v plugs where common code in trailers/mfgr. homes as frames where not properly grounded. Even though green ground and white neutral share a ground rod in many cases IE common bonding.
I'm not an electrician but 46 yrs. of repairing 240v appliances has taught me how things work, current flow and that the ''electrician'' is usually a helper and not the main license holder.
 
Vern_in_IL said:
if you do install a ground rod, you will need to run a 4 gauge wire seperately to bond the ground rod to the main panel rod, direct-diorect connection. Also if more than one rod, they are only supposed to be so many feet apart, depending on ground conductivity. You want the two rods at equal potental.
Click to expand...
Mostly true. Ground rods should be spaced double the distance of the ground rod length in most soils (8' ground rods spaced 16' apart). This is done to compensate for the impedance losses in the length of the bonding wire. Also, 6 gauge solid bare copper wire is acceptable per NEC.
 
So if my 240v cord from my generator to the panel has a ground and that ground runs to the panel, I should switch my Genset from neutral bonded to floating neutral?

What happens it I don't?
 
repairman54 said:
Ground rod issues happen in rocky terrain with a home's main ground. That's why they like 2 separate grounding points now.
Click to expand...

The current standard is an Ufer ground where they stub a piece of rebar from the foundation out and ground to it. Also known as a CEE, concrete encased electrode.

When using an Ufer ground no other ground is needed.

Any house built in the last few years will have an Ufer ground.
 
supton said:
I’ve never understood it. If it is ungrounded and you touch any one wire… nothing happens. Tie to ground and if you touch the hot wire… bad things happen.

The tie to ground comes from years of using earth ground for getting power to us, plus for lightning dissipation. That is my understanding. For a temporary setup it doesn’t seem necessary.

(On an ungrounded generator the “ground” wire should be tied to neutral at the generator, and then you do have that safety still working. Any fault to chassis will still trip the breaker.)

In your setup though you will have a ground rod: the one at your house. bond to that appropriately and forget about it. That is why your electrician isn’t listing one, as it is already there.
Click to expand...
I hope you don't come to my house
 
If plugged into your house system, then it would be grounded thru the circuit it's plugged into. Your house should have a double ground, that's normally code now. But, he's talking about moving it around the property and using it where, obviously, there is no electrical service, not and emergency type situation. So, yes, it would be better to have a good ground in that scenerio, but I gotta tell you there's a million of them out there with no ground whatsoever. I've done it with small generators a lot, I mean that's their use, but to cover their ars, they put that in there and we all know if you're working on a barn with no electric in it, you're not normally going to install a ground rod, but that's the safety you bargain with.
 
I believe that’s for the purpose of the GFCI receptacles on the machine. Going through a transfer switch all the neutrals and grounds will be bonded at the service panel. You can test using a receptacle tester it’ll read open ground/neutral if the machine isn’t bonded.

If you don’t already have the electrician install one of these and buy yourself #6 wire the length you desire to safely run the machine near the inlet box for the generator cord.
 
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