Help me understand grounding portable generators with a transfer switch

[PWMDMD]

This is solely for my own understanding - I'm not asking any of you to be a replacement for a qualified and licensed electrician who I'm going to call anyway no matter what is said here.

Currently, I have a Westinghouse 9000/7500 generator connected to a Connecticut #6-7500 EmerGen Switch manual transfer switch. When it was first installed I believe the electrician had to remove the bonded neutral neutral jumper that bonded the neutral to frame as the transfer switch keeps the neutral/ground intact and the generator can use the neutral/ground for the house. My recollection may not be accurate here and it may be the exact opposite. Looking at the owners manual for the Predator all it says is it needs a grounding rod. Some Youtube videos claim if the transfer switch maintains the neutral/ground to house it should not need its own grounding rod since it uses the houses neutral/ground.

I'm thinking of buying a Predator 9500 inverter which I believe has a bonded neutral to frame. Can anyone help me understand this a little better? If they he Predator should not have a bonded neutral is there a way to unbond the neutral - The Westinghouse manual discusses this procedure but I did not see anything about it in the Predator's manual.

Again, I know local codes can vary and no I'm not about to go and burn my house down or kill myself based on asking a question on BITOG - I will call my electrician out just to take a look - this is just for my conceptual knowledge.

 

[wpod]

Here is a start.

 

[PWMDMD]

Here is a start.

That video covers portable generators used with electrical cords in the field and portable generators used on vehicles - neither of which is applicable to a portable generator used with a transfer switch to supply electricity to a house.

 

[eljefino]

I have a "sidecar" six-circuit Gentran transfer switch. It takes the incoming neutral and ground and sends them off to the main box, where they are bonded together. It only switches the hots.

Generally speaking, you only want neutral and ground bonded at one spot, and the main box is that location. But, if you have an outbuilding with subpanel, it should have its own ground rod and you should *not* run a ground between sub and main panel.

So to me that raises more questions than answers. If the generator faults its own hot wire to chassis, you wouldn't want to touch that! So its own grounding rod makes sense.

As a matter of practicality, I ground my generator through its cord through the sidecar box to the main breaker panel. Wrong? Probably. But it's less stuff to hook up in the dark.

 

[Pablo]

We just went through 4 daily outages. ON -off - on OFF (longest was about 4 hours off) The Predator 9500 did fine supporting everything I asked it to do. Well pump, septic pump, two fridges and a freezer. Lights. Etc

The starter battery....hmm maybe gone already. We will see. Used my tiny TackLife jump starter. But battery seems OK today. Hope!!

Anyway: I never did a separate ground for it. 4 wire cord. 240V. Still kicking. It's grounded at the panel which just opposite wall where the generator plug is (I have a positive lock out manual transfer switch)

 

[football]

If you are hooking gen up to the house via a 4 wire cord, in most cases you have to convert your generator to a floating neutral. Read the manual on how to do this. Usually the green and white wire will be connected somewhere in the generator and you have to disconnect them.

As for grounding your generator via a grounding rod, I watched a very intriguing video on that and the electrician said it was actually dangerous and made the generator far more dangerous. He had a demonstration by creating a fault and proved this out on video. I dont know the why or the science behind that… but he said that the ground wire in the 4 prong cord, that was thus hooked to your houses grounding rod, was sufficient. When you attach your generator to your home via the 4 prong cord, you are grounding it appropriately.

 

[brianl703]

Generally speaking, you only want neutral and ground bonded at one spot, and the main box is that location. But, if you have an outbuilding with subpanel, it should have its own ground rod and you should *not* run a ground between sub and main panel.

]You used to be allowed to not run a ground between a house and an outbuilding ONLY IF there were no parallel metallic paths between the two buildings (like a water pipe). You were never prohibited from running a ground; only not required to run one.

The rule has since changed, according to what I read elsewhere. Now, for a new installation, you must run a ground AND a neutral to an outbuilding, regardless of the existence of a parallel metallic path or not.

See https://iaeimagazine.org/2004/january2004/grounding-and-bonding-methods-for-outbuildings/

(note that this is from 2004, prior to the rule change eliminating the exception of the requirement of a grounding conductor between the buildings if no parallel paths exist).

 

[dlundblad]

I would not drive a separate ground rod for a portable generator. You aren’t even suppose to do it on a home standby. It simply needs to be connected to the building’s grounding system.

 

[dlundblad]

]You used to be allowed to not run a ground between a house and an outbuilding ONLY IF there were no parallel metallic paths between the two buildings (like a water pipe). You were never prohibited from running a ground; only not required to run one.

The rule has since changed, according to what I read elsewhere. Now, for a new installation, you must run a ground AND a neutral to an outbuilding, regardless of the existence of a parallel metallic path or not.

See https://iaeimagazine.org/2004/january2004/grounding-and-bonding-methods-for-outbuildings/

(note that this is from 2004, prior to the rule change eliminating the exception of the requirement of a grounding conductor between the buildings if no parallel paths exist).

I’ve never heard of the no “parallel metallic path” rule, but it makes sense from a bonding perspective.

It does make sense to have a grounding conductor with the feeders and the neutral, but then again, the utility can get away with not doing it… they are just buried a little deeper so any sort of damage/shorts should be unlikely.

 

[LouC]

When I had my transfer switch installed (Gen Tran 7500 watt unit) I asked about this and the tech guy from Briggs & Stratton actually explained how to to it. Very easy actually. I used it several times over the past 11 years I have it including 14 days during Hurricane Sandy. One thing I would do is if your gen set had an adjustable voltage regulator get a meter that measures hertz & AC voltage. Both of mine were off now they’re right on the money. Hertz is adjusted via idle speed voltage vis adjusted on the adjustable voltage regulator via a small screw.
If the gen set has a bonded neutral and your transfer switch switches the hots you have to unbond it from what I read.