portable generator hookup questions

[Coppersmith]

My son-in-law would like to use a portable generator to power his house in case of outage. Three questions:

1) The neutral from the generator will not be switched. (Backfed breaker with interlock on main). Is there any danger if the generator neutral is connected while using utility power?

2) Should he tie the generator frame to the same ground rod as the service?

3) The generator inlet will be about 40 feet from the backfed breaker in the panel. Does there need to be a breaker closer to the generator inlet to protect the cable like there would be for a service entrance cable?

 

[infinity]

1) No.
2) No, it is not a separately derived system.
3) No, the output breaker in the generator will protect those conductors.

When set up like this the generator neutral to ground bond must be lifted and the inlet and panel require signage.

 

[tom baker]

1) No.
2) No, it is not a separately derived system.
3) No, the output breaker in the generator will protect those conductors.

When set up like this the generator neutral to ground bond must be lifted and the inlet and panel require signage.

Inlet signage is in Art 702.7(C)
If you don't lift the neutral then generator GFCI will trip.
With the neutral lifted generator can't be used on jobsite

 

[Coppersmith]

1) No, it is not a separately derived system.

Inlet signage is in Art 702.7(C)

So am I correct that the below sign is the one I need? What's the definition of "floating neutral" here? Does that mean it's not grounded? How would the system be a bonded neutral? Does it matter which system I use?

WARNING:
FOR CONNECTION OF A NONSEPARATELY DERIVED
(FLOATING NEUTRAL) SYSTEM ONLY

 

[Coppersmith]

When set up like this the generator neutral to ground bond must be lifted and the inlet and panel require signage.

I just re-read your post and saw this. I see there are three and four wire generator inlets. I'm assuming the four wire have a separated ground and neutral that are bonded at generator. When the cord is removed from the inlet, this would break that bond, correct? What happens if the generator is left connected while under utility power? (I don't know if his generator uses a three or four wire outlet.)

 

[infinity]

If you're using a 30 amp setup most generators use a 4-wire cord set to a 4-wire inlet. This is a non-SDS so the neutral/EGC bond in the generator is removed. The signage required is as you've mentioned.

 

[tom baker]

Its not complicated but to understand this you need to understand SDS and non SDS generators
Here is a great video clip from Mike Holt on generator grounding
https://www.youtube.com/watch?v=M3lX4XtlYXk

 

[JFletcher]

I just re-read your post and saw this. I see there are three and four wire generator inlets. I'm assuming the four wire have a separated ground and neutral that are bonded at generator. When the cord is removed from the inlet, this would break that bond, correct? What happens if the generator is left connected while under utility power? (I don't know if his generator uses a three or four wire outlet.)

The interlock Kit only allows either the breaker that the generator is backfeeding or the main to be on, not both at the same time. The point of the interlock is twofold one so that you cannot parallel out of phase with the power company and blow up your generator (and/or loads)and two, you do not backfeed the grid while the generator is running. If the power company restores power while your generator is running, it is shut off by your main breaker and the power stops there, while you're generator breaker which is closed is feeding your panel and all your loads. You have to shut off the generator breaker before you can turn the main breaker back on. With a properly installed interlock and dead front, it is physically impossible for both Breakers to be on at the same time.

Eta: if his panel does not have a main breaker, I am not sure that you can install a generator Inlet perhaps an ATS, but not an MTS, don't know what code it violates but it would be extremely dangerous to manually transfer generator and Poco power without an interlock

 

[Coppersmith]

The interlock Kit only allows either the breaker that the generator is backfeeding or the main to be on, not both at the same time. The point of the interlock is twofold one so that you cannot parallel out of phase with the power company and blow up your generator (and/or loads)and two, you do not backfeed the grid while the generator is running. If the power company restores power while your generator is running, it is shut off by your main breaker and the power stops there, while you're generator breaker which is closed is feeding your panel and all your loads. You have to shut off the generator breaker before you can turn the main breaker back on. With a properly installed interlock and dead front, it is physically impossible for both Breakers to be on at the same time.

My concern was only that the generator neutral would remain connected when the breaker interlock was switched to the main.

Eta: if his panel does not have a main breaker, I am not sure that you can install a generator Inlet perhaps an ATS, but not an MTS, don't know what code it violates but it would be extremely dangerous to manually transfer generator and Poco power without an interlock

He has a convertible panel which currently does not have a main breaker. We will install one so we can use an interlock kit.

 

[infinity]

My concern was only that the generator neutral would remain connected when the breaker interlock was switched to the main.

I don't see that as a problem. The neutral is floating in the generator so it's not really doing anything.

 

[cuba_pete]

I don't see that as a problem. The neutral is floating in the generator so it's not really doing anything.

IF he lifts the bond at the generator.

The previous video mentioned at 10:00 explains the objectionable current if he does not: https://youtu.be/M3lX4XtlYXk?t=555

It's easier if he just gets a neutral switched ATS. Then he can unplug and use the generator other places without removing or replacing the bond in the generator as needed.

 

[infinity]

I don't know if I would call adding an ATS and a GES easier but it would make using the generator for offsite purposes more simple. I guess if you used it offsite quite often it would be a good choice. Mine has never left the shed in the 4 years since I bought it. :roll:

 

[cuba_pete]

I don't know if I would call adding an ATS and a GES easier but it would make using the generator for offsite purposes more simple. I guess if you used it offsite quite often it would be a good choice. Mine has never left the shed in the 4 years since I bought it. :roll:

It'd be nice if I had two.

I move mine around my "estate" of two acres every now and again.

 

[infinity]

It'd be nice if I had two.

I move mine around my "estate" of two acres every now and again.

Someone mentioned here that it would be nice if the generators came with a factory switch to select between a bonded neutral and a floating one. I like that idea, although it makes too much sense therefore it will never happen.

 

[Coppersmith]

It's easier if he just gets a neutral switched ATS.

He wants to do this job on the cheap. No ATS. We are using an MTS (panel breaker interlock kit). Beside nothing automatic is going to happen since the pull starter on the generator requires "pulling".