Generator - Neutral Question ~ 2 Generators

[San Jacinto]

Ok, I've searched to the ends of the Internet, reading various forums and I *think* I know the answer to this question, but I would like to put it out there to any professional electricians who may be reading.

First, here's my setup for my backup power to the house during power outages:

Main panel in house with manual safety interlock switch connected to a Reliance PB30 L14-30P power inlet on the outside wall for connection to the backup generator. The generator #1 used for powering the home is configured neutral floating, so neutral/ground is in the main panel. The only 220V circuits in the house are the Central AC and the submersible deep well pump. (Well pump and Air conditioning breakers are shut down when on generator power - no way my 9000 watt model could power a 5 ton unit and a well)

The well house is about 50 feet from the house/main panel and I have a second generator that I would prefer to dedicate to running the 1.5HP submersible. There is a sub panel installed in the well house that feeds the pump. The sub panel does not have a main breaker for the 4-wire feed coming from the main house. It is a properly configured panel, neutral and ground are NOT bonded here. In addition to the 220V for the well, there is one 110V outlet for the well UV disinfection light.

What I would like to do is replace the well house sub panel with something that has a main breaker I can shut down, and wire in an identical Reliance power inlet to connect generator #2. Note: generator #2 is also configured as neutral floating. As previously mentioned the well pump breaker in the main panel is OFF when running generator #1 on the main panel at the house. Running generator #2 at the well would still be energizing the 50 feet of wire from the well house BACK to the well breaker at the main panel. Doesn't seem right and I'm sure it violates code.

Now that we have that out of the way, here's the ultimate question - is there any reason two independent generators can (or cannot) share a common neutral/ground bond back in the main panel? If they cannot or should not, then I will need to wire up a second panel for the well that is completely isolated from the main when running the well generator. I think a full blown transfer switch is overkill for a well pump and single outlet. If it weren't for the single 110V circuit in the well shed, I wouldn't care about the neutral issue if I was just powering the 220V well pump.

Few things before anyone asks why two generators - I want the generator #2 as close as I can get it to well, which is why I'm not attempting to power the well from the main panel. I'm cutting out 50-feet of current loss. There a long thread about this in the forums.

 

[grsthegreat]

As long as both panels have true transfer switches, and each is powered by its OWN generator, there should be no issues.

I have a gen and transfer switch on my house and a separate setup on my shop 400 feet away. Had it for years. No issues.

The neutrals are not switched, and both services share the main 400 amp service. However, the teansfer switch kills the incomming power.

I am not paralleling the generators as each runs its own transfer switch.

My subpanels have neutrals and grounds separated.

It should also be noted, many housing tracks will power up to 6 houses from a common transformer and they each can have a generator. Never been an issue.

 

[Ken45101]

It sounds to me that you are NOT using a proper transfer switch, otherwise the 220 line from the pump house to the main panel would not be energized when running the well from the generator. If I am correct, that is an illegal and dangerous setup. Assuming the same setup on the main panel, mistake by you, or someone else could backfeed the service line and endanger someone off of your property.

Note, one of the dangers here is that there would be hot wires in the main box even when the mains are disconnected. This setup requires too much understanding of complex wiring to be safe.

But maybe I misunderstood your description.


Ken

 

[San Jacinto]

Ken45101,

If I wire to wire it "as is" yes,the hot 220V running back to the home would be energized, which I do obviously do NOT want.

I am planning on replacing the sub-panel in the well house with one that has a main breaker disconnect. I wasn't clear on that in my original post. That's what I get for attempting to convey a complicated description when I'm half asleep.

The question was can the generator #2 connected at the sub panel to share the common neutral/ground at the main panel when generator #1 at the main panel is also running. The post by grsgreat above describes a setup very much like the one I'm planning.

It sounds to me that you are NOT using a proper transfer switch, otherwise the 220 line from the pump house to the main panel would not be energized when running the well from the generator. If I am correct, that is an illegal and dangerous setup. Assuming the same setup on the main panel, mistake by you, or someone else could backfeed the service line and endanger someone off of your property.

Note, one of the dangers here is that there would be hot wires in the main box even when the mains are disconnected. This setup requires too much understanding of complex wiring to be safe.

But maybe I misunderstood your description.


Ken

 

[Ken45101]

Ken45101,

If I wire to wire it "as is" yes,the hot 220V running back to the home would be energized, which I do obviously do NOT want.

I am planning on replacing the sub-panel in the well house with one that has a main breaker disconnect. I wasn't clear on that in my original post. That's what I get for attempting to convey a complicated description when I'm half asleep.

The question was can the generator #2 connected at the sub panel to share the common neutral/ground at the main panel when generator #1 at the main panel is also running. The post by grsgreat above describes a setup very much like the one I'm planning.

Actually you were clear. Hoewever, adding a box with a main breaker will still be illegal (and unsafe). There MUST be an absolute positive lockout that prevents the generator power from going to the feed no matter what mistake anyone makes. There are some mechanical lockouts that prevent the main breaker from being on when the generator feed is on (so I have heard) or you can get a generator transfer switch that prevents the same situation but does it electrically. The Reliance transfer switch is one example (Amazon.com : Reliance Controls 31406CRK Pro/Tran 6-Circuit 30 Amp Generator Transfer Switch Kit With Transfer Switch, 10-Foot Power Cord, And Power Inlet Box For Up To 7, 500-Watt Generators : Manual Transfer Switch : Patio, Lawn & Garden). I just installed the 10 circuit version here at home.

 

[Stimw]

If you wanted to just be simple I would put a female plug-in on the wire to the pump house and a male plug/pigtail on the pump breaker.
A regular 4 pole dryer set would work then you can plug the generator in while disconnecting the regular power and you have total disconnect.

 

[Redneck in training]

You can also install mechanical transfer switch similar to this: GE Industrial - TC10323 - 100 Amp Double Throw - Outdoor Nema 3R - 120/240V Non-Fused Transfer Switch

 

[hr3]

Actually you were clear. Hoewever, adding a box with a main breaker will still be illegal (and unsafe). There MUST be an absolute positive lockout that prevents the generator power from going to the feed no matter what mistake anyone makes. There are some mechanical lockouts that prevent the main breaker from being on when the generator feed is on (so I have heard) or you can get a generator transfer switch that prevents the same situation but does it electrically. The Reliance transfer switch is one example (Amazon.com : Reliance Controls 31406CRK Pro/Tran 6-Circuit 30 Amp Generator Transfer Switch Kit With Transfer Switch, 10-Foot Power Cord, And Power Inlet Box For Up To 7, 500-Watt Generators : Manual Transfer Switch : Patio, Lawn & Garden). I just installed the 10 circuit version here at home.

Actually his remote panel in a separate building is illegal now without a main breaker. Any separate building of the main service will have disconnecting means. So I would say the cheapest way is to replace the panel with a main and a breaker interlock like you have in the house and your all set.. like grsgreat said it's fine.

The only problem I can see is You will see the outbuilding load on your house generator until you go up and throw the main off..