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Questions on installing a standby generator

Posted by jdg678 (My Page) on
Fri, Apr 15, 11 at 7:31

Hello everyone,
Allow me to explain what I am planning to do so that my questions make sense.
I am planning the instal of a 12Kw standby generator. It will sit roughly 40 away from where it will be tied to the house panel through a Ronk DPDT transfer switch. My feed wires from the generator will be 6 Ga triple rated THHN/THWN-2/MTW. 3 appropriately colored conductors along with a bare copper 6 Ga ground. I will be running this underground through 2" sch 80 PVC conduit. Overkill on the conduit, but given the tiny price difference what the hey.

My first question.
I also plan to have a 15 amp (I will use 12 Ga triple rated THHN) line run from the breaker panel to a single outlet inside of the generator enclosure. I would assume that using the 6 Ga ground that will be tied to the ground inside the house at the panel would be acceptable to ground this circuit? Or would I need to run a seperate ground to meet code?

Second question.
Given that the 15 amp circuit I just described above will be live all of the time, would there be any reason that it would need to be isolated from the 6 Ga wires? I will run it and a dedicated ground through a seperate conduit if needed, but thought I would not be even close to fill capacity on the 2" PVC.

Third question.
I am also running an additional 1" schedule 80 PVC conduit for engine control and battery maintainer wires. Because these wires will all be only 12 VDC and be dedicated to only engine systems and not tied into the 120 VAC wiring, would it also need to meet code as far as color? I ask this because it would be a lot more convienent to purchase a 500' roll of wire to run these circuits instead of 10 50' lengths of wire.

My fourth and final question.
This may not be the appropriate forum, but I am willing to bet someone here knows the answer.
This genset is natural gas fueled. My question pertains the the trace wire I plan to bury along with the 1" CTS PE pipe I am going to run to feed it.
I plan to have 2 "T's" in the pipe. One to run a feed for the potential future use of a natural gas fired heater for a hot tub we have planned on down the road, and a feed for an outdoor kitchen i also have planned down the road.
Do I need to run dedicated lengths of tracer wire from the connection point of the pipe to the termination point of my pipes, I.E., 3 seperate lengths of wire, or is it permuissible (and practical) to have spliced connections to in effect only have 1 wire? Given the cost of quality direct burial splices, it may actualy be cheaper to just run three seperate wires. I have not done the math on that yet.

For those that may wonder, I have been in touch with the utility companies and the local zoning department to determine if I can do the install myself. Basicly as long as I get the appropriate permit and have it inspected, I'm good.

Anyway, thanks for bearing with me and thanks in advance.


Follow-Up Postings:

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RE: Questions on installing a standby generator

Something I failed to mention that likely will not matter, but figured I should mention.
The outlet on the 15 amp circuit I mentioned in question 1 and 2 will be used to supply power to a thermostaticly controlled battery heater and oil heater. This would be live no matter if we are on utility or standby power.


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RE: Questions on installing a standby generator

One large ground is fine.
Running the 15A circuit in with the larger one in the same conduit is fine.
There's no code for coloring for low voltage stuff.


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RE: Questions on installing a standby generator

A #6 ground is way overkill. All that is needed is a #10.
If it will make you feel better you can bump up to a #8, but it will serve NO other purpose.

Also, the 2" sch80 is pretty absurd. It is not a matter if price. It is a matter of running and terminating it. You'll probably have to reduce down in size at some point any way.
1-1/4" is more than enough.


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RE: Questions on installing a standby generator

Make sure you remove and ground-neutral bond in the generator.


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RE: Questions on installing a standby generator

Thanks for all the replies!
My reason for running the #6 ground is that I already have it. If I didn't, I'd go with the #8 for sure.

I know that code here does not require sch80, and my only reason to run 2" was ease of pulling the #6 conductors. If memory serves, the conduit fill calculator I checked specified 1" or 1 1/4" for 4 pieces of #6 and 2 of #12. That would indeed make termination easier. Maybe pulling the #6 through 1" or 1 1/4" won't be that difficult, I do not know. I have never pulled #6 through conduit before.

I have not verified as of yet, but this generator was previously installed localy (same codes apply). I have yet to install the generator itself into the enclosure and reconnect the leads from the generator head.
However, I was under the understanding that the critical thing on the ground is that it is not grounded except to be connected to the ground wire that will run back to the ground bar in the breaker panel? Ditto on the neutral. Am I not understanding something correctly, or am I missing something?


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RE: Questions on installing a standby generator

As a separately derived system the neutral and ground should be bonded one time in the disconnect for the generator and than kept separate in every other panel.

Every panel after the generator disconnect is a sub-panel.


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RE: Questions on installing a standby generator

Ok, I have the disconnect that came with the generator, but whoever removed it removed all of the internals. Basicly I have a metal box that says "Generator Disconnect". Why someone would have removed the internals puzzles me. But they also removed the key start switch for the set that was on the remote panel too.
Would an appropriately rated disconnect of any kind work?
Alternately, Given I have breakers that can be manualy operated on the generator and it will be feeding a DPDT switch, is the disconnect even needed?
If it is, I have no issue buying what I need, just didn't see the reason it needed one.
That said, I always assume that there is something I did not take into account.


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