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Old 04-26-2010, 09:28 PM   #16
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wiring a detached shed for AC power *and* generator backhaul


The more than one feeder or branch circuit limitation is found in 225.30

Basically, it states that only one feeder is allowed except for certain conditions. One of these conditions is an emergency system.

Therefore, you certainly can run wire from the house to the shed for lights, receptacles, or even a sub-panel plus another feeder from the generator back to the house.

Since this is an optional standby system, there's no requirement for a separate conduit. In fact, 702.9 specifically allows the generator wiring to be in the same conduit as normal wiring.

If it were me, I would run a separate conduit for the gen. I'd also run a big enough conduit for the lights, etc. to allow for a 60 amp sub-panel to be installed in the future. A 1" would be OK.

If the gen is auto-start, and it's more than about 20' from the transfer switch, I'd run a separate conduit for the controls.

Consider a bug-eye type of emergency light somewhere near the gen. That way, if it fails to start (or needs to be started by hand), you'll have light to work with.

Rob

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Old 05-10-2010, 12:26 PM   #17
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wiring a detached shed for AC power *and* generator backhaul


This is a really interesting topic. I'm actually considering the exact same thing.

I've written up a crude diagram about how the setup should look.


I have a detached shed about 50 feet from the back of the house, and I'm thinking of running 3 types of wiring to the shed.
1) A generator inlet box going to the sub panel in the garage with an interlock breaker. The sub panel runs everything except for the stove, A/C and furnace, which are powered from the main panel outside. I have a Generac 7500w, 13,500w surge portable generator with a NEMA 14-50 240V 50A plug on it. I'll use a short 10/4 connector cable with a 14-50 plug on the generator side and a 50a female plug on the inlet box side. In the shed, the generator will sit right next to a 16" "shutter type" exhaust fan facing away from the house that will run directly off of the generator instead of being hard wired into the house-supply.


2) Regular 120v power to a 40a sub panel in the shed for lights, outlets, etc. I don't see the need to run 240v TO the shed.

3) Low voltage wiring, such as a coax cable for TV, and I'll probably run 4 CAT-5e or maybe CAT-6 cables as well. While I don't plan on having 4 computers out there, I can use "Baluns" to run pretty much any type of signal out there over CAT-5/6 cables including HDMI video, USB, etc.

The question I have is: Is there a maximum length you should use when running the generator to the sub panel? The extension cord will probably be 3-5 feet, and the buried cable in conduit will be at least 50 feet.

What do you think of the exhaust fan setup? Would this be a good idea? Or should I just sit the generator on the "covered porch" portion of the detached shed? The main reason why I want to put the generator inside the detached shed is for noise reasons. The Generac 7500 is LOUD. I don't want anyone knowing that I'm running a generator or where it's located.

Homer
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Old 05-11-2010, 01:48 PM   #18
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wiring a detached shed for AC power *and* generator backhaul


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Originally Posted by homerb View Post
I've written up a crude diagram about how the setup should look.
14/3 out to the shed 50 feet away?
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Old 05-11-2010, 02:01 PM   #19
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wiring a detached shed for AC power *and* generator backhaul


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14/3 out to the shed 50 feet away?
I only plan on having a few power outlets and a couple compact fluorescent lights for the 120v powered side. 15 amps MAX. That's not for the generator circuit.

What would you recommend? 12 AWG? 10 AWG?

Since the generator circuit and power circuit would share a ground and neutral, I guess you wouldn't need to run two grounds and two neutrals bac to the house, all you'd need to run would be two 10 AWG hots, a 10 AWG neutral, perhaps a 10 AWG ground, and then a 10 or 12 AWG single hot for the 120 V power outlet circuit that'll be on regardless of whether or not the generator is running? Correct?

Or do you think it'd be good practice to run 10/4 with its own separate neutral and ground for the generator (240V) , and maybe 12/3 with it's own neutral and ground for the power outlets (120V)?

Or, depending on how many power outlets and devices you'll have out in the shed, you can run two separate hots for two sets of 120v circuits?

Homer
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Old 05-28-2010, 11:59 AM   #20
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wiring a detached shed for AC power *and* generator backhaul


Quote:
Originally Posted by homerb View Post
What would you recommend?
12AWG.

Quote:
Originally Posted by homerb View Post
Since the generator circuit and power circuit would share a ground and neutral
Don't do this.

Quote:
Originally Posted by homerb View Post
Or do you think it'd be good practice to run 10/4 with its own separate neutral and ground for the generator (240V) , and maybe 12/3 with it's own neutral and ground for the power outlets (120V)?
Do that.

Quote:
Originally Posted by homerb View Post
Or, depending on how many power outlets and devices you'll have out in the shed, you can run two separate hots for two sets of 120v circuits?
Yes you could do that -- google "MWBC".

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