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proper wire sizing for run from generator in garage to house

Tom in Madison's picture

Hi,

I've been reading up on all my electrical how-to books and consulting Code Check, but I'm still unsure about how to size my wires for this project.  Here are the details:

Generac 5500 watt generator out by the garage.  I'd like to plug the generator in here, have a cable carry the power to the transfer panel in my basement.

I have a free 2" buried pvc pipe already in place that comes up through the garage floor and exits just outside of the house.  Perhaps the previous owners wanted to do something like this?

The distance from the garage to the house is 75'

The transfer panel is a a Reliance 10 circuit 30 Amp panel.

Normally, I'd say that a 10 gauge wire would be fine for carrying a 30A load.  Would the distance dictate that I go down to an 8?  

Even though the wire will be carried in a plastic conduit, would code require I use a UF rated cable rather than NM?

Lastly, would I need to use a cable, or would it be kosher to use individual wires?

Thanks guys.

Tom

Find any of several wire size (post #207080, reply #1 of 5)

Find any of several wire size calculators on the web, to find out if you need larger wire for the 75-foot run.

You can use individual wires so long as the wires are entirely contained inside conduit.  In fact, individual wires generally can carry more current than the same wires in cable.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Stranded vs. solid? (post #207080, reply #2 of 5)

Thanks Dan.  Any difference in carrying capacity between stranded and solid wire?  My first impulse is solid would be better but I don't have data on that.  

There's no difference.  The (post #207080, reply #3 of 5)

There's no difference.  The wire size numbers take stranding (if present) into account.  (And stranded is a lot easier to pull, and about all you'll find in individual wires.  The only disadvantage is that it's a bit harder to terminate.)


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

I would run # 6 thwn or (post #207080, reply #4 of 5)

I would run # 6 thwn or thhn2 individual wires to make sure that you dont have any voltage or amperage drop over the 75 feet. According to the code, wires run underground( even through conduit) must be rated for wet locations.

Better safe (post #207080, reply #5 of 5)

Thanks everyone for taking the time to respond.  It probably can't hurt to do a little overkill on this, particularly since I'll be (hopefully) using this infrequently.  I think I'll stick with #8 wet location wire.

Tom