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jayman4him · Feb 8, 2010, 09:36 AM

I want to energize a sub panel in my lower garage. I want to have a sub panel rated
At somewhere between 70 and 100 amps. What size copper wire can I use to to do this in a romex style conductor ?

donf · Feb 8, 2010, 11:29 AM

The end to end Voltage Drop can be no greater than 5% (Feeder Cable + Branch Circuit).

From the 2008 NEC code, T 310.16 you can use three #1 AWG copper conductors with a #4 copper ground conductor type TW insulation listed at 60C or Three #3 with a #4 ground listed conductors listed as 90C with insulation types of THHN/THHW.
At the sub panel you connect the Black & Red to the Hot Connection Lugs. Green will go to ground and White or Gray goes to Neutral. DO NOT BOND Ground and Neutral together in the sub-panel.

jayman4him · Feb 8, 2010, 07:56 PM

Thank you - donf -
Just what I needed. Now I can get started.
Thanks again.

tkrussell · Feb 9, 2010, 06:56 AM

Jay, let us know what kind of cable you can find in your area, before you run out and buy any.

TW is no longer popular, may not even be available.

THHN/THWN is often single conductor.

You should be looking for NM-B or SER cable, see attached product datasheets.

You mention #2 copper, but want something rated 70 -100 amps?

Pick one.

Keep in mind, and of the cables I offered must only be rated at the 60 Deg C column.

jayman4him · Feb 12, 2010, 06:33 AM

Originally Posted by tkrussell

Jay, let us know what kind of cable you can find in your area, before you run out and buy any.

TW is no longer popular, may not even be available.

THHN/THWN is often single conductor.

You should be looking for NM-B or SER cable, see attached product datasheets.

You mention #2 copper, but want something rated 70 -100 amps?

Pick one.

Keep in mind, and of the cables I offered must only be rated at the 60 Deg C column.

tkrussell - Thanks for your reply - Do you work for Southwire ? Do you have a phone number ( preferably 800 or 888 ) ? If I get the 4 wire conductor ( 1/1/1/3 ) copper, can I run this in a 1 1/4 PVC conduit -
Or a bit overkill ? Thanks again -

tkrussell · Feb 12, 2010, 07:41 AM

No I do not work for Southwire, or any manufacturer.

Find contact info here:
Southwire

Do not pull feeder cable of any kind through long run of conduit.

You original mentioend Romex type cable, which I provided datasheets on.

If you want to run conduit, then you need to pull individual conductors with THHN/THWN insulation in a complete conduit system with proper fittings.

For 100 Amp, you can use #3 THHN/THWN copper.

jayman4him · Feb 12, 2010, 08:29 AM

Originally Posted by tkrussell

Jay, let us know what kind of cable you can find in your area, before you run out and buy any.

TW is no longer popular, may not even be available.

THHN/THWN is often single conductor.

You should be looking for NM-B or SER cable, see attached product datasheets.

You mention #2 copper, but want something rated 70 -100 amps?

Pick one.

Keep in mind, and of the cables I offered must only be rated at the 60 Deg C column.

So - IF is can get this ( 1/1/1/3 ) copper, then just lay it up in the attic, through floor joists, etc.

tkrussell · Feb 12, 2010, 08:43 AM

Should be able to lay in the attic, where there will not be any chance of physical damage, stuff stored on top ,or where someone would walk on it.

Keep it away from walkways, out near the edge of the attic.

This calbe would need a decent size hole through any wood framing members, use protective nail plates at those points, to protect the cable from nails/screws.

I would not drill holes through joists.

jayman4him · Feb 12, 2010, 09:58 AM

Then, when I get to the lower basement and I need to go across floor joist -??

tkrussell · Feb 12, 2010, 10:18 AM

Across, OK.

Through? I do not recommend.

jayman4him · Feb 12, 2010, 11:39 AM

Earlier you said: " This cable would need a decent size hole thru any wood framing members, use protective nail plates at those points, to protect the cable from nails/screws. " I don't want the cable to hang below the basement side of the floor joist. Is a notch better than drilling a hole, etc. The path will be from upper garage up to attic, down a chase to the basement then past a few floor joist to the new sub panel..

tkrussell · Feb 12, 2010, 01:57 PM

OK I was imagining going through vertical partitions.

If possible don't drill through floor joists. A few, not a big deal, but keep the hole at least 1.25 in away from the edge,and only drill through the outer thirds, not the center third, of the span.

Don't notch. It is allowed, but I don't like the look of it.Looks like the supporting strength was compromised.