Which size conductor should I use?

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Old 01-30-17, 10:04 AM
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Which size conductor should I use?

Oh my...my ongoing new construction wiring project; I am going to have install a 220 (240) outlet in the garage. The run is approximately 70' from the service panel. I was planning on putting the circuit on a 40a breaker. The recepticle will power my 3 hp table saw-13. And 2 hp dust collector-16 amps. Since wire is pricy per foot I want to error on the good and safe side. So what size/type conductor should I run? Thanks
Jim
 
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Old 01-30-17, 10:14 AM
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Large tools should have their own circuits sized specifically for the motor load.

A 3hp motor should be on a 240V 30A circuit with #10-2g cable and a NEMA 6-30 receptacle. A 2 HP motor should be on a 240V 20A circuit with #12-2g cable and a NEMA 6-20 receptacle.

An alternative plan would be to install a subpanel in your workshop space and run the specific tool circuits from there. In this case, I would run #6-3/g cable from the main to the sub and use a 60A breaker.
 
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Old 01-30-17, 02:10 PM
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Thank you for your very helpful comments
 
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Old 02-05-17, 06:20 PM
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What conductor should I use?

Again I'm still working on my new construction residence. I am installing a 100a sub panel in the attached garage. I planned to land it in the main service panel on a 90a breaker. The sub panel will have (3) 30a breakers to support my woodworking tools. The sub panel is a30' run from the service panel. Here's my questions; what size conductors should I use to connect the sub panel to the main service panel. And is aluminum acceptable? And lastly do I need to run only 3 conductors between the service panel and the sub panel? 2 hots and 1 neutral? Thanks for your advice.
Jim
 
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Old 02-05-17, 06:49 PM
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You would be running #3 copper or #2 or #1 aluminum. You will need 4 wires, hot, hot, neutral and ground. You will also need to sink one if not two grounding rods and run a #4 grounding conductor to them continuously. In your sub panel you will need to separate your neutral and grounds, and isolate the neutral, necessitating a possible additional buss bar unless it is equipped with two. You say you will only have 3 30 amp breakers. What will you be running your lighting on? How about your regular 10 volt recepticals.
 
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Old 02-05-17, 06:52 PM
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Threads merged................
 
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Old 02-05-17, 07:12 PM
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Thanks. I already have all the 110 GFCI receptacles and separate lighting circuit installation completed. The 240v circuits are planned to run separately my table saw (16amps). My dust collector (14 amps) and occasionally my 5 hp air compressor. I was not aware the sub panel needed a separate ground stake. Thanks for your help. Each one of those tools I was planning on a dedicated circuit/receptacle out of the sub panel.
 
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Old 02-05-17, 07:43 PM
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The receptacles are 120 volts not 110.
I was not aware the sub panel needed a separate ground stake.
Not need if it is attached but it needs a bonded ground bar, an EGC and an isolated neutral bar. All grounds including the EGC go to the ground bar. Do you have that?
 

Last edited by ray2047; 02-05-17 at 08:12 PM.
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Old 02-05-17, 07:48 PM
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You don't need separate ground rods for subpanel in attached garage.
 
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Old 02-05-17, 08:11 PM
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Thanks. Didn't know it was an attached garage. I will amend my post.
 
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Old 02-05-17, 09:20 PM
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Ok folks thanks for your many responses. Let's see if I have this right; since the garage is attached I don't need a grounding stake in the earth for this sub panel. But I do need to put the neutrals on the neutral ground bar and put he grounds on the separate bonded grounding bar. And since I'm coming off the main service panel from a 90a breaker I would only need 3 conductors from the main panel to the sub panel. That being 2 hots and the neutral. Is this all correct? Thank you much for your help
Jim
 
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Old 02-05-17, 09:51 PM
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What is the term EGC

I'm still learning ....so one of the replies to my previous sub panel panel question used the term EGC. I don't know what that stands for.?
 
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Old 02-05-17, 10:52 PM
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That being 2 hots and the neutral. Is this all correct?
No. You need two hot, one neutral and one Equipment Grounding Conductor (EGC), four wires. The EGC for 90 amps can be #8 copper (#6 aluminum). It and all others go to the bonded ground bar. The neutral bar is isolated and only neutrals go to it.

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Old 02-06-17, 03:26 AM
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I missed the "attached" part, too, so no rod is needed. I was interpreting this to be a new installation for all your power, but see it is attached and you already have some power there. Had it been detached, you could only make one run for power, thus my misguided question.
 
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Old 02-06-17, 07:30 AM
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Thank you...

I think I have it all digested now. The only thing I may be a bit confused about is the size of the conductor AWG the main to the sub. The last response recommended is #8 copper or #6 aluminum. I have a friend who is an electrician and by chance he recommended that I use #1 or 2 aluminum. This will be landed on 90a breaker in the main panel. Thanks for your help...just want to be 100% ...
Jim
 
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Old 02-06-17, 07:42 AM
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Ray was only referring to the EGC (a.k.a. the ground) between the main and the sub.

For a 90A feeder using a cable assembly like SER cable or NM cable you need at least #1 aluminum or #3 copper for the hots. Copper is much more expensive than aluminum so I'm assuming you want the info for aluminum. The closest standard size I'm aware of is 1-1-1-3 aluminum SER. However #1 aluminum SER is not a commonly stocked material at many suppliers so you may have special order or go with a slightly larger cable such as 1/0-1/0-1/0-2 which is common size. If you do use the #1/0 cable, then you can also increase the breaker size to 100A.

If you plan to use copper cable or you plan to use individual wires in conduit, please post back as the details will be different.
 
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Old 02-06-17, 03:05 PM
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As long as the SER is not buried in insulation to cause a heat issue #2-2-2-4 Aluminum(AL) SER is good for 90A. That is sizing from 75 deg. C. Otherwise if the SER is buried in insulation then 60 deg C. is used which means #1-1-1-3 AL SER is needed for 90A.
 
 

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