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Forum topic by Jason Tetterton posted 03-15-2010 12:00 AM 1171 views 0 times favorited 8 replies Add to Favorites Watch
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Jason Tetterton

54 posts in 2483 days


03-15-2010 12:00 AM

I am moving my “shop” from my one car garage to the basement. The total space in the basement will be about 600 sf. I have a 240 volt table saw, and the rest are all 110 (Planer, jointer, HF 1.5hp dust collector). That’s it for big tools. My main panel is in the basement, but I want to add a lockable sub-panel to turn off power to all the tools. The panel is going to be about 15-20 feet away from the main panel.

I plan on doing the majority of the work myself (I’m going to have an electrician connect the subpanel to the main panel). I plan on wiring several 110 circuits with 14 gauge and maybe 2 220 circuits with 12 guage. What type of breaker do I need to install in the main panel to feed the sub-panel? What type of main breaker in the subpanel, and what gauge/type of wire should I run between the two panels?

Thanks

-- Jason, Central Virginia


8 replies so far

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SKFrog16

661 posts in 2661 days


#1 posted 03-15-2010 02:16 AM

A sub-panel requires two insulated hot wires fed from a breaker of the main service panel as well as an insulated neutral and a grounding wire. All of these wires (contained within the sheathed service-entrance cable) must connect into the sub-panel and tie all the way back to the main service panel.

In most main panels you’ll find that the neutral bus bars (the common bars that are isolated from the panel case) are connected via a metal tie bar. In a sub-panel, however, the neutral has to be totally isolated from the ground, so you must remove this tie bar.

By code, the neutral for a residential installation is only bonded to the ground at the main service panel. At all other points throughout the house, there is no connection between the bare (or green) grounding conductor and the white neutral conductor. Under normal conditions, the grounding conductor carries no current. If you bond the neutral and the ground at the sub-panel, stray currents from the neutral return could go through the equipment ground on the electrical devices fed from this sub-panel. But if you isolate the neutral and the ground at the sub-panel, stray currents would go back to the main panel and to the service ground.

I would think that a 60 amp breaker in both the main and sub-panel wired to 4AWG wire would be adequate.

-- Methods are many,Principles are few.Methods change often,Principles never do.

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TopamaxSurvivor

17655 posts in 3137 days


#2 posted 03-15-2010 03:17 AM

I would thnk 60 amp should do you just fine.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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Jason Tetterton

54 posts in 2483 days


#3 posted 03-15-2010 03:18 AM

Wow, you just blew my mind… I think I might just have an electrician handle the sub-panel installation completely.. And I’ll just wire the circuits :)

-- Jason, Central Virginia

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Jason Tetterton

54 posts in 2483 days


#4 posted 03-15-2010 03:29 AM

My main service is 200

-- Jason, Central Virginia

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Jason Tetterton

54 posts in 2483 days


#5 posted 03-15-2010 03:31 AM

So 12-2 with 20 amp breakers for all the 110 circuits and 10-2 for the 220 circuits? 30 amp breakers for the 220s?

-- Jason, Central Virginia

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TopamaxSurvivor

17655 posts in 3137 days


#6 posted 03-15-2010 04:37 AM

12-2 fpr 20 amp at any voltage. 10-2 for 30 amp at any voltage. Look at yoiu equipment mane plates. They will give you a full load amperage. I would not do any 15 amp circuits because of starting equipment motors.
20 amp minumim.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View SnowyRiver's profile

SnowyRiver

51452 posts in 2942 days


#7 posted 03-15-2010 04:39 AM

Jason…that sounds correct as glivingston has said. I would run 60 amps to the subpanel. and like you have recapped, use 20 amps/12-2 w ground for the 110 v and 30 amps/10-2 w ground for the 220 v. This is the exact arrangement that I have and it works just fine.

-- Wayne - Plymouth MN

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TopamaxSurvivor

17655 posts in 3137 days


#8 posted 03-15-2010 05:13 AM

I’ll vote for having a real live electrician involved ;-) Do not arbitrarily fuse 220 circuits at 30 amps. It depends on the load of the 220 circuit, you do not want to over fuse any equipment. It defeats the purpose of the fusing system. READ NAMEPLATES! That is where the answers are.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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