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Old 11-21-2008, 01:06 AM   #1
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Wire size for sub-panel


Before I finish the ceiling in my basement I want to run a wire to my attached garage to power my 220V welder. According to the manual the welder should be on a 40 amp circuit. My intention is to use this circuit for only my welder now, but later to power a sub panel when I build a detached garage. Once this is built my welder will be relocated to the detached. My question is what size wire do I need? Note I will only ever be using one large appliance and lights at the same time in my detached.

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Old 11-21-2008, 02:10 AM   #2
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Wire size for sub-panel


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Originally Posted by deepstuff View Post
Before I finish the ceiling in my basement I want to run a wire to my attached garage to power my 220V welder. According to the manual the welder should be on a 40 amp circuit. My intention is to use this circuit for only my welder now, but later to power a sub panel when I build a detached garage. Once this is built my welder will be relocated to the detached. My question is what size wire do I need? Note I will only ever be using one large appliance and lights at the same time in my detached.
Are you saying that when you build the new garage, that you want to be able to extend this wire outside to the new garge, and your main concern now is that you don't want to have to mess with the basement ceiling again later.?

I would strongly suggest you run ridgid conduit, like ENT, the grey plastic PVC conduit. I would run atleast 1" size.

Jamie

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Old 11-21-2008, 03:30 AM   #3
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Wire size for sub-panel


Let's not get too complicated. Since the garaged is attached, you can just use a 3-wire cable with a ground. I don't see any use for a subpanel less than 50 A. If your welder needs a 40 A 240 V circuit, run a 6-3 NM, aka "Romex". Leave the red unused at both ends and capped off. Put the black and white on a double pole 40 A breaker of the appropriate type for your panel. Put a piece of black tape on the white wire for now. Terminate the other end of the cable into the appropriate receptacle for your welder. Leave some slack to install the future subpanel.

When you change to a subpanel, place the white wire on the neutral bar, and place the black and red wires on a 50 A breaker. At the subpanel, wire the white to the neutral bar, and make sure it isn't bonded the the panel in any way. The ground goes on the bround bar, and the black and red land on the main breaker or main lugs, whichever you choose.

If 50 A isn't enough for the sub, check back in because you need a bigger wire size then.
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Old 11-21-2008, 06:48 AM   #4
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Wire size for sub-panel


I was thinking a 60 amp sub panel. Yes Jamie the main reason for worring about this now is so I won't have to taer up my ceiling when I build me detached garage. Fow now I only want to go as far as my attached garage for my welder but want the option of a sub for a detached later.
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Old 11-21-2008, 07:56 AM   #5
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Wire size for sub-panel


I would follow Inphase's directions, but with one change.... since you only want a 240V load now, use the black and red wires and leave the white unused. Less confusion down the road about what should go where when you extend the circuit to the garage.
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Old 11-21-2008, 08:12 AM   #6
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Wire size for sub-panel


ho, and my welder has a range style plug.
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Old 11-21-2008, 10:46 AM   #7
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Wire size for sub-panel


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I would follow Inphase's directions, but with one change.... since you only want a 240V load now, use the black and red wires and leave the white unused. Less confusion down the road about what should go where when you extend the circuit to the garage.
I have no idea why I said that. Sorry. I was half asleep.
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Old 11-21-2008, 10:57 AM   #8
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Wire size for sub-panel


I can't see why you need a sub-panel, unless you are planning to install that panel in the detached garage, for convenience of shut-off or if the welder trips the breaker, you won't have to go back into the house to reset it.
In that case, you need to have a higher capacity feed to the sub than the welder's breaker in the sub, so that it will be the one that trips, not the one in the main panel.

I would run cable for 60Amps. You shouldn't ever need more than that, considering your use.
You can then have the sub-panel in the garage with a 40A breaker for the welder, and plenty left over for lighting, etc.
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Old 11-21-2008, 10:59 AM   #9
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Wire size for sub-panel


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I was thinking a 60 amp sub panel. Yes Jamie the main reason for worring about this now is so I won't have to taer up my ceiling when I build me detached garage. Fow now I only want to go as far as my attached garage for my welder but want the option of a sub for a detached later.
As Inphase mentioned, you can put a sub on the 6/3, however it will only support about 50A (I am not positive that is the correct number for Romex / NM cable, could not find the chart, but it is close).

I understand your concern about the ceiling, thus the reason I mentioned conduit. Inphase is correct that the NM is a easy quick solution, however, as he also mentioned, you may have to replace that wire later for a sub panel upgrade, which I understand may be a problem in you situation due to the ceiling.

If you don't want to have to risk changing stuff in that ceiling later, then the only option I can think of is to run 1.5" conduit and pull the necessary wires. You can pull 6 gage now like Inphase said, but if you want larger service later, you will have to figure out how to get new wire or conduit run.

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Old 11-21-2008, 01:13 PM   #10
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If you don't want to have to risk changing stuff in that ceiling later, then the only option I can think of is to run 1.5" conduit and pull the necessary wires.
Wow you really have a conduit fetish! 1.5 inch conduit in a residential setting!
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Old 11-21-2008, 03:49 PM   #11
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Wire size for sub-panel


#6 is fine on a 40, 50, or 60 amp breaker feeding the receptacle for the welder or the future sub panel. You need to run 4 wires if the sub panel is in the future. So a 6/3 NM inside will work just fine.
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Old 11-21-2008, 06:56 PM   #12
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Wire size for sub-panel


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Wow you really have a conduit fetish! 1.5 inch conduit in a residential setting!
My thought was that he wants to run a sub panel in the future for a detached structure through this line, and he wants to make sure he does not have to disturb his basement ceiling again.

I went with the largest reasonable sub panel that he might want for a detached garage in the future, 100A. 3 -2awg copper and a 6awg ground wire come to a total of 0.3981 cuin 1" ENT is .314 so it won't fit, 1.25" at .546 will deffinatly allow it to fit. 1.5" is just easier to get the wires through and the cost difference is miniumal here.

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Old 11-22-2008, 01:08 PM   #13
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Wire size for sub-panel


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My thought was that he wants to run a sub panel in the future for a detached structure through this line, and he wants to make sure he does not have to disturb his basement ceiling again.

I went with the largest reasonable sub panel that he might want for a detached garage in the future, 100A. 3 -2awg copper and a 6awg ground wire come to a total of 0.3981 cuin 1" ENT is .314 so it won't fit, 1.25" at .546 will deffinatly allow it to fit. 1.5" is just easier to get the wires through and the cost difference is miniumal here.

Jamie
A 100 amp sub panel only needs 3-#3's and 1-#8. 1" conduit minimum with THHN or THWN wire. Check art 310.16

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