220 off garage sub-panel?

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Old 02-18-20, 03:26 PM
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220 off garage sub-panel?

So I have a 40 amp sub panel in my garage that runs off two 20 amp circuits from the main. Can I run a 220 circuit off my sub?

Thanks
Josh
 
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Old 02-18-20, 03:38 PM
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You have a 20 amp sub panel.
Yes you can run any 240 volt device that only requires 20 amps.
 
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Old 02-18-20, 03:54 PM
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Thanks! General question... if I have 20amps run to each bar on my sub, would I not be able to draw 40 amps w/a dual pole breaker?
 
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Old 02-18-20, 04:44 PM
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You have two 120V circuits at 20A each, so 40A at 120V or one 20A circuit at 240V.
 
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Old 02-18-20, 06:39 PM
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What you have in the garage will depend on the wire size of the feeder that feeds the sub panel and what size breaker/fuses is/are protecting those wires. It will also depend on if the feeder has two hots and a shared neutral or if it is just one not and one neural.
 
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Old 02-19-20, 06:11 AM
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It's a 12 gauge 3 wire feeding the sub, so 2 hots and a shared neutral. On the main it's a 20 amp dual pole breaker. On the sub I have a couple of 20 and 15 amp circuits. Sounds like I can get a 20 amp 220v circuit off the sub as well...
 
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Old 02-19-20, 06:19 AM
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Yes you can have a branch circuit fed by a double pole breaker in the subpanel provide 240 volts (or both 120 and 240 volts).

You just have to be careful that the 240 volt item(s) together with the 120 volt item(s) on one leg on at the same time don't draw more than 20 amps from the subpanel and that the same 240 volt item(s) together with the 120 volt item(s) on the other leg on at the same time don't draw more than 20 amps.

Another way of saying it (with or without a 240 volt branch circuit) is that, although you could power 40 amps worth of 120 volt items from that subpanel, you may not draw 30 amps from one leg using any or all of the branch circuits in that subpanel when you are only drawing 10 amps from the other leg.

Double check (no pun intended) to be sure that you indeed measure 240 volts across the two terminals of the double breaker for this subpanel at the feeding panel. If the polarities of the breaker slots in the supra panel are not as expected (must be on opposite legs) you could overload the shared neutral. This applies with or without a 240 volt branch circuit in the subpanel.
 
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Old 02-19-20, 09:26 AM
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Makes sense... thank you!
 
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