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Old 01-29-2009, 11:50 AM   #1
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Multiple 220 volt outlets


I apologize if this has already been answered -- I did look before posting.
I need to add wiring in my garage for both a table saw and a dust collector system. Both use 220 volt, single phase motors. Each motor's plate says 15 amps.

Is 15 amps the maximum, starting or continuous amps? If 15 amps is the starting load it's unlikely that both items would be starting at exactly the same time? I need to run 50 feet from the main breaker box to the outlets. I already have 75 feet of 10/3 cable. I believe this cable would handle a maximum of 30 amps.

Keeping in mind that I already have 75 feet of 10/3:
Should I run a single 10/3 and wire the two outlet boxes in series, run a seperate 10/3 to each outlet box, or a single larger cable in series to the two outlet boxes, or is there a more preferred way to do this?

Also, what size breakers should I use?
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Old 01-29-2009, 11:55 AM   #2
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Multiple 220 volt outlets


The table saw will draw more when you are actually sawing. The dust collector will draw more when it's getting full.

The nameplate amps are closer to the maximum than the continuous load. It should be fine to run both of them on a single 30 amp circuit. 10 gauge wire gets 30 amp breaker.

When you say "wire in series", I guess you don't mean literally in series, outlets are always in parallel.
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Old 01-29-2009, 12:07 PM   #3
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Multiple 220 volt outlets


Thanks for the quick reply. Yeah, I meant to say parallel. By 30 amp breaker, does that mean two 30 amp breakers or two 15 amp breakers?
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Old 01-29-2009, 12:08 PM   #4
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Multiple 220 volt outlets


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Originally Posted by Strider View Post
Thanks for the quick reply. Yeah, I meant to say parallel. By 30 amp breaker, does that mean two 30 amp breakers or two 15 amp breakers?
One double pole 30 amp breaker.
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Old 01-29-2009, 05:03 PM   #5
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Multiple 220 volt outlets


To utilized the 10/3 cable, I'd install a small sub panel in the workshop with two 15 amp 240 breakers for the equipment. You can use the 10/3 to the equipment but you want to somewhat protect the equipment with a 15 amp breaker.

You dont wan't to install both pieces on a single 30 amp circuit.
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Old 01-30-2009, 12:12 AM   #6
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Multiple 220 volt outlets


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You dont wan't to install both pieces on a single 30 amp circuit.
Why not? Breakers aren't designed to take the place of overloads. The motor can burn up almost as easily on a 15 amp breaker. If you have a fault that isn't going to magnetically trip a 30 amp breaker, it won't magnetically trip a 15 amp breaker either. So you are down to the thermal trip profiles, and the 15 amp just trips a few minutes sooner. Not soon enough to keep the motor from burning up in most cases.
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Old 01-30-2009, 02:10 AM   #7
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Multiple 220 volt outlets


I don't see how you can suggest a 30 amp branch circuit for 230 volt power tools that are going to have cords and plugs rated either 15 or 20 amps (6-15's or 6-20's). The receptacles those tools will plug into must be rated 30 amps the minute you put that multi receptacle branch circuit on a 30 amp double.
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Old 01-30-2009, 03:31 AM   #8
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Why not? Breakers aren't designed to take the place of overloads
Knock yourself out then. What I meant was, I wouldn't. Doesn't seem smart. Motor says 15 amps, I'd put it on a 15 amp circuit.
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Old 01-30-2009, 05:48 AM   #9
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Multiple 220 volt outlets


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Originally Posted by Gigs View Post

It should be fine to run both of them on a single 30 amp circuit. 10 gauge wire gets 30 amp breaker.
Its actually a code violation to do what you suggest. A 30 amp circuit gets a 30 amp receptacle...
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Old 01-30-2009, 06:07 AM   #10
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Multiple 220 volt outlets


According to 430.24 the feed wires should be a #8
Need more name plate information to figure out the breaker size.
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Old 01-30-2009, 01:17 PM   #11
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Originally Posted by chris75 View Post
Its actually a code violation to do what you suggest. A 30 amp circuit gets a 30 amp receptacle...
Thanks, I didn't think about the receptacle.
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Old 01-30-2009, 01:52 PM   #12
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Multiple 220 volt outlets


Thanks for the input. The users manual for the table saw says to use a 20 amp time lag fuse. The users manual for the dust collector says to use an appropriately rated circuit breaker (the motor plate says 14.7 amps).

I suspect that what I need to do is:
1) Add a double 30 amp breaker to the main panel (I assume this breaker is really 15 amps per side)?
2) Run 10/3 cable from the main panel to a small sub panel.
3) Use a 20 amp breaker for the output to the table saw.
4) Use a 15 amp breaker for the output to the dust collector.

What say you?
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Old 01-30-2009, 03:26 PM   #13
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Multiple 220 volt outlets


Quote:
Originally Posted by Strider View Post
Thanks for the input. The users manual for the table saw says to use a 20 amp time lag fuse. The users manual for the dust collector says to use an appropriately rated circuit breaker (the motor plate says 14.7 amps).

I suspect that what I need to do is:
1) Add a double 30 amp breaker to the main panel (I assume this breaker is really 15 amps per side)?
2) Run 10/3 cable from the main panel to a small sub panel.
3) Use a 20 amp breaker for the output to the table saw.
4) Use a 15 amp breaker for the output to the dust collector.

What say you?
I say buy some 12-2 and be done with it.
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Old 01-30-2009, 03:30 PM   #14
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Multiple 220 volt outlets


The other thing when you use the 12-2 NM or UF's cables make sure you remarked the white conductor with either tape or sharpie permenant marker.

That way you know it is not wired for 120 volt set up.

Merci,Marc
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Old 01-30-2009, 06:23 PM   #15
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Multiple 220 volt outlets


Quote:
Originally Posted by Strider View Post
1) Add a double 30 amp breaker to the main panel (I assume this breaker is really 15 amps per side)?
?
The double 30 amp breaker is 30 amps per side.

With 15/20 amp cord and plug equipment you don't have the problem of a 15 amp motor safeguarded only with a 30 amp breaker because the matching (15 or 20 amp) receptacle needs a breaker no more than 20 amps either at a subpanel or at the main panel. With cord and plug equipment you have to be conscious of not plugging both into receptacles served by the same 20 amp. subcircuit.

With cord and plug equipment, it is easy to overlook installing a 40 amp feed with 8 gauge wire in anticipation of connecting motorized equipment and sizing up the implications of the 125% load provisions of 420.34 of the NEC. Meanwhile not plugging both pieces of equipment into receptacles on the same side of the 30 amp. line would avoid random breaker trips.
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Last edited by AllanJ; 01-30-2009 at 06:53 PM.
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