Question about adding a 30 amp breaker to sub panel

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  #1  
Old 09-19-13, 06:44 PM
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Question about adding a 30 amp breaker to sub panel

I'm installing a 230 volt outdoor water pump that pulls 18 amps on start-up next to the garage. I'm planning on using a 30 amp dbl pole breaker with 12 gauge wire to power it. I assume this part is fine.

My question is with the main panel in the house. The garage sub panel is powered by a 20 amp dbl pole breaker from the house main with 10 gauge wire.

Can I just pop out the 20 amp breaker on the main and replace with a 30 amp dbl pole breaker and be good to go or are there other things I need to deal with? The rest of the sub panel powers some lights and outlets and I don't use any other heavy duty electrical gear.

Thanks in advance for your responses!
 
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Old 09-19-13, 07:09 PM
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Can I just pop out the 20 amp breaker on the main and replace with a 30 amp dbl pole breaker and be good to go or are there other things I need to deal with?
As long as the feeder to the garage is #10 copper (you said it was) and as long as the subpanel is rated at least 30 amps, your plan is fine.
 
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Old 09-19-13, 07:12 PM
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I'm planning on using a 30 amp dbl pole breaker with 12 gauge wire to power it
I'd either drop this breaker back to 20 amps or increase the wire to 10 gauge, even though the draw isn't that much. Dropping the breaker will coincide with the wire size.
 
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Old 09-19-13, 07:22 PM
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Thanks. Will the rating be listed on the panel? I didn't notice it, but there is a big label on the inside cover. It's a Murry panel.
 
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Old 09-19-13, 07:27 PM
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Thanks, chandler. That's easy enough. Are wire gauges and breaker amps paired like that as a standard or is that just a little extra margin of safety that an owner would do to go above and beyond?
 
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Old 09-19-13, 07:27 PM
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Thanks. Will the rating be listed on the panel? I didn't notice it, but there is a big label on the inside cover. It's a Murry panel.
You didn't mention how big this panel is, but I assume it's about 6 to 12 circuits. The voltage rating is probably about 100 amps. Many small 2 to 4 circuit panels are rated 40 to 70 amps. It should be on the label inside the cover. Any doubts, post a picture of the label here so we can see it.

By the way, what is the horsepower of the pump motor?
 
  #7  
Old 09-19-13, 07:32 PM
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The pump is 1 hp. The sub panel has 8 circuits. Since there is a double pole breaker at the main I can assume the panel carries 220+ volts, correct?
 
  #8  
Old 09-19-13, 07:38 PM
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I just ran out and checked. The panel is rated to 125 amps and has four circuits used (2-20 amps and 2-15 amps). So with only 70 amps used I have 55 amps headroom.

So given all the specs would you decrease the breaker to 20 or increase the wire gauge to 10?
 
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Old 09-19-13, 07:44 PM
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The pump is 1 hp. The sub panel has 8 circuits. Since there is a double pole breaker at the main I can assume the panel carries 220+ volts, correct?
I can tell you the panel is good for a 30 amp feed without you even looking, but you should look to satisfy yourself. The panel would be 120/240 volts. I just checked the Square D Motor Data Calculator. For a 1 HP 240 volt motor you only need #14 AWG wire and a 15 amp 2 pole breaker.

Single Phase Motor Data
 
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Old 09-19-13, 08:45 PM
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Except the pump label says the amperage draw maxes out at 18.6 amps. There were two specs, one labeled "Amps" and the other "Amps SW" or something like that. there were two listings for each spec. I remember the lowest number was 6 amps and the highest was 18 point something (18.6 I think).

It looked like this:

Amps 6.3/9.8
Amps SW 12.4/18.6
 
  #11  
Old 09-20-13, 07:23 AM
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Except the pump label says the amperage draw maxes out at 18.6 amps.
The starting amperage is momentary. You can still use #12 wire and a 20 amp breaker if you would feel more comfortable with that, but it isn't necessary. Personally, I would rarely use wire smaller than #12.
 

Last edited by CasualJoe; 09-20-13 at 08:01 AM.
  #12  
Old 09-20-13, 07:48 AM
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Yes, CasualJoe, I just got confirmation that the Maximum Service Factor amps on that motor are 9.2. So you are correct. Thanks.
 
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