Upgrade 20A to 30A breaker?

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  #1  
Old 09-28-19, 05:37 PM
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Upgrade 20A to 30A breaker?

I have a 20A 220V circuit in my wood shop that Iíd like to convert to 30A. I canít change the wiring without ripping up a lot of sheet rock in finished basement.

I want to run a 5hp Jointer/Planer that is rated at 25A. The specs for the machine say it comes with a 12 gauge cord but only 10í long. My wiring is 12 gauge. Itís a pretty short run from the panel to the shop. (Certainly less than 50í of wire, but probably less).
Iíve read that for some motors its ok to run 30A on 12Gauge wire.

Can I just change the circuit breaker to 30A? If not is there anything else I can do? Special breaker to handle higher peak at start up?

Thanks
 
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Old 09-28-19, 05:41 PM
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Motor specs

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Here are the specs for the motor I intend to run.
 
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Old 09-28-19, 09:02 PM
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If the circuit is an outlet circuit for use with cord and plug equipment then you are limited to 20A using #12 wire. If the jointer is hardwired (no plug) then you can get by with a 30A breaker.
 
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Old 09-29-19, 07:12 AM
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I need to backup a bit. Did the jointer come with a factory cord and plug? Since the manufacturer is saying 30A circuit minimum I'm assuming not. If the motor is a true 5HP then by the NEC the circuit should be a 35A circuit. Since the manufacturer is saying 30A then for the circuit to be correct you'd need to use #10 wire. The building wire size requirement and the cord size used by the manufacturer do not go hand and hand. If the jointer came wired with a cord it should have a 30A plug and in that case you need a 30A outlet and the wiring also needs to be 30A or #10Cu.

As I said earlier if you hardwire it using the #12 circuit wire with a 30A breaker it will most likely be okay. But I'll add that the motor needs to have its own overload protection (reset button). Using the #12 is not to the letter of the NEC.

Based on your comments I assume the circuit wiring is NM-b, not THHN in conduit.
 
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Old 09-29-19, 07:38 AM
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Thanks Pattenp,

I tried to upload a screenshot of the specs on the motor and electrical from the mfr website, but it isn’t clear.
Here is what it says about the electrical requirements and the motor:

Minimum circuit size...30A
Switch...Magnetic with Thermal Overload Protection
Cord Length....10ft
Cord Gauge....12gauge
Plug included....No
Reccomended Plug type....NEMA L6-30

For the Motor:
Type....TEFC Capacitor Start Induction
Horsepower....5HP
Amps....25A
Speed....3450RPM.
Cycle....60Hz

Does that help determine what I can do?
 

Last edited by mchristo; 09-29-19 at 07:39 AM. Reason: Spell correct
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Old 09-29-19, 07:44 AM
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Sorry, based on that info you need #10 wire to provide the correct circuit size of 30A per the manufacturer.
 
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Old 09-29-19, 08:24 AM
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The startup current is likely to be north of 100 Amps. The 30a breaker needs to be HACR rated and even then MIGHT not hold at startup. This device is not too demanding on starts, like an air compressor, so maybe my fear is unfounded.
 
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Old 09-29-19, 08:35 AM
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I'll add that if the jointer does trip the 30A breaker on startup, which it shouldn't based on manufacturer circuit requirements, as an example increasing the breaker to a 40A on the #10 wire requires the equipment to be hardwired. You aren't allowed to upsize the breaker to account for startup surge on an outlet circuit for cord and plug connected motor operated equipment. Welder circuits are the only cord and plug circuits where you can have breakers larger than the wire capacity.
 
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Old 09-29-19, 10:54 AM
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Unhappy

Thanks everyone. Not what I was hoping to hear, but its what I thought you all would say. Iíll have to go with a less powerful machine. Or put a 5hp machine in my garage which has a 50A circuit (not ideal due to humidity in there).
Iím curious why a welder is permitted to use #12 wire on 30A breaker though?
Also curious why the cord can be #12. Probably b/c it is so short?
Thx again!
 

Last edited by mchristo; 09-29-19 at 10:55 AM. Reason: Additional comment
  #10  
Old 09-29-19, 11:45 AM
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An STOW cord to an appliance carries a 25A rating for 12awg. A nmb 12 awg cable in a wall carries a 20 a rating. No length factor.
 
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Old 09-29-19, 01:06 PM
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Welders duty cycle is what determines the wire size required.
 
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