Figuring motor circuit 14's on a 30?

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ritelec

ritelec

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I'm aware that for ac units, It's permissible to have 14's and 12's on 30 and 40 amp circuits.

If a motor (non ac related) is 2 hp 240v 1 phase ( 12 amp) can it be installed with 14's on a 30 amp cb ?

I had asked motor questions concerning thermal protected motors at 250% but I believe in those cases the wire would be upgraded to match the ocp. 14's on 15, 12's on 20 etc..

thank you.
 
For a motor the conductor size and the OCPD size do not need to match. The OCPD is there to only provide short circuit and ground fault protection and can be many times greater than the ampacity of the conductor. Overload protection is provided by an overload device either integral to the motor or externally in the starter.
 
infinity said:
For a motor the conductor size and the OCPD size do not need to match. The OCPD is there to only provide short circuit and ground fault protection and can be many times greater than the ampacity of the conductor. Overload protection is provided by an overload device either integral to the motor or externally in the starter.
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So throw 240.4 (D) (3) out the window?

I see references to 240.4 (G),

Is this motor thing not just in reference to "AC" units as I thought, but also pool pumps, lathes, drill presses, basically "all" motor loads..?
 
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infinity said:
For a motor the conductor size and the OCPD size do not need to match. The OCPD is there to only provide short circuit and ground fault protection and can be many times greater than the ampacity of the conductor. Overload protection is provided by an overload device either integral to the motor or externally in the starter.
Click to expand...
Critical point highlighted for emphasis, in other words be careful about this issue and NEVER use ASSumptions.
 
ritelec said:
So through 240.4 (D) (3) out the window?

I see references to 240.4 (G),

Is this motor thing not just in reference to "AC" units as I thought, but also pool pumps, lathes, drill presses, basically "all" motor loads..?
Click to expand...


That is correct. Many guys were install 25 or 30 amp breakers on pool pumps with #12 wire to avoid the gfci. Fortunately the 2014 has changed it so that any single phase pool motor will require gfci not just 15 and 20 amp circuits
 
240.3 has a list of other articles that may have differences from the general rules of art 240. If you have an application in that list you need to go to that section to see what applies to that application. Most any inductive load will have a certain amount of "inrush" current that may give nuisance tripping if the general rules of 240 are followed. For motors (and AC compressors) the motor overload still protects the conductor from overload while the branch circuit device is primarily there for short circuit and ground fault protection.
 
Thinking about this it's still messing with my brain

I had a post about a larger receptacle on a smaller circuit.

Here you could have a 30 amp breaker. 14 wire. And a 30 amp receptacle.

For grins let's say it was installed by the laundry area for a motor

The house is sold and the new owner decides to install a electric dryer.
And uses this existing 3 wire receptacle fed from an existing 30 amp breaker

Would he have been in the wrong to use it.


Let's say anyone else wanted to use it for any other type of 30 amp.
Heat. Small oven. Ac window unit ( would window unit ac be allowed 14s on a 30)?

Not fighting this. Just trying to get it to make sense in my head.

Thank you.
 
For the motor circuit I think you could only consider the wires protected by the motor overload if it was hard wired. Introduce the general purpose 30A receptacle (not a special purpose connector used as a motor disconnect) and you can no longer justify the 14ga wire.

Tapatalk!
 
GoldDigger said:
For the motor circuit I think you could only consider the wires protected by the motor overload if it was hard wired. Introduce the general purpose 30A receptacle (not a special purpose connector used as a motor disconnect) and you can no longer justify the 14ga wire.

Tapatalk!
Click to expand...
The rules start to blur a little when you are talking about your usual 5-15 and 5-20 type receptacles. I will need to do some looking before giving much more comment on that subject.
 
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