Motor question - Can a 1/6 hp motor be connected to a single pole 20 amp breaker? As I see it, you can go no higher than 250 % of the FLA of the motor or to the next size breaker. That would equate to a 15 amp breaker. Additionally, I understand that multiple motors or a motor and other loads can be connected to general purpose branch circuits. However, I only have this one motor so it doesn't seem to fit that criteria.
Fractional horsepower motor on 20 amp breaker
- Thread starter khkn1598
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hbiss
EC, New York NEC: 2017
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- Little Falls, New York NEC: 2017
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- EC
Re: Fractional horsepower motor on 20 amp breaker
Normaly motors that small are internally protected so there should be no problem.
-Hal
Normaly motors that small are internally protected so there should be no problem.
-Hal
Re: Fractional horsepower motor on 20 amp breaker
You are correct. The motor does have thermal overload protection. But I do not see a section that allows for connection above 250% of the name plate rating. Can anyone help me find the section that allows for ground fault, short circuit, and overcurrent protection on a permanently mounted motor to be larger than 250% or the next size?
You are correct. The motor does have thermal overload protection. But I do not see a section that allows for connection above 250% of the name plate rating. Can anyone help me find the section that allows for ground fault, short circuit, and overcurrent protection on a permanently mounted motor to be larger than 250% or the next size?
richwaskowitz
Senior Member
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- Shelby Twp. MI, near Detroit
Re: Fractional horsepower motor on 20 amp breaker
If the circuit breaker is the sole overcurrent and short circuit protection provided then the answer is no. Generally there would be a two component protection provision. The fuse or circuit breaker would protect the wiring between the fuse/breaker and the motor from the higher but shorter duration short circuit currents and a thermal type overcurrent would protect the wiring within the motor from a sustained overload current that would not harm the wiring to the motor but could damage the much smaller (and more vulnerable to fire) wire within the motor.
If the circuit breaker is the sole overcurrent and short circuit protection provided then the answer is no. Generally there would be a two component protection provision. The fuse or circuit breaker would protect the wiring between the fuse/breaker and the motor from the higher but shorter duration short circuit currents and a thermal type overcurrent would protect the wiring within the motor from a sustained overload current that would not harm the wiring to the motor but could damage the much smaller (and more vulnerable to fire) wire within the motor.
Re: Fractional horsepower motor on 20 amp breaker
Again, that is the case, the motor has its own internal thermal overload protection. The 15 amp breaker protects the wiring to the motor. It would seem that this motor could be installed on a 20 branch circuit, but I can't find a code section that would allow it.
Again, that is the case, the motor has its own internal thermal overload protection. The 15 amp breaker protects the wiring to the motor. It would seem that this motor could be installed on a 20 branch circuit, but I can't find a code section that would allow it.
Re: Fractional horsepower motor on 20 amp breaker
430.32 (A) concerns motors greater than 1 horsepower. The motor in question is a 1/6 horsepower motor on a 20 amp breaker. The motor has thermal overload. Is this compliant. My understanding is that it would have to be served by a 15 amp breaker.
430.32 (A) concerns motors greater than 1 horsepower. The motor in question is a 1/6 horsepower motor on a 20 amp breaker. The motor has thermal overload. Is this compliant. My understanding is that it would have to be served by a 15 amp breaker.
Re: Fractional horsepower motor on 20 amp breaker
I don't have my 2002 code book here so I referenced a 1999 handbook. Article 430-53 Several Motors or loads on one branch circuit or one motor and other loads.would allow allow you to procede with the 20amp install if I am reading it correctly.
(A) Not over 1 horsepower. Several Motors each not exceeding 1hp in rating shall be permitted on a nominal 120v branch circuit protected at not over 20 amps or a branch circuit of 600volts, nominal or less on a 15 amp if all of the following are met
a.FLA of each motor does not exceed 6 amps
B. the rating of the branch circuit short circuit and ground fault protective device marked on any of the controllers is not exceeded.
3. Individual overload conforms to section 430-32
I don't have my 2002 code book here so I referenced a 1999 handbook. Article 430-53 Several Motors or loads on one branch circuit or one motor and other loads.would allow allow you to procede with the 20amp install if I am reading it correctly.
(A) Not over 1 horsepower. Several Motors each not exceeding 1hp in rating shall be permitted on a nominal 120v branch circuit protected at not over 20 amps or a branch circuit of 600volts, nominal or less on a 15 amp if all of the following are met
a.FLA of each motor does not exceed 6 amps
B. the rating of the branch circuit short circuit and ground fault protective device marked on any of the controllers is not exceeded.
3. Individual overload conforms to section 430-32
Re: Fractional horsepower motor on 20 amp breaker
I think you are correct, a 1/6HP motor requires a 15A breaker:
430.52(C)(1) exception #1:
Where the values for branch circuit short-circuit current.......do not correspond to the standard sizes.... the next higher standard size may be used.
Since 15A is the smallest standard breaker, it may be used when it is larger than 250% of the rated motor current.
Steve
[ September 15, 2004, 12:52 PM: Message edited by: steve66 ]
I think you are correct, a 1/6HP motor requires a 15A breaker:
430.52(C)(1) exception #1:
Where the values for branch circuit short-circuit current.......do not correspond to the standard sizes.... the next higher standard size may be used.
Since 15A is the smallest standard breaker, it may be used when it is larger than 250% of the rated motor current.
Steve
[ September 15, 2004, 12:52 PM: Message edited by: steve66 ]
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Re: Fractional horsepower motor on 20 amp breaker
khkn1598,
I agree with your initial analysis and Steve66's recent one.
When interpreting the NEC it is important to consider overall context as well as the specific Section cited. In this case, Art 430 is broken down in to "Parts" as well as "Sections." Since the motor has integral overload protection, we are only discussing the "Motor Branch-Circuit Short-Circuit and Ground-Fault Protection:" i.e., Part IV.
There is no provision for the motor you have described beyond Sections 430.52(A),(B) and (C)(1).
Of course, if the SC or GF actually occurred in the motor itself, the branch-circuit conductors will still be adequately protected by an otherwise properly applied OCPD and the motor would still have to be replaced or repaired. Since there is no logical reason not to be able to apply 430.53 other than the fact there are no other loads on the circuit, if necessary,it might be a good application of 90.4's "special permission" clause.
I feel a Proposal coming on.
khkn1598,
I agree with your initial analysis and Steve66's recent one.
When interpreting the NEC it is important to consider overall context as well as the specific Section cited. In this case, Art 430 is broken down in to "Parts" as well as "Sections." Since the motor has integral overload protection, we are only discussing the "Motor Branch-Circuit Short-Circuit and Ground-Fault Protection:" i.e., Part IV.
There is no provision for the motor you have described beyond Sections 430.52(A),(B) and (C)(1).
Of course, if the SC or GF actually occurred in the motor itself, the branch-circuit conductors will still be adequately protected by an otherwise properly applied OCPD and the motor would still have to be replaced or repaired. Since there is no logical reason not to be able to apply 430.53 other than the fact there are no other loads on the circuit, if necessary,it might be a good application of 90.4's "special permission" clause.
I feel a Proposal coming on.
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