1/4 HP 1 PH 115 V Motor On A 20 Amp Breaker? - Electrician Talk - Professional Electrical Contractors Forum
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Old 06-09-2019, 12:32 PM   #1
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Default 1/4 HP 1 PH 115 V Motor On A 20 Amp Breaker?

Engineered drawings show a basic 1/4 HP 1 PH 115 volt motor on a 20 amp breaker. I believe this is in violation of 430.52(C)(1) which states 'A protective device that has a rating or setting not exceeding the value calculated according to the values given in Table 430.52 shall be used'.

An exception states that if the value does not correspond with a standard rating, the next higher one can be used.

Table 430.52 states that the breaker can be 250% of the current listed in Tables 430.247 - 250. The value listed for this motor is 5.8 amps. 5.8 X 2.5 = 14.5, therefore a 15 amp breaker is the maximum.

Is there anything that allows a 20 to be used in this case? Or is the engineer an Ijit?
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Old 06-09-2019, 12:37 PM   #2
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is this motor will be hardwired or not ?

Keep in your mind most single phase motors do have interal overload protection so you may get some leeway on that. but if that motor do not have any overload protection then yuh you have to swap the breaker downsized it.
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Old 06-09-2019, 01:58 PM   #3
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Originally Posted by frenchelectrican View Post
is this motor will be hardwired or not ?

Keep in your mind most single phase motors do have interal overload protection so you may get some leeway on that. but if that motor do not have any overload protection then yuh you have to swap the breaker downsized it.
It is hardwired and it does have integral O/L.

It's a vent fan controlled by a basic wall switch.
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Old 06-09-2019, 09:33 PM   #4
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Go to 430.52(C)(1)Exception No. 2(c). He may have used that, IF the motor didn't start using the table#. Has this install already been tried with the 15amp?
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Old 06-09-2019, 10:34 PM   #5
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Quote:
Originally Posted by micromind View Post
Engineered drawings show a basic 1/4 HP 1 PH 115 volt motor on a 20 amp breaker. I believe this is in violation of 430.52(C)(1) which states 'A protective device that has a rating or setting not exceeding the value calculated according to the values given in Table 430.52 shall be used'.
If you're installing it as a motor circuit that is true. But for something this small there is little point to doing so. If you're running #12 conductors you may consider this a general purpose branch circuit. 430.32 would then apply:

Quote:
430.42 Motors on General-Purpose Branch Circuits. Overload protection for motors used on general-purpose branch circuits as permitted in Article 210 shall be provided as specified in 430.42(A), (B), (C), or (D).
The motor has its own overload protection, is not over 1 HP, and is permanently installed so only (D) would be relevant.

Quote:
(D) Time Delay. The branch-circuit short-circuit and ground-fault protective device protecting a circuit to which a motor or motor-operated appliance is connected shall have sufficient time delay to permit the motor to start and accelerate its load.
I can't see a 1/4 HP vent blower being a problem in this regard.
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Old 06-09-2019, 11:18 PM   #6
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Since I was pretty sure it was a violation, I used a15 amp breaker and it was able to start it, no problems.
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Old 06-10-2019, 04:48 AM   #7
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If you installed it on a circuit with lights it would be fine on a 20 amp circuit.

Quote:
210.23(A)(2) Utilization Equipment Fastened in Place. The total rating
of utilization equipment fastened in place, other than luminaires,
shall not exceed 50 percent of the branch-circuit ampere
rating where lighting units, cord-and-plug-connected utilization
equipment not fastened in place, or both, are also supplied.
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Old 06-10-2019, 08:40 PM   #8
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If you installed it on a circuit with lights it would be fine on a 20 amp circuit.
I thought of that too but it's on a dedicated circuit.

A lot of vent hoods have lights, not this one.
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Old 06-10-2019, 08:54 PM   #9
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I thought of that too but it's on a dedicated circuit.

A lot of vent hoods have lights, not this one.
It doesn't know that.
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Old 06-11-2019, 09:36 AM   #10
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1/4hp fan motor ... could have LOTS of lights and a fridge on that circuit
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Old 09-09-2019, 05:35 PM   #11
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Quote:
Originally Posted by micromind View Post
Engineered drawings show a basic 1/4 HP 1 PH 115 volt motor on a 20 amp breaker. I believe this is in violation of 430.52(C)(1) which states 'A protective device that has a rating or setting not exceeding the value calculated according to the values given in Table 430.52 shall be used'.

An exception states that if the value does not correspond with a standard rating, the next higher one can be used.

Table 430.52 states that the breaker can be 250% of the current listed in Tables 430.247 - 250. The value listed for this motor is 5.8 amps. 5.8 X 2.5 = 14.5, therefore a 15 amp breaker is the maximum.

Is there anything that allows a 20 to be used in this case? Or is the engineer an Ijit?
SD has a 10 Amp
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Old 09-09-2019, 08:12 PM   #12
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SD has a 10 Amp
I use those in control panels a lot. There are about 10 of them in the one I'm building for the plant I'm working on.
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Old 09-10-2019, 01:00 PM   #13
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430.42 has to do with the overload protection, 430.52 is about the short circuit protection. Different issues.

MM, I would have done it the way you did, install the 15A (but run #12) and if worked (which I would have known it would), leave it alone. If someone complains that it was "supposed" to be a 20A breaker, make them prove why.

And "because I said so" doesn't count...
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Old 10-06-2019, 04:31 PM   #14
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Quote:
Originally Posted by micromind View Post
Engineered drawings show a basic 1/4 HP 1 PH 115 volt motor on a 20 amp breaker. I believe this is in violation of 430.52(C)(1) which states 'A protective device that has a rating or setting not exceeding the value calculated according to the values given in Table 430.52 shall be used'.

An exception states that if the value does not correspond with a standard rating, the next higher one can be used.

Table 430.52 states that the breaker can be 250% of the current listed in Tables 430.247 - 250. The value listed for this motor is 5.8 amps. 5.8 X 2.5 = 14.5, therefore a 15 amp breaker is the maximum.

Is there anything that allows a 20 to be used in this case? Or is the engineer an Ijit?
I would use a 15 Amp breaker and a AC Manual Motor Switch with OL. used them on sub pump up to 2 hp for years and no problems
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Old 10-06-2019, 04:38 PM   #15
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Quote:
Originally Posted by micromind View Post
Since I was pretty sure it was a violation, I used a15 amp breaker and it was able to start it, no problems.
Why wouldn't it? Millions of furnace blower motors run on a 15A breaker.
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Old 10-06-2019, 07:43 PM   #16
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Why wouldn't it? Millions of furnace blower motors run on a 15A breaker.
A furnace blower motor is almost always the PSC type. This one was cap-start.....much higher starting current.
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Old 10-06-2019, 08:57 PM   #17
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A furnace blower motor is almost always the PSC type. This one was cap-start.....much higher starting current.
Even so, what's the running amps, about 5ish? No reason it wouldn't start on a 15A breaker
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