Load calculation for fans

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Dmc16 said:
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So smart $ your saying less then my theory? I've been back and forth between 5 at a min and as much as 7.
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I'd not think twice about running 7 units on a 20A circuit. All I'm saying is 10 (since you have 20 to power) may be just a tad too much and trip the breaker on a power restoration. Could the circuit handle 10 day in and day out... yes.
 
Thanks smart $, just clearing up details. Have to complete this install by end of August which is possible for sure with the forums guidance. When you said padding on circuit wasn't sure. I was taught to be cautious by the guy who helped me get licensed, hence the original post.
And I'm avoiding the classroom outlets since the district uses most for technology, laptops, smartboard, computer tower to name a few. Plus random stuff such as soup warmers etc, power strips and extensions chords run rampant. I've spent good part of last year installing outlets to keep the usage of such items down.


Smart $ said:
I'd not think twice about running 7 units on a 20A circuit. All I'm saying is 10 (since you have 20 to power) may be just a tad too much and trip the breaker on a power restoration. Could the circuit handle 10 day in and day out... yes.
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Dmc16 said:
Thanks smart $, just clearing up details. Have to complete this install by end of August which is possible for sure with the forums guidance. When you said padding on circuit wasn't sure. I was taught to be cautious by the guy who helped me get licensed, hence the original post.
And I'm avoiding the classroom outlets since the district uses most for technology, laptops, smartboard, computer tower to name a few. Plus random stuff such as soup warmers etc, power strips and extensions chords run rampant. I've spent good part of last year installing outlets to keep the usage of such items down.
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You're welcome. :thumbsup:
 
Dmc16 said:
Yes, it's a motor. According to specs 1/6 hp
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1/6 hp @ 115vac from T.430.248 corresponds to 4.4 FLA

Nameplate may show 1st speed at 1.5 FLA, so highest 3rd speed may be 1.5 x 3 ~4.5 FLA for each motor 430.22(B)
 
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ramsy said:
1/6 hp @ 115vac from T.430.248 corresponds to 4.4 FLA

Nameplate may show 1st speed at 1.5 FLA, so highest 3rd speed may be 1.5 x 3 ~4.5 FLA for each motor
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I suppose I should have verified the FLA per table as you have. Nevertheless, this certainly casts a different light on the matter. The weird thing is how the manufacturer provides the data on their website and datasheet if the 4.4A is anywhere close to being accurate:
http://www.airkinglimited.com/page/industrial-wall-mount-fans.html#sixth
http://www.airkinglimited.com/specsheets/9518Spec.pdf

With this "revelation", a maximum of only 5 fans at would be permitted on a 25A #12 copper conductor circuit (4.4A×5.25=23.1A). This is assuming a circuit terminal temp' of 75°C.
 
Smart $ said:
First thing you have to understand, motors are never continuous for the purpose of determining service, feeder, and branch circuit requirements involving 125% factoring of continuous loads...
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2011 NFPA 210.19(A)(1) under 600 volts, declares 125% continuous rating shall be made "before the application of any
adjustment or correction factors"

I believe, Motor power factors (pf) are separate adjustments, (Informational Note 2) along with Temperature limits (Note 3), and Voltage drop (Note 4).
 
Smart $ said:
5 fans would be permitted on a 25A #12 copper conductor circuit (4.4A×5.25=23.1A). This is assuming a circuit terminal temp' of 75°C.
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Five 4.4 FLA Motors running at 23.1A would need a pf of 0.95. Can Inductive motors do that? What pf do tables 430.248 - 430.250 assume?
 
ramsy said:
Five 4.4 FLA Motors running at 23.1A would need a pf of 0.95. Can Inductive motors do that? What pf do tables 430.248 - 430.250 assume?
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The tables assume about the worst case power factor and efficiency you may find. I think one of the main ideas of doing it that way is that you won't need to redesign the circuit just because you replaced a failed motor with one of same horsepower rating.
 
Motors typically operate at their lowest power factors 0.1 when spinning with no load. If no windows are open before running the fans, there's no ventilation, and the blades spin with no load.

5 fans spin @ 0.1 pf until a window opens. (4.4A×5)/0.1=220A) How long can a 20A breaker hold?
 
ramsy said:
Motors typically operate at their lowest power factors 0.1 when spinning with no load. If no windows are open before running the fans, there's no ventilation, and the blades spin with no load.

5 fans spin @ 0.1 pf until a window opens. (4.4A×5)/0.1=220A) How long can a 20A breaker hold?
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If the fan is turning because of torque applied to the shaft, there is load on it. If the fan is supplying a duct that is blocked off, the load is less but there is still some load.

The room doesn't have a vacuum inside of it just because the windows are closed, that fan will move air within the room, these are just room circulation fans from what I understand not intake or exhaust fans which would have less load if shutters happened to be closed.
 
If Op's model 95185 Air King does not have a Nameplate, like my Air King does not, Nameplate FLA is not available as directed in last sentence of 430.6(A)(1). Spec sheets don't use 430.7 Nameplate convention, nor qualify as Nameplate FLA.

Therefore, fully-adjusted table values must be used. Since, 430.22(B) requires the largest value provided for multi-speed fans, I believe table 430.248 is needed to interpolate 1/6 horsepower to 4.4A. I use a similar model Air King, just framed for window mount, which needs ventilation in my case.
 
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ramsy said:
If Op's model 95185 Air King does not have a Nameplate, like my Air King does not, Nameplate FLA is not available as directed in last sentence of 430.6(A)(1). Spec sheets don't use 430.7 Nameplate convention, nor qualify as Nameplate FLA.

Therefore, fully-adjusted table values must be used. Since, 430.22(B) requires the largest value provided for multi-speed fans, I believe table 430.248 is needed to interpolate 1/6 horsepower to 4.4A. I use a similar model Air King, just framed for window mount, which needs ventilation in my case.
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I am not familiar with the model. I'm basing my comments strictly on information provided here and manufacturers from their website. I believe if the motor is spec'd as 1/6 horsepower on the nameplate, if it has one, the Table value of 4.4A must be used no matter what. If no nameplate and spec'd elsewhere as a 1/6 HP motor, still have to use the table value. Only if there is no mention whatsoever of HP rating can you use a published or nameplate ampere value... and even then Code has us interpolate the non-table FLA with Table FLA and HP. With 1/6 HP being the smallest listed for 1Ø, is there any other size one can interpolate to?
 
A partial excerpt from the NEC, bolding by me:

2011 NEC 430.6(A)(1) said:
Other than for motors built for low speeds (less than 1200 RPM) or high torques, and for multispeed motors, the values given in Table 430.247, Table 430.248, Table 430.249, and Table 430.250 shall be used to determine the ampacity [. . . ] multispeed motors will have full-load current varying with speed, in which case the nameplate current ratings shall be used.
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The OP says the fans are multispeed. So it seems clear you use the nameplate rating, not the table values. [Although grammatically, the first sentence should say "or multispeed motors," not "and multipseed motors".]

Cheers, Wayne
 
wwhitney said:
A partial excerpt from the NEC, bolding by me:



The OP says the fans are multispeed. So it seems clear you use the nameplate rating, not the table values. [Although grammatically, the first sentence should say "or multispeed motors," not "and multipseed motors".]

Cheers, Wayne
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Multispeed motor.... good point.

We are back to using a 1.5A FLA for sizing...???
 
Have not checked in recently,(my wife deleted page off I pad). That was a lot of info guys. I believe the motor has 1.8 amps stamped on it. I'd have to look tomorrow when on job. Yes they are multi speed with the 1.8 being high speed. And yes where are we???:?

Smart $ said:
Multispeed motor.... good point.

We are back to using a 1.5A FLA for sizing...???
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Let me add this as well, if the motor is stamped with something (volts,amps at a minimum)that is the reference we use if my memory serves.


QUOTE=Dmc16;1760233]Have not checked in recently,(my wife deleted page off I pad). That was a lot of info guys. I believe the motor has 1.8 amps stamped on it. I'd have to look tomorrow when on job. Yes they are multi speed with the 1.8 being high speed. And yes where are we???:?[/QUOTE]
 
Ok

Dmc16 said:
Let me add this as well, if the motor is stamped with something (volts,amps at a minimum)that is the reference we use if my memory serves.


QUOTE=Dmc16;1760233]Have not checked in recently,(my wife deleted page off I pad). That was a lot of info guys. I believe the motor has 1.8 amps stamped on it. I'd have to look tomorrow when on job. Yes they are multi speed with the 1.8 being high speed. And yes where are we???:?
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[/QUOTE]
 
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