Load calculation for fans

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Dmc16

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Installing wall mount fans in classrooms. Plug and chord, three speed with pull chain. 1.5 a each, 120 v. Considering them continuous duty equip, according to my math 1.8 (1.5x1.25) amp draw each. I have total of 20 to install. I think six to seven per circuit. Run 12-2 mc. Install a single receptacle at each so no other load can be plugged in. They are not accessible anyway. Have I missed anything? Thanks for help.
 
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Dmc16 said:
Installing wall mount fans in classrooms. Plug and chord, three speed with pull chain. 1.5 a each, 120 v. Considering them continuous duty equip, according to my math 1.8 (1.5x1.25) amp draw each. I have total of 20 to install. I think six to seven per circuit. Run 12-2 mc. Install a single receptacle at each so no other load can be plugged in. They are not accessible anyway. Have I missed anything? Thanks for help.
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#12 wire on 20A OCPD, loaded to 80% for continuous load yields 16A continuous. 16A / 1.5A per fan = 10.7 fans/circuit or 10 fans that can run on high, continuously, simultaneously, assuming that the 1.5A is the current draw on high. Not sure if there are any demand factors you could apply to allow more fans to be run on one circuit.

If you ran a MWBC you could run 21 fans on high at the same time continuously while only needing one more conductor on a 120/240V service, or 32 fans on a 3ph service w/2 more conductors with a 120/208 3ph service.
 
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Still figuring this out
JFletcher said:
Welcome to0 the forum
Thanks for the reply, I actually planned on pulling a 12-3 up to feed since I have some in stock, typo my apologies. I was trying to apply the continuous duty multipler, but I see how the 80% is same thing. Double checked nameplate on fan today says 1.8 on high, doing the math its 8.8 fans. Even did a load check with extension chord and it was right where it should be. But I was curious if I needed to consider article 430, but I think it is utilization equip fixed in place.


#12 wire on 20A OCPD, loaded to 80% for continuous load yields 16A continuous. 16A / 1.5A per fan = 10.7 fans/circuit or 10 fans that can run on high, continuously, simultaneously, assuming that the 1.5A is the current draw on high. Not sure if there are any demand factors you could apply to allow more fans to be run on one circuit.

If you ran a MWBC you could run 21 fans on high at the same time continuously while only needing one more conductor on a 120/240V service, or 32 fans on a 3ph service w/2 more conductors with a 120/208 3ph service.
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Dmc16 said:
Yes, it's a motor. According to specs 1/6 hp
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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. All 125% factoring for motors is done in Article 430 and trickles into Article 440, and perhaps a few other Articles such as 695 for fire pumps.

As such, in determining ampacity, only the largest motor is factored by 125%. The rest are just added (at 100%).

If you put 20 of these fan motors on two circuits at 10 each, that'd be 1.5A × 10.25 = 15.4A per circuit.

You want to run 6 per circuit, 1.5A × 6.25 = 9.4A per circuit. This would be in the right area if you want to allow for start-up inrush on a 20A breaker.
 
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Ok I see. So I followed 430.42 over to 430.53 which I believe is saying yes we can put the fans on 120v circuit but nothing to do with sizing, which is where your references brought me. If I am understanding correct, its late for me.
The part that I'm stuck on is they are really just a fan which bolts to the wall, not much different from floor fan. But once it's mounted it needs power, and if there is 20 then we have to be careful.
So I will stay conservative and try to keep it to 6 no more than 7 per circuit.
I also have a call into the ahj as well to be safe.

Smart $ said:
See 430.24

For future reference, see 220.14(C).
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430.24 deals with multiple motors on single circuit.

I would not be concerned with inrush/startup current on such a small fan. 1.8 FLA ea, on high, on a 20A circuit, you could still run 10 per circuit (1.8 x 125% + 9 x 1.8 = 18.45A). What are the odds that all 10 fans will be on simultaneously on high, for hours on end? Fans on high tend to make a fair amount of noise, something that might be a problem in a classroom setting. Is there any AC, or are these fans it? If the latter, then they could very well be on high all day.

You dont have to consider them a continuous load, tho if they are going to be, then running one additional circuit wouldnt hurt. The cost of a bit of extra wire and another breaker or 3 vs 2 pole is probably quite low compared to the labor on the job.

Besides, if you push the wiring to the max, and they decide on slightly more powerful fans (say 2.5A draw) now or down the road, or plug in a floor fan in addition to the wall fan, they arent going to be able to do it
 
Just to be a killjoy. This appears to me to be a group Motor installation assuming the overcurrent protection is built into the motor. Are you allowed to even use a 20 amp circuit breaker in group Motor installation like this?
 
That is why I posted the question where does it fall, fixed in place utilization equip or motors. It's blurry to me. I think I could get away with the 20 amp breaker as long as I keep it light. 6 to 7 fans at most per leg. They pull 1.8x6=10.8. Plenty of room left on breaker in my humble opinion. And I think diversity will play a role as well, not running on high at same time, or starting up at same time. Also they are a bit noisy for classrooms so I anticipate low to med.
one issue I need to call manufacture on is built in thermals, did not see it on nameplate. If not then what?????

petersonra said:
Just to be a killjoy. This appears to me to be a group Motor installation assuming the overcurrent protection is built into the motor. Are you allowed to even use a 20 amp circuit breaker in group Motor installation like this?
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petersonra said:
Just to be a killjoy. This appears to me to be a group Motor installation assuming the overcurrent protection is built into the motor. Are you allowed to even use a 20 amp circuit breaker in group Motor installation like this?
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I looked it up. 430.53 says you can have a 20A CB on 120V group motor installations so I am inclined to think this is OK.
 
electrofelon said:
Ive always been unclear on how to handle this: consumer type items with motors. If 430 applies, how do we determine the current? I am not sure that I see the exceptions to 430.6(A)(1) applying to most consumer fans....?
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Dealing with one motor can be complex, yet you ask vaguely about multiple consumer grade fans... :sick:

Can you be more specific?
 
JFletcher said:
...
I would not be concerned with inrush/startup current on such a small fan. ...
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I would not either when turning on or plugging in one, even a couple, three at a time... but have 6 to 7 come on instantaneously, such as on power restoration after an outage... I think it's best to provide a bit of padding. :happyyes:
 
All ol the fans are wall mounted. Air king model #9518 listed for commercial/industrial locations. Not heavy industrial (explosion proof). They actually have 10' chord, which would reach some of classroom receptacles. But I thought it prudent to mount single receptacle closer to fan to keep them off general classroom outlets.
So smart $ your saying less then my theory? I've been back and forth between 5 at a min and as much as 7.
thanks for the help! :thumbsup:

Smart $ said:
I would not either when turning on or plugging in one, even a
couple, three at a time... but have 6 to 7 come on instantaneously, such as on power restoration after an outage... I think it's best to provide a bit of padding. :happyyes:
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Dmc16 said:
All ol the fans are wall mounted. Air king model #9518 listed for commercial/industrial locations. Not heavy industrial (explosion proof). They actually have 10' chord, which would reach some of classroom receptacles. But I thought it prudent to mount single receptacle closer to fan to keep them off general classroom outlets.
So smart $ your saying less then my theory? I've been back and forth between 5 at a min and as much as 7.
thanks for the help! :thumbsup:
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Why not use the existing outlet? Typically classroom outlets are seldom used. Also saves a lot of installation costs. Is this a public or private school? That could make a difference from a contractual standpoint.

RC
 
electrofelon said:
Ive always been unclear on how to handle this: consumer type items with motors. If 430 applies, how do we determine the current? I am not sure that I see the exceptions to 430.6(A)(1) applying to most consumer fans....?
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I agree with you. Who knows what the design of these motors truly is. Seldom would such an appliance even mention horsepower, and any amp rating is the maximum design for the motor but not necessarily what it might typically draw, though it is probably still close to actual draw.

Is also likely a shaded pole motor and doesn't have too high of a starting current, I'd bet you could start 20 of them without tripping the breaker in many instances, you just couldn't run all 20 for extended periods of time as it would trip on overload.
 
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