Nope.
It's general.
If you think it's incorrect, then I once again invite you to post what you believe to be the correct equation.
Fan Airflow vs Power Consuption
- Thread starter bpk
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It's general.
If you think it's incorrect, then I once again invite you to post what you believe to be the correct equation.
Rick Christopherson
Senior Member
Bes, I'm going to step away from the discussion for a few hours to do something with my son. In the mean time, I would invite you (actually beg you) to take a closer look at what you are saying here. I am throwing away the posting that I started to write here in order to give you some more time to think about this.
I am not challenging your equation, but I am challenging how you are using it as it relates to this THREAD. As you think about this discussion, please re-read the OP's comments, and also understand that I am NOT the same person that earlier questioned a statement you made.
Please pause and reread what has been written here. Please make sure that you are not arguing a topic that is not the same as what I (personally) have stated.
If you do this and still believe that we are arguing the same thing, then I will take the time to engage you. I will be back in a couple of hours.
You disputed its general validity.
If you think you have a better equation then please post it.
Hope what you are going to to do with your son goes well for both.
Rick Christopherson
Senior Member
I'm having a good weekend with my son, so I have decided that I am not going to bother trying to argue with you and spoil it. However, I will at least point out that I have repeatedly mentioned the "g" (acceleration of gravity) term that you have yet to address.
If you want to discuss this without blowing off that rather critical topic, then I am open to it. However, I am not going to spoil a good weekend butting heads otherwise.
Electchicken
Member
- Location
- Canada
I agree
I agree
A fractional HP motor will draw almost all it's FLA unloaded, but for motors above 1 or 2 HP it will draw 30% of its FLA unloaded.
I agree
A fractional HP motor will draw almost all it's FLA unloaded, but for motors above 1 or 2 HP it will draw 30% of its FLA unloaded.
- Occupation
- Licensed Electrician
Jumping in here to ask- If the pump (or fan, since that is what the OP was asking) is stopped from doing any work, other than keeping its moving parts moving, why do the amps go through the roof?
jumper
Senior Member
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- 3 Hr 2 Min from Winged Horses
Bad tempers?
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- Licensed Electrician
Further compounded by high ambient temperatures. Without a doubt those are highest on the roof.
- Location
- Massachusetts
The answer is obvious, place the fan motor away from any roofs. 
You need mass to calculate power.
And, yet again, if the think the formula is invalid, please post what you think is right.
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jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
I dunno crap about about pump/ fan flow equations, but I know that if I forget to change the AHU filter and the cooling/heating don't work my wife threatens to throw me off the roof.
I wouldn't dispute that. I don't very often deal with motors smaller than a few tens of kW.
Rick Christopherson
Senior Member
The "system" isn't doing work, but that doesn't mean the "motor" isn't doing work. That is the problem that is being overlooked in many of the original responses.
If you would like an analogy, consider a belt-driven compressor. If the compressor stalls, then no work is being performed by the compressor. However, we all know that the motor driving the compressor will still expend power just for the slipping belt.
- Location
- Massachusetts
bpk said:
I happen to have this squirrel cage fan in my basement.
With it operating as unrestricted as possible at full speed. 4.8 amps
With it operating with only the the inlet blocked at full speed 3.8 amps
With it operating with only the outlet blocked at full speed 3.7 amps
I have to assume you have switched the topic to positive displacement pumps and not centrifugal blowers.
Rick Christopherson
Senior Member
OK, if you say so. But why do you need WEIGHT?
To get mass, of course.
Let me give you a very simple statement to demonstrate the difference between weight and mass.
A force of one newton acting on a mass of one kilogram fives it an acceleration of one metre per second.
That force would give that 1kg mass the same acceleration here on earth or on the moon. But the weight would be much less on the moon.
Now, instead of disputing the formula, why don't you simply provide the one you believe to be correct.
Enjoy your day with your sun.
- Occupation
- Licensed Electrician
Equations are everything unless domestic tranquillity is involved.I dunno crap about about pump/ fan flow equations, but I know that if I forget to change the AHU filter and the cooling/heating don't work my wife threatens to throw me off the roof.
Rick Christopherson
Senior Member
No. The question stands. Why does your equation need a weight?
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