Bill Dunlap Posted May 2 Share Posted May 2 I bought a new tool, called an Anemometer, which measures air flow in a number of different ways. I'm really only interested in CFM measurements since that's what the factories used when advertising their fans. I set up a test rig so that I could reliably compare different 12 inch fans for efficiency. I used CFM divided by watts consumed to come up with a number which I could use to compare fans to each other and to their advertised claims. I set the fans and the meter at exactly 3 feet apart with the meter center in the wing rather than the blade itself. I assumed that at least some fans will have a dead spot in the center due to wing design and differing badges. Results from four fans tested so far. Emerson 73646 4568 CFM @ 68.5 watts 66.6 CFM/W Verity's Junior 7772 CFM @ 68.2 watts 113.9 CFM/W Emerson 79646 APG 9200 CFM @ 36 watts 255 CFM/W GE BMY 5550 CFM @ 35.6 watts 155.9 CFM/W No surprise that the APG came out on top. It's well known as an excellent and efficient fan. A little more surprising is how well the BMY stacks up against the Emersons, especially the 73646. However, The Emerson lacks a motor tag so I suspect that it may actually be a 648 instead, which means it's spins a bit slower than the 12 inch models. You can guess which fan I use every day, all day long and have for years. That's a no brainer. All fans are well maintained, run at full speed and cleaned before use. Cheers, Bill 7 Quote Link to comment Share on other sites More sharing options...
David Allen Posted May 3 Share Posted May 3 This is a very interesting test! I am trying to understand how that instrument is measuring CFM based only on the velocity of air at one point. Did you have to program in the area of the aperture through which the air is passing? I've assisted technicians at industrial sites using meters similar to that for measuring CFM from HVAC systems in the past. They usually had a large funnel-shaped hood which brought the air together into an opening of known diameter; where the meter was located. The hood part was baffled to smooth out turbulent and uneven airflow; as well as capture all the air from the source. 1 Quote Link to comment Share on other sites More sharing options...
Doug Wendel Posted May 3 Share Posted May 3 I have the same question as David Allen. I see how this measures velocity at a certain distance, but I don't see how it measures volume of air moved over time (CFM). I'm sure I'm missing something. 1 Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted May 3 Author Share Posted May 3 This meter measures wind speed in mph and kph, volume in lpm and cfm. The math is done internally and is essentially mysterious to me. The accuracy, even according to their manual isn't great, but the numbers can be useful anyway, especially when used for comparisons. Cheers, Bill 1 Quote Link to comment Share on other sites More sharing options...
Louis Luu Posted May 3 Share Posted May 3 1 hour ago, Bill Dunlap said: This meter measures wind speed in mph and kph, volume in lpm and cfm. The math is done internally and is essentially mysterious to me. The accuracy, even according to their manual isn't great, but the numbers can be useful anyway, especially when used for comparisons. Cheers, Bill The whole system is all rigged I tell yah! Quote Link to comment Share on other sites More sharing options...
John Landstrom Posted May 3 Share Posted May 3 The whole idea blew me away ! Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted May 3 Author Share Posted May 3 (edited) This exercise showed me that at the least, I have a fan that bears looking at more closely. The fan which I thought was a 73646 probably isn't that at all, and running it with a 12 inch four wing blade buys me nothing. It may be a six wing motor, or 16 inch and maybe it's designed for overlapping blades. So, maybe this weekend I'll pop the cover off and have a another look. In the meantime, I'm going to use something that moves air more cheaply. Cheers, Bill Edited May 3 by Bill Dunlap Quote Link to comment Share on other sites More sharing options...
John McComas Posted May 3 Share Posted May 3 Good job Bill. I came to the same conclusion years ago about the Emerson 12 & 16" APG fans. Mike Coup of Vornado had quite a setup for measuring fan capacity & efficiency. They demo'd it to the AFCA members years ago when we had Fan Fair in Wichita. You can also find testing by GE labs back in the 1940's using weight scales and suspending the whole fan facing downward and measuring weight change based on air flow thrust. I always thought that would be an easy setup to compare all different styles of fans by measuring watts consumed and change in weight caused by thrust. Sorry, I could not find the picture of the test setup, but I did find one of Stan's boy doing some testing... Quote Link to comment Share on other sites More sharing options...
Russ Huber Posted May 3 Share Posted May 3 28 minutes ago, John McComas said: You can also find testing by GE labs back in the 1940's using weight scales and suspending the whole fan facing downward and measuringweight change based on air flow thrust. Billy Skolfield in the flesh. Quote Link to comment Share on other sites More sharing options...
Lawrence Smith Posted May 4 Share Posted May 4 This custom fan would be a great candidate to test , it has a .5 capacitor stator , new speed coil with a 71666 blade . I’ve ran it for hours already with no issues , high speed is a wind machine with the higher rpm, low speed is less than 400 rpm Quote Link to comment Share on other sites More sharing options...
Bill Dunlap Posted May 4 Author Share Posted May 4 Turns out, the inefficient fan is a 77648AL which is a 16 inch fan with overlapping blades. My suspicions were correct. I don't think I'll be changing this blade. When I tested the fan on low speed, the efficiency went up to where it's usable now. No point in running in high speed when there's little difference in air flow, but significant difference in amp draw. Cheers, Bill 1 Quote Link to comment Share on other sites More sharing options...
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