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 VAcuum motors & CFM 
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Joined: Fri Aug 26, 2016 7:08 pm
Posts: 77
Which Ametek or Lighthouse vacuum motor pulls the most CFM @ 28" and 44" in a 220v or 240v Motor? Posted this elsewhere by but no reply.


Mon Mar 20, 2017 1:26 am
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Joined: Fri Jan 08, 2010 10:36 pm
Posts: 1157
Location: Maryland
Lots of discussion on motors Here viewforum.php?f=15

This is a loaded question, there is no single best motor unless you are not constrained by any of the following,

Money
Mains Current supply
Space
control current limit.

Rick

PS. Please try not to multiple post in different areas, if you did not get the desired response to your first post maybe those viewing it did not have the answer or did not feel like doing the research for you. in the future id no response just post in the same thread with question marks or a nice Hello or Help.


Mon Mar 20, 2017 8:54 am
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Joined: Fri Aug 26, 2016 7:08 pm
Posts: 77
My replies aren't always coming thru. My method for calculating CFM is, example: The number just higher than 44" and the number just higher than 28" and divide the 44" into the next highest number to get a percentage ratio difference. Then take that ratio percentage to calculate the CFM @ 44" and 28" respectively from the Lighthouse bulletin. In my case a LH 2093-240 would be 106 @ 44" and 114 @ 28". Having said all this I don't know if my method is right or wrong. HELP!!!!! THANKS RON


Mon Mar 20, 2017 5:23 pm
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Location: Pennsylvania
As we discussed a few times you are way over thinking the whole motor flow at 44" it is not an "exact science" it gets you close but the motors do not add up inside the flowbench.

I would not be to worried about getting an exact calculation, I simply look at the motor flow chart and rough estimate the flow at 44", again it is just an approximate of potential to get you headed in the right direction.

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Tue Mar 21, 2017 8:01 am
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Location: Maryland
Ron just be clear what the motor can flow at 28" has no affect on your bench performance unless you plan on testing at 12" test pressure.

44 = 28" test pressure + the 16" delta P at full scale so the 44 number is just what the potential is at WFO pulling 28" and pegging the Delta P.

Rick


Tue Mar 21, 2017 7:30 pm
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Joined: Fri Aug 26, 2016 7:08 pm
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Hopefully I won't need to test that low. I was just curious about the individual motor CFM on the data sheet as to what it would be at 44" & 28". I feel confident that my motors will be more than enough for what I will be flowing. Thanks for your help, Rick!


Tue Mar 21, 2017 7:55 pm
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Joined: Wed Mar 03, 2010 3:40 pm
Posts: 1274
Location: Melbourne, Australia
ronm wrote:
Which Ametek or Lighthouse vacuum motor pulls the most CFM @ 28" and 44" in a 220v or 240v Motor? Posted this elsewhere by but no reply.

Ron, are you planning to use only one very large vacuum motor ?
But more seriously though, if you are planning to use multiple motors, the biggest individual motors available may not be the best choice.

Usually it comes down to most CFM per dollar, or maximum CFM per amp of available power.

Most of us are limited by the available power source to some maximum total flat out amperage, and we are (or should be) looking for the most efficient motors to get the highest possible CFM flow from whatever available power we have.

If there is then a choice between four motor "A" or six much smaller "B" motors, and both have similar efficiency, we might logically choose the lower cost option.

Asking what is the largest size motor available is not really asking the right question, especially if it turns out to be by far the most expensive and the least efficient. All of this is not immediately obvious when first starting out with building a flow bench, so don't be too concerned..

The trick is to find motors that have their efficiency peak around 44 inches, and the magic number for judging motors is CFM per amp at 44 inches.
The worst may be about 8CFM per amp, the very best about 18CFM per amp, and most "average" motors maybe around 12 CFM per amp.
That will give you some idea of how to judge the numbers from the available data.

Some of the smaller motors can be pretty good, some of the larger ones can have a high efficiency, but not in a pressure range that is very useful for us.

Cost can vary all over the place, as can quality. Some of the cheapies can be a real bargain.

Good deals on motors come and go. Some supplier might offer a real super bargain price, but then quickly runs out of stock. So hot tips on where best to buy motors can age very quickly.

Another problem is that most of us already have our motors and are no longer actively looking around for good deals. Many people come here and ask where the good deals are and get no replies. That can be very discouraging.
Its not that we are not interested, but unless someone is also actively looking around at the time for motors, there is no real advice most of us can offer on what is currently out there and available.

Finally getting a set of motors is a huge and important step, and its well worth spending some time to research the whole issue.
Most of us are not really in a position to help you directly with that for all of the above reasons.
Its a process we have all gone through ourselves...

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Sat Oct 14, 2017 7:03 pm
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Joined: Fri Aug 26, 2016 7:08 pm
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Thanks Tony for your valuable input. I did buy the LH 2093 - 240v motors. I wanted motors that were too big while using Bruce's PID SO I wouldn't have to run the motors at full throttle hoping the motors might last longer. And it would give me a cushion power wise. I don't feel I will ever need the full power of the bench. If you saw my build pictures you will see I did brace the bench internally. I will post numbers later. Again thank for your input.


Sat Oct 14, 2017 8:50 pm
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Joined: Wed Mar 03, 2010 3:40 pm
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Location: Melbourne, Australia
One day you might want to flow test mufflers or air filters, there can never be such a thing as having too much available airflow.

Yup, always good to have extra motors in there, they will each run slower for any given airflow with less noise and wear and tear on the motors.

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Sat Oct 14, 2017 9:30 pm
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