4B247 swapped out with 2Z499 - Effect on CFM?

by dan_t
(BC, Canada)

Hi all,


I'm somewhat new to the world of air compressors so I did what research I could and selected a compressor off of Craigslist that had a reasonable CFM rating.

Only when I got home I realized that it looks like both the motor and the compressor have been replaced at some point in their lives.

The compressor is marked up as a Speedaire 4B228B.

Its listed as having a Speedaire 4B247 compressor head but the reality is that it has a Speedaire 2Z499 compressor.

The motor is 240v 15amp listed at 2.96kw (4hp).

The original specs for this compressor was 10.8 SCFM @ 90PSI - I'm trying to figure out the effect on this having had the compressor head changed.

Any information greatly appreciated

Comments for 4B247 swapped out with 2Z499 - Effect on CFM?

Click here to add your own comments

Apr 23, 2012
quick reply
by: Anonymous

I don't see that having more HP on the motor should be any issue. Its rated at the same RPM as the stock motor it just produces more torque at that same RPM.

I'm now not so sure that this has been modified from its original specifications. Both motor and pump are Drayco units and I believe they are the original manufactures.

I did a simple test of filling 50 gallons from 90-125psi and recording the amount of time it took. From that test I got an average of 8.2CFM at 107.5psi.

I've only had time to quickly scan your posts so far but I'll make sure I'll check it over again later if I get time.

Many Thanks :)

Dan

Apr 21, 2012
FOLLOW UP ON PRIOR POSTING
by: pcbeachrat

I could not find the actuall cfm info you asked for the motor that is supposed to be sized up with the pump model you have should only have a max of a 1 1/2 horsepower motor on it.

The motor you have is rated at 3.1 horsepower and will literally burn that pump up after a little use.

All pumps have a minimum and maximum speed at which they should turn,and they pair them up with a motor and/or the proper pulley size*(is very important) for the speed of the pump .On recipricating compressors the lower speed you can run the pump the better and longer wear you will get from it,but it cannot be ran lower or higher than recommended.SPEED KILLS....Take an automobile for example,it can go 120 plus miles per hour,but if you keep it at that speed constantly it will wear out or blow up alot quicker than if you slow the car down and run it at 55 miles per hours during it's life span....You get alot more life and better performance on the car .

My 2 stage pump is rated at 1150 rpm's per minute,but I got the pump set(by putting right size of pulley on the mortor) to running 850 rpms,which is it's suggested min imum,and a good pump run low rpm's you can get 30 years usage out of if maintained properly...THIS IS A FOLLOW UP ON MY FIRST REPLY TO THIS POSTING BY THE WAY...If you need help with this I would be happy to help ,but your going to have to get a different motor or pump to make that compressor last long..as far as the cfm....Yours with that 1.5 horsepower motor on it will be very low,probably around 3 to 5 cfm@ 90 psi,I would think.That rating is not a known fact just the estimate that came into my head.I do build compressors and sandblasters as well as repair them here...E mail is pcbeachrat@yahoo.com if you need some additional info,will be glad to help out...Your motor is too big for that pump so something needs changed...HERES A HINT...I have had no luck with the Tractor Supply century motors...I have had 4 fry and one within 6 hours work on it...I go with granger and ao smith motors now....

Apr 21, 2012
air compressor horsepower
by: pcbeachrat

First your true running horsepower on that motor is just barely over 3 horsepower.I will see if this link will paste on how to calculate TRUE HORSEPOWER..

www.onlineconversion.com/motor_horsepower.htm

And it pasted okay..on this calculator keep the effieciency rating at 65% for this is about the most that air compressors run at full load.


Next I will post an article about scfm which is an imaginary scenario compressor manufacturers use now days which is basically an imaginary calculation to use.SCFM has nothing to do with true CFM,and can only calculate at certain altitudes,certain ambient temperatures,certain regular temperatures and many other factors.No One can calculate scfm by using these factors in different regions,so scfm is totally useless and means nothing.Let me look for the proper article on this...

First here is a very important article,again on true horsepower..please read this to understand true horsepower better.

www.kevinsbrady.net/motors.pdf


Here is a quick skit on SCFM..

en.wikipedia.org/wiki/SCFM


About the 6th paragraph on the following link tells you more about scfm being calculated,and that it means total different calculations depending on the certain conditions,temps etcetera in the area the compressor is operating from.

personalpages.tds.net/~thompson_wp/misc/cfm%20mystery.htm

Now I have shown you how to get true horsepower,but the scfm thing is about as real as rumplestiltskin,andf something that cannot be truthfully answered .For this,I cannot answer,but this will at least explain the truth about scfm...

personalpages.tds.net/~thompson_wp/misc/cfm%20mystery.htm

Basically you can search the net and come up with many many descriptions of how scfm came about or figures out.CFM can be figured alot closer to true regardless of altitude,temperature,ambient temperature,humidity etc . Scfm is closer to just simply conning the purchaser to believing they have something they don't.

____________________
A lot of good content here PCBEACHRAT. Thanks!

B.


Click here to add your own comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Speedaire.

GETTING A NEW COMPRESSOR HEAD

by BEN LADD
(MAKAWAO, HI. 96768)

I HAVE A MODEL 5Z185A SPEEDAIRE COMPRESSOR. THE COMPRESSOR HEAD HAS GOTTEN TO THE POINT WHERE I CAN'T EVEN BE IN THE SHOP WHILE IT RUNS. EXTREMELY LOAD! THE NUMBER PRINTED ON THE COMPRESSOR HEAD IS 2Z630C.... CAN I STILL GET A REPLACEMENT?






Bill says...

Howdy Ben. I'd love to say yes, but I don't supply anything but information about using compressed air. The only way you'll know for sure is to contact Speedaire directly.

Go to the Speedaire page linked from the Nav bar on about-air-compressors.com , and follow the guidelines for locating your nearest Speedaire / Grainger dealer.

I'm sure you can contact them on line as well.

Cheers and good luck.

Bill

Click here to post comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Speedaire.