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How many,

CFM's of air are discharged thru a 3/4 " ID  condensate drain line fitting,? It's in the bottom of an 8' Salad Display  in a Deli . For  15 years ,non-stop.!  We put in an air dam today , to stop the air from exitihg the case.So, how do you figure this out? I need a little help here .Today Francisco demolished many spider webs,spider condo's,spider retirement villas,spider outhouses, spiders , then I was able to enter the CRAWL space.


  • Are you kidding me?

    If you have a 3/4" ID condensate line, that equates to a cross sectional area of about 0.44 square inches, or about 0.003 square feet. If you had an air velocity of 1000 feet per minute (which is a zillion times greater than the airflow you have in your salad box), you would only have an airflow through the condensate line of 3 cfm. This is assuming that there is no trap and no water in it.

    I am almost afraid to ask why you need to know this but, here goes. Why do you need to know this?
  • Techman
    Techman Member Posts: 2,144
    Lot's of reasons.

    Professor,thanks for your concern &caring.I guess EVERYONE else is busy trying to figure this out.One morning at 6AM while laying on the floor in front of this case,with customers easing by me and their dumb jokes about "too much to drink". I was playing with 1" ,3/4 " 1/2 " PVC ,tubing ,clamps & stuff. So, my hands and face were being blasted by this cold air [35-40* F] comming out the drain holes, O.K.  O.K. it was  a little breeze. The 3/4 "id and the 5/8 "id  untrapped drains had been doing this for 15 years. There had to be 10"s of thousands  of CFM's of refrigerated air wasted. and the wasted labor in mopping up ,emptying the bucket,and so forth. But mostly ,I'm just courious . After we get #'s for the 3/4" hole ,then there's the 5/8 " line to do !
  • You have your answer

    Just get the velocity of the air and multiply it by 0.003, which is the cross-sectional area of the condensate line.

    For the 5/8"line, multiply the velocity by 0.002 to get the cfm.

    Have Fun!
  • Techman
    Techman Member Posts: 2,144
    I Thank You.

    All those #'s gives me the hebe-jebes, THINKING  I'm good at .And saying Thanks! I feel a good sleep comming on !!
    [email protected] Member Posts: 139
    No stupid questions!

    Techman, thousands have wondered the same thing for years, only they where afraid to ask!!  Thank you for the answer to at least one question no one wanted to ask.

    Don in MO
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