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Calculating Correct Blower Capacity

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  • Calculating Correct Blower Capacity

    I've calculated the necessary blower size for a "straight" organ, and I don't believe what I'm getting. Would you please check my calculations?</P>

    The organ will have a 56-note compass, small scale pipes, and we hope to voice it on only 2-1/2 inches of wind.</P>

    <U>The Meidinger Blower Method of Figuring Wind</U> is what I used. Here's the input to that method:</P>

    <U>4-foot ranks:</U></P>

    2 in Great, 2 in pedal</P>

    <U>8-foot ranks:</U></P>

    4 in Great, 2 in Swell</P>

    <U>16-foot ranks:</U></P>

    2 in pedal</P>

    <U>Upper Work</U></P>

    4 in the Great (Nazard, 1-3/5' Tierce, 2' Gemshorn, Sifflote)</P>

    4 in the Swell (Flachflote, 1-1/3 Quint, 4/5 Tierce, Blochflote)</P>


    Swell to Pedal 8'</P>

    Great to Pedal 8'</P>

    Swell to Great 8'</P>


    Counting the upper work as 1/2 stop each, I come up with 950 CFM as preliminary, neglecting any pressure requirement.</P>

    Does this sound right?</P>


  • #2
    Re: Calculating Correct Blower Capacity

    950 cfm sounds like way too much for an organ of that size. The blower for my organ is rated at 500 cfm at 15" pressure using a 3 hp motor. My organ is a higher pressure instrument with several "wind hog" flue ranks. I would guess that something like a 1/2 hp blower should handle your requirements. This is just a guess, but check with someone else before buying a blower.


    • #3
      Re: Calculating Correct Blower Capacity

      don't know cfm speak but my 822's original 5 ranks (all 8's plus one big wood 16' gedeckt) worked fine with a 1/2 horse blower..unitized out the wazoooooooo) 5 inches of wind...Organ Supply Industries somewhere on their webpage has a chart for figuring wind requirements.


      • #4
        Re: Calculating Correct Blower Capacity


         I'd go with a 3/4 or 1HP blower.  You're going to average about 40CFM per rank at 2 1/2".  Keep in mind also that if you're running a 3 phase blower on single phase, you'll lose at least 1/3 of the power unless you drive it with a rotary converter or a VFD.</p>

         My 7 1/2HP blower is rated at 900CFM @ 30" static... and that converts roughly to about 200 ranks at 3" WP!!! </p>