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  1. #1
    Join Date
    Jul 2008
    Location
    Edmonton Alberta Canada
    Posts
    89

    Cook DB series cabinet fans under performing

    Got two fans that are under performing.

    Here is what is happening from the air balancer

    1) Fans are high RPM
    2) Static is 0.2" and fans are rated for .35"
    3) Flow is roughly 50-60% of rated airflow
    4) Motor is near the max amps.
    5) Fans are single phase

    Someone took the side panel off the fan and it didnt suck any air from the side. They also cut a hole in the bottom of the discharge ductwork before two square 90 elbows and a louver. No airflow through that hole.

    My guess is that the hole in the outlet had more static than the two elbows and louver and that the side panel is not meant as a means to measure airflow.

    BOTH fans have a round mitered elbow NEAR the fan inlet.

    My suggestion is to check the fan rotation and to add some round ductwork and give the fan 3 wheel diameters worth in straight inlet duct.

    Good starting point?

  2. #2
    Join Date
    Jun 2006
    Location
    Charlotte, NC area
    Posts
    87
    Those small fans are notorious for coming up short on static. The main reason is that the manufacturer (and all do it, not just cook) list their fans under basically ideal conditions with very long straight duct runs in and out of the fan. When the field installation is not perfect (and it never is) you end up with a higher static pressure than the fan can handle.

    I think your solutions are on the right track although I don’t think your rotation will be wrong on a single phase fan. Get as much straight duct as you can upstream of the fan and hope for the best.

  3. #3
    Join Date
    Mar 2003
    Posts
    7,321
    that brand specifically, we see a lot of problems, especially if, as noted static isnt near perfect. most of their single phase fans are two speed. problem is worse on high speed than low. also, their motors are chinese made pieces of ,well you know what, but you can get them in 24 hours if really needed. maybe they know something about their product?, yep, so do i, first cost sells, first cost sells.

  4. #4
    Join Date
    Jul 2008
    Location
    Edmonton Alberta Canada
    Posts
    89
    If it comes to fan replacement, i was just going to specify a higher static on the fan and bigger HP. I really don't want it to come to that. I've specified many inline fans, but always work with greenheck. I always get cook, i should take them off my list of approved manufacturers .

  5. #5
    Join Date
    Mar 2003
    Posts
    7,321
    i like that idea. they are not 'equal' in my view. we just had to replace a bunch of them for the reason of motor failures in just over a year from start up. balancer got good readings at high seed, but didnt check amps. due to slightly higher static than design, even though ductwork was exactly as it appeared on drawings, fan motors overamp and burned themselves up. no room for error. they just dont make stuff with a decent service factor like they used to do. these were all fractional horsepower motors.

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