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  1. #1
    Join Date
    Aug 2018
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    Blower Balancing

    Firstly, I'm curious what to do if a blower motor tag does not list power factor or efficiency. Should I really be concerned with this or is it not that valuable? Either way I would like to understand more about calculating horsepower for field use.

    Is there a resource, rule of thumb or manufacturer database for motor efficiency ratings?

    I found an engineering toolbox piece with a chart of roundabaout power factors for various size motors at loads between 25 and 100 percent. Is this reasonable to use? Would any power factor given on the tag be true at 100 percent load for that motor?

    Secondly, I'm curious where manufactirers are taking or recommend taking static pressure readings as it pertains to their blower performance charts? I remember reading in a Carrier manual something like 18" down the supply trunk from the end of the unit for the SA but this is often not possible to take. The return air static reading location is my bigger concern. Would it be at the blower inlet or upstream of the coil/filter rack?

    Side note: for the most part I'd be applying this to package units 3-12 tons.

    Thanks in advance,


    Sent from my SAMSUNG-SM-G891A using Tapatalk

  2. #2
    Join Date
    Feb 2004
    New Mexico
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    There is a Government site (US) called Motor Master. The site is full of all sorts of information and one being a list of the qualities of about any motor you might think of
    including efficiency and PF. Without these precise numbers exact HP can't be accurately known.
    Static pressure location isn't as important as a velocity measurement. If you want to compare static readings with a fan performance chart be advised these charts are based on a lab measurement with no return restrictions. They are not able to reflect field conditions. It's ok if all you want are SWAG (Scientific Wild A$$ Guess)measurements. In the field, a traverse of the duct is the accepted standard. And sometimes it's very hard to get a good location for this.
    I should have played the g'tar on the MTV. MK

    You can be anything you want......As long as you don't suck at it.

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