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  1. #1

    277 volt fan powered box rheostat

    277 volt fan powered box rheostat. I don't even know if I am spelling it correctly....

    Anyway, I have about 40 dual fan powered boxes that run single phase 277 volt motors. The original configuration had a rheostat that you could dial in the desired RPM of the motor.

    Does any one know where I could find suitable replacements with out having to buy 80 multi tap motors and spend all that time and money?

  2. #2
    Join Date
    Dec 2007
    Location
    Southern, CA
    Posts
    520
    Be helpful to know what you're doing. Is this a job, or a big pile in your back yard? What do you want to run them on now, 460 - 3, 460 - 1, solar, husky mice?

  3. #3
    Their in a old county building. Most of them are running just fine, but a few are over blowing the registers and making too much noise, causing complaints in courtrooms, etc.

    All motors are 277 single phase.

    In years past balancing the air was as easy as dialing the desired rpm via the rheostat. Someone somewhere must make drop in replacement.

  4. #4
    Join Date
    Jan 2003
    Location
    Kansas City
    Posts
    1,482
    Grainger carries one I believe, but I cannot find it online. Worst case scenario, call a Nailor distributor or any other fan powered box distributor and they will be able to get you one.

  5. #5
    Join Date
    Nov 2004
    Posts
    210
    what brand box do you have? got a model # you can get speed controllers at most hvac/electrical wholesale houses.
    AIRFLOW IS CRITICAL

  6. #6
    You can get multi tap motor controllers and or temp sensor and pressure controllers at the parts house but not rheostats, but these are single speed motors.

    The rheostat system worked well with these single speed motors but now that the building is 10-12 years old the rheostats are starting to fail.

    I must of left the Mfg. and Part #'s at work, I will get them today.

    I was hoping that one of you commercial guys had run across this be for and had a source for me.

    Did look through the Grainger book and found nothing. Still looking.

  7. #7
    Join Date
    Nov 2004
    Posts
    210
    hey j-fish, here is a data sheet on the ones we use.You can get them at johnstone supply.http://www.johnstonesupply.com/corp/...t_Code=G32-399 good luck
    Attached Images Attached Images
    AIRFLOW IS CRITICAL

  8. #8
    airdata870, that is exactly what I was looking for. Funny, they were one of the first places I called and they were not able to help me. Guess they are only as good as the knowledge they posses of their products they offer.

    Thank you all for your help!

  9. #9
    Join Date
    Jun 2005
    Location
    Ohio
    Posts
    1,720
    If it's a series VAV box, forget about the multi-tap motor. You'll need to dial in the design cooling CFM with the rheostat.
    jogas

  10. #10
    Join Date
    Jun 2004
    Location
    St Paul, minnesota
    Posts
    1,244
    using those controls will cause the motors to overheat. they're usually only used on small exhaust fans ect. For VAV boxes what you need is a SCR solid state speed controller. they use a triac to adjust voltage sometimes called phase proportioning or wave chopping.

    look here

    http://www.nailor.com/OnlineCatalogs...6/CATGENIN.pdf

    see page G17 & G18.

    good luck

  11. #11
    Join Date
    Nov 2004
    Posts
    210
    Quote Originally Posted by superfittertech View Post
    using those controls will cause the motors to overheat. they're usually only used on small exhaust fans ect. For VAV boxes what you need is a SCR solid state speed controller. they use a triac to adjust voltage sometimes called phase proportioning or wave chopping.

    look here

    http://www.nailor.com/OnlineCatalogs...6/CATGENIN.pdf

    see page G17 & G18.

    good luck
    superfittertech, could you explain the diference,the kb uses a triac to adjust voltage. my uderstanding of the overheating comes from slowing the motor down to far.
    AIRFLOW IS CRITICAL

  12. #12
    Join Date
    May 2005
    Location
    Lubbock Texas
    Posts
    773
    KB electronics

  13. #13
    Join Date
    Nov 2003
    Location
    Montreal, Qc.
    Posts
    790
    What is the HP and RPM of the motor and what is the percentage you want to slow them down?

    I installed around 150 of these back in the mid 90's.
    They were reliable as long as the reduction in speed wasn't over 40%-45A%.
    From 50% and above the instances of failure increased greatly.
    There is a minimum speed trim pot on the controller.

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