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  1. #1
    Join Date
    Jan 2015
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    Gulf Breeze Florida
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    Belt tension and alignment

    OK, this may seem trivial to some but I have 25 plus years experience in residential HVAC and now have started a new job where I am the only HVAC tech in a commercial building. 5 to 30 ton units including water source, makeup air, and some split systems. Systems have been maintained by a local HVAC company but now its up to me.
    My question is this........I have looked at 5 of the 32 systems. Each one so far seems to have had the belts adjusted by an "auto mechanic". All seem very tight. Also, since my first day on the job was replacing belts and worn bearings..... what is a good way to align pulleys and tension belts? Is there a tool to tension belts? Is a long level good enough to align the pulleys?
    Wanting to get it right!!!!! Thanks
    Mark-
    No call, no weekends, no over time......not sure I'm still in the HVAC business!!!!!!!

  2. #2
    Join Date
    Jun 2004
    Location
    St Paul, minnesota
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    1,386
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    long level or straight edge is fine. Belt tension usually 3/4" to 7/8" I usually use my finger and a tape measure. More than likely HVAC contractor had them that tight, because belt does 70-80% of it's stretch in the 1st month, so since they're only coming there 2-4 times a year that sounds correct.

  3. #3
    Join Date
    Jul 2007
    Location
    The Hot South
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    1,446
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    I use a string or laser to align sheaves.

  4. #4
    Join Date
    May 2008
    Location
    Central Pennsylvania
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    I also use a piece of string for alignment. Browning makes a fairly cheap tension gauge, which basically uses the formula of 1/64" of deflection per inch between the motor and blower shafts, from the center of the shafts. In my opinion that formula works pretty good, whether using the gauge or just measuring using a tape measure.

  5. #5
    Join Date
    May 2011
    Location
    Las Vegas, Nevada
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    Proper belt tension for a new belt is 3/16" per foot of distance between the motor and blower shafts. The belt(s) will stretch and should be checked after 2 weeks. 3/16" will not put excessive strain on the bearings and will generally be great after the belt(s) stretch. Auto tensioners make life easy. I use a straightedge or a string to align pulleys.
    "Quality is never an accident; it is always the result of intelligent effort. The bitterness of poor quality lingers long after the sweetness of low price is forgotten" --- John Ruskin

  6. #6
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
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    I use a belt tension and a laser alignment tool. Then you won't ever have to go back. I have some belts that look perfect after over 7 years of use. Keep in mind that the belt tension tool chart will cionsider the worst case scenario for belt tension which isn't all bad. With the proper formula, you can get away with much less tension than the ol' "1/64th" formula. Also keep in mind that most belt driven equipment has too few belts. In some applications, I would consider upping the number of belts if you are to be changing the sheaves.

  7. #7
    Join Date
    Feb 2010
    Location
    Newnan Ga,
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    197
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    Quote Originally Posted by R123 View Post
    I use a string or laser to align sheaves.
    This is also what we do
    our trucks have a laser line level you can set to a 1/25th of an mm

  8. #8
    Join Date
    May 2008
    Location
    Central Pennsylvania
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    The lasers are nice...unfortunately I haven't gotten the opertunity to use one yet.

  9. #9
    Join Date
    Sep 2011
    Location
    Huntington Beach, CA
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    Are there belt tensioners (spring-loaded or hydraulic) applications in the HVAC industry?

  10. #10
    Join Date
    Aug 2006
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    Mixing oil and fire with a big spoon.
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    Quote Originally Posted by Mr. Chain Blue Lightning View Post
    Are there belt tensioners (spring-loaded or hydraulic) applications in the HVAC industry?
    I have seen them in catalogs....but not in person. Bending the belt backwards shortens its life.

  11. #11
    Join Date
    Sep 2011
    Location
    Huntington Beach, CA
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    Quote Originally Posted by jayguy View Post
    I have seen them in catalogs....but not in person. Bending the belt backwards shortens its life.
    Jay, not sure I quite follow.

  12. #12
    Join Date
    Feb 2008
    Location
    Western Wa.
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    Quote Originally Posted by Mr. Chain Blue Lightning View Post
    Jay, not sure I quite follow.
    Auto tensioners sometimes is a roller system that rides and pushes down on the back side of the belt which could bend the belt backwards causing premature wear on the belt.

    If it is something that gets regular maintenance I pull the auto tensioners off or something like this happens

    Last edited by buttwheat; 02-17-2015 at 12:05 AM. Reason: added a picture
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  13. #13
    Join Date
    Sep 2011
    Location
    Huntington Beach, CA
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    Quote Originally Posted by buttwheat View Post
    Auto tensioners sometimes is a roller system that rides and pushes down on the back side of the belt which could bend the belt backwards causing premature wear on the belt.

    If it is something that gets regular maintenance I pull the auto tensioners off or something like this happens


    Ahhhhhhhhhhhhhhhhhhhhh! Thanks, buttwheat!

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