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  1. #1
    Join Date
    Jun 2017
    Location
    MI
    Posts
    2
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    Cooling/heat loss due to slipping belts

    Hello to all,
    I have been searching and searching to find data or test studies on the loss of energy due to inadequate belt tension. How many times have we gone up on the roof and find the blower turning about half speed. We wont consider the addition of the dirty filter to boot! I just replaced a 4 ton scroll compressor on a roof top. Had the gauges on for startup wow lower suction pressure than I would like to see. Opened the filter door filter was clean seemed to be moving air. Dang. Shut it down and opened the blower compartment to find the belt loose. Wasn't squealing or making any adverse noises. Tightened the belt, fire it up bam were in business.Since then I have been trying to dig up info on this. I am going to go out on a limb and say I think that the higher efficiency unit with a loose belt is less efficient than the old 22 unit running good. wow long post huh. I could put a drive on 3phase blower motor and monitor evap pressures. How many percent blower speed must be lost to get the coil to start frosting. Hum. Bored. Heating mode would do what? hotter heat exchanger , more heat lost in increased combustion exhaust temp, possible cycle hi-limit. Low velocity hot air stratification coming out of ceiling diffusers. wow I get too worked up on this. Anybody run across any hard data on this or actual lab testing?
    Thanks to all!
    Bill

  2. #2
    Join Date
    Jun 2017
    Location
    MI
    Posts
    2
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    Thread Starter
    Good day all,
    It was also my intention to provoke thought and input from others of their experience and thoughts on this apparently overlooked variable quotient in establishing a true out of the lab seer rating on typical moderately serviced equipment in service. We know there are a lot of things to consider, filters, dirty coils, improper duct sizing etc. I am focusing on nthe belt drive system efficiency.
    Cheers
    Bill

  3. #3
    Join Date
    Apr 2003
    Location
    St. Louis
    Posts
    248
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    go sell your customers a service contract and spend more time thinking about how hot the roof is and how to keep your tools cool.

  4. #4
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,901
    Post Likes
    Be more concerned about the drive pulley.

    Slipping belts cause the drive pulleys to wear into a U shape. If a new V shaped belt is installed on a worn pulley, the new belt will soon fail and become loose because it is not contacting enough of the pulley surface.
    "I have never let my schooling interfere with my education."
    Mark Twain
    NEVER STOP LEARNING.

  5. #5
    Join Date
    Feb 2016
    Location
    Louisburg Kansas
    Posts
    1,195
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    Loss of efficiency is directly proportional to how fast the fan is turning. Since the amount of slip varies with each unit there is no rule of thumb. Having said that you can run some tests and determine about how much is lost at different speed proportions, say 25%, 50% and 75%. Even that will vary per machine but you can use that info in example discussions. Not worth the effort unless you can use the info to sell service contracts.

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