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Thread: RTU

  1. #1
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    RTU

    How long does a evp blower belt normaly last and how often should very be replaced?how tight shouldthe belt be ? Also how to check pulley alignment?

  2. #2
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    Belts usually need to be replaced every year. Tightness depends on the unit, it should tell you in the owners/service manual. If you can't find it then I would go 5/16" of play. To check pulley alignment take a straight edge and put it on the motor sheave. It should stay flat against the motor sheave and the blower pulley if alignment is correct.

  3. #3
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    Too many variables to say how often and how it should be adjusted.

    This is why you hire a trained tech, to solve these issues.
    UA LU189

    10mm, because it's better than .45acp

  4. #4
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    Quote Originally Posted by zw17 View Post

    This is why you hire a trained tech, to solve these issues.
    isnt this a forum for questions.
    Thanks jpaulsmith . I know very simple question just was never explained to me

  5. #5
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    Talk to your local rep where you buy belts and they will sell you a tension pen with a book with the belt sizes and correct tensions. Wear all depends on alignment if its across line start or on a VFD. Are they fixed sheaves or did someone leave varible pitch sheaves on after start up.

  6. #6
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    Check them on quarterly PMs. Adjust or replace as needed.

  7. #7
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    i'm actually in a debate now with a co worker on whether or not to cycle the blower (belt driven) on & off during occupied modes. for years and at all my accts. i keep the fan on when unit is in occupied mode. he just can't see my points

  8. #8
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    Quote Originally Posted by commtech77 View Post
    Check them on quarterly PMs. Adjust or replace as needed.
    Hummm so every fan belt in all equipment in the world has the same PM...all you have to do is check it every quarter....

    I think i like zw17's advice

  9. #9
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    Quote Originally Posted by coolerinfrederick View Post
    i'm actually in a debate now with a co worker on whether or not to cycle the blower (belt driven) on & off during occupied modes. for years and at all my accts. i keep the fan on when unit is in occupied mode. he just can't see my points
    i agree with with you. I most cases and depending on the system and the space its supplying, running Fan during occupancy times is the way to go for a few reasons.

    You don't have the start and stop belt jerking, amp spikes, you maintain a better temp over the course of the day. Anyone that trends temps will tell you, you don't have the spikes and valleys in temps when the fans goes off/on for a call for heat or cool. Starting and stopping cost more to operate and wears the motor and belts out faster. IMO

  10. #10
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    Quote Originally Posted by killeentech View Post
    How long does a evp blower belt normaly last and how often should very be replaced?how tight shouldthe belt be ? Also how to check pulley alignment?
    It's hard to say how long belts should last, mainly because of conditions as some have mentioned. But if the alignment is true and the sheave and pulley is not worn you should be able to get a year or longer out of the better belts.If money isn't an issue, it is a better policy to just change it after a year or so. And by all means don't use fractional hp belts on anything over 3 hp or better. You're asking for trouble. Also do yourself a favor and only buy quality belts and a belt tension checker. You'll save yourself a lot of grief and it's a nice tool to have in your tool bag.Ok, I'm off my soapbox now.
    Good Luck!

  11. #11
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    All belts are not equal, cogged belts last longer, some brands are better than others, I prefer Gates over Browning, Dayton etc. good sheaves make belts last longer, just tension it enough to where it wont slip.

  12. #12
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    Ventilation is required in occupied mode

    Quote Originally Posted by dlove View Post
    i agree with with you. I most cases and depending on the system and the space its supplying, running Fan during occupancy times is the way to go for a few reasons.

    You don't have the start and stop belt jerking, amp spikes, you maintain a better temp over the course of the day. Anyone that trends temps will tell you, you don't have the spikes and valleys in temps when the fans goes off/on for a call for heat or cool. Starting and stopping cost more to operate and wears the motor and belts out faster. IMO
    And you can't ventilate continuously during occupancy times without the fan running. That is a code requirement in all NYC 1968 code, NYC new code, IMC based jurisdictions, CA and probably everywhere. Sorry for continuing the hijack...

    Closer to the topic, is it generally recommended to put non adjustable sheaves on after TAB has determined the final required fan RPM? I had not heard that before.

  13. #13
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    I dont like the idea of running the blower all the time in RTU's, there are huge temperature differences between the roof and the living space, most RTU's are poorly insulated, meaning the air being circulated is gaining or loosing BTU's through the RTU walls and gaps, the problems become more noticeable in hot humid weather and cycling the blowers with demand helps a lot.

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