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  1. #1

    Confused 100% Fresh Air Feed

    I am the Maint. Super. at a Highrise Condo community. I have a couple of Carrier package units that are used to cool the hallways. We have been unable to get the hallway temps below 79 degrees. We recently replaced the condenser coils, and are getting spit temps of 23 degrees. My manager insists that when they were first installed,(2006) they were getting low 70s at night, and mid 70s during the day. I have discussed this problem with a few of the local techs, and no one seems to have any ideas for bringing the temps down. I am hoping someone here will. Remember, it's 100% fresh air fed, and I'm in South Florida. Any, and all help will be greatly appreciated.

  2. #2
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,062
    Quote Originally Posted by FloridaWolf View Post
    I am the Maint. Super. at a Highrise Condo community. I have a couple of Carrier package units that are used to cool the hallways. We have been unable to get the hallway temps below 79 degrees. We recently replaced the condenser coils, and are getting spit temps of 23 degrees. My manager insists that when they were first installed,(2006) they were getting low 70s at night, and mid 70s during the day. I have discussed this problem with a few of the local techs, and no one seems to have any ideas for bringing the temps down. I am hoping someone here will. Remember, it's 100% fresh air fed, and I'm in South Florida. Any, and all help will be greatly appreciated.
    What ventilation rate are you following that requires 100% fresh air?

  3. #3
    Join Date
    Apr 2012
    Location
    Paper Street Soap Company
    Posts
    2,304
    Your set up is not uncommon. Provides conditioned air for pressurization and humidity control.

    Got a some hotels here in Houston that have that set up.

    Whos the equipment manufacturer ?

  4. #4
    Join Date
    Oct 2001
    Posts
    6,966
    typical NYC hi rise hallway units are the same 100% OA no returns,just a supply truck dropped down the middle of the building. then with say a 6"X14" single register per floor.i always said the unit has to over sized and spec'd to maintain a 70F hallway no matter what the outside is.
    "when in doubt...jump it out" http://www.youtube.com/watch?v=U1qEZHhJubY

  5. #5
    Join Date
    Oct 2010
    Location
    Baton Rouge, LA
    Posts
    1,118
    Yeah we duct the fresh air into other air handlers not a hallway. lolol

    You could add a second fan coil unit with some chilled water or duct in a hallway return so you mix fresh air and return air.

    Maybe add a bypass with damper actuator that returns a % of air directly back to the return by supply temp. You would most likely have to increase your CFM by changing out the sheaves and belts. You would have to first make sure the motor can handle it. Might need to add a VFD.
    If you're too "open" minded, your brains will fall out.
    Artificial intelligence is no match for natural stupidity.

  6. #6
    Join Date
    Apr 2012
    Location
    Paper Street Soap Company
    Posts
    2,304
    That unit should hace been sized accordingly when installed.

    Ive got a Munters HCU 8000 that does a 30+ degree delta in Houston and thats with our humidity.

  7. #7
    Join Date
    Oct 2001
    Posts
    6,966
    it is just a standard rooftop and realize the evap coil is going to take the hit the condenser will filters arn't going to matter as the years take there toll
    "when in doubt...jump it out" http://www.youtube.com/watch?v=U1qEZHhJubY

  8. #8
    Carrier

  9. #9
    Join Date
    Apr 2012
    Location
    Paper Street Soap Company
    Posts
    2,304
    Is it a make up air unit ? Is it specifically designed to pull in 100% outside air or is it just a standard package unit ?

  10. #10
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,645
    It is all about the cfm of air and the out door temp. Its been hot as hell. In WI we are up 10-15^F over the hot temps of the last couple years. Hotter in give hotter out!! Slow the air flow or increase the capacity??
    Check wunderground weather.com for the outdoor temps 10 years ago in your area.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  11. #11
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    I don't think Florida has been much above normal.

    In the midwest it's been hot, but actually the dewpoints have been somwhat moderate, onl in the mid to upper 60's most days. Well below design. I suspect the complete lack of ground moisutre is keeping humidty low.

    Oh wait I think it rain a 1/4-1/2" last night. I'm not sure since I think it evaporated on contact with the ground. Not kidding... at 5AM this morning the ground was steaming. I've seen that before durign an afternoon rain, but not at 5AM.

  12. #12
    I do not know if they are "make up air units", I don't even know what that means :-( I do believe they were designed for the way they are being used.

  13. #13
    I've been giving this a little bit of thought, and I'm wondering if cleaning the Evap coil would make a dramatic difference. The machines are about 6 years old. they are maintained on a quarterly basis, and we are roughly 3/4 of a mile from the ocean.While this is something that I am sure I will have to do eventually, due to the cost, it is not something that I want to do if it is not going to make a huge difference. Thoughts?

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