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Thread: Desiccant Wheel

  1. #14
    Join Date
    Mar 2004
    Location
    Minnesota
    Posts
    38

    Humidity problems

    I want to thank all of you for your valuable info. I agree with you that the heating coil should best be after the cooling coil to help drop the moisture content. I was not lucky enought to have my system set up that way. But what I am trying to do is pull the moisture that the outside air has been introducing to my building. Also, with a return air of 55 degrees and an outside temp this morning of 57 the cooling valve does not have much of a load on it. But by heating the air it forces the cooling valve open to help remove more condensate/mositure. So,its not a perfect system, but we are trying to do the best with what we have.
    GD

  2. #15
    Join Date
    Aug 2003
    Location
    Ft Worth Tx ( North Richland Hills)
    Posts
    2,143
    [i]Originally posted by ts ac tech [/

    Hey ozone drone...I too am responsible for two archival photograph vaults. And I have four Munters, two in each vault, designed as redundant/lead/lag systems. I have never seen them work properly because the condensation builds up so quickly inside the unit, it actually rains on the circuit board and fries the board withing hours of operation. As a result, I have portable space dehumidifiers doing the job instead. I would be very interested in putting our heads together to come up with a solution. [/B]
    ac tech

    At what temperatures are you keeping your vaults? we keep one at 20 degrees @ 30% rh and the other at 60 degrees @ 40% rh. I've noticed some condensate on the return air housings...but other than that no problems.

    Are you familiar with the "Pre Dry" Procedure? When we were first commisioning and testing the systems, we found a problem with our cooling coils icing up. We solved the problem by "pre drying" the wheels before enabling the cooling.

    All the procedure consists of is removing the fuses for the supply fan motor and running the desiccant wheels with the reactivation fan and heater on for about 45 minutes. If your wheels were idle for any length of time before starting the system, they become saturated and unable to get a handle on the load. By pre drying the wheels, they start off ready to get rid of the moisture.

    My work # is 817-989-5129 (direct line) I'll give you my work e-mail address and we can see if I can be of any help.

    [Edited by ozone drone on 08-10-2004 at 10:25 AM]
    How can you have any pudding if you don't eat your meat?

  3. #16
    Join Date
    Oct 2002
    Posts
    44
    good doctor,
    It appears to me that while you are trying to remove moisture, you probably are not doing it. To remove moisture by cooling, you must cool the air down to or below its dewpoint to acheive condensation on the cooling coil. The air is then reheated to avoid subcooling the space. Unless I am missing something, all you are doing is heating the air up and then cooling it back down to its starting point. This will not remove any moisture. Changing temperature without reaching dewpoint will not affect the moisture content of the air. The desiccant systems work on a different principle so they can remove moisture without cooling.

    I hope this helps.

  4. #17
    Join Date
    Jan 2004
    Posts
    82
    You have a company in Owattona, Mn. that makes dissicant units.. website is CDI-HVAC.com I have used several on ice rink projects and find them very reliable..

  5. #18
    Also check out Semco, as they put out studies on microbial cross-contamination of their wheels vs. others, as well as variable frequency motor relations to air flow and optimizing economizer 'time' with running the wheel alone. Also they considered purge cycles and energy losses and effects on the overall system. They are great whether adding to your primary system or for dedicated OA.

    It's good stuff.

  6. #19
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,260
    Originally posted by the good doctor
    I am looking for some information on a good Desiccant Wheel to help remove mositure from a testing lab here in Minnesota. We are having trouble keep a handle on the humidity level in the summer months. We have three chillers along with three steam boilers that run year round. I am working on changing the program (energy management) to open the heating valves before the cooling coil to help remove so moisture; but is taking a lot of energy and not able to keep a handle on the system yet. This building runs 24/7 so you would think that one could get in the ballpark. But the levels bounce all the up to 75% on a rainy day! Any info would be very much welcomed. GD
    Desiccant Wheels are most practical when the desired dew point is near or below freezing because of ice formation on refrigerant dehumidifiers. The operating cost for +40^F dew points of Desiccant Wheel dehumidification is 2-3X more than the new high efficiency dehumidification system like Ultra-aire/Santa Fe or heat pipe assisted dehumidifiers. The investment for Desiccant Wheel is higher than hi eff dehus. is much higher.
    For maintaining 75^F, <50%Rh, the "hi eff dehus" are the lowest investment and lowest operating cost.


  7. #20

    Is anyone familiar with Kathabar?

    Front end cost is higher but Kathabar Liquid Desiccant dehumidifier is the best across all temp. ranges and kills 94% of mold and bacteria.

  8. #21
    Join Date
    Aug 2004
    Location
    Currently in Phoenix, AZ
    Posts
    31
    It would seem that the doctor has his homework ("due diligence") cut out for him.

    I visited Kathabar's site. Interesting technology. I guess there's a lot of ways to "skin this cat" as it were.

    It's unfortunate that the current system has been mis-designed or undersized in some way. Now doc is forced to make an investment in one of the above technologies in order to salvage the sizeable costs already sunk into this under-performing system. A desiccant wheel may be the most cost-effective means of reducing energy costs WHILE dehumidifying and also keeping this second initial investment in the "fix" low.


  9. #22
    Join Date
    Jul 2001
    Location
    Canada
    Posts
    1,806
    MUNTERS does a great job , just be sure to size the cooling for the HI SUPPLY AIR temp coming off the wheel.

    Just finished a MUNTER installation and with 122'F supply air the customer was happy when we oversized the chilled water coil and did not go with the engineers suggestion.


  10. #23
    Join Date
    Oct 2002
    Posts
    970
    Originally posted by Control Man
    MUNTERS does a great job , just be sure to size the cooling for the HI SUPPLY AIR temp coming off the wheel.

    Just finished a MUNTER installation and with 122'F supply air the customer was happy when we oversized the chilled water coil and did not go with the engineers suggestion.

    Did Reg do the start-up?
    I work with the Chiller Whisperer...

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