Results 1 to 5 of 5
  1. #1
    Join Date
    Dec 2006
    Location
    Henryville IN
    Posts
    248

    Liebert mini mate

    Sorry no model or serial no. Unit serves 20x20 server room, very light load, only 2 small server racks. Sensor is located at about 7 feet elevation immediately to side of walk in door. I have replaced the sensor circuit board. This unit has been in service about 5 years and this problem just recently occured and it has been driving me nuts. I get a big swing in humidity. Set points are temp 70 w/3 diff, rh 45 w/4 diff. I'm even starting to get mold occasionally near the liebert. The wall the unit is mounted to is common to a large maintenance shop which is non conditioned, although it is insulated it does not have a vapor barrier. We are having 90 degree days and 80% rh quite frequently, also shop overhead door is typically open. I'll typically check unit stat a couple times a day. Sometimes I'll have as high as 85% rh . As soon as the unit starts to dehum rh will drop 5% a minute but by the time the rh drops to set point room temp will also drop to low 60s bringing on the heater. Unit's charge is good. Are my parameters way off? Yesterday I disabled the humidifer and set temp @ 69 degree with no diff when I left the site to see what would happen over the weekend. Any suggestions?

  2. #2
    Join Date
    Jan 2007
    Location
    Charm City--the city that bleeds
    Posts
    2,790
    Sounds like the cooling/dehumidification is overwhelming the reheat. The cooling tonnage vs. the reheat capacity.
    You could reduce the temp differential to 2 just to use reheat that much sooner, but the low 60s?? And to have humidity in the high 80s sounds like someone doesn't have a large concern for the design environment, whether that is due to infiltration or neglect.
    Not enough reheat is happening
    It's great to be alive and pumping oxygen!

  3. #3
    Join Date
    May 2006
    Location
    Western NY
    Posts
    4,355
    Mini-Mates often have two fan speeds, high and low. Looks like you got quite the load, so make sure it is in high or at the highest speed.
    Doc hit right about the reheat. Give it a close check. I'm interested at what it is amping at. When is the last time it has been cleaned also?
    "Excellence is the gradual result of always striving to do better"
    -Pat Riley

  4. #4
    Join Date
    Jun 2008
    Location
    Apopka, Florida
    Posts
    110

    Mini Mate

    blewbyu2,

    Sounds like the unit is preforming to the setpoints.
    Liebert units and other speciality units for Data Centers work with 0% outside air, from what you are describing you do not have a great vapor barrier on the room and outside air from the maintenace garage area is causing the room swings per your description. The units control is based on temperature first and then humidity, you should try and seal the room a bit further. If the load is light as described you may want to try and run the unit with the low fan speed enabled so that it can cool and dehumidify at a slower rate.
    Possible relocation of the sensor may be needed depending on the rooms seal.

    Try and get the model and the heat load of the room so that we can help you further.

    Domcort

  5. #5
    Join Date
    Dec 2006
    Location
    Henryville IN
    Posts
    248
    Quote Originally Posted by Domcort View Post
    blewbyu2,

    Sounds like the unit is preforming to the setpoints.
    Liebert units and other speciality units for Data Centers work with 0% outside air, from what you are describing you do not have a great vapor barrier on the room and outside air from the maintenace garage area is causing the room swings per your description. The units control is based on temperature first and then humidity, you should try and seal the room a bit further. If the load is light as described you may want to try and run the unit with the low fan speed enabled so that it can cool and dehumidify at a slower rate.
    Possible relocation of the sensor may be needed depending on the rooms seal.

    Try and get the model and the heat load of the room so that we can help you further.

    Domcort
    Thanks for the suggestions. I'll check fan and amps tommorrow and follow up with a post to let you know what I've found out.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event