×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Help With Liebert 3000 Unit

Help With Liebert 3000 Unit

Help With Liebert 3000 Unit

(OP)
We have a room that is being converted to a calibration lab.  The environmental conditions that have to be met are 68 F +/- 5 and less than 55% RH.  A Liebert 3000 unit was installed.  The installer left the setpoints at 68 F & 40% RH.  The Liebert display reports the actual temperature & humidity are near these values.  However, a chart recorder in the room says the temperature is 69 F & RH is 65%.      

I know very little about HVAC and the project engineer will probably contact the installer.  However, for future reference & to gain additional knowledge, how should we adjust the setpoints to achieve a RH less than 55%?

Thanks.    

RE: Help With Liebert 3000 Unit

68F and 40% is pretty tough with DX cooling in an non-arid area. Pretty much need a desicant.Be an easy condition to maintain in the winter smile

65% sounds excessive, but you should be able to maintain 50%.

Usually labs are pressurized to prevent infiltration and therefore outside humidity from entering the space.

You would be better of having the tech adjust the setpoints, or better yet a factory rep.

  

RE: Help With Liebert 3000 Unit

Chemee,

Put your chart recorded and the sensor for the Liebert in close proximity to each other.  If the chart reader is still reading a different measurement, have  a tech come in to calibrate the instruments/sensors and verify the actual space conditions.

RE: Help With Liebert 3000 Unit

68 deg F is really to cold for a Liebert, I belive there spec's say they are ok down to 68 but they perform much better at 72 deg F and that should be there field Min setpoint for temp, as for humidity pushing this much below 50% on DX alone might be trouble some, I hope you have a tight vapour barrier and have all air tight openings (doors)

my info comes from Henry Fudge from Leiberts Training Center in Columbus,Ohio

RE: Help With Liebert 3000 Unit

(OP)
Thank you for your responses.  We raised the unit setpoint to 71 degrees & placed a chart recorder by the unit.  The recorder is reading a temperature of 70 F & humidity of 58%.  We have been successful in dropping the humidity 7% by increasing the temperature. However, we still need to be below 55% & we can't go any higher on temperature due to environmental requirements.  The Liebert is reading 69 F and 37% humidity (the setpoint was lowered from 40-35%).  So the recorder & Liebert agree on temp but not on humidity.  We will have someone check the Liebert's humidity operation.

Also, the room is not tight.  There is no vapor barrier.  So in-leakage is an issue.  The room that is becoming this mini-lab is a room that served as storage for another lab.  If this is an issue in 75 F weather, I know we are doomed during summer.

RE: Help With Liebert 3000 Unit

You won't Liebert publish performance data for anything less than 72F @ 50%.

I have a redundant pair of 40 ton industrial DX models doing a telco room data centre, and the client was pushing for 67F as a setpoint as the old systems had poor air distribution and therefore hotspots when the set point was any higher than that.

After a haggling period, I managed to get the client to agree with a 70 degree set point. The system maintains that temperature with no hot spots, however IT people are set in their ways and the room is maintained at 67F and 50%.

A humid climate, however a pressurized space with a big internal sensible load. So 68 at 50% is not impossible, but 68F @ 40% is not happening in the summer time.

RE: Help With Liebert 3000 Unit

All your answers will be given in 2 minutes with a sling psychrometer.  And a nice piece of kit to get the calibration lab started =)

Digital R. humidity is expensive to measure accurately; 3% is your typical RH sensor, with a big cost jump to 2%.  Trust the instruments accordingly.

RE: Help With Liebert 3000 Unit

Slings not always that accurate. Impurities in the water, swing them too slow and they read high on the wet bulbs

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources