Cooling & Dehumidification

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Cooling & Dehumidification Measurement & Verification (M&V)

Goals of Experiment

  • Verify capacity of dehumidification coil.
  • Verify performance of Altherma in dehumidification mode.
  • Demonstrate that return air mixing adequately performs to reheat dehumidified air.

Decisions to be made from Experiment

  • Acceptance of coil performance as installed.
  • Acceptance of Altherma cooling performance as installed.
  • Confirm that duct may remain uninsulated.

Expected Outcomes

  • Proper dehumidification and reheat of ventilation air with no condensation.



  • Dehumidification load is comprised of moisture brought in with outside air for ventilation and from people in the occupied spaces.
    • Outside air is preconditioned by energy recovery wheel to reduce some heat/humidity (included in calculations).
    • Annex may have additional process latent load that is not accounted for anywhere yet.
  • Inside dehumidification coil is sized for a design day of 88F/74F/52%RH outside air conditions, but air mixing and system performance is based on energy wheel being on.
    • On design day, inside conditions resulting from system capacity and capability is estimated to be approximately 78F, 53% RH (dewpoint 59.5F); target was 78F, 45% RH so that 78F, 60% would not be exceeded as installed and operated.
    • Altherma water temperature to coil required to be 45F to provide enough latent cooling (insulation required on associated piping).
    • Discharge air temperature from dehumidication coil is designed to be 50F DB / 50F WB (duct insulated at coil until mixed with return air as surface temp will be below design dewpoint).
    • Airflow through coil 750 CFM (54% of total), airflow through return 650 CFM, for a total of 1400 CFM. Return air reheats ventilation air from 50F coil discharge to 63F so that duct does not need to be insulated.
    • Air in duct must be no more than 15F away from the room temperature being served (78 - 15 = 63F).

Process Measurements

Resources Required

  • Temperature controls do not appear to be set up with monitoring or control to maintain the above parameters. Intend to test system to verify this is true.
    • Dehumidification system needs to modulate to maintain desired conditions without wasting energy by going below required multi-faceted parameters.
    • Cycling of coil may impact minimum operation time of Altherma unless Altherma switches to other mode to keep running?




Help Wanted

Scheduling & Sequencing




  • Plan / Do / Study / Act / Repeat