P
PMS · TROUBLESHOOT
Procedure Mgmt System · DC-Lagos-03
PMS-COOL-014SEV P1Cooling

CRAC unit high return-air temperature

CRAC-04 / Hall B Cold Aisle 3
Symptom
Return air > 32°C, supply fan @ 100%, no compressor cycle.
Required PPE
Mech gloves · Ear protection · Safety glasses
Permits
PRM-MECH-Hot-Work-N/A · Floor-tile lift authorization
Procedure Steps
0/6 · 0%
  1. S-01Confirm setpoint vs. actual on CRAC controller (Liebert iCOM).
    Verify · Setpoint 22°C ± 1°C.
  2. S-02Inspect chilled-water supply valve V-CHW-04 position.
    Verify · Valve indicator = OPEN, ΔP > 12 psi.
  3. S-03Check return-air filter ΔP via Magnehelic gauge.
    Verify · ΔP < 0.8 inH₂O. Replace if higher.
  4. S-04Verify compressor head pressure and refrigerant charge.
    Verify · Discharge 250–280 psi at 22°C ambient.
  5. S-05Inspect under-floor for blockage (cables, tiles).
    Verify · Air velocity ≥ 2.5 m/s at perforated tiles.
  6. S-06If unresolved, fail-over to redundant CRAC-05 and isolate.
    Verify · Hot-aisle delta returns within ASHRAE A1 envelope.
References
ASHRAE TC 9.9 (2021) · Vendor: Vertiv Liebert DSE Service Manual §7.3
Actions
Check at least one step to begin the run timer.
END · PMS-COOL-014