ASHRAE Guideline 36 — Section 5.18

ASHRAE Guideline 36 — Monitoring Requirements

Temperature trend data should have at least 0.1 degree resolution. Whole-number-only resolution (e.g., 72 vs. 72.3) loses critical information needed for analyzing control loop performance, setpoint drift, and energy optimization.

ASHRAE Guideline 36 — Redundant Equipment / high-rise office Mechanical Specification

Redundant CRAC units must have automatic failover capability. If the lead CRAC unit fails (compressor fault, high-head pressure, loss of refrigerant), the vNSA switch must automatically start the lag unit without manual intervention. Critical cooling spaces cannot wait for a building engineer to respond, especially during off-hours. The Liebert vNSA network switch is specifically designed for automatic lead/lag coordination and failover — disabling this feature defeats the purpose of redundancy and risks equipment damage from overheating.

ASHRAE Guideline 36 — Redundant Equipment Staging

Redundant CRAC units must have one designated as lead and one as lag. Setting both as lead causes both units to run at full capacity simultaneously, wasting energy and eliminating redundancy protection. The Liebert vNSA switch must coordinate lead/lag sequencing so only one unit operates at a time under normal conditions.

ASHRAE Guideline 36 — Sensor Placement

Temperature sensors must not be placed in direct airflow from supply diffusers. The supply air temperature causes false readings, making the controller unable to maintain proper space temperature setpoint.

ASHRAE Guideline 36 / Crestline Controls Specification

Duct temperature probes must be inserted 25-50% of the duct width to obtain a representative reading. Inserting only 10% places the sensor in the boundary layer near the duct wall where temperature is not representative of the airstream, causing inaccurate control.

ASHRAE Guideline 36 / Manufacturer maintenance requirements

Dirty CRAH coils reduce heat transfer efficiency significantly, potentially losing 20-40% of cooling capacity. Regular coil cleaning is required per ASHRAE maintenance guidelines. Reduced capacity leads to higher server inlet temperatures and potential thermal shutdowns.