ASHRAE Guideline 36 — Damper/Fan Interlocks

ASHRAE Guideline 13 — Data Management

Storing trend data only in field controllers risks data loss when controllers are reset or lose power. Trend data should be archived to the BAS server or a dedicated historian. Controller memory is limited and will overwrite oldest data.

ASHRAE Guideline 36 — Chiller Staging

Staging a lag chiller immediately at 100% lead capacity causes hunting and instability. A time delay (typically 10-15 minutes) and sustained load confirmation are required to prevent short-cycling. ASHRAE Guideline 36 specifies staging criteria with time delays and load verification.

ASHRAE Guideline 36 — Cooling Coil Control

Cooling coil control valves should fail closed (spring return to closed) on loss of signal or power. Failing open causes uncontrolled cooling and potential freezing of downstream coils or spaces.

ASHRAE Guideline 36 — Freeze Protection

A freeze stat alarm must automatically shut down the AHU fan, close the outdoor air damper, and open the heating valve. An alarm-only response without automatic action risks coil freeze-up and catastrophic water damage.

ASHRAE Guideline 36 — High-Performance Sequences of Operation

The DP sensor is located at the pump discharge instead of at the most remote coil or 2/3 of the way out in the system. Sensing DP at the pump header causes the VFD to maintain artificially high system pressure, defeating the purpose of variable flow. The sensor must be relocated to represent the actual system load point.

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.