ASHRAE Guideline 36 — Chiller Staging

ASHRAE Guideline 12 — Minimizing the Risk of Legionellosis

Without automatic blowdown control, condenser water cycles of concentration are unmanaged. Manual blowdown is unreliable and either wastes water (over-blowing) or allows mineral concentration to build (under-blowing). An automatic conductivity controller with a motorized blowdown valve is required to maintain proper cycles of concentration (typically 3-6 cycles).

ASHRAE Guideline 13 — Alarm Management

Alarms must be prioritized based on severity. A freeze stat alarm (life-safety) should be higher priority than a dirty filter alarm (maintenance). Without prioritization, critical alarms get lost in nuisance alarms, a condition called 'alarm flooding'.

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 — 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 — Damper/Fan Interlocks

An end switch or position feedback must confirm the motorized outside air damper is fully open before the evaporator fan is allowed to start. Starting the fan with the damper closed creates high negative pressure in the ductwork and starves the unit of ventilation air, potentially damaging ductwork and causing inadequate outdoor air delivery.

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.