ASHRAE 90.1-2019, Section 6.4.3.3.3

ASHRAE 90.1-2019 Section 6.5.5 / CTI Standard 140

Damaged drift eliminators allow excessive water loss through carryover of water droplets into the discharge airstream. This wastes water and chemical treatment, and can create safety hazards from ice formation on nearby surfaces in winter. Drift loss should be limited to 0.001-0.005% of circulating flow per ASHRAE.

ASHRAE 90.1-2019 Section 6.5.5.2 (Heat Rejection Equipment — Fan Speed Control)

ASHRAE 90.1-2019 Section 6.5.5.2 (Fan Speed Control) requires that each fan on heat-rejection equipment (cooling towers, closed-circuit coolers, evaporative condensers) powered by a motor of 7.5 HP or larger have controls that automatically change fan speed — a two-speed motor, a variable-speed drive, or other approved modulating control. The trigger is the fan motor horsepower, not the condenser-water flow rate. This 30 HP single-speed fan is well above the 7.5 HP threshold, so simple on/off contactor control violates the requirement. A single-speed fan cycling on and off also wastes significant energy and causes large swings in condenser water temperature, reducing chiller efficiency. Variable-speed control is preferred because fan power varies with roughly the cube of speed — operating at 80% speed uses only about 51% of full-load power. A VFD on the cooling tower fan typically pays for itself within one to two cooling seasons through reduced energy consumption.

ASHRAE 90.1-2019, Section 6.4.3.3

Night setback/setup is required by ASHRAE 90.1 for buildings with DDC. The heating setback to 55 degrees F prevents freezing while saving energy. The 90 degrees F cooling setup prevents extreme overheating while allowing the cooling system to rest. The 30-minute pre-start is an acceptable fixed lead time, though optimal start is preferred for larger buildings.

ASHRAE 90.1-2019, Section 6.5.1.1

In humid climates, dry-bulb economizer control can introduce excessive moisture. ASHRAE 90.1 and Guideline 36 require differential enthalpy or fixed-enthalpy control for climate zones where humidity is a factor.

ASHRAE 90.1-2019, Section 6.5.1.1 / ASHRAE 62.1

This economizer setup is code-compliant on multiple fronts. The 75 degrees F dry-bulb lockout aligns with ASHRAE 90.1 Table 6.5.1.1.3 for most climate zones. The enthalpy limit adds humidity protection per ASHRAE 90.1 Section 6.5.1.1. The 20% minimum outdoor air damper position during occupied hours ensures ventilation compliance with ASHRAE 62.1 — the damper never fully closes when people are present. The CO2-based demand-controlled ventilation above 1,000 PPM is an accepted method per ASHRAE 62.1 Section 6.2.7 for adjusting ventilation based on actual occupancy. This is a well-programmed, energy-efficient, code-compliant sequence.

ASHRAE 90.1-2019, Section 6.5.3.2.2

ASHRAE 90.1 requires static pressure reset for VAV systems with DDC. A fixed setpoint wastes fan energy during part-load conditions. The setpoint should reset down based on zone damper positions — when all dampers are less than 90% open, the static pressure setpoint should decrease. ASHRAE Guideline 36 specifies Trim and Respond reset logic for static pressure.