BAS, PAS, and EMCS
What this domain tests
BAS/PAS/EMCS questions test control strategies, point data, and commissioning. The exam expects you to know what a control system can and cannot save.
Core rules
- DDC controllers run schedules, setpoints, and PID loops; the value is in sequences, not hardware.
- Optimal start learns building mass and brings equipment on just in time.
- Night setback and setup save energy only when terminal units and dampers actually close.
- Trending and alarms turn the BAS into a persistence tool; uncommissioned systems drift.
- Sensor calibration is critical: a 2°F error in a discharge sensor can waste more than a setpoint change saves.
Worked example
An office runs 24/7 at 70°F. A schedule shuts off HVAC for 12 hours on weekdays and all weekend. If the building uses 1,200 MMBtu/yr and 35% of run hours are unoccupied, roughly 420 MMBtu is at stake; realistic setback savings of 30% on those hours yield about 126 MMBtu/yr, or $1,260 at $10/MMBtu.
Traps
Assuming a BAS saves energy without re-commissioning; ignoring overrides and manual modes; forgetting that pneumatic-to-DDC conversions need point verification; and specifying controls without a sequence of operations.