Different Types of HVAC Systems

A: Governing principle: At part load, airflow control dominates energy use and comfort, not coil capacity. Here, excessive VAV minimums force reheat even when sensible load is low, so energy is burned to fix a self-created problem; lowering minimums while protecting ventilation breaks the loop. Option B traps engineers who know about low-ΔT but misapply a waterside fix to an airside control error.

A: Governing principle: Safeguards mitigate specific consequences, not every failure mode in the system. Leak detection and ventilation reduce occupant exposure and escalation, but they don't address oil management, which is a piping velocity and geometry problem. Option D catches people who blur mitigation with root-cause prevention.

A: Governing principle: Processes with continuous operation and humidity sensitivity favor stable central plants with controllable coils. Chilled water allows precise dewpoint control and N+1 strategies aligned with GMP expectations. Option C attracts engineers focused on efficiency who overlook refrigerant-in-space and control stability issues.

A: Governing principle: Energy codes target annual energy, not peak design. Economizers capture free cooling during the many hours below design conditions. Option B trips engineers who associate economizers with ventilation rather than energy reduction.