System Design Flashcards
7 cards from real HVAC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 System Design flashcards as text
In a VAV system, a minimum airflow setpoint for VAV terminal boxes is required primarily to:
Answer: Maintain adequate ventilation and thermal comfort at low cooling loads
Minimum airflow setpoints ensure each zone receives sufficient ventilation air and prevents 'dead air' conditions even when the cooling load is near zero.
What is 'infiltration' as it applies to HVAC load calculations?
Answer: Uncontrolled air leakage into a building through cracks and gaps in the envelope
Infiltration is uncontrolled outdoor air that enters through gaps, cracks, and openings in the building envelope, adding to both heating and cooling loads.
Which of the following best describes a 'dedicated outdoor air system' (DOAS)?
Answer: A separate system that provides pre-conditioned outdoor air to each zone independent of sensible cooling/heating equipment
A DOAS handles ventilation by conditioning 100% outdoor air to neutral conditions before delivering it to zones, while separate equipment (fan-coils, radiant panels) handles sensible loads.
When designing refrigerant piping for a split system with the outdoor unit above the indoor unit, what special design consideration is required?
Answer: Adding oil traps in the suction line riser at regular intervals
When the compressor is above the evaporator, suction line risers need oil traps (P-traps) at the bottom and at every 20 feet of vertical rise to return lubricating oil to the compressor.
In HVAC system design, 'diversity factor' is applied to:
Answer: Reduce the total calculated peak load when all zones are unlikely to peak simultaneously
A diversity factor reduces the sum of individual zone peak loads to reflect that zones rarely all peak at the same time, allowing smaller central plant equipment.
What is the primary design advantage of a four-pipe hydronic fan-coil system over a two-pipe system?
Answer: Simultaneous heating and cooling to different zones year-round
Four-pipe systems have separate hot water and chilled water circuits, allowing individual fan-coil units to heat or cool independently based on each zone's demand at any time of year.
Which ASHRAE standard governs energy efficiency requirements for commercial building HVAC systems in the US?
Answer: ASHRAE 90.1
ASHRAE 90.1 (Energy Standard for Buildings Except Low-Rise Residential) sets minimum energy efficiency requirements for HVAC, lighting, and envelope in commercial buildings.