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
When sizing a refrigerant suction line, the primary concern is avoiding excessive:
Answer: Pressure drop that reduces compressor capacity
Excessive suction line pressure drop lowers suction pressure at the compressor, reducing capacity and efficiency, and can cause liquid refrigerant slugging.
What is the 'effective length' of a duct fitting used for in duct design?
Answer: The equivalent straight duct length that produces the same pressure drop as the fitting
Effective length (or equivalent length) converts the pressure drop of a fitting into an equivalent straight duct length to simplify total system friction calculations.
In a chilled water plant, what does 'delta T' (ΔT) across the cooling coil represent?
Answer: Temperature difference between entering and leaving chilled water
Chilled water ΔT is the difference between return water temperature and supply water temperature, typically designed at 10–12°F for optimal plant efficiency.
Which system type is best suited for a large open-plan office requiring individual occupant control without ductwork to each desk?
Answer: Underfloor air distribution (UFAD) with floor diffusers
UFAD systems deliver conditioned air through raised-floor diffusers near occupants, offering flexible zone control and good air quality without overhead ductwork to every work area.
The Coefficient of Performance (COP) of a heat pump in heating mode is always:
Answer: Greater than 1.0 because it moves heat rather than generating it
A heat pump's heating COP exceeds 1.0 because it moves (transfers) heat from outdoor air into the building, delivering more energy as heat than it consumes as electricity.
In HVAC design, an 'economizer' cycle saves energy by:
Answer: Using cool outdoor air directly for cooling when conditions permit
An air-side economizer uses 100% outdoor air for cooling when the outdoor temperature and/or enthalpy is below a setpoint, reducing or eliminating mechanical cooling energy.
What does the 'leaving air temperature' (LAT) of a cooling coil determine in system design?
Answer: The supply air temperature delivered to the space after the coil
The LAT is the temperature of air exiting the cooling coil, which becomes the supply air temperature delivered to conditioned spaces to offset the sensible cooling load.