Air Conditioning 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 Air Conditioning flashcards as text
Which type of air distribution system delivers conditioned air through a single large duct and uses a mixing box at each zone to control temperature?
Answer: Dual-duct system
A dual-duct system supplies both cold and hot air through separate ducts to mixing boxes at each zone, where they blend to achieve the desired temperature.
A compressor that is 'pumping down' correctly should result in what suction pressure reading?
Answer: Near 0 psig or slightly into a vacuum
When pumping down, the compressor evacuates refrigerant from the low side until the suction pressure reaches approximately 0 psig or a slight vacuum, then the low-pressure control shuts it off.
What is the primary cause of 'liquid slugging' in an air conditioning compressor?
Answer: Liquid refrigerant or oil entering the compressor suction
Liquid slugging occurs when liquid refrigerant or oil enters the compressor suction, and since liquids are incompressible, this can bend connecting rods or break valve reeds.
What does a high superheat reading at the evaporator outlet combined with low suction pressure most likely indicate?
Answer: Restricted metering device or low refrigerant charge
High superheat with low suction pressure indicates the evaporator is starved of refrigerant, which is caused by a restricted metering device or insufficient refrigerant charge.
Which component in a residential split-system air conditioner is responsible for moving air across the indoor coil?
Answer: Air handler blower motor
The air handler blower motor (typically a multi-speed or ECM motor) circulates indoor air across the evaporator coil for heat exchange.
What is the significance of the 'critical charge' in a fixed-orifice AC system versus a TXV system?
Answer: Fixed-orifice systems are far more sensitive to charge amount than TXV systems
Fixed-orifice (piston/capillary) systems are critically sensitive to refrigerant charge because the metering device cannot compensate for variations, while a TXV actively adjusts flow to maintain proper superheat.
When measuring the outdoor ambient temperature for AC system performance diagnosis, where should the measurement be taken?
Answer: At the condenser air inlet in the shade, away from the unit's discharge air
Outdoor ambient temperature should be measured in the shade at the condenser air inlet, away from the hot discharge airstream, to get an accurate reference for system performance charts.