Air Handler Units and Coils 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 Handler Units and Coils flashcards as text
What does 'superheat' refer to in the context of an evaporator coil?
Answer: The temperature of refrigerant vapor above its saturation temperature
Superheat is the number of degrees the refrigerant vapor temperature exceeds its saturation (boiling) temperature at a given pressure at the coil outlet.
What is the recommended minimum clearance around an air handler unit for service access?
Answer: 12-18 inches on service side, 6 inches on other sides
HVAC industry standards typically require 12-18 inches on the service access side and at least 6 inches on other sides for proper maintenance access.
Which coil configuration uses two rows of tubes in a 'A' shape to maximize surface area?
Answer: A-coil (cased coil)
An A-coil or cased coil uses two slanted coil sections arranged in an A-shape, maximizing heat exchange surface area while fitting within a compact housing.
What is the purpose of the blower wheel fins being curved backward (backward-inclined) in an air handler?
Answer: To improve efficiency and reduce power consumption at high airflows
Backward-inclined blower wheel fins are non-overloading, meaning they consume less power as airflow increases, improving efficiency compared to forward-curved designs.
What is the recommended pH range for condensate drain water in a properly functioning system?
Answer: 5-7 (mildly acidic to neutral)
Normal condensate drain water is slightly acidic (pH 5-7) due to dissolved CO2, but excessively acidic condensate can indicate microbial growth or system problems.
What is the primary cause of a humming or buzzing noise from an air handler blower motor?
Answer: Electrical issues such as capacitor failure or voltage imbalance
A humming or buzzing blower motor often indicates electrical problems like a failing start/run capacitor, loose wiring, or voltage imbalance causing abnormal electromagnetic operation.
In a variable air volume (VAV) air handler system, what component modulates airflow to different zones?
Answer: Zone dampers controlled by a central DDC controller
VAV systems use motorized zone dampers controlled by a Direct Digital Control (DDC) system to modulate airflow to each zone based on its thermostat demand.