Ductless Mini-Split Systems 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 Ductless Mini-Split Systems flashcards as text
What is the purpose of the defrost cycle in a heating-mode ductless mini-split system?
Answer: To melt frost accumulation on the outdoor coil that restricts airflow and heat transfer
During heating operation in cold, humid conditions, frost builds on the outdoor coil; the defrost cycle temporarily reverses refrigerant flow to melt this frost and restore efficiency.
A technician is sizing a mini-split for a sunroom with large south-facing glass walls. Which load calculation adjustment is most critical?
Answer: Adding significant solar heat gain through the glass to the cooling load
South-facing glass creates substantial solar heat gain that must be added to the cooling load calculation, often requiring a larger unit than square footage alone would suggest.
What does the term 'cold climate heat pump' or 'hyper heat' refer to in the context of ductless mini-splits?
Answer: A mini-split that maintains meaningful heating capacity at very low outdoor temperatures, often down to -13°F or lower
Cold climate or hyper-heat mini-splits use advanced compressor technology to extract heat from outdoor air even at extremely low temperatures, often rated to -13°F (-25°C) or below.
When vacuuming a mini-split system before charging, what minimum vacuum level should be achieved and held?
Answer: 100 microns or below, held for at least 15 minutes
Industry best practice requires pulling a vacuum to 500 microns or less (ideally 100-300 microns) and verifying it holds to ensure all moisture and non-condensables are removed.
A mini-split system's outdoor unit makes a loud cracking or banging noise when the defrost cycle ends. What is the most likely explanation?
Answer: Normal thermal expansion and contraction of the outdoor coil as it rapidly changes temperature
The sudden temperature change as the outdoor coil transitions from cold frosted conditions to warm defrost temperatures causes normal thermal expansion noises in the coil tubing.
Which factor determines whether a mini-split installation requires a dedicated electrical circuit?
Answer: The unit's minimum circuit ampacity (MCA) rating as listed on the nameplate
The nameplate Minimum Circuit Ampacity (MCA) determines the required wire size and whether a dedicated circuit is needed, as specified by NEC and the manufacturer.
A homeowner wants to install a mini-split in a garage that is not insulated and frequently sees temperatures below 0°F in winter. What is the most important recommendation?
Answer: Select a cold climate-rated unit AND insulate the garage to improve efficiency and protect the equipment
A cold climate-rated mini-split paired with proper insulation ensures the unit operates within its design limits while efficiently maintaining the desired temperature in extreme cold.