Ductless Mini-Split Systems Flashcards

A technician is troubleshooting a multi-zone mini-split where one zone is not cooling but others work fine. What should be checked first?

Answer: Check the individual zone's expansion device and indoor unit controls

In a multi-zone system, zone-specific problems typically stem from the individual indoor unit's expansion valve, thermistor, or control board rather than the shared outdoor unit.

What is the purpose of the flash guard or line set cover used during mini-split installation?

Answer: To protect and bundle refrigerant lines, electrical wiring, and drain line on the exterior wall

Line set covers (also called line hide or lineset cover kits) bundle and protect the refrigerant lines, electrical wiring, and condensate drain on the exterior of the building.

Which refrigerant is most commonly used in modern ductless mini-split systems sold in the United States?

Answer: R-410A or R-32

R-410A has been the dominant refrigerant in modern mini-splits, with R-32 gaining adoption as a lower-GWP alternative; R-22 is phased out.

What is the function of the Electronic Expansion Valve (EEV) in a variable-speed mini-split system?

Answer: Precisely control refrigerant flow rate to match system load

The EEV modulates refrigerant flow with precision, allowing the system to fine-tune capacity and maintain efficiency across varying load conditions.

A mini-split outdoor unit is installed on a rooftop in a northern climate. What installation accessory is essential for winter operation?

Answer: Wind baffles and elevated mounting brackets or snow stand

Snow stands elevate the unit above snow accumulation and wind baffles protect from prevailing winds, both critical for reliable heating operation in cold climates.

What does 'inverter-driven' mean in the context of a ductless mini-split compressor?

Answer: The compressor speed is continuously variable based on demand, improving efficiency

An inverter-driven compressor uses variable-frequency drive technology to continuously modulate compressor speed, matching output precisely to load and reducing energy cycling losses.

During a mini-split commissioning, a technician measures the suction line temperature and compares it to the suction pressure to determine superheat. Why is this measurement important?

Answer: To ensure refrigerant entering the compressor is fully vaporized, preventing liquid slugging

Adequate superheat confirms that refrigerant is fully vaporized before reaching the compressor, preventing liquid refrigerant slugging which can cause compressor damage.