HVAC Ductless Mini-Split Systems 5

Question 1

What is the purpose of the defrost cycle in a heating-mode ductless mini-split system?

Accepted Answer

To melt frost accumulation on the outdoor coil that restricts airflow and heat transfer

Answer

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.

Question 2

A technician is sizing a mini-split for a sunroom with large south-facing glass walls. Which load calculation adjustment is most critical?

Accepted Answer

Adding significant solar heat gain through the glass to the cooling load

Answer

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.

Question 3

What does the term 'cold climate heat pump' or 'hyper heat' refer to in the context of ductless mini-splits?

Accepted Answer

A mini-split that maintains meaningful heating capacity at very low outdoor temperatures, often down to -13°F or lower

Answer

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.

Question 4

When vacuuming a mini-split system before charging, what minimum vacuum level should be achieved and held?

Accepted Answer

100 microns or below, held for at least 15 minutes

Answer

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.

Question 5

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?

Accepted Answer

Normal thermal expansion and contraction of the outdoor coil as it rapidly changes temperature

Answer

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.

HVAC - Heating, Ventilation, and Air Conditioning Practice Test

HVAC - Heating, Ventilation, and Air Conditioning Practice Test

HVAC Ductless Mini-Split Systems 5