Mini-splits are unique because they are compartmentalized in ways that traditional central-air ducted systems are not. Mini-splits come in many varieties, including ducted and ductless types, as well as multi-zone types. Many are inverter-driven and have more electrical efficiency as a result and can vary their capacities based on load variation.
Mini-splits have metering devices at their outdoor units, and these devices may be electric expansion valves (EEVs) or capillary tubes. Inverter mini-splits also don’t have filter driers because their PVE oil doesn’t have the same acid concerns as POE oil, and they don’t have traditional liquid lines.
Flare connections are also critical when installing ductless systems, especially because you want systems to be tight to prevent leaking and contamination. Craig likes eccentric flaring tools with offset cones, and he recommends using flare nuts from the equipment manufacturer, not the line set manufacturer. He covers other flaring best practices as well.
The charge is quite small in mini-splits, so weighing the charge and being careful and deliberate during charging is critical. Refrigerant leaks can also be highly problematic; corrosion and poor flare connections are common causes of leaks.
Craig and Bryan also discuss:
Hyper-heat systems
Coefficient of performance (COP) and BTU output
Moving between PSC and ECM or inverter technologies
Mini-splits vs. VRF/VRV technologies
Pressure testing and leak detection
Compressor diagnosis
Thermistors and electrical resistance
Heat sinks and mounting circuit boards
Selecting a location to install a mini-split
Things to consider when checking the charge
Why measure superheat and subcooling?
Cleaning and maintenance best practices
Check out Craig’s YouTube channel at https://www.youtube.com/@acservicetechchannel.
Starting January 1st, 2023, you can buy Craig’s book on his website, which has a bunch of other good resources. Visit that site at https://www.acservicetech.com/.
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