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Ductless Mini-Splits and VRF

Ductless mini-splits and variable refrigerant flow (VRF) systems use inverter-driven outdoor units that serve one or more indoor units through refrigerant piping. This sheet covers the system types, the parts that must match and the rating standards behind the published numbers.

Ref HV-0009AHRI 1230AHRI 210/240

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

A mini-split has an outdoor inverter unit connected by a line set and communication cable to one indoor unit (single zone) or several (multi-zone). Indoor units can be wall-mounted, ceiling cassette, floor console or slim ducted. A VRF system is a larger commercial version. One outdoor unit or module group serves many indoor units through branch fittings or branch controllers. Heat pump VRF heats or cools all zones at once. Heat recovery VRF can heat some zones and cool others at the same time by moving heat between them.

How to identify

Read the outdoor unit nameplate for model, refrigerant, capacity and electrical data. Multi-zone outdoor units list the number of indoor ports. VRF outdoor units carry series names and module sizes, and VRF piping uses factory branch kits (Y-joints or headers) rather than field tees. Indoor units list the matching outdoor series in the installation manual.

System types

Type	Zones	Piping	What must match
Single-zone mini-split	1	One line set	Indoor and outdoor from the same rated combination
Multi-zone mini-split	2 or more	One line set per indoor unit, to ports on the outdoor unit	Indoor units approved for that outdoor unit; total connected capacity within the maker's range
Slim ducted mini-split	1 or more	Line set plus short duct runs	Static pressure range of the indoor unit
VRF heat pump	Many	Main and branch piping with factory branch kits	Same series indoor units, branch kits and controls
VRF heat recovery	Many	Branch controllers or 3-pipe systems	Branch controller model and series

Key points

Published efficiency applies to a rated combination. For residential and light commercial units under 65,000 Btu/h, ratings come from AHRI 210/240. VRF multi-split ratings come from AHRI 1230. Look up the combination in the AHRI directory.
Indoor units, branch kits, controllers and communication wiring are usually brand and series specific. Do not mix series.
Line set sizes, maximum lengths and lift limits come from the installation manual.
Many current units use A2L refrigerants. Check the refrigerant safety group chart and the manual for charge and room size rules.
Flare connections must be made with the right flare tool and torque method from the manual.

Common mistakes

Quoting an indoor unit without confirming it is approved for the customer's outdoor unit.
Substituting a field tee for a VRF branch kit.
Using generic thermostat wire in place of the specified communication cable.
Assuming a mini-split rated SEER2 applies with any indoor unit.

Governing standards: AHRI 210/240 (unitary air-conditioning and heat pump equipment); AHRI 1230 (variable refrigerant flow multi-split equipment). Manufacturer installation manuals for matching, piping and wiring.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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