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Split System Components Explained

A split system puts the compressor and condenser outdoors and the evaporator coil and blower indoors, joined by a refrigerant line set. This sheet names each component, what it does and what a counter typically sells for it.

Ref HV-0004AHRI 210/240

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

What it is

A split air conditioner or heat pump has two main sections. The outdoor unit (condensing unit or heat pump) holds the compressor, outdoor coil, fan and electrical controls. The indoor section is an evaporator coil paired with a furnace or an air handler that moves air through the ductwork. A copper line set carries refrigerant between them, and low-voltage controls tie the system to the thermostat. Efficiency ratings under AHRI 210/240 apply to a tested combination of outdoor and indoor equipment, not to the outdoor unit alone.

How to identify

Read the data plates. The outdoor unit plate shows model and serial numbers, refrigerant type, charge, electrical data and the maximum overcurrent device. The indoor coil or air handler has its own plate with model, metering device and refrigerant. The AHRI certificate or directory lists which indoor and outdoor models are a rated match.

Components and common counter items

Component	Job in the system	Common replacement items
Compressor	Pumps refrigerant and raises its pressure	Compressor, start components, hard-start kits
Outdoor coil and fan	Rejects heat to outdoor air (cooling mode)	Fan motor, fan blade, coil cleaner
Contactor and capacitor	Switch and start the compressor and fan	Contactors, run capacitors (single or dual)
Metering device	Controls refrigerant flow into the indoor coil	TXV, piston or orifice, as the coil maker specifies
Evaporator coil	Absorbs heat from indoor air	Cased or uncased A-coils, slab coils, drain pans
Furnace or air handler	Moves air; furnace or heat strips supply heat	Blower motors, control boards, filters
Line set	Carries refrigerant: insulated suction line and smaller liquid line	Pre-insulated line sets, fittings, line hide
Filter drier	Removes moisture and debris	Liquid-line driers, bi-flow driers for heat pumps
Controls	Thermostat and low-voltage wiring	Thermostats, thermostat wire, float switches
Electrical	Disconnect and whip to the outdoor unit	Disconnects, whips, pads and risers

Key points

The indoor coil must be matched to the outdoor unit for refrigerant, capacity and metering device. Check the AHRI listing and the manufacturer's match-up.
Line set sizes come from the outdoor unit's installation instructions. Long or vertical runs may need different sizes or added charge. Use the maker's tables.
Cooling capacity is often given in tons. One ton equals 12,000 Btu/h.
Replace the filter drier whenever the system is opened.
Electrical sizing comes from the data plate. Do not size breakers or wire from this sheet.

Common mistakes

Replacing only the outdoor unit with a new-refrigerant model and leaving an incompatible coil.
Selling a line set by tonnage without reading the install instructions.
Treating a cased coil and an uncased coil as interchangeable without checking cabinet size.
Quoting an efficiency rating for an outdoor unit without the matched indoor section.

Governing standards: AHRI 210/240 (performance rating of unitary air conditioning and air-source heat pump equipment); manufacturer installation instructions.

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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