NOTE This standard covers air-cooled condensing units (ACCUs) furnished as the remote outdoor section of a split direct-expansion (DX) cooling system. (1.1)

NOTE The condensing unit comprises one or more compressors, air-cooled condenser coil(s), condenser fan(s), refrigerant-circuit accessories, and integral controls in a weatherproof outdoor cabinet. It rejects heat from a refrigerant circuit whose evaporator is located elsewhere — in an indoor fan-coil unit, a DX air handler, a refrigerated display coil, or a process cooling coil — and is joined to that evaporator by field-installed refrigerant piping. (1.2)

NOTE Capacities covered range from approximately 1.5 tons (18,000 Btu/h) to 130+ tons (1,560,000 Btu/h) nominal, with the common light-commercial and commercial range falling between 3 and 25 tons. (1.3)

NOTE This standard applies to single-circuit and dual-circuit units with scroll, reciprocating, or screw compressors, and to both cooling-only units and heat-pump condensing units operating in the cooling mode. (1.4)

NOTE This standard applies to rooftop-mounted, ground-level pad-mounted, and wall-bracket-mounted installations on commercial buildings, light-industrial facilities, retail spaces, server rooms, and similar occupancies. (1.5)

NOTE The obligation to verify matched ratings appears as a clause under Quality Assurance. (1.7)

NOTE The following are outside the scope of this standard and are governed elsewhere. (1.8)

NOTE UL 60335-2-40 replaces the older UL 1995 and is required for A2L refrigerant products (such as R-454B and R-32) under the IMC and UMC 2024 editions. It governs leak detection, refrigerant-concentration mitigation, and ignition-source control specific to mildly flammable refrigerants. (4.4)

NOTE AHRI 365-2024 sets published-rating tolerances: cooling capacity and EER shall be at least 95% of the published value, and IEER at least 90% of the published value. Verifying the directory listing before acceptance prevents accepting a model whose certified ratings differ from the catalog sheet. (4.6)

NOTE Published AHRI ratings are established at 95°F outdoor dry-bulb and 45°F saturated suction temperature at sea level. Actual delivered capacity falls below the published value at higher altitude and higher outdoor design dry-bulb temperature, so the selection must be derated for the project site rather than read directly from the nameplate tons. (5.2)

NOTE A rooftop in a hot or high-altitude location (for example Phoenix or Denver) can lose 5% to 15% of nameplate capacity; specifying nominal tons without this correction is a common cause of undersized systems. (5.4)

NOTE Representative ASHRAE 90.1-2022 minimum EER values are 11.2 for units below 65,000 Btu/h, 11.0 for 65,000 to 134,999 Btu/h, 10.6 for 135,000 to 239,999 Btu/h, and 9.5 for 240,000 Btu/h and above; the adopted local code year governs the actual threshold and must be confirmed for the project. (5.6)

NOTE Representative DOE minimum IEER values are 12.9 for units 65,000 to 134,999 Btu/h and 12.4 for 135,000 to 239,999 Btu/h, per the rule effective January 2023. A unit can satisfy the full-load EER minimum yet fail the part-load IEER threshold, so both must be checked; verify the effective DOE rule edition for the procurement year. (5.8)

NOTE The transition from R-410A (an A1 refrigerant) to A2L refrigerants such as R-454B and R-32 is actively underway under the AIM Act, and manufacturers are discontinuing R-410A equipment on a model-by-model basis. New construction should not assume R-410A availability; the specified refrigerant must be procurable for the anticipated equipment order date, and the condensing unit and evaporator must share the same refrigerant. (6.2)

NOTE ASHRAE 34 assigns the safety group (A1, A2L, A2, B2L, and so on) that determines maximum charge per occupied space, ventilation requirements, and whether leak detection and mitigation are mandatory. ASHRAE 15 Table 1 establishes the maximum refrigerant charge for the smallest occupied space served. (6.5)

NOTE Units are typically factory-charged for a default equivalent line-set length (commonly 25 ft); additional charge for longer line sets, oil-trap requirements, and maximum equivalent length are governed by Refrigerant Piping and must be coordinated there rather than assumed in this section. (6.7)

NOTE Scroll compressors are the most common choice for commercial units up to roughly 30 tons; reciprocating compressors appear in smaller and legacy units; screw compressors are used in large commercial units above roughly 50 tons. The selection affects part-load behavior, sound, and serviceability. (7.2)

NOTE Single-circuit units are simpler and suit smaller or non-critical loads. Dual-circuit units provide capacity redundancy and staging flexibility and are recommended for critical, 24/7, or process facilities such as server rooms, where loss of a single circuit must not take the whole system offline. (7.5)

NOTE Options range from on/off single-stage through two-stage compressors, variable-speed condenser fans, and inverter-driven compressors. Variable-speed and inverter control improve part-load efficiency and capacity matching but cost more; the IEER requirement and the load profile drive the choice. (7.7)

NOTE Bare copper-tube aluminum-fin (RTPF) coils are the standard for benign environments. Coastal (saline) and corrosive industrial environments require a protective coating; bare RTPF coils in saline or chemically aggressive air can corrode within two to five years, so coating selection must reflect the actual site exposure. (8.2)

NOTE Standard units are rated to a minimum outdoor ambient of about 55°F. Below that, without low-ambient control, head pressure falls too low and the unit short-cycles or locks out. Year-round process, server-room, and data-center duty requires a low-ambient kit (condenser-fan cycling, fan speed control, or flooded-head-pressure control), typically extending operation to 0°F or down to −20°F. (9.2)

NOTE Standard units produce roughly 72 to 80 dB(A) re 1 pW; sound-attenuated or low-sound models, with acoustically insulated compressor compartments and low-speed fans, produce roughly 65 to 72 dB(A). Omitting a sound limit where noise sensitivity exists is a frequent source of post-installation complaints and RFIs. (10.2)

NOTE The nameplate MCA (minimum circuit ampacity) and MOCP (maximum overcurrent protection) per NEC 440.22 must agree with the electrical engineer's panel schedule and feeder sizing. Mismatches discovered at submittal commonly force circuit resizing RFIs, so the electrical characteristics must be coordinated early. (11.2)

NOTE Integral rubber isolators are standard and adequate for most slab and grade installations. Spring isolators are used where the supporting structure is sensitive to transmitted vibration, such as lightweight roof framing over occupied spaces. (12.2)

NOTE Most standard units ship with rubber isolators only, which do not by themselves satisfy ASCE 7 anchorage requirements. Supplemental seismic restraint clips or snubbers and an anchorage detail are required, and the detail must be engineered for the applicable Seismic Design Category. (12.4)

NOTE Target field readings are typically 8°F to 12°F suction superheat, 8°F to 12°F subcooling, and a phase-voltage imbalance below 2%. Recorded values outside the manufacturer's acceptance band indicate an improper charge, line-set, or electrical condition that must be corrected before acceptance. (13.3)

NOTE Representative clearances are 18 to 24 in. on non-service sides, 36 in. on the service/access side, and 48 to 60 in. above the fan discharge; these vary by model and jurisdiction and must be taken from the approved submittal. Clearances must not conflict with rooftop fire-egress or AHJ working-space requirements, which should be checked against the roof plan during design development. (14.2)

NOTE These quantities are not part of the condensing-unit section and must be explicitly delegated to the piping standard; the design also must confirm maximum equivalent line-set length (commonly up to 150 to 200 ft with oil traps) and maximum equivalent height difference (commonly 50 ft without special piping) for the selected unit. (14.6)

NOTE A separate extended compressor warranty is commonly available and frequently required by owners for critical or 24/7 facilities; where required it should be specified explicitly, as the standard parts warranty period and the compressor warranty period often differ. (16.2)