1 Scope
NOTE This standard governs the performance, configuration, and installation of matched split-system unitary equipment in which a refrigerant lineset connects an outdoor unit to one or more indoor units. (1.1)
NOTE It covers cooling-only split-system air conditioners and reversible air-source heat pumps in two physical arrangements: ducted split systems pairing an outdoor unit with an indoor air handler or a coil mounted on a separate furnace, and single-zone ductless mini-split systems pairing an outdoor unit with a wall-mounted, ceiling-cassette, or concealed-duct indoor unit. (1.2)
NOTE The standard addresses unit type and capacity, rated efficiency, refrigerant selection under the current low-GWP transition, indoor-unit configuration, auxiliary and backup heat for heat pumps, the refrigerant lineset, controls, electrical coordination, and field commissioning. (1.3)
1.4 A split system conditions only recirculated air and provides no outdoor air; where the served space requires ventilation, outdoor air shall be furnished by separate means coordinated under Testing Adjusting And Balancing. NOTE This standard does not satisfy any ASHRAE 62.1 ventilation-rate requirement. (1.5)
1.6 Multi-zone systems that modulate compressor capacity across several indoor units on a common refrigerant circuit shall be specified under Variable Refrigerant Flow Systems, not as split systems. NOTE Variable-refrigerant-flow systems are excluded because their rating procedure (AHRI 1230) and refrigerant-volume safety analysis differ fundamentally from split systems. (1.8)
2 Referenced Standards
NOTE The following documents are referenced. (2.1)
NOTE Where editions are not stated, the edition in force at the date of equipment manufacture governs. (2.2)
- AHRI 210/240 — Performance Rating of Unitary Air-Conditioning and Air-Source Heat Pump Equipment (rated under the U.S. DOE "M1" test procedure using SEER2, EER2, and HSPF2).
- AHRI 340/360 — Performance Rating of Commercial and Industrial Unitary Air-Conditioning and Heat Pump Equipment (for single-phase and three-phase equipment above the AHRI 210/240 scope, generally cooling capacity ≥ 65,000 Btu/h).
- AHRI 270 — Sound Performance Rating of Outdoor Unitary Equipment.
- ASHRAE 90.1 — Energy Standard for Buildings Except Low-Rise Residential Buildings (minimum equipment efficiencies).
- ASHRAE 15 — Safety Standard for Refrigeration Systems (machinery-room and refrigerant-quantity limits).
- ASHRAE 34 — Designation and Safety Classification of Refrigerants (A1, A2L flammability classes).
- ASHRAE 62.1 — Ventilation for Acceptable Indoor Air Quality (referenced to confirm that split systems do not provide outdoor air).
- UL 60335-2-40 — Safety of Household and Similar Electrical Appliances; Particular Requirements for Electrical Heat Pumps, Air-Conditioners and Dehumidifiers (the safety standard governing A2L-refrigerant equipment).
- NFPA 70 (NEC) — National Electrical Code (branch circuits, disconnects, overcurrent protection).
- U.S. EPA AIM Act regulations — refrigerant global-warming-potential (GWP) limits applicable to new equipment.
2.3 All referenced documents apply in the edition in force at the date of equipment manufacture where no edition is stated.
3 Submittals
3.1 Product Data
3.1.1 The Contractor shall submit manufacturer technical data for each unique outdoor unit and indoor unit, including AHRI-certified rated capacity and efficiency, the AHRI Certified Reference Number for the matched combination, refrigerant designation and ASHRAE 34 safety class, factory and field refrigerant charge, electrical characteristics (MCA and MOCP), sound rating per AHRI 270, and operating-envelope limits.
3.2 Matched-Combination Certification
3.2.1 Submitted ratings shall reflect the specific outdoor/indoor combination installed, identified by AHRI Certified Reference Number.
3.2.2 A rating for the outdoor unit paired with a different indoor coil is not acceptable.
NOTE Mismatched coils change measured SEER2, EER2, and HSPF2. (3.2.3)
3.3 Wiring and Control Diagrams
3.3.1 The Contractor shall submit point-to-point wiring diagrams, thermostat or controller wiring, and, for heat pumps, the auxiliary/emergency-heat staging and defrost-control sequence.
3.4 Refrigerant Lineset and Charge Calculation
3.4.1 The Contractor shall submit the proposed lineset routing, line sizes, total equivalent length, vertical separation, and the calculated field charge adjustment for line length, demonstrating compliance with the manufacturer's maximum-length and lift limits.
3.5 Startup and Commissioning Report
3.5.1 A completed manufacturer startup report shall be submitted, including evacuation level, final charge by weight or subcooling/superheat, voltage and amperage per phase, and verified airflow.
3.6 Required Submittals
NOTE The submittals required for this equipment are the product data, certifications, diagrams, calculations, and reports listed below. (3.6.1)
- Product data for each unique outdoor and indoor unit
- Matched-combination certification by AHRI Certified Reference Number
- Wiring and control diagrams (including defrost and auxiliary-heat staging for heat pumps)
- Refrigerant lineset routing and field charge calculation
- Startup and commissioning report
☑ Product data for each unique outdoor and indoor unit
☑ Matched-combination certification by AHRI Certified Reference Number
☑ Wiring and control diagrams (including defrost and auxiliary-heat staging for heat pumps)
☑ Refrigerant lineset routing and field charge calculation
☑ Startup and commissioning report
4 Quality Assurance
4.1.1 Equipment with cooling capacity below 65,000 Btu/h shall carry an AHRI 210/240 certification for the as-installed matched combination.
NOTE Listing the combination in the AHRI Directory is the basis for verifying rated SEER2, EER2, and HSPF2. (4.1.2)
4.1.3 Equipment at or above 65,000 Btu/h cooling capacity shall be rated to AHRI 340/360 and shall meet the applicable ASHRAE 90.1 minimum EER/IEER and COP.
4.2 Product Safety Listing
4.2.1 All equipment shall be listed to UL 60335-2-40.
4.2.2 For equipment charged with an A2L refrigerant, the listing shall include the standard's A2L provisions (charge-limit calculation, leak detection and mitigation where required, and ignition-source controls).
4.3 Installer Qualification
4.3.1 The installer shall be trained in handling the specified refrigerant.
4.3.2 Where an A2L refrigerant is used, the installer shall hold current certification for flammable-refrigerant handling and shall follow the manufacturer's A2L installation instructions.
5 Environmental and Service Conditions
5.1 Design conditions shall be taken from the project basis-of-design and the unit schedule.
5.2 The designer shall confirm that net capacity at the actual outdoor design temperature, indoor entering conditions, and site elevation meets the load, applying the manufacturer's capacity-correction tables.
NOTE Capacity ratings are referenced to AHRI standard conditions. (5.3)
6 System Configuration
6.1 System Type Selection
cooling_only_ac
air_source_heat_pump
Per drawings
ducted_split_air_handler
ducted_split_coil_on_furnace
ductless_mini_split_single_zone
Per drawings
6.1.1 The system shall be configured as a cooling-only air conditioner or a reversible heat pump as scheduled.
6.1.2 The physical arrangement shall be ducted-split or ductless mini-split as scheduled.
NOTE A cooling-only air conditioner provides no heating and requires a separate heat source; an air-source heat pump reverses the refrigerant cycle to provide heating and is selected where electric heating, electrification, or dual-fuel operation is intended. The choice drives the controls, the presence of a reversing valve and defrost cycle, and the need for auxiliary heat. (6.1.4)
NOTE A ducted split with a dedicated air handler serves spaces through a duct system. A coil-on-furnace arrangement places the indoor coil on the supply side of a separate furnace and is used for dual-fuel or gas-heat applications. A ductless single-zone mini-split serves one space directly with no ductwork and is selected for zones lacking duct space or requiring independent control. (6.1.5)
6.2 Capacity
single_stage
two_stage
variable_speed_inverter
6.2.1 Rated cooling and heating capacity shall match the scheduled load.
6.2.2 Equipment shall be selected to the calculated block load, not to a rule-of-thumb area factor.
6.2.3 Heat-pump heating capacity shall be stated at both 47 °F and 17 °F outdoor temperature.
6.2.4 Compressor capacity modulation shall be as scheduled.
NOTE Oversized cooling equipment short-cycles, runs too briefly to remove latent load, and leaves the space cool but humid; right-sizing to the sensible and latent load is the primary defense against poor humidity control. Heat-pump capacity falls as outdoor temperature drops, and the low-temperature figure governs the balance-point and auxiliary-heat analysis. (6.2.5)
NOTE Single-stage compressors run at full capacity whenever on. Two-stage and variable-speed (inverter) compressors run longer at reduced capacity, improving part-load efficiency, dehumidification, and comfort, and are generally required to reach high-efficiency tiers and to sustain heating capacity at low outdoor temperatures. (6.2.6)
7 Condensing / Outdoor Unit
7.1 Cabinet and Coil
standard
coated_coil_coastal
7.1.1 The outdoor unit shall have a corrosion-resistant cabinet and a finned coil suitable for the installation environment.
7.1.2 In coastal or corrosive environments, a coated coil or a manufacturer's corrosion-protection package shall be provided as scheduled.
7.2 Mounting
ground_pad
wall_bracket
roof_curb_rail
elevated_stand_snow_region
Per drawings
7.2.1 The outdoor unit shall be mounted level on a stable base with the manufacturer's required service and airflow clearances maintained.
7.2.2 In snow regions, the unit shall be elevated above the design snow depth on a stand so that drainage and airflow are not obstructed.
7.3 Low-Ambient Operation
not_required
low_ambient_kit_to_0F
7.3.1 Where mechanical cooling is required at low outdoor temperatures, the outdoor unit shall include low-ambient head-pressure control to maintain stable operation below the standard minimum cooling temperature.
7.3.2 The required minimum operating temperature shall be stated on the schedule.
8 Indoor Unit / Air Handler and Coil
8.1 Indoor Unit Type
air_handler_upflow
air_handler_downflow
air_handler_horizontal
coil_only_on_furnace
ductless_wall_mount
ductless_ceiling_cassette
ductless_concealed_duct
Per drawings
8.1.1 The indoor unit configuration shall be as scheduled.
8.1.2 The air-handler orientation (upflow, downflow, horizontal) shall match the duct connection and the equipment-room arrangement.
NOTE A coil-only unit installs on the supply plenum of a separate furnace. Ductless indoor units (wall-mount, ceiling cassette, concealed-duct) serve a single zone directly. (8.1.4)
8.2 Indoor Coil and Metering
8.2.1 The indoor coil shall be the manufacturer-matched coil for the certified combination, with a thermostatic or electronic expansion valve sized for the refrigerant and capacity.
8.2.2 Field substitution of a non-matched coil is prohibited.
8.3 Drain Pan and Condensate
primary_drain_only
overflow_switch
secondary_pan_and_switch
8.3.1 The indoor unit shall provide a corrosion-resistant primary drain pan.
8.3.2 A condensate trap shall be installed per the manufacturer's instructions to prevent air bypass and to ensure drainage.
8.3.3 Where the unit is located above a finished space or where overflow would cause damage, a secondary drain pan, a condensate overflow switch, or both shall be provided to shut down the unit on high condensate level.
8.3.4 Condensate routing shall be coordinated with the architectural and plumbing work.
NOTE Condensate routing is the most common cause of water damage from split systems. (8.3.5)
9 Efficiency
9.1 Minimum Rated Efficiency
code_minimum
high_efficiency
9.1.1 Equipment shall meet or exceed the scheduled SEER2, EER2, and HSPF2 tier.
9.1.2 Rated efficiency shall be expressed in SEER2, EER2, and HSPF2 as measured under the DOE M1 test procedure adopted in AHRI 210/240.
9.1.3 Schedules, submittals, and rebate documentation shall not mix legacy and "2" metrics, and a legacy SEER value shall never be compared directly to a SEER2 minimum.
9.1.4 The minimum tier shall satisfy the applicable ASHRAE 90.1 and federal minimum efficiency for the equipment class and heating type.
9.1.5 The high-efficiency tier shall be set on the schedule to meet the project energy target or utility-incentive threshold.
NOTE The M1 procedure raised the external static pressure used in testing to better represent installed ducted systems; consequently the "2" metrics read lower than the legacy SEER, EER, and HSPF for the same equipment. (9.1.6)
10 Auxiliary / Backup Heat (Heat Pumps)
10.1 Balance Point
10.1.1 For heat pumps, the designer shall determine the balance point — the outdoor temperature at which the heat pump's declining capacity equals the building heating load.
10.1.2 The auxiliary-heat capacity shall be sized to make up the difference between heat-pump capacity at the winter design temperature and the design heating load.
NOTE Below the balance point, supplemental heat is required. (10.1.3)
10.2 Auxiliary and Emergency Heat
none_cooling_only
electric_resistance
fossil_fuel_furnace_dual_fuel
Per drawings
10.2.1 Heat pumps shall be provided with auxiliary heat as scheduled.
10.2.2 Electric-resistance auxiliary heat shall be staged so that it engages only when the heat pump cannot meet the load or during defrost, not as the primary heat source.
10.2.3 In dual-fuel arrangements, the controls shall switch to the fossil-fuel furnace below an economic balance point and shall lock out simultaneous compressor heating and furnace firing.
NOTE Resistance heat has a far lower effective efficiency than the heat pump. (10.2.4)
10.3 Defrost Coordination
10.3.1 The heat-pump control shall manage the defrost cycle and shall energize auxiliary heat during defrost to temper the supply air.
10.3.2 The defrost and auxiliary-heat sequence shall be demand- or time/temperature-based and shall avoid nuisance defrost.
NOTE Lack of coordination between defrost and auxiliary heat produces cold supply-air complaints and excess energy use. (10.3.3)
11 Refrigerant and Lineset
11.1 Refrigerant Selection
11.1.1 The refrigerant shall comply with the applicable GWP limit and be the factory-charged type for the equipment.
11.1.2 New equipment shall use a refrigerant that meets the EPA AIM Act GWP limit applicable to its equipment class.
11.1.3 A2L refrigerant equipment, charge limits, leak mitigation, and installation practices shall comply with UL 60335-2-40 and ASHRAE 15.
11.1.4 The refrigerant shall be the type for which the equipment is factory-charged and listed; refrigerants of different safety classes shall never be interchanged or mixed.
NOTE The industry has transitioned from R-410A (ASHRAE 34 class A1, high GWP) to lower-GWP A2L refrigerants such as R-32 and R-454B, which are mildly flammable. (11.1.5)
11.1.6 Where an A2L refrigerant is used, the maximum allowable charge for the room served by the indoor unit shall be calculated per UL 60335-2-40 / ASHRAE 15 based on the smallest conditioned space and its floor area.
11.1.7 Where the system charge exceeds the limit for that space, the manufacturer's leak-detection and mitigation provisions (or a different equipment selection) shall be applied.
11.2 Lineset
11.2.1 Refrigerant lines shall be clean, dehydrated, sealed copper sized and lengthed per the manufacturer.
11.2.2 The lineset shall not exceed the manufacturer's maximum equivalent length or maximum vertical separation.
11.2.3 Where length or lift approaches the limit, the field charge shall be adjusted by the manufacturer's per-foot allowance, and oil traps shall be installed where required.
11.2.4 Suction lines shall be insulated.
NOTE Exceeding the maximum equivalent length or vertical separation starves the coil of refrigerant, impairs oil return, and voids capacity ratings. (11.2.6)
12 Controls
12.1 Thermostat / Controller
programmable_thermostat
communicating_thermostat
manufacturer_controller_ductless
bas_integrated
12.1.1 The control shall manage compressor staging, fan operation, and — for heat pumps — reversing-valve, defrost, and auxiliary/emergency-heat staging.
12.1.2 Communicating controls shall be used with variable-speed equipment to enable full modulation and fault reporting.
12.1.3 Where the project has a building automation system, the unit shall be integrated and monitored per Building Automation System. 12.2 Sequence of Operation
12.2.1 The controls submittal shall include a written sequence covering cooling and (for heat pumps) heating modes, staging logic, auxiliary-heat lockout above the balance point, defrost initiation and termination, emergency-heat operation, and safety shutdowns on high condensate level and refrigerant-detection (A2L) where applicable.
13 Electrical Coordination
208-230V/1
208-230V/3
460V/3
Per drawings
13.1 Branch-circuit conductors, overcurrent protection, and the disconnecting means shall be sized and installed to NFPA 70 using the MCA and MOCP marked on the equipment nameplate.
13.2 A disconnecting means shall be provided within sight of the outdoor unit.
13.3 Field-installed electric auxiliary heat shall be on its own branch circuit as required by the nameplate.
13.4 Electrical characteristics shall be coordinated with the electrical drawings and confirmed against the unit schedule.
14 Installation and Charging
14.1 General
14.1.1 Equipment shall be installed level, with manufacturer service and airflow clearances, vibration isolation at the outdoor unit, and supports rated for the equipment weight.
14.1.2 Ductless line-hide and penetrations shall be sealed weathertight.
14.2 Evacuation and Charging
14.2.1 The system shall be evacuated and charged per the manufacturer.
14.2.2 The refrigerant circuit shall be pressure-tested for leaks, then evacuated to the manufacturer's required deep vacuum (typically to 500 microns or better) and held to confirm the absence of leaks and noncondensables before charging.
14.2.3 The system shall be charged to the manufacturer's specified subcooling or superheat target for the actual lineset length, by weight where the manufacturer so directs.
14.2.4 A2L charging shall follow the manufacturer's flammable-refrigerant procedures, including ventilation of the work area and elimination of ignition sources.
14.3 Airflow Verification
14.3.1 Indoor airflow shall be set to the manufacturer's required external static pressure and cfm and verified.
NOTE The SEER2/EER2/HSPF2 ratings and the dehumidification performance depend on rated airflow. (14.3.3)
15 Startup
15.1 Manufacturer Startup
15.1.1 Startup shall be performed per the manufacturer's commissioning checklist and documented in the startup report.
15.1.2 The startup shall record evacuation level, final charge and subcooling/superheat, supply/return temperatures in each mode, voltage and amperage per phase, verified airflow, condensate drainage, safety-control operation, and — for heat pumps — a defrost-cycle observation and auxiliary-heat staging verification.
15.2 Functional Demonstration
15.2.1 The Contractor shall demonstrate cooling and (for heat pumps) heating operation, mode changeover, auxiliary/emergency-heat operation, defrost, and all safety shutdowns to the Owner's representative before acceptance.
16 Warranty
16.1 The Contractor shall provide the manufacturer's standard warranty on the compressor and on parts, and the installing contractor's labor warranty, for the periods stated on the schedule.
16.2 The refrigerant charge, A2L compliance documentation, and the completed startup report shall be delivered as a condition of warranty acceptance.
16.3 Warranty registration, where required by the manufacturer to obtain the full term, shall be completed and submitted.