This is the outdoor condenser (outdoor unit) only for a Carrier Infinity 27 single-zone ductless heat pump system — Carrier model 37MAHAQ18AA3, an 18,000 BTU/h size in the 37MAHA family. It is built for homeowners or contractors who already have (or are separately sourcing) a matched Carrier indoor head, line set, and installation accessories; this listing does not include an indoor unit, line set, or mounting hardware.
The 37MAHAQ18AA3 is the outdoor half of a Carrier Infinity 27 single-zone ductless heat pump system rated at 18,000 BTU/h cooling. Carrier publishes ENERGY STAR® certification and AHRI-rated system efficiencies for this outdoor unit only when paired with a specific, AHRI-certified indoor head — the indoor unit sold and shipped with your matched combination determines the exact rated SEER2/HSPF2 you will see on the AHRI certificate. Note: If you would like to review the manufacturer Product Specifications, Warranty, Brochure, etc., for this system, please refer to the "Resources (System Manuals and Warranty)" Tab above on this page.
System Components
- Outdoor condenser: Carrier 37MAHAQ18AA3, 18,000 BTU/h nominal cooling capacity, variable-speed (inverter-driven) compressor, R-454B refrigerant.
- Indoor head: NOT included. This listing is the outdoor unit only. Select an AHRI-certified matching Carrier indoor head separately.
Installation Requirements & Accessories
- Voltage: 208/230V; 1-phase; 60Hz. Not compatible with 115V-only circuits.
- Liquid line: 3/8 in (9.52mm). Suction line: 1/2 in (12.7mm). Line set is sold separately — not included with this listing.
- MCA: 19A. MOCP: 20A. Dedicated circuit sizing must be confirmed by your installer per local code.
- Not included: indoor unit, line set, wall sleeve, mounting bracket, disconnect, or condensate accessories.
- Not compatible with 115V-only circuits.
- Not a listed match for indoor heads outside the AHRI-certified 37MAHAQ18AA3 combination list — verify AHRI directory match before ordering an indoor head.
- Professional installation by a licensed HVAC contractor is required; this is a flare-connection R-454B (A2L mildly flammable refrigerant) system, not a pre-charged DIY kit.
Pro-Installer Tip
Flare connections on R-454B systems are unforgiving of under-torqued or over-torqued joints — both conditions lead to slow refrigerant leaks that surface later as reduced capacity or an intermittent fault code. Use a calibrated digital torque wrench set to the flare nut size specified in the installation manual, and always use 14/4 stranded control wiring between indoor and outdoor units rather than solid-core wire, which fatigues and loosens at terminal blocks over time. Pull the system down and hold vacuum per the manufacturer's evacuation procedure before releasing charge — do not skip a standing vacuum check. Because R-454B is an A2L mildly flammable refrigerant, this work falls under EPA Section 608 certification requirements; only a certified technician should handle recovery, evacuation, and charging.
Key Benefits
- Variable-speed (inverter-driven) compressor for smoother capacity modulation than fixed-speed compressors.
- Outdoor sound pressure as low as 59 dBA at this size, for quieter operation near bedrooms or patios.
- Puron Advance™ (R-454B) refrigerant, rated by the manufacturer as reducing global warming potential by 75% versus prior refrigerants.
- Published low-ambient heating capacity down to 5°F (H42 test condition) for cold-climate performance.
- ENERGY STAR® certified system efficiency when paired with a matched indoor head.
Technical Table
| Spec | Value | Unit |
|---|---|---|
| Cooling Capacity (DOE A2 - 95°F) | 18000 | BTU/h |
| Heating Capacity (DOE H12 - 47°F) | 18000 | BTU/h |
| Heating Capacity (DOE H32 - 17°F) | 15000 | BTU/h |
| Heating Capacity (DOE H42 - 5°F) | 18000 | BTU/h |
| SEER2 | 21.5 | Btu/h.W |
| EER2 (DOE A2 - 95°F) | 12.5 | Btu/h.W |
| HSPF2 (Region IV) | 11 | Btu/h.W |
| HSPF2 (Region V) | 8.5 | Btu/h.W |
| Voltage | 208/230; 1Ph; 60 | V/Ph/Hz |
| MCA | 19 | A |
| MOCP | 20 | A |
| Outdoor Sound Pressure Level | 59 | dBA |
| Net Weight | 99.87 | lb |
| Refrigerant Type | R-454B | — |
| Liquid Pipe Size | 3/8 (9.52) | in (mm) |
| Suction Pipe Size | 1/2 (12.7) | in (mm) |
| Cooling Operating Range | -22 to 122 (-30 to 55) | °F (°C) |
Note: See "Resources (System Manuals and Warranty)" Tab above for full specifications.
Compatibility & Fitment
- Compatible with dedicated 208/230V, single-phase, 60Hz circuits only.
- Must be paired with an AHRI-certified matching Carrier indoor head from the 37MAHA family match list for the 18K size.
- Requires 3/8 in liquid and 1/2 in suction line set, sized for your specific run length — sold separately.
- NOT compatible with 115V-only circuits.
- NOT a listed match for indoor units outside the certified AHRI combination for 37MAHAQ18AA3.
- Indoor unit, line set, wall sleeve, and mounting bracket are NOT included with this listing.
FAQ
What breaker size do I need for this system?
The 37MAHAQ18AA3 outdoor unit has a Minimum Circuit Ampacity (MCA) of 19A and a Maximum Overcurrent Protection (MOCP) of 20A on a 208/230V, single-phase, 60Hz dedicated circuit. Confirm final breaker sizing with a licensed electrician based on your local code and wire run.
Is professional installation required to keep the warranty valid, or is this a true DIY kit?
This is not a DIY pre-charged kit. It is a standard flare-connection heat pump condenser using R-454B refrigerant, and professional installation by a licensed HVAC contractor is required.
Is the line set included, and if not, what size do I need to buy?
No line set is included with this listing. For the 37MAHAQ18AA3, the manufacturer specifies a 3/8 in (9.52mm) liquid line and a 1/2 in (12.7mm) suction line. Purchase a matching line set sized for your run length separately.
Does this system work in cold climates (low-ambient heating)?
The manufacturer publishes a heating capacity at DOE H42 (5°F) test conditions of 18,000 Btu/h and at DOE H32 (17°F) of 15,000 Btu/h for the 37MAHAQ18AA3, indicating continued heating output in cold outdoor conditions. Published operating range for cooling is -22 to 122°F (-30 to 55°C).
Will this outdoor unit work with any indoor head I already own?
No. This outdoor unit must be paired with a Carrier indoor head that is AHRI-certified as a matched combination with the 37MAHAQ18AA3 model. It is not rated for use with arbitrary third-party indoor heads or with indoor units outside the certified match list.
Compliance & Warranty
This outdoor condenser uses R-454B (A2L, mildly flammable) refrigerant and must be installed, evacuated, and charged by a technician holding current EPA Section 608 certification. Installation by a licensed HVAC professional is required to maintain warranty. Carrier's Consumer Choice Warranty, upon timely registration on eligible equipment, offers either a 10-year parts-only limited warranty or a 5-year parts plus 3-year labor limited warranty; refer to the manufacturer warranty documentation in the Resources tab for exact terms and registration requirements.
