This is the outdoor condenser (outdoor unit) only for a Carrier Infinity 35 single-zone ductless heat pump system — model 37MPRAQ18AA3, an 18,000 BTU/h unit. It's built for homeowners or contractors who already have (or are separately purchasing) a matched Carrier 615PHAQ18XA3 indoor head, line set, and installation accessories, and need the outdoor half of the system. Professional installation is required.
This listing covers the outdoor condensing unit only — Carrier model 37MPRAQ18AA3, part of the 37MPRA family, size code 18K. It is AHRI-rated as a system alongside the matched Carrier indoor head, model 615PHAQ18XA3. 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 (included in this listing): Carrier 37MPRAQ18AA3, 18,000 BTU/h nominal, variable-speed inverter-driven compressor, R-454B refrigerant.
- Indoor Head (NOT included — sold separately): AHRI-matched pairing is Carrier 615PHAQ18XA3. Indoor unit architecture for that model is [NEEDS VERIFICATION] — not specified in the outdoor-unit data provided.
Installation Requirements & Accessories
- Voltage: 208/230V, single-phase, 60Hz. Not compatible with 115V-only circuits.
- Minimum Circuit Ampacity: 24.9A. Maximum Overcurrent Protection: 25A.
- Line set sizes: 3/8" liquid, 5/8" suction. Standard length 24.6 ft; minimum 9.8 ft; maximum total 164.04 ft.
- Line Set Sold Separately. This outdoor unit ships with a full R-454B charge but does not include the line set.
- NOT included: indoor head, wall sleeve/mounting bracket, disconnect box, and line-hide/mounting accessories.
- NOT compatible with: 115V circuits; indoor heads outside the AHRI-matched 615PHAQ18XA3 pairing.
- Professional installation is required — this is not a DIY / pre-charged quick-connect system.
Pro-Installer Tip
Flare connections on R-454B (A2L) systems need the same discipline as any refrigerant joint, but the mildly flammable classification raises the stakes on a leak. Torque every flare fitting to the manufacturer spec with a digital torque wrench rather than "feel" — an under-torqued flare is the most common source of a slow leak that shows up months later as reduced capacity or a fault code on the indoor head. Confirm the line set is pulled to a proper vacuum before charging; the outdoor unit ships fully charged for its standard piping length, but any additional length needs correction per the manufacturer's charge chart. This work falls under EPA Section 608 refrigerant handling requirements, and only a certified technician should open, evacuate, or charge this system.
Key Benefits
- Variable-speed inverter compressor for smoother temperature control instead of on/off cycling.
- Outdoor sound level as low as 61.5 dBA at this 18K size.
- Rated heating output down to 5°F (22,600 Btu/h) and 17°F (19,300 Btu/h) ambient conditions.
- Puron Advance (R-454B) refrigerant, reported by the manufacturer to reduce global warming potential by 75% versus older refrigerants.
- ENERGY STAR certified system rating (with matched 615PHAQ18XA3 indoor head).
| Spec | Value | Unit |
|---|---|---|
| Cooling Rated Capacity (DOE A2, 95°F) | 18000 | BTU/h |
| Heating Rated Capacity (DOE H12, 47°F) | 20000 | BTU/h |
| Heating Capacity (DOE H32, 17°F) | 19300 | BTU/h |
| Heating Capacity (DOE H42, 5°F) | 22600 | BTU/h |
| SEER2 | 25.8 | Btu/h.W |
| EER2 (DOE A2, 95°F) | 15 | Btu/h.W |
| EER2 (DOE B2, 82°F) | 21 | Btu/h.W |
| HSPF2 (Region IV) | 16.2 | Btu/h.W |
| HSPF2 (Region V) | 12.9 | Btu/h.W |
| Voltage | 208/230 | V |
| Phase / Frequency | 1-Phase, 60 | Hz |
| Minimum Circuit Ampacity (MCA) | 24.9 | A |
| Maximum Overcurrent Protection (MOP) | 25 | A |
| Outdoor Sound Level | 61.5 | dBA |
| Refrigerant | R-454B | — |
| Liquid Line Size | 3/8 | in |
| Suction Line Size | 5/8 | in |
| Standard Piping Length | 24.6 | ft |
| Minimum Piping Length | 9.8 | ft |
| Maximum Total Piping Length | 164.04 | ft |
| Net Weight | 130.29 | lbs |
| Unit Height | 31.89 | in |
| Unit Width | 37.24 | in |
| Unit Depth | 16.14 | in |
Note: See "Resources (System Manuals and Warranty)" Tab above for full specifications.
Compatibility & Fitment
- Matched AHRI-certified pairing: outdoor 37MPRAQ18AA3 with indoor 615PHAQ18XA3.
- Requires a dedicated 208/230V single-phase circuit. Not compatible with 115V-only circuits.
- Not a listed match for indoor heads outside the 615PHAQ18XA3 pairing named in the AHRI rating table.
- Line set, indoor head, wall sleeve/mounting bracket, and disconnect are NOT included — all sold separately.
FAQ
What breaker size do I need for this system?
The 37MPRAQ18AA3 outdoor unit has a Minimum Circuit Ampacity (MCA) of 24.9A and a Maximum Overcurrent Protection (MOP) rating of 25A, on a dedicated 208/230V, single-phase, 60Hz circuit. A licensed electrician should size the breaker and wiring per NEC and local code requirements.
Is professional installation required to keep the warranty valid, or is this a true DIY kit?
This is not a DIY kit. It uses R-454B (A2L) refrigerant and requires professional installation, including EPA Section 608 certified refrigerant handling. Installation by a licensed HVAC professional is required to maintain warranty.
Is the line set included, and if not, what size do I need to buy?
The line set is sold separately. This outdoor unit requires a 3/8-inch liquid line and 5/8-inch suction line. Standard rated piping length is 24.6 ft, with a minimum of 9.8 ft and a maximum total of 164.04 ft.
Does this system work in cold climates (low-ambient heating)?
Yes. The manufacturer states heating operation down to -22°F for the 37MPRA family. Rated heating capacity at 17°F is 19,300 Btu/h and at 5°F is 22,600 Btu/h for this 18K size.
Will this outdoor unit work with any indoor head I choose?
No. Rated efficiencies (SEER2, HSPF2, EER2) are AHRI system ratings tied to a specific matched indoor unit — for this outdoor model, that is the 615PHAQ18XA3. Pairing with an unmatched indoor head is not a listed AHRI combination.
Compliance & Warranty
Installation by a licensed HVAC professional is required to maintain warranty. This unit uses R-454B (A2L, mildly flammable) refrigerant and falls under EPA Section 608 handling requirements. Per the manufacturer, eligible equipment with timely registration qualifies under Carrier's Consumer Choice Warranty for either a 10-year parts-only limited warranty or a 5-year parts plus 3-year labor limited warranty — confirm current terms and registration deadlines in the manufacturer documentation referenced above.
