This is the indoor high-wall unit only β Carrier model 45MAHAQ18XA3, an 18,000 BTU/h wall-mounted fan coil designed to pair with a compatible Carrier outdoor condenser. It's for homeowners or installers assembling a ductless system for one room, where the outdoor unit, line set, and mounting accessories are purchased separately.
The 45MAHAQ18XA3 is a Carrier Performance Series high-wall indoor fan coil, sized at 18,000 BTU/h and built to operate with Puron Advanceβ’ (R-454B) refrigerant. It is engineered for wall-mount installation and depends on a matched Carrier outdoor condenser for full system performance β refer to AHRI-certified combination data before purchasing an outdoor unit. 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
- Indoor Unit: Carrier 45MAHAQ18XA3, 18,000 BTU/h wall-mounted fan coil (this listing)
- Outdoor Condenser: NOT included β must be selected separately from a Carrier-matched, AHRI-certified outdoor unit
- Wireless remote controller: included with the indoor unit
Installation Requirements & Accessories
- Power supply: 208/230V; 1Ph; 60Hz (per manufacturer data table)
- Liquid line size: 3/8 in (9.52mm)
- Suction line size: 1/2 in (12.7mm)
- Line set is sold separately β not included with this indoor unit
- Refrigerant: R-454B (A2L, mildly flammable classification) β professional installation required
- Not compatible with 115V-only circuits
- Not included: outdoor condenser, line set, wall mounting bracket/sleeve
- This listing is not a matched system β pair only with a Carrier outdoor unit confirmed as AHRI-certified for the 45MAHAQ18XA3
Pro-Installer Tip
Flare connections on R-454B systems are unforgiving of shortcuts β an under-torqued or over-torqued flare nut on the 3/8 in liquid or 1/2 in suction line is a leading cause of slow refrigerant leaks and callback "low charge" complaints. Confirm every flare joint with a calibrated digital torque wrench to the manufacturer's spec rather than "feel," and pull the system down to the vacuum level specified in the installation manual before charging. This isn't optional paperwork: R-454B is an A2L mildly flammable refrigerant, and proper evacuation and leak-free joints are both an EPA Section 608 handling requirement and the difference between rated efficiency and a system that underperforms from day one.
Key Benefits
- Inverter-driven system compatibility for variable-speed comfort (when paired with a compatible Carrier outdoor unit)
- Sound level as low as 16 dBA for quiet indoor operation
- Puron Advanceβ’ (R-454B) refrigerant reduces global warming potential by 75% compared to prior-generation refrigerants
- Wireless remote controller included
- Supports single-zone or multi-zone system configurations
- Consumer Choice Warranty available upon timely registration on eligible equipment
| Spec | Value | Unit |
|---|---|---|
| Cooling Rated Capacity (DOE A2, 95Β°F) | 18000 | Btu/h |
| Heating Rated Capacity (DOE H12, 47Β°F) | 18000 | Btu/h |
| Heating Rated Capacity (DOE H32, 17Β°F) | 15000 | Btu/h |
| Heating Rated Capacity (ODE H42, 5Β°F) | 18000 | Btu/h |
| Cooling Rated Capacity (DOE B2, 82Β°F) | 18500 | Btu/h |
| Power Supply | 208/230;1;60 | V;Ph;Hz |
| Refrigerant Type | R454B | β |
| Refrigerant Oil | ESTER OIL | β |
| Liquid Pipe Size | 3/8 (9.52) | in (mm) |
| Suction Pipe Size | 1/2 (12.7) | in (mm) |
| Sound Level (low end of range) | 16 | dBA |
| SEER2 / HSPF2 / EER2 | Dependent on paired outdoor unit | β |
Note: See "Resources (System Manuals and Warranty)" Tab above for full specifications.
Compatibility & Fitment
- This is the 45MAHAQ18XA3 indoor high-wall unit only β it is not a complete system and is not sold with an outdoor condenser
- Must be paired with an AHRI-certified matching Carrier outdoor unit for rated performance; do not assume compatibility across the 45MAHA family without confirming the certified combination
- Requires a 208/230V, 1-phase, 60Hz electrical supply β not compatible with 115V-only circuits
- Uses R-454B (Puron Advanceβ’) refrigerant β not for retrofit onto R-410A-only outdoor units
- Line set (3/8 in liquid, 1/2 in suction) is required but sold separately
- Wall mounting bracket/sleeve is not included
- Professional installation is required β this is not a DIY pre-charged kit
FAQ
What breaker size do I need for this system?
Breaker/circuit sizing (MCA/MOP) is determined by the outdoor unit you pair with this indoor coil, not by the indoor unit itself. [NEEDS VERIFICATION] β refer to the matched outdoor unit's data plate and the manufacturer specifications.
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 proper refrigerant handling and EPA Section 608 certification for anyone handling the refrigerant circuit.
Is the line set included, and if not, what size do I need to buy?
No, the line set is sold separately. For the 18K indoor unit, the manufacturer data specifies a 3/8 in liquid line and 1/2 in suction line.
Does this system work in cold climates (low-ambient heating)?
Low-ambient heating performance depends on the matched outdoor unit. [NEEDS VERIFICATION] for this indoor-unit listing β check the paired outdoor unit's published heating capacity at 17Β°F and 5Β°F ambient.
What is this unit's efficiency rating (SEER2/HSPF2)?
SEER2, HSPF2, and EER2 are system-level ratings that depend on which outdoor unit this indoor coil is paired with. No single efficiency number applies to the indoor unit alone.
Compliance & Warranty
Installation by a licensed HVAC professional is required to maintain warranty. This unit uses R-454B (A2L classification) refrigerant, and installation must comply with applicable ANSI/ASHRAE 15 requirements and local codes. 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 Resources tab for full warranty terms and registration requirements.
