This is an indoor ceiling cassette unit only — the indoor half of a Carrier ductless mini split system. It's built for homeowners or installers pairing it with a compatible Carrier outdoor condenser to cool and heat a single zone from a low-profile ceiling cassette instead of a wall-mounted head.
Carrier's 45MCCA series slim one-way cassette is engineered to sit flush between standard ceiling joists rather than requiring a full drop-ceiling grid, which is what separates it from a traditional 4-way cassette. It uses Puron Advance (R-454B) refrigerant and is designed to pair with compatible single- or multi-zone Carrier outdoor condensers for AHRI-matched system performance. 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 45MCCAQ18XA3 — slim one-way ceiling cassette, 18K size class (this listing)
- Outdoor Condenser: Sold separately — select a Carrier outdoor unit AHRI-matched to the 45MCCAQ18XA3 indoor head
Installation Requirements & Accessories
- Voltage: 208/230V; 1Ph; 60Hz (per manufacturer power supply data for this family)
- Line Set: Sold separately — not included with this indoor unit
- Refrigerant: Puron Advance (R-454B) — A2L mildly flammable classification; professional handling required
- Not Included: Outdoor condenser, line set, decorative grille/panel, and ceiling mounting sleeve are not included with this indoor unit
- Not Compatible With: 115V-only circuits are not supported; do not treat SEER2/HSPF2/EER2 figures from other outdoor pairings as guaranteed for your configuration
- Professional Installation Required: This is a standard flare-connection unit, not a pre-charged DIY kit
Pro-Installer Tip
R-454B is a mildly flammable (A2L) refrigerant, which raises the stakes on flare connection quality at both the indoor cassette and the outdoor unit. A loose or improperly seated flare is the most common source of slow refrigerant leaks and nuisance low-charge faults over the life of the system. Torque flare nuts to the connection manufacturer's spec with a calibrated digital torque wrench rather than "feel," and confirm the flare surface is clean and free of scoring before final connection. Under EPA Section 608, only certified technicians may handle refrigerant charging and recovery on this system — factor that into your installation planning.
Key Benefits
- Slim profile fits standard 16-inch on-center joist bays without a drop ceiling
- Follow Me function with temperature-sensing remote for more consistent zone comfort
- Four fan speeds for finer airflow control
- Compatible with single- and multi-zone Carrier outdoor systems
- Uses Puron Advance refrigerant, rated by the manufacturer as reducing global warming potential by 75% versus traditional refrigerants
- Sound level as low as 23.5 decibels per manufacturer overview data
| Spec | Value | Unit |
|---|---|---|
| Model | 45MCCAQ18XA3 | — |
| Indoor Unit Architecture | Slim One-Way Ceiling Cassette | — |
| Voltage | 208/230; 1; 60 | V;Ph;Hz |
| Cooling Rated Capacity (DOE A2 - 95°F) | 16700 | Btu/h |
| Cooling Rated Capacity (DOE B2 - 82°F) | 17500 | Btu/h |
| Heating Rated Capacity (DOE H12 - 47°F) | 20000 | Btu/h |
| Heating Rated Capacity (DOE H32 - 17°F) | 14500 | Btu/h |
| Heating Rated Capacity (ODE H42 - 5°F) | 17500 | Btu/h |
| SEER2 / HSPF2 / EER2 | Dependent on paired outdoor unit | — |
| Refrigerant | Puron Advance (R-454B) | — |
| Sound Level | As low as 23.5 | dBA |
| Ceiling Joist Compatibility | 16-inch on-center | in |
| Zone Count | 1 indoor head; single- or multi-zone outdoor compatible | — |
| DIY Status | No — Professional Installation Required | — |
| Line Set | Sold Separately | — |
Note: See "Resources (System Manuals and Warranty)" Tab above for full specifications.
Compatibility & Fitment
- Fits standard 16-inch on-center ceiling joist bays for a low-profile, near-flush installation
- Compatible with AHRI-matched Carrier single- and multi-zone outdoor condensers — confirm the specific outdoor pairing before ordering
- Runs on a 208/230V; 1Ph; 60Hz supply — not compatible with 115V-only circuits
- Line set, decorative grille/panel, and ceiling mounting sleeve are NOT included and must be purchased separately
- Outdoor condenser is NOT included — this listing is the indoor ceiling cassette only
- SEER2, HSPF2, and EER2 ratings are system-level figures that depend on the outdoor unit paired with this indoor cassette — do not assume a fixed efficiency rating from this listing alone
FAQ
Is professional installation required to keep the warranty valid, or is this a true DIY kit?
This is a standard flare-connection system requiring professional installation. It is not a pre-charged DIY kit.
Is the line set included, and if not, what size do I need to buy?
The line set is sold separately. Manufacturer data for the matched 18K outdoor pairing lists a 3/8in (9.52mm) liquid line and 5/8in (15.9mm) suction line for that size class; confirm exact sizing against the specific outdoor unit you pair with this indoor cassette before ordering.
Will the ceiling cassette fit between standard 16-inch on-center joists?
Yes. The manufacturer describes this cassette's slim, compact design as fitting neatly between 16-inch joists, allowing installation without significant remodeling.
Does this system work in cold climates (low-ambient heating)?
Heating performance at low outdoor temperatures depends on the paired outdoor unit. [NEEDS VERIFICATION] for this specific indoor/outdoor combination — refer to the outdoor unit's published low-ambient heating data.
What breaker size do I need for this system?
Breaker sizing (MCA/MOP) is determined by the paired outdoor condenser, not this indoor cassette alone. [NEEDS VERIFICATION] for the specific outdoor model you select.
Compliance & Warranty
Installation by a licensed HVAC professional is required to maintain warranty. This unit uses Puron Advance (R-454B), an A2L mildly flammable refrigerant, and its handling is regulated under EPA Section 608 — only certified technicians may charge or recover refrigerant. Per manufacturer data, Carrier's Consumer Choice Warranty offers, upon timely registration on eligible equipment, 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 for full terms and registration requirements.
