Fujitsu model numbers pack the series, capacity and configuration of the unit into one string. Once you know where to split it, a Fujitsu model number tells you almost everything except the unit's age. This guide decodes Fujitsu indoor and outdoor model numbers position by position, using the key the manufacturer prints on its product data sheets.
Fujitsu is built by Fujitsu General (Halcyon / single-zone and multi-zone ductless). Fujitsu Halcyon residential strings are ductless-first. Indoor wall units use ASU*; outdoor units use AOU* (heat pump). The two-digit capacity in the middle is the size key.
Positions follow Fujitsu General Halcyon naming (ASU/AOU + kBTU + series letters) as used on US product literature. Confirm indoor and outdoor share the same series family before ordering parts.
Where to Find the Fujitsu Model Number
On a furnace, the rating plate is inside the front door or on the side of the cabinet, usually a foil or paper label with the model (M/N) and serial (S/N) side by side. On an outdoor AC or heat pump it is on the side of the condenser near the refrigerant line connections. Copy the model number exactly as printed, including dashes: the position of each character is what carries the meaning.
Fujitsu Indoor Unit Model Number Format
A typical Fujitsu model number in this family looks like: ASU12RLF1. Use the table to split it up:
| Position | Characters | Meaning | Example |
|---|---|---|---|
| Product family | ASU | ASU = wall-mounted indoor; ARU = ducted / slim duct; AGU = floor; AUU = cassette | ASU (wall) |
| Capacity | 12 | Nominal thousands of BTU/h: 9, 12, 15, 18, 24, 30, 36 (common Halcyon sizes) | 12,000 BTU/h ≈ 1 ton |
| Series / features | RLF | Series letters (RLF, RLFC, RLXB, etc.) encode generation, efficiency and extras | RLF |
| Revision / region | 1 | Minor revision / market digit when present | 1 |
Buy the same name-brand HVAC system the pros install — shipped factory-direct to your door. No middleman, 5-star rated, and financing available.
Common Fujitsu Families
The first few characters identify the family, and the family tells you the tier, staging and blower (or inverter class) before you read a single digit of capacity.
| Model prefix | Family | Stages | Blower | Efficiency |
|---|---|---|---|---|
| ASU*RLF / AOU*RLF | Halcyon wall single-zone | Inverter | Variable-speed | Mid–high SEER class |
| ASU*RLXB / XLTH | Extra-low-temp heat pump pairs | Inverter | Variable-speed | Cold-climate HSPF |
| ARU* / AUU* | Ducted / cassette indoor | Inverter | Variable-speed | Hidden or ceiling installs |
| AOU* multi-zone | Multi-zone outdoor families | Inverter | Variable-speed | Multiple indoor ports |
Fujitsu Outdoor Unit Model Numbers
Outdoor units use a different string. A typical Fujitsu outdoor model number looks like: AOU12RLF1.
| Position | Characters | Meaning | Example |
|---|---|---|---|
| Product family | AOU | AOU = outdoor unit (heat pump on Halcyon residential lines) | AOU |
| Capacity | 12 | Same kBTU code as the paired indoor unit | 12,000 BTU/h ≈ 1 ton |
| Series / features | RLF | Must match the indoor series for a rated system | RLF |
| Revision / region | 1 | Minor revision digit when present | 1 |
Fujitsu Tonnage by Model Number
Fujitsu prints capacity as a two-digit kBTU code (12, 18, 24…). Divide by 12 for tons. The 018–060 table below still applies when a larger ducted string uses three-digit BTU coding.
| Model code | Size | Cooling capacity |
|---|---|---|
| 018 | 1.5 ton | 18,000 BTU/h |
| 024 | 2 ton | 24,000 BTU/h |
| 030 | 2.5 ton | 30,000 BTU/h |
| 036 | 3 ton | 36,000 BTU/h |
| 042 | 3.5 ton | 42,000 BTU/h |
| 048 | 4 ton | 48,000 BTU/h |
| 060 | 5 ton | 60,000 BTU/h |
Common Fujitsu outdoor families and where they sit:
| Model prefix | Family | Efficiency |
|---|---|---|
| AOU*RLF / AOU*RLFC | Single-zone Halcyon outdoor | Paired to matching ASU indoor |
| AOU*RLXB / XLTH | Cold-climate outdoor | Extra-low ambient heating |
| Multi-zone AOU* | 2–5 indoor ports by family | Total connected capacity in the family name |
Buy the same name-brand HVAC system the pros install — shipped factory-direct to your door. No middleman, 5-star rated, and financing available.
What the Fujitsu Model Number Does Not Tell You
The model number says nothing about the unit's age. That is in the serial number, and Fujitsu (like most brands) has changed serial date formats over the years. Use the Fujitsu serial number lookup to turn a serial into a manufacture date, or the HVAC serial number decoder hub for any other brand. The model number also does not tell you whether the unit was installed and charged correctly, which matters as much as the SEER digit for what it actually costs to run.
Decoded Your Fujitsu? Here Is What to Do With It
If the unit is under 10 years old and the model number shows a mid- or high-efficiency family, it is usually worth repairing. If the serial dates it past 12 to 15 years for an AC or 15 to 20 years for a furnace, the capacity and cabinet width you just decoded are exactly what you need to size a replacement. A new system at the same tonnage and input will drop straight into the same duct and gas connections.
Related: how to read any furnace data label · Goodman model number decoder.
Fujitsu, and related marks, are trademarks of their respective owners. Furnace Direct is not affiliated with or endorsed by Fujitsu's manufacturer. This page is nominative fair-use reference for homeowners decoding a nameplate.
Get your system replaced.
Tell us a little about your home and what you're replacing. A specialist will call you to work out exactly what you need, go over the price, and get it replaced. No obligation.