HVAC Decoder
American Standard Tonnage From Model Number
Where American Standard puts the capacity code, what each code means, and the readings that look like capacity but are not. Read out of 3 documents American Standard publishes itself, named further down with the date each was fetched.
Starting the decoder. The capacity tables below this box are already loaded, so you can read your code off them now.
Nominal capacity from a model number is a nameplate convention, not a measurement. Actual delivered capacity depends on the matched indoor unit, line set, airflow and conditions. Confirm against the data plate's BTU/h rating and the AHRI certificate for the matched system.
American Standard Capacity Codes and Tonnage
R-454B outdoor units (2026 handbook, 5A)
Capacity sits at positions 7-8, with the refrigerant at position 1, the brand at 2, the system type at 3, the product family at 4, Nominal Rated SEER2 at 5 and the field connection at 6, per American Standard's own 2026 handbook. Example: 5A7A4024A1000AA.
The tonnage is the one the maker's own document prints for this capacity code; any BTU/h shown beside it is converted from that tonnage.
| Code | Nominal BTU/h | Tons | Code / 12 |
|---|---|---|---|
| 12 | 12,000 | 1 | same answer |
| 18 | 18,000 | 1.5 | same answer |
| 19 | 18,000 | 1.5 | 1.58, so the division is wrong here |
| 24 | 24,000 | 2 | same answer |
| 25 | 24,000 | 2 | 2.08, so the division is wrong here |
| 30 | 30,000 | 2.5 | same answer |
| 31 | 30,000 | 2.5 | 2.58, so the division is wrong here |
| 36 | 36,000 | 3 | same answer |
| 37 | 36,000 | 3 | 3.08, so the division is wrong here |
| 42 | 42,000 | 3.5 | same answer |
| 43 | 42,000 | 3.5 | 3.58, so the division is wrong here |
| 48 | 48,000 | 4 | same answer |
| 49 | 48,000 | 4 | 4.08, so the division is wrong here |
| 60 | 60,000 | 5 | same answer |
| 61 | 60,000 | 5 | 5.08, so the division is wrong here |
Table transcribed from 2026 RESIDENTIAL & LIGHT COMMERCIAL PRODUCT HANDBOOK (14-1011-43, Effective 1/1/26 (page 12, NOM-1)), published by americanstandardair.com (a distributor's copy, served from the distributor host of Denver Winair Co., which American Standard lists as a distributor), fetched 2026-10-12.
The American Standard codes that dividing by 12 gets wrong
The usual shortcut is that a capacity code is the nominal BTU/h divided by 1,000, so dividing it by 12 gives the tonnage. American Standard prints 7 codes where that arithmetic disagrees with American Standard's own table, and the table is what the equipment is sold against:
| Code | American Standard prints | Code / 12 gives |
|---|---|---|
| 19 | 1.5 tons | 1.58 |
| 25 | 2 tons | 2.08 |
| 31 | 2.5 tons | 2.58 |
| 37 | 3 tons | 3.08 |
| 43 | 3.5 tons | 3.58 |
| 49 | 4 tons | 4.08 |
| 61 | 5 tons | 5.08 |
These are not derivable, only transcribable, which is why this decoder carries American Standard's printed table rather than a formula. If you meet one of these codes in the field, arithmetic will land you between two real sizes, and the printed table is the only thing that resolves it.
Worked example: American Standard 5A7A4024A1000AA
Capacity code 24 at characters 7-8 of 5A7A4024A1000AA: 24,000 BTU/h, which is 2 tons at 12,000 BTU/h per ton. Positions 7-8 are the Nominal Tonnage: American Standard's handbook 14-1011-43 prints "24 = 2.0" under that heading, in tons.
- Refrigerant: R-454B. Position 1 reads "5": American Standard's handbook 14-1011-43 prints "5 = R-454B" under Refrigerant Type.
- Brand letter: American Standard. Position 2 reads "A": American Standard's handbook 14-1011-43 prints "A = American Standard" under Brand.
- Product type: Split AC condenser. Position 3 reads "7": American Standard's handbook 14-1011-43 prints "7 = AC" under System Type.
- Efficiency: 14 SEER2. Position 5 reads "4": American Standard's handbook 14-1011-43 prints "4 = 14 SEER2" under Nominal Rated SEER2. That is the nominal rating the model number encodes, not a measured one.
What is specific to American Standard
The American Standard documents behind this page
Published by americanstandardair.com. This is a distributor's copy, served from the distributor host of Denver Winair Co., which American Standard lists as a distributor. Fetched 2026-10-12. Covers American Standard's Model Nomenclature Residential - Outdoor on p12 (NOM-1): Refrigerant Type 5 = R-454B; Brand A = American Standard; System Type 5 = Cold Climate HP, 6 = HP, 7 = AC; Product Family A = Silver/Gold AC, C = Light Commercial, H = Silver/Gold HP, V = Platinum VSPD; Nominal Rated SEER2; Field Connection 0 = Brazed, 5 = Mechanical straight fitting; Nominal Tonnage 12 = 1.0 to 61 = 5.0 at positions 7-8.
Published by www.asdealernet.com. Fetched 2026-10-11. Covers American Standard's Outdoor Units model nomenclature on p6: Refrigerant Type 2 = R-22, 4 = R-410A; position 2 AMERICAN STANDARD; Product Type 6 = Split Heat Pump, 7 = Split Cooling; Family SEER 0 = 10 to 9 = 19; Split System Connections 1-6 Tons 0 = Brazed; Nominal Capacity in 000s of BTUs at positions 7-8.
Published by www.asdealernet.com. Fetched 2026-10-11. Covers the same Outdoor Units model nomenclature as 12-1173-03, on p6.
Frequently asked questions
How do I find the tonnage of an American Standard unit from the model number?
Read the capacity code: on American Standard it sits at positions 7-8, with the refrigerant at position 1, the brand at 2, the system type at 3, the product family at 4, Nominal Rated SEER2 at 5 and the field connection at 6, per American Standard's own 2026 handbook. On 5A7A4024A1000AA that code is 24, which is 24,000 BTU/h, or 2 tons, because one ton of cooling is 12,000 BTU/h. Use the OUTDOOR unit's model number for system cooling capacity; the indoor air handler or coil carries its own number. This position comes from American Standard's own 14-1011-43, not from a third-party chart.
Can I just divide the American Standard capacity code by 12?
Not on every code. American Standard prints 7 capacity codes where that division gives the wrong answer: 19 is 1.5 tons where dividing gives 1.58, 25 is 2 tons where dividing gives 2.08, 31 is 2.5 tons where dividing gives 2.58, 37 is 3 tons where dividing gives 3.08, 43 is 3.5 tons where dividing gives 3.58, 49 is 4 tons where dividing gives 4.08, 61 is 5 tons where dividing gives 5.08. Those values come from American Standard's own printed table rather than from arithmetic, which is the whole reason the table exists. On every other code in the table the division does work.
Where is the model number on an American Standard unit?
On the data plate on the outdoor unit's cabinet. It is labeled M/N, MODEL or MODEL NO., usually printed directly above or beside the serial number. The model number describes what the unit is, including its capacity. The serial number describes when it was built and carries no capacity information at all.
Which American Standard document is this based on?
2026 RESIDENTIAL & LIGHT COMMERCIAL PRODUCT HANDBOOK (14-1011-43, Effective 1/1/26 (page 12, NOM-1)), published by americanstandardair.com (a distributor's copy, served from the distributor host of Denver Winair Co., which American Standard lists as a distributor) and fetched 2026-10-12, which covers American Standard's Model Nomenclature Residential - Outdoor on p12 (NOM-1): Refrigerant Type 5 = R-454B; Brand A = American Standard; System Type 5 = Cold Climate HP, 6 = HP, 7 = AC; Product Family A = Silver/Gold AC, C = Light Commercial, H = Silver/Gold HP, V = Platinum VSPD; Nominal Rated SEER2; Field Connection 0 = Brazed, 5 = Mechanical straight fitting; Nominal Tonnage 12 = 1.0 to 61 = 5.0 at positions 7-8. SPLIT SYSTEM COOLING MODELS 4A7A4018-24C/30-060B (12-1173-03, May 2008), published by www.asdealernet.com and fetched 2026-10-11, which covers American Standard's Outdoor Units model nomenclature on p6: Refrigerant Type 2 = R-22, 4 = R-410A; position 2 AMERICAN STANDARD; Product Type 6 = Split Heat Pump, 7 = Split Cooling; Family SEER 0 = 10 to 9 = 19; Split System Connections 1-6 Tons 0 = Brazed; Nominal Capacity in 000s of BTUs at positions 7-8. SPLIT SYSTEM HEAT PUMP MODELS 4A6H4018-060B (12-1175-03, June 2008), published by www.asdealernet.com and fetched 2026-10-11, which covers the same Outdoor Units model nomenclature as 12-1173-03, on p6. Every capacity value on this page traces to one of those documents, and each is named with the date it was fetched so you can pull it yourself.
Is the decoded tonnage the size I should install?
No. Nominal tonnage is what the unit was built to deliver, not what the building needs, and the old unit may have been oversized or sized before insulation and window changes. Treat it as a starting clue and run a load calculation before matching a replacement. Actual delivered capacity also depends on the matched indoor unit, line set, airflow and conditions.
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Got a central system's tonnage? Check it against the house's load.
The old unit's nominal size is a clue, not a load calculation. Oversized systems short-cycle and dehumidify poorly. For central equipment that conditions the whole house, run the numbers before you match a replacement. A PTAC, a single package vertical unit, a room air conditioner or one unit of a VRF system conditions a room or a zone, which this load calculator does not size.