HVAC Decoder
HVAC Tonnage From Model Number
Pick the brand or paste any AC, heat pump, or mini split model number and get the nominal tonnage and BTU/h, plus the SEER class and refrigerant generation when the brand's scheme encodes them. 9 of the 15 brand schemes behind it are backed by a manufacturer document we fetched and quoted; the rest are read by documented pattern and labelled for what they rest on.
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. Always confirm against the data plate's BTU/h rating and the AHRI certificate for the matched system.
Capacity Code Reference Table
| Model code | Nominal BTU/h | Tons |
|---|---|---|
| 018 | 18,000 | 1.5 |
| 024 | 24,000 | 2 |
| 030 | 30,000 | 2.5 |
| 036 | 36,000 | 3 |
| 042 | 42,000 | 3.5 |
| 048 | 48,000 | 4 |
| 060 | 60,000 | 5 |
Mini splits use the same BTU/1000 idea but print the class directly, including sizes that are not divisible by 6: 09, 12, 15, 18, 24, 30, 36 (9,000 to 36,000 BTU/h, 0.75 to 3 tons). One ton of cooling = 12,000 BTU/h, so any code on the two tables above divided by12 is the tonnage. That division is not universal: several brands publish capacity codes it gets wrong, and this tool reads those from the manufacturer's own table instead. The brands with a dedicated page below print them as follows. Trane prints 19 = 1.5 tons, 25 = 2 tons, 31 = 2.5 tons, 37 = 3 tons, 43 = 3.5 tons, 49 = 4 tons and 61 = 5 tons; Lennox prints 041 = 3.5 tons, 047 = 4 tons and 059 = 5 tons; Goodman and Amana print 019 = 1.5 tons, 025 = 2 tons, 031 = 2.5 tons, 037 = 3 tons and 043 = 3.5 tons. Payne prints 037 as 3 tons on its 16 SEER sheet. Each of those is a code where dividing by 12 lands between two real sizes, so the manufacturer's printed tonnage is the only correct answer. Read each scheme's own source line below rather than treating this list as complete.
Brand Scheme Reference
9 of these 15 schemes are backed by a manufacturer document we fetched and quoted, named in the sources below. The other 6 decode capacity from third-party decoders, distributor listings or naming convention. Read each scheme's own source line below for which it is: the Confidence column rates how well the capacity POSITION is established, not whether a manufacturer document stands behind it, and several schemes still read high on third-party sources. Where a source conflict or single-sourced claim exists, this decoder either drops the claim or publishes it at reduced confidence with the gap named, rather than guessing: Allied Air's 2025 A7 nomenclature is excluded until verified, so that brand decodes capacity only, while LG's single-sourced BTU/100 convention is published as a medium-confidence estimate that says so. The ICP series prefix key was on that list and is now verified against ICP's own model number identification guide, which settled it by showing that ICP gives one digit-1 letter to several of its brands at once, so this decoder publishes the product line and refuses to name a maker from the model number.
| Brands | Where the capacity code sits | Also encoded | Confidence | Source |
|---|---|---|---|---|
| Trane, American Standard | Positions 7-8 are the nominal capacity code (4TTR4036N1000 = 36 = 3 tons). Position 6 is the field-connection digit, not part of the capacity. Trane also ships odd codes that are NOT the code divided by 12: 19 is 1.5 tons, 25 is 2, 31 is 2.5, 37 is 3, 43 is 3.5, 49 is 4 and 61 is 5. | Position 1 = refrigerant (2 = R-22, 4 = R-410A, 5 = R-454B), position 5 = the efficiency digit (0 = 20, 3 = 13, 4 = 14, 5 = 15, 6 = 16, 8 = 18, 9 = 19; the R-454B generation reads it as SEER2 and adds 7 = 17). On R-410A models position 2 is the brand letter and position 3 is AC vs heat pump; on the R-454B generation positions 2-3 are instead a two letter system type (HP = heat pump, HC = cold climate heat pump). | high | 22-1904-1M-ENDLR-PSD004A-ENODR-PSD038A-EN |
| Carrier | Positions 7-8 are the 2 digit BTU/1000 code in the 24 and 25 families (24ABC636A0030 = 36 = 3 tons). The older 38 family carries a 3 digit code after the series letters (38CKC036 = 036). | Leading digits: 24 = AC condenser, 25 = heat pump, 58/59 = gas furnace, and on the R-454B generation 26 = air conditioner and 27 = heat pump. Position 6, the digit before the capacity code, is the SEER class in lettered series (3 = 13, 6 = 16, 1 = 21 in the 24ACC6 family). Refrigerant is not in a fixed digit. This tool reads a capacity out of the 24, 25 and 38 families only: no nomenclature document we hold covers where the capacity code sits in a 26 or 27 model, so those are identified as Carrier and their tonnage is refused rather than guessed. | high | Catalog No 24ABC6-8PD2016cac_nomen |
| Bryant | Positions 7-9 are the 3 digit capacity code, which Bryant labels 1,000 Btuh nominal (126BNA036000A = 036 = 36,000 BTU/h = 3 tons). Bryant numbers these model positions 1 to 12 and then 14, with no position 13. | Position 1 is the product family (1 = air conditioner), position 2 the tier, position 3 the SEER family digit (3 = 13 SEER on the 113A, 6 = 16 SEER on the 126B), position 4 the major series (B = Puron on the 126B) and position 5 the voltage (N = 208/230-1; the 113A also documents P = 208/230-3 and E = 460/3). The two sheets differ after the capacity: the 126B prints a variation digit at position 6 and leaves 10 to 12 undefined, while the 113A uses 6 for the grille, 10 for a design variation and 11 for the region (N = North). Position 14 is the minor series on both, and neither numbers a position 13. | high | Catalog No. PDS126B-10Catalog No. PDS113A-17 |
| Payne | On the two documented families the Nominal Capacity code sits at positions 7-9 (PA13NA036 = 036 = 3 tons). Both fetched sheets print a code-to-tonnage table, so those values are transcribed rather than calculated, and the two families do not print the same set: PA13 prints 018, 024, 030, 036, 042, 048 and 060, while PA16 omits 018 and adds 037, which its own table reads as 3 tons rather than the 3.08 the code divided by 12 would give. Payne's other families are read by pattern, at whatever position the code falls, and are reported as estimates. | On PA13 and PA16, positions 3-4 are the SEER family digits (PA13 = 13 SEER, PA16 = 16 SEER). That is the family designation, not the unit's rating: SS-PA16NA-08 rates its own tested AHRI combinations between 14.0 and 15.0. Position 5 is the electrical supply and position 6 is the refrigerant (A = R-410A), so on those two families the refrigerant is in the model number. The electrical legend differs between them: SS-PA13NA-08 prints N (208/230-60-1) and P (208/230-60-3, offered only in sizes 036, 048 and 060), while SS-PA16NA-08 prints N alone. Payne's current air conditioners are the PA4S, PA5S and PA8T families, and no fetched sheet covers any of them. | high | Catalog No. SS-PA13NA-08Catalog No. SS-PA16NA-08Catalog No. SS-PA13NA-07 |
| Heil, Tempstar, Comfortmaker, Arcoaire, KeepRite, Day & Night, Airquest | Digits 5-6 are the nominal capacity code on the R-410A generations (N4A518GKC100 = 18 = 18,000 BTUH = 1−1/2 tons), which ICP prints as 18, 24, 30, 36, 42, 48 and 60. The current R-454B line inserts an OD Design Type digit at position 5, so its capacity code sits at digits 6-7 instead (N5H5S18AKAAA = 18 = 1-1/2 tons). | Digit 1 is the branding TIER on the R-410A generation, not the brand. That tier key is printed by the R-410A guides only: the current R-454B sheet prints digit 1 as Brand, N =Tempstar, with no tier language at all, so this tool publishes no product line for that generation. On the R-410A layout ICP assigns each letter to SEVERAL brands at once, including the one that looks unique: H to Heil, Arcoaire, Airquest, Kenmore and ICP Commercial; C to Comfortmaker, Day & Night, Keeprite and Kenmore; T to Tempstar AND Kenmore; N to the Entry tier of all of them. So no model number can say which of them built the unit and this tool does not guess. The documents spell it Keeprite, and they also cover Kenmore and ICP Commercial, which this tool does not offer as brands. Digit 3 is the type (A = air conditioner, H = heat pump). Digit 2 is the refrigerant, and each sheet prints exactly one value for it: Form 421 21 6250 01 prints only "4 = R−410A" and Form N5H5S-21-01PD prints only "5 = R-454B". On the two-stage manuals digit 2 is instead the key characteristic (C = Communicating), so no refrigerant is published for that layout. R-22 is NOT decoded here: the only "2 = R−22" in any of these documents sits in the ACCESSORIES part number guide lower on the same page, where it is digit 5 of an accessory number and not an outdoor unit refrigerant. | high | Form 421 21 6250 01Form 421 04 1701 00Form 428 04 1801 00Form N5H5S-21-01PD |
| Goodman, Amana | Goodman GSX/ASX R-410A models put a 3 digit capacity code at positions 6-8, after the SEER digits (GSX140361 = 036 = 3 tons). That line also ships FIVE codes that are NOT the code divided by 12: 019 is 1.5 tons, 025 is 2, 031 is 2.5, 037 is 3 and 043 is 3.5. Goodman's R-32 GLXS/GLZS line uses a 2 digit code at positions 8-9 (GLXS4BA3610 = 36 = 3 tons), and Amana's current ASXS S-series uses a 2 digit code at positions 7-8 (ASXS6S3610A = 36 = 3 tons). | On the GSX/ASX layout position 3 is the unit type (X = R-410A condenser, Z = R-410A heat pump, C = the older R-22 era line) and positions 4-5 are the SEER rating. On the R-32 GLXS/GLZS layout position 2 is L for the R-32 split system line, position 3 is the outdoor type (X = condenser, Z = heat pump) and the tier digit is 4 = 14.3 SEER2, 5 = 15.2 SEER2. Amana's ASXS layout gives position 3 as the unit type and position 4 as the side-discharge cabinet; this tool publishes no refrigerant for that line, because Amana's own spec sheet labels it R-410A while Amana markets it as R-32. | high | SS-GSX14SS-GLXS4B-R32SS-ASX14SS-ASXS6SS-ALXS5B-R32 |
| Daikin | Unitary: 3 digit BTU/1000 code (DX16SA036 = 3 tons). Mini splits: BTU/1000 class printed directly (FTX12NMVJU = 12,000 BTU/h, about 1 ton). | Unitary: 2 digits after DX = nominal SEER series, next letter = stage (S = single stage). DX prefix = R-410A era per Daikin spec sheets. | medium | None fetched |
| Lennox | Capacity is the dash group in BTU/1000 (XC21-036-230 = 3 tons; EL16XC1-048 = 4 tons; SL25KCV-036-230A-1 = 3 tons). The current R-454B line also ships odd codes that are NOT the code divided by 12: 041 is 3.5 tons, 047 is 4 and 059 is 5. The group AFTER the capacity is the voltage (230, 233, 463), not a second capacity. | On the legacy XC/EL/ML models the efficiency lives in the series name, not a dedicated digit (XC21 targets up to 21 SEER, EL16XC1 = Elite 16, ML14XC1 = Merit 14), and the refrigerant is not encoded in a stable position. The current R-454B scheme is different and is documented: SL/EL/ML is the product tier, the next two digits sit in the position Lennox labels Nominal Efficiency, K is the refrigerant (R-454B), then the unit type (C = air conditioner, P = heat pump, L = cold climate heat pump) and the compressor stage (1, 2 or V). | high | Form 210965Model Numbering Systems, section 3.1 |
| Armstrong Air, AirEase, Ducane, Concord | Two digits immediately before the trailing revision letter, in BTU/1000 (4SCU16LS36P = 3 tons; 4SCU13LE136P = 3 tons). | 4 = R-410A generation, digits after SCU = SEER, stage letter: E = single stage enhanced, S = two stage, B = base, X = variable. The 2025 R-454B A7 nomenclature is not yet dual sourced and is excluded. | high | None fetched |
| Rheem, Ruud, WeatherKing, Sure Comfort | Two layouts are documented and the capacity sits in a different place in each. The current families run brand, product category, SEER2, region, refrigerant, then the Capacity cell at characters 7-8 (RA14AZ36AJ1NA = 36 = 3 tons; RD18AY60AJVCA = 60 = 5 tons). The older nine-field layout has no region or refrigerant cell, so the same code sits at characters 5-6 instead (RA1636AJ1NA = 36 = 3 tons). The two cannot be confused: the older layout puts a DIGIT where the current one requires the region letter. ⚠ THE TWO GENERATIONS DOCUMENT DIFFERENT CAPACITY SETS AND THIS TOOL DOES NOT POOL THEM. Both current books print exactly four codes, 24 = 24000 BTU/HR, 36 = 36000, 48 = 48000 and 60 - 60000, and each corroborates its own legend on the facing page with an Available Models list and an Electrical and Physical Data table running over those same four. The nine-field book prints all seven, 18 through 60. So a current-layout model whose size code is 18, 30 or 42 is REFUSED with the reason printed, because reading it off the code = BTU/1000 pattern would be extrapolating from the manufacturer's own list rather than reading it. | Brand cell: R = Rheem / Ruud, U = Ruud Ultra, S = Sure Comfort / Russel By Rheem, ML = Mainline. ML is two characters and is refused rather than decoded, because this tool carries no Mainline badge and would have to print a Rheem or Ruud label over it. Product category: A = air conditioner, P = heat pump, D = side discharge heat pump. Refrigerant: Z = R-410A, Y = R-454B, W = a future refrigerant. Voltage J = 1 phase 208-230 V 60 Hz is the only voltage either current book prints. Type 1/2/3/V = single, two, three stage and fully variable. Controls C/N/U = communicating, non-communicating, other communicating. The region cell prints one value, A for All Regions; a model carrying anything else still reports its size, because that cell is one character wide whatever it holds and the refrigerant letter before the size and the voltage, stage and control letters after it all match the printed key, but this tool publishes no meaning for the letter itself and says so on the result. | high | None fetched |
| York, Luxaire, Coleman (HVAC), Fraser-Johnston, Guardian | Two layouts are documented, and each prints its own tonnage legend rather than leaving it to arithmetic. On the current R-454B generation the model runs brand, product type, efficiency, then the Nominal unit capacity (MBH) code at characters 4-5 (YC436E2S11 = 3 tons). On the R-410A YC2/YH2 generation the efficiency-and-staging field is two characters wide (2D, 2E, 2F), so the same capacity code sits at characters 5-6 instead (YC2E36SB21S = 3 tons). The two cannot be confused: that field always begins with 2 and the R-454B efficiency character never does. ⚠ THIS LAYOUT IS NOT THE LX SERIES, AND CALLING IT THAT WAS WRONG ON A PUBLISHED SURFACE: the manufacturer brands guides for XC3, YC3 and YC6 as LX Series too, and every one of those carries the R-454B table with the capacity at characters 4-5. Both legends read 18 = 1.5 ton, 24 = 2, 30 = 2.5, 36 = 3, 42 = 3.5, 48 = 4 and 60 = 5, identically, across a refrigerant change. One code sits OFF that legend: the 2 ton class ships as two units, and YC425E2S11 is published as 2 tons by its own guide's performance section even though 25 appears in no nomenclature table. | Digit 1 is the brand and the manufacturer prints only three values for it: Y for YORK, X for a private brand and R for OTC. It never names which private brand, so this tool refuses to read Luxaire, Coleman, Fraser-Johnston or Guardian out of a model number. Digit 2 is the product type (C = AC, H = HP). The refrigerant is published only from the model's own generation: the R-454B table prints E = R-454B, the LX table prints B = R-410A, and neither key is carried across the generation boundary. The modulating YH9 line is documented as DUAL TONNAGE and is reported as an estimate rather than a single confident decode. | high | Form 6788932-YTG-A-0526Form 6788936-UTG-A-0526Form 6552867-YTG-D-0226Form 6644185-UTG-C-0625Form 6260578-YTG-C-0823Form 6552871-UTG-D-0226Form 6601763-YTG-B-0725Form 6515461-YTD-A-1225 |
| Intertherm, Miller, Gibson, Frigidaire, Maytag, Westinghouse, Tappan, Kelvinator | 3 digit BTU/1000 code in the model suffix, 018 to 060 (ET4BE-036K = 3 tons). | Capacity only per our sources. | medium | None fetched |
| Mitsubishi Electric, Fujitsu, Gree, MrCool, Bosch, Samsung, Midea, Senville, Pioneer, Daizuki, Friedrich | The digits in the model are the BTU/h class divided by 1,000: 09, 12, 15, 18, 24, 30, 36 (MSZ-GL15NA = 15,000 BTU/h = 1.25 tons; BOVA-36 = 3 tons). | Capacity only. Friedrich odd sizes are approximate (PDH09 is actually 9,400 BTU/h). | high | None fetched |
| LG | The 3 digit code is BTU/h divided by 100, not 1,000: 090 = 9,000, 120 = 12,000, 180 = 18,000, 240 = 24,000 (LS120HSV5 = 12,000 BTU/h = 1 ton). | Capacity only. Note LG uses a different divisor than every other brand here. | medium | None fetched |
| Bard | Digits 2-3 are the Nominal Capacity code, and each of the five fetched Bard sheets prints its tonnage in words rather than leaving it to arithmetic: 12 is 1 ton, 18 is 1.5, 24 is 2, 30 is 2.5, 36 is 3, 42 is 3.5, 48 is 4, 60 is 5 and 72 is 6. The ranges differ by product: the ducted wall-mount air conditioners run 18 to 72 with the one-ton W12 on its own sheet, and the heat pump line stops at 60. Bard's MEGA-TEC line instead carries a THREE digit code at digits 2-3-4 (090 to 180, 7.5 to 15 tons); it is light commercial and this tool refuses it rather than reading two of its three digits. | Digit 4 is the unit type and control location: A is an air conditioner with right or centre controls, L is an air conditioner with left side controls (offered on W18 to W36 only) and H is a heat pump (W18 to W60). Digit 5 is the revision, and on the current generation it carries the refrigerant: F is Bard's R-454B revision, printed as such in both current sheets. The R-410A sheets label digit 5 only as a revision level and never tie it to a refrigerant, so this tool publishes a refrigerant for the F models and none for the others rather than inferring one from the document title. | high | Form No. S3678-0626Form No. S3659-0326Form No. S3595-1124Form No. S3586-1123Form No. S3565-0525 |
5 brands have been re-sourced to their own manufacturer nomenclature documents and have a dedicated page naming those documents: Carrier tonnage by model number, Trane tonnage by model number, Lennox tonnage by model number, Goodman tonnage by model number, Amana tonnage by model number. The remaining schemes above are served by this decoder with the confidence label their sources earn.
The manufacturer documents we hold
34 documents behind 9 of the 15 schemesabove. Each is listed with the reference that makes it re-findable, the edition where the document prints one, the manufacturer host it came from and the date we fetched it, so you can look the same document up and check what we read. Some manufacturers put their literature behind a login. The remaining 6 schemes decode from published brand conventions, distributor listings and third-party decoders, each named below, and we are working through them.
These documents print the code's unit but no per-code tonnage table, so each tonnage is arithmetic on a manufacturer-stated unit rather than a transcribed value.
These documents print a per-code tonnage table, so each tonnage is transcribed from the manufacturer's own table rather than calculated.
These documents print a per-code tonnage table, so each tonnage is transcribed from the manufacturer's own table rather than calculated.
These documents print a per-code tonnage table, so each tonnage is transcribed from the manufacturer's own table rather than calculated.
These documents print a per-code tonnage table, so each tonnage is transcribed from the manufacturer's own table rather than calculated.
What the other 6 schemes rest on
Worked Examples
Position 1: digit 4 = R-410A (2 = R-22, 5 = R-454B). Position 2: T = Trane. Position 3: T = split AC condenser (W would be a heat pump). Position 5: digit 4 = SEER class 14. Position 6: 0 = brazed field connection, not part of the capacity. Positions 7-8: 36 = 36,000 BTU/h = 3 tons. Per Trane's own Model Nomenclature diagram in Product Data 4TTR4-L (22-1904-1M-EN).
G = Goodman, S = split system, X = R-410A condenser (the older GSC line was R-22). Digits 13 = 13 SEER. Then 036 = 36,000 BTU/h = 3 tons, and the trailing 1 = 208/230V single phase. Per Goodman's model nomenclature and GSX13 spec sheet.
Leading 24 = AC condenser (25 = heat pump, 58/59 = gas furnace). ACC = series letters. The digit 6 before the capacity code = 16 SEER in the 24ACC6 family (3 = 13 SEER, 1 = 21 SEER). Final 36 = 36,000 BTU/h = 3 tons. Carrier does not put refrigerant in a fixed model digit; it follows from series and manufacture year. Per Carrier 24ACC6 product data.
Mini splits skip the divisible-by-6 ladder and print the BTU class directly: 15 = 15,000 BTU/h, which is 1.25 tons. The same convention runs across Fujitsu (ASU12RLS3 = 12,000), Gree (GWH12 = 12,000), MrCool (DIY-36 = 36,000), and Bosch (BOVA-36 = 3 tons). Watch LG: its codes are BTU/h divided by 100, so LS120 = 12,000 BTU/h, per LG product listings.
Why Furnace Model Numbers Break the Rule
Gas furnace model numbers encode heating input in MBH, thousands of BTU/h of gas input: 070 = 70,000, 090 = 90,000, 110 = 110,000. Many also carry a blower airflow code (16 = 1,600 CFM class) that looks like a capacity code. Neither number is cooling tonnage. Carrier flags its furnaces with the model prefixes 58 and 59, and this decoder reports those as furnaces instead of guessing a tonnage. For system cooling capacity, always decode the outdoor unit's model number. The 060 code is the one collision to watch: on an outdoor unit it means 5 tons of cooling; on a furnace it means 60,000 BTU/h of heating input.
Frequently Asked Questions
How many tons is a 036 model number?
3 tons. The 036 capacity code means 36,000 BTU/h nominal, and one ton of cooling equals 12,000 BTU/h, so 036 divided by 12 is 3 tons. The same math covers the whole residential ladder: 018 = 1.5 tons, 024 = 2, 030 = 2.5, 036 = 3, 042 = 3.5, 048 = 4, and 060 = 5 tons.
Do I use the model number or the serial number to find tonnage?
The model number. It describes what the unit is: capacity, and on many brands the SEER class and refrigerant generation. The serial number describes when the unit was built and carries no capacity information. If you need the unit's age or refrigerant era, decode the serial number instead with our serial number lookup tool.
Where is the model number on the nameplate?
On the data plate (rating plate), a metal or foil sticker on the outdoor unit's side panel near the refrigerant line connections, or inside the front panel on indoor equipment. It is labeled M/N, MODEL, or MODEL NO., usually printed directly above or beside the serial number. Use the outdoor unit's model for system cooling capacity; indoor air handlers and coils carry their own numbers.
Does the model number show the SEER rating?
On many brands, yes, as a rounded class rather than the exact rating. Trane and American Standard carry a SEER digit in position 5 (4TTR4 is a 14 class), Goodman and Amana spell it out (GSX16 = 16 SEER), Rheem and Ruud use positions 3-4 (RA16 = 16 SEER), and Lennox puts it in the series name on the legacy generation (XC21) but gives it a dedicated position on the current R-454B line (the two digits after the SL/EL/ML tier, which Lennox labels Nominal Efficiency rather than SEER or SEER2). Carrier encodes it as a single digit in lettered series (24ACC6 = 16 SEER per Carrier product data). The exact SEER2 rating for a matched system is on the AHRI certificate, not in the model number.
Do the indoor and outdoor model numbers have to match in size?
They should be a rated match, which is not always the same digits. A 036 condenser is often paired with an 037 or 042 coil or air handler, and manufacturers publish approved combinations through AHRI. Mismatched capacity between indoor and outdoor sections costs efficiency and can hurt dehumidification, so verify the pairing in the AHRI directory rather than assuming equal codes.
My furnace model has 070 or 090 in it. Is that tonnage?
No. Furnace model numbers encode heating INPUT in MBH, thousands of BTU/h: 070 = 70,000 BTU/h input, 090 = 90,000. Some furnace models also carry a blower airflow code (16 = 1,600 CFM class) that can be misread as a capacity code. Cooling tonnage for a split system lives in the outdoor unit's model number. Carrier makes this easy to spot: model prefixes 58 and 59 are gas furnaces.
Can I size the replacement system from the old unit's tonnage?
Treat the old tonnage as a starting clue, not an answer. Industry studies have found a large share of residential systems oversized, and an oversized unit short-cycles, dehumidifies poorly, and wears out faster. The original unit may also have been sized before insulation, window, or envelope changes. Run a load calculation first: our BTU calculator estimates the load from climate zone, square footage, insulation, and windows, and a Manual J from your contractor settles it.
What if two digit groups in my model number both look like capacity codes?
It happens, especially with voltage blocks (230, 208) and series numbers next to the real capacity code. This decoder ranks every plausible group and shows its reasoning instead of guessing silently: 3 digit zero-padded groups like 036 outrank bare pairs, and leading digits are usually a product family code, not capacity. When the brand is selected, the brand's documented position wins. If two readings survive, check the nameplate's RLA or BTU/h rating to break the tie.
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The old unit's nominal size is a clue, not a load calculation. Oversized systems short-cycle and dehumidify poorly. Run the load numbers before you match a replacement.