Frigidaire, Gibson and Maytag HVAC age by serial number (Nortek brands)
Nortek Global HVAC, long known as Nordyne, builds the central air conditioners, heat pumps and furnaces sold as Frigidaire, Gibson, Maytag, Westinghouse, Tappan, Intertherm and Miller, and it states for all of them that the 4th and 5th characters of the serial number are the year. A full serial in Nortek's form 837F layout also gives the month and the plant.
Where the serial number is
On split systems the plate is on the outdoor unit; on furnaces it is on or inside the cabinet. It lists the model and serial numbers and the electrical and gas ratings.
The serial number interpreter
Form 837F, Nortek's Serial Number Interpreter, splits the serial into five parts: two characters taken from the start of the model number, a plant letter (D for Poplar Bluff, F for Dyersburg, G for Saltillo), two digits for the year, two for the month and a six-digit sequence. The form gives no real example, so the worked examples below are built by its rule and labelled that way: GBF0307123456 reads as July 2003 from the Dyersburg plant.
When only the year can be read
Older serials often have another plant letter or a shorter sequence. Nortek's statement about the 4th and 5th characters still applies, so the decoder reads the year from them and leaves the month blank rather than assuming the rest of the layout. GBB030708229, for example, gives 2003 and nothing more. Nortek does not say which century the two digits mean; we read them as 2000 or later and report a serial that would fall in the 1990s as not confirmed.
Model numbers
Current SEER2 split systems such as SA4BE5M1SN18K, often with a brand letter in front, name the refrigerant in the digit after the efficiency letter, 4 for R-410A and 5 for R-454B, and end with the size in thousands of BTU per hour before the voltage letter. Older models such as FS4BI-036K or Maytag CSH4BE-036KA put the size after the dash; the 4 in those names is a design series, not a refrigerant code.
Furnace models such as G7SA-126C-V23C give the nominal heating input after the dash, and the 23 near the end is the airflow for 2 to 3 tons of cooling. Intertherm M7RL-072A is listed at 72,000 BTU/h.
How to read the plate, step by step
- Count to the 4th and 5th characters of the serial: that is the year.
- If the 3rd character is D, F or G and 13 characters follow the 837F pattern, the 6th and 7th are the month.
- Select the brand on the plate for your own reference; the layout is the same for all of them.
- Add the model number for the nominal size or the furnace input.
Serial formats the decoder reads
| Format | How it is read |
|---|---|
| Nortek model digits + plant + year + month (form 837F) | Nortek (Nordyne) serial interpreter, form 837F: two characters from the start of the model number, a plant letter, two digits for the year, two for the month, then a 6-digit sequence. |
| Nortek year in characters 4-5 | Nortek's literature pages for all its brands state that the 4th and 5th characters of the serial are the year. This serial does not fully match the current 837F layout, so we read the year only. |
Model number codes the decoder reads
Only the codes listed here are translated. A code outside this list is shown as "not in the table", and you read the size or input from the plate instead.
| Nomenclature | Position | Codes |
|---|---|---|
| Nortek SEER2 split system | Nortek SEER2 split systems such as SA4BE5M1SN18K (a brand letter may come first): the digit after the efficiency letter is the refrigerant (4 = R-410A, 5 = R-454B), and the two digits before the final voltage letter are the size in thousands of BTU/h (18 = 1.5 tons). | 18 = 1.5 tons, 24 = 2 tons, 30 = 2.5 tons, 36 = 3 tons, 42 = 3.5 tons, 48 = 4 tons, 60 = 5 tons |
| Older Nortek split system | Older Nortek split systems such as FS4BI-036K or Maytag CSH4BE-036KA: the three digits after the dash are the nominal capacity in thousands of BTU/h. The digit after the first letters is a design series or generation, not the refrigerant. | 018 = 1.5 tons, 024 = 2 tons, 030 = 2.5 tons, 036 = 3 tons, 042 = 3.5 tons, 048 = 4 tons, 060 = 5 tons |
| Nortek G7 gas furnace | Nortek G7 gas furnaces such as G7SA-126C-V23C: the three digits after the dash are the nominal heating input. The 23 later in the model is airflow for 2 to 3 tons of cooling, not a cooling capacity. | 126 = 126,000 BTU/h, 045 = 45,000 BTU/h |
| Intertherm / Miller M7 furnace | Intertherm and Miller M7 furnaces such as M7RL-072A: the input is read from Nortek's table (072 = 72,000 BTU/h). | 072 = 72,000 BTU/h |
Worked examples
Each serial below is either printed in a source or built by us strictly by the source's rule (marked "by the rule"), and each is an automated test of the decoder. Readings that depend on today's date are as of October 27, 2026.
| Serial | Result | Why |
|---|---|---|
| GBF0307123456Gibsonby the rule | July 2003Decoded | Model digits GB, plant F (Dyersburg), year 03, month 07. Nortek's form has no real example, so this one is built by its rule. |
| GBB030708229Frigidaireby the rule | 2003Decoded | An older serial whose plant letter and length do not match form 837F; by Nortek's note on the 4th and 5th characters we read the year (2003) only. |
| G6R990505028Westinghouseby the rule | Not confirmed by the manufacturer | Year digits 99: Nortek does not say which century, and our sources do not cover this layout in the 1990s, so we give no date. |
Edge cases and limits
- A month of 13 or more in a full 837F serial does not fit; check for a typing error.
- Frigidaire, Westinghouse and Philco units from before Nortek's current layouts use formats that only third parties describe.
- Furnace input codes that are not in our transcription of Nortek's tables are not translated.
Questions
Why does the decoder show only a year for my serial?
Your serial does not fully match form 837F, for example because its plant letter is not D, F or G. Nortek still states that the 4th and 5th characters are the year, so we show that and nothing more.
Does the 4 in FS4BI-036K mean R-410A?
No. In that older nomenclature the digit is a design series or generation. A refrigerant code appears only in the newer SEER2 model numbers.
Are Maytag central air conditioners covered by the Nortek rule?
Yes. Maytag-branded central air conditioners and furnaces are documented in Nortek's literature library, and the same serial interpreter applies to all of Nortek's brands.
Related pages
- Goodman, Amana and Daikin: Goodman, Amana and Daikin also print the year and the month in digits.
- Carrier and Bryant: Carrier and Bryant put the production week first.
- All HVAC brand families: Every brand family we decode, and the brands we do not decode yet with the reason.
- Where to find the data plate: Where the serial number sits on each type of equipment and how to copy it without mistakes.
- Refrigerants and EPA dates: Why the date of manufacture alone does not tell you whether a unit uses R-22, R-410A or R-454B.
- Service life estimates: What ENERGY STAR publishes about typical ages, and what kind of number each figure is.
Sources
Every rule on this page comes from the documents below, published by the manufacturer or a U.S. government agency. The date is when we last checked each one.
- Nordyne product identifier, form 837F-0725 (Serial Number Interpreter) Nortek Global HVAC. Checked .
- Nordyne product identifier, form 837F-0522 Nortek Global HVAC. Checked .
- Literature library, Air Conditioner - Split (note on the serial number year) Nortek Global HVAC. Checked .
- Form 287C-0506 (archived product literature) Nortek Global HVAC. Checked .
- Maytag split system literature 119E Nortek Global HVAC. Checked .
- Intertherm M7 furnace literature 709264A Nortek Global HVAC. Checked .