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Somebody posted this awhile ago. From this, it is week 31 of 1964

"The great majority of gas furnaces that I see are made by Carrier and sold under a variety of brand names - Carrier, Rheem, Bryant and others. These are identified by the first four digits of the serial number by week and year beginning around 1980. Before that, they used the first two digits as the week of the year and a letter to represent the year, beginning with R for 1964 skipping the letter z and ending in 1979 with the letter H."

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Courtesy of Home Tech. I can't guaranty its accuracy but it's what I use. Based on this, the previous poster is correct.

OT - OF!!!



AMANA: For tonnage refer to FLA & RLA. For age use the serial number and the "B-L-A-C-K-H-O-R-S-E" code wherein S=1969, E=70, B=71, L=72.

B = 71, 81, 91, 01

L = 72, 82, 92, 02

A = 73, 83, 93, 03

C = 74, 84, 94, 04

K = 75, 85, 95, 05

H = 76, 86, 96, 06

O = 77, 87, 97, 07

R = 78, 88, 98, 08

S = 79, 89, 99, 09

E = 80, 90, 00, 10


Bryant:From 1964 to 1979 use the first two numbers of the serial number followed by a date code

1964 = R

1965 = S

1966 = T

1967 = U

1968 = V

1969 = W

1970 = X

1971 = Y

1972 = A

1973 = B

1974 = C

1975 = D

1976 = E

1977 = F

1978 = G

1979 = D

Example: 27Rxxxxxx = 27th week of 1964

After Bryant became Bryant, Day-Night, Payne the system changed. In the new systm the first and second digits of the serial number are the week and the last two are the year (Applies to all BDP).

Example: 2799xxxxxx = 27th week of 1999.


Carrier: Age is incorporated into the serial number. Through 1969, the first digit of the serial number indicates the year of manufacture. Example: 3xxxxxx = 1963, 4xxxxxx = 1964, etc.

1970 and later, a letter followed by a number indicates the month and year of manufacture. Example: A1 = January 1971, B1 = February 1971, C4 = March 1974 etc.

A = Jan

B = Feb

C = Mar

D = Apr

E = May

F = Jun

G = Jul

H = Aug

J = Sep

K = Oct

L = Nov

M = Dec


Climatrol: No known age code


Climate Master: Serial number indicates age from 1972 on


Chrysler Air Temp: Age is shown by the first digit of the serial number and correspons to the last number of the year of manufacturer. Example 0C893745 = 1970. 1 = 1971, 2 = 1972, etc. Use common sense and visual observation to distinguish decades from one another.


Day-Night: (Prior to BDP in 1979) Age coded into the serial number. First letter is the month followed by the second letter which is the year. A = 1970, B = 1971, Etc. Example: AAxxxxxx = January 1970, BExxxxxx = May 1971.


Fedders: Through 1977, the last two letters of the serial number show the month/year of manufacture, beginning with September 1964. Example: xxxxAA = Sept 66, xxxxBC = Oct 68.(I is not used)


General Electric: Age is the last 3 digits of the serial number. First digit being the year and the second and third digits being the month. Example xxxxx241 = 41st week of 1982, 92, 02 etc., xxxxx533 = 33rd week of 1985, 95, 05 etc..


Lennox: Before 1974 the first 2 digits indicated the year and the next digit the month. Example: 732xxx = February 1973.

After 1973, the first two digits indicate the plant, the 3rd and fourth indicate the year and the 5th is a letter month (I is not used). Therefore 5598C = March o 1998.


Rheem/Ruud: The age is coded into the last four digits of the serial number by week and year. Therefore xxxx2302 = 23rd week of 2002.


Tappan: Age is the last 3 characters (digits and letter) of the serial number for the year and month of manufacturer.

Example: xxxxx85C = March 1985. (I not used)


Trane: Begins in 1971. Age is a number followed by a letter in the serial number. Example: 1C-xxxx = March 1971, 81, 91, 01 (Use common sense to distinguish one decade from the next.) Beginning around 1982 the date of manufacturer is stamped on the ID plate.


Whirlpool: Begins in 1970. The letter indicates the decade followed by the week. G = 1970's, H=1980's, J=1990's, K=2000's Example: H416XXXXX = 16th week of 1984.

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There was a secret meeting in a large blacked out room. A large group of men and women sat around a circular table. The only light in the room came from footlights at the base of the table and nobody knew one another's name.

As first order of business, the unknown chairman stood up and said, "Now, statistically, we know that he is likely to become a home inspector 20 30 years from now. I make a motion that we create a confusing system of manufacturing dates for HVAC equipment. If we do this right, young Neal Lewis will be driven right up the wall. Now, for the first piece of the puzzle, I suggest using the word Blackhorse..."

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