Day & Night furnace and AC age by serial number
Day & Night furnaces and air conditioners have used more than one serial style. Type the serial into this Day & Night serial number lookup and it checks each one, listing every Day & Night manufacture date that fits.
Where do I find the serial number?
On a Day & Night furnace, the serial plate is inside the blower compartment, so switch off power and remove the lower door. Outdoor Day & Night units carry the plate on a side panel of the cabinet.
How to read a Day & Night serial number
Older Day & Night serials start with a plant letter followed by the year and week. Since 2006, some lines have used a week-first style: four digits, then a letter, then five digits, where the first pair is the week and the second the year.
Plant letter, year, week, sequence
- Used
- 1980s to present
- Format
- Plant letter, year, week, sequence
- Example
- E072514528
Example, read
Year, week, letter, sequence
- Used
- 1990s onward
- Format
- Year, week, letter, sequence
- Example
- 9845B12345
Example, read
Only one source documents this format. It has the same shape as the week-first format, so we try both readings and show every one that fits.
Week, year, letter, sequence (Carrier style)
- Used
- 2006 onward on some lines
- Format
- Week, year, letter, sequence (Carrier style)
- Example
- 2806A12345
Example, read
Reported on some Day & Night units from 2006 on.
Where to find the serial number
On a Day & Night furnace, the serial plate is inside the blower compartment, so switch off power and remove the lower door. Outdoor Day & Night units carry the plate on a side panel of the cabinet.
Brands with the same format
Heil, Tempstar and Comfortmaker use the same serial format as Day & Night.
Questions
How old is my Day & Night furnace?
If the serial starts with a letter, the next two digits are the year. If it starts with four digits and a letter, the decoder tries both orders and lists each real date.
What does 2812A12345 mean?
It reads as week 28 of 2012. The 28 cannot be a year in this style, so only the week-first reading fits.
Why are some Day & Night formats marked less well documented?
The four-digit styles each come from a single source. We still decode them, but suggest checking against a printed date.
Does Day & Night use the same serial format as Heil?
Yes. Day & Night, Heil, Tempstar and Comfortmaker are read with the same set of rules.
Is the manufacture date on a Day & Night the same as when it was installed?
No. It tells you when the unit was built, which is usually a little before it was installed.
Can I look up a Day & Night model number here?
No. A Day & Night model number shows the equipment type and capacity. The serial number is what gives the age.