HVAC Serial Number Lookup
Day & Night Serial Number Lookup
Day & Night is part of the ICP family, alongside Airquest, Arcoaire, Comfortmaker, Heil, ICP, KeepRite, Tempstar. Enter the serial from the data plate below to get the manufacture date with a character-by-character explanation, the unit's age, its refrigerant era, and the warranty picture.
Decode schemes compiled from manufacturer literature and inspector references, cross-checked across two sources wherever possible (Day & Night sources: building-center.org + pickhvac + inspectorhandbook; icptempstarparts.com + inspectapedia + building-center.org; building-center.org + honesthomeinspections furnace age chart; building-center.org Carrier + Bryant + Day & Night pages). Single-sourced rules are labeled low confidence instead of being presented as fact. A date stamped or printed on the data plate always outranks a serial decode.
Day & Night Serial Number Formats
| Format | Era | Example | Confidence |
|---|---|---|---|
| 4 digits + letter + 4-6 digits; digits 1-2 = week, digits 3-4 = year, the letter is a plant code | ~1980 to present | 4006A17330 = week 40 of 2006 | high |
| Plant letter (sometimes omitted) + 2-digit year + 2-digit week + sequence. Year FIRST: the reverse of the Carrier order | ~late 1980s to present | L943321238 = week 33 of 1994 | high |
| 2-digit year + 2-digit week + letter + sequence. Visually identical to the Carrier layout but with the digit pairs swapped | 1990s | 9414B39332 = week 14 of 1994 (Tempstar) | medium |
| 9-10 digits, no letters; digits 1-2 = year, digits 3-4 = month | 1980s (BDP-built units) | 850304091 = March 1985 | medium |
Some older or conflicting Day & Night formats are recognized but deliberately not decoded; the decoder explains why when it sees one instead of guessing.
Worked Example: Day & Night 4006A17330
Expected decode: week 40 of 2006. Character by character:
40 = week 40 of the year (digits 1-2)
06 = year 2006 (digits 3-4)
A = plant/assembly code, 17330 = production sequence
Carrier-family serials are week-first. ICP brands (Heil, Tempstar) use the same visual layout with year first; the brand on the nameplate decides which reading applies.
Day & Night Refrigerant Timeline
| Manufacture year | Typical refrigerant | Notes |
|---|---|---|
| through 2005 | R-22 | Standard refrigerant of the era. Production of new R-22 ended in 2020; supply is reclaim-only. |
| 2006 to 2009 | R-22 or R-410A | Mixed window during the 13 SEER transition. The model prefix digit is the reliable signal (4 = R-410A). |
| 2010 to 2024 | R-410A | EPA banned R-22 in new equipment from January 1, 2010; R-410A was the standard through 2024. |
| 2025 and later | R-454B | All ICP brands moved to R-454B for the January 1, 2025 EPA deadline, matching parent Carrier, with a factory leak-dissipation system on A2L units. |
The refrigerant printed on the nameplate is authoritative; this timeline tells you what is typical for the age, not what is in a specific unit.
Day & Night Warranty Baseline
Current policy: 10-year parts limited warranty registered within 90 days, 5-year parts unregistered. Premium tiers add No Hassle Replacement coverage (one-time unit replacement, 1 to 10 years by model tier). Pre-2010 units commonly carried 5/5 or 5/10 terms.
Source: heil-hvac.com + ICP warranty PDF. Decode the manufacture date above, then confirm coverage through the manufacturer's own serial-number warranty lookup.
Frequently Asked Questions
How old is my Day & Night unit?
Day & Night had two corporate lives, first as a Carrier BDP brand and later as an ICP brand, and its serials follow both families' layouts. Carrier-era: digits 1-2 = week, digits 3-4 = year (4006A17330 = week 40 of 2006). ICP-era: year first, then week. No single source documents which layout modern units carry, so enter the serial above and the decoder runs both rules, showing every reading that passes the validity checks, ranked. Units past 15 years are replacement candidates, and past 20 a major repair rarely pays off.
Which brands share the Day & Night serial number format?
Day & Night is part of the ICP family, alongside Airquest, Arcoaire, Comfortmaker, Heil, ICP, KeepRite, and Tempstar. These brands come off shared production lines with the same data plates, so one decode rule dates all of them, and the refrigerant and warranty picture is the same across the family.
What refrigerant does a Day & Night unit use?
By manufacture year: through 2005: R-22; 2006 to 2009: R-22 or R-410A; 2010 to 2024: R-410A; 2025 and later: R-454B. The refrigerant printed on the nameplate is authoritative; the year-based mapping tells you what is typical for the age, not what is in a specific unit.
Is my Day & Night unit still under warranty?
Current policy: 10-year parts limited warranty registered within 90 days, 5-year parts unregistered. Premium tiers add No Hassle Replacement coverage (one-time unit replacement, 1 to 10 years by model tier). Pre-2010 units commonly carried 5/5 or 5/10 terms. Decode the manufacture date above, then confirm coverage by running the full serial through the manufacturer's own warranty lookup. Terms shown are the current policy; older units often carried different terms.
Why do some Day & Night serial numbers refuse to decode?
Day & Night had two corporate lives: a Carrier BDP brand, then an ICP brand. No single source documents which layout modern units carry, so this tool runs both decoders and shows every reading that passes the week/month validity checks. This matches the 1960-1979 Bryant/Carrier style (week digits + a year letter). The year-letter chart is documented by only one source and the unit would be 45+ years old, so this tool does not decode it. A unit that age is far past service life. This matches a pre-1988 ICP style whose lookup charts are not publicly documented. The unit predates 1988 either way; if the data plate has an MFG DATE field, that is the reliable source.
Related Tools
HVAC Serial Number Lookup (All Brands)
The full decoder: 50+ brands across every major manufacturer family, with ambiguous formats shown honestly.
Tonnage From Model Number
The serial tells you the age; the model number tells you the size. Decode BTU capacity and tons from the model.
A2L Refrigerant Charge Limit Calculator
Replacing an old unit with R-454B or R-32 equipment? Check the room-size charge limits per UL 60335-2-40.
Same family, same decode rules: Airquest serial number lookup, Arcoaire serial number lookup, Comfortmaker serial number lookup, Heil serial number lookup, ICP serial number lookup, KeepRite serial number lookup, Tempstar serial number lookup.
Different brand on the data plate?
The full lookup covers 50+ brands across every major manufacturer family, with the same honest handling of ambiguous and undocumented formats.