Lennox Model L LCM

Sizes and filter sizes

Source: Form 211131, pages 1, 21; Form 211132, pages 1, 22; Form 211133, pages 1, 27, 28, 29. Factory filter sizes. Check the rack before ordering; filters get changed over the years.

Lennox Model L LCM model number nomenclature

Example: LCM120U5EN3Y. Select a position to jump to its codes.

How old is this unit? Reading a Lennox serial number

A two-digit plant code, a two-digit year, a month letter, then a five- or six-digit sequence number. Lennox’s own example 5178M 99989 came from plant 51 in December 1978.

Example: 5178M99989

• Scope: One serial numbering system across Lennox products
• Positions 1–2: Plant (location) code, e.g. 56 = Stuttgart, Arkansas
• Positions 3–4: Year (21 = 2021)
• Position 5: Month letter: A = January, B = February, C = March … M = December (no I)
• Positions 6 onward: Five- or six-digit unique number

Source: Lennox 3.1 Model Numbering Systems, pages 1, 3; Lennox EHB model ID, R-454B and R-32, page 9. This is the manufacture date, not the install date.

• Lennox’s commercial rooftop handbooks don’t explain the serial. Its current table is in the residential model ID handbook and lists only January to March; its all-products numbering guide shows the same layout in a diagram with every month, A to M without I. We use that month list.
• Plant codes have changed over the years, so we date the unit but don’t name the plant.

Serial number dates for every rooftop brand we cover →

Notes and limits

• Covers R-454B Model L LCM electric/electric units (refrigerant character 5) from 3 to 25 tons. Earlier R-410A LCM units (character 4) and Model L heat pumps are not decoded here. Gas/electric LGM units are a separate record.
• Code L at position 10 means 60 kW electric heat on an LCM; on an LGM it means low gas heat. Read the second character (C or G) first.
• Blower and heat codes depend on the cabinet: E and P blowers are 3–12.5 tons, M and V are 13–25 tons; 7.5 and 22.5 kW heat are listed only up to 12.5 tons, 45 and 60 kW from 7.5 tons, and 90 kW only on 13–25 tons.
• Lennox prints one minor design sequence per cabinet in these sheets (1 for 3–6 and 13–25 tons, 3 for 7.5–12.5 tons). A different digit on a nameplate means a revision these sheets do not describe.
• Filter sizes are the factory MERV 4 return-air filters from the specification tables. Confirm against the rack in the unit.
• No serial-number date decoder: no Lennox-owned document found states the commercial rooftop serial format.