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The Lennox EL296UHV furnace uses a 16 x 25 x 1, 20 x 25 x 1 or 24 x 25 x 1 filter, depending on cabinet width (or model) and return location (per the Lennox document cited on this page). The table below shows which size applies to each cabinet and return.
Verified from manufacturer doc Filter sizes hand-checked against the manufacturer document
Last checked against the manufacturer document:
Model numbers printed in the linked Lennox document:
EL296UHV045P24B
| Cabinet width | Side return | Bottom return |
|---|---|---|
| 17-1/2 in. | (1) 16 x 25 x 1 | (1) 16 x 25 x 1 |
| 21 in. | (1) 16 x 25 x 1 | (1) 20 x 25 x 1 |
| 24-1/2 in. | (2) 16 x 25 x 1 | (1) 24 x 25 x 1 |
Number in parentheses = filter quantity, as printed in Lennox Table 1. Sizes are nominal (in.).
General guidance (not from this manual): check monthly and replace 1-in. filters every 1–3 months, or follow the filter maker's guidance and your owner's manual.
Pull the old filter and read the size printed on its frame. Nominal sizes are rounded up: a 15.5 x 24.5 in. filter is sold as 16 x 25.
Your furnace manual lists the filter's dimensions, not its MERV rating. Higher-MERV filters restrict more air. Manufacturers such as Carrier recommend keeping the clean-filter pressure drop under 0.2 in. w.c. (ideally under 0.1). Lennox warns that an over-restrictive filter can trip the high limit in winter and freeze the coil in summer. If you want MERV 11–13, a 4-in. media cabinet is the usual route. Ask an HVAC tech to check static pressure. Nominal sizes are rounded: a filter labeled 16 x 25 x 1 actually measures about 15.5 x 24.5 x 0.75.
Installation Instructions 508247-01, Table 1 – recommended filter sizes
Last checked 2026-10-26. Manufacturers revise documents. If your unit's label disagrees, trust the label.
The Lennox EL296UHV furnace uses a 16 x 25 x 1, 20 x 25 x 1 or 24 x 25 x 1 filter, depending on cabinet width (or model) and return location (per the Lennox document cited on this page). The table below shows which size applies to each cabinet and return. 17-1/2 in. – (1) 16 x 25 x 1 – (1) 16 x 25 x 1; 21 in. – (1) 16 x 25 x 1 – (1) 20 x 25 x 1; 24-1/2 in. – (2) 16 x 25 x 1 – (1) 24 x 25 x 1.
General guidance (not from this manual): check monthly and replace 1-in. filters every 1–3 months, or follow the filter maker's guidance and your owner's manual.
Filter sizes are nominal (rounded). A filter sold as 16 x 25 x 1 actually measures about 15.5 x 24.5 x 0.75 in. Buy by the nominal size printed on the frame.
Side return filter size by cabinet width: 17-1/2 in.: (1) 16 x 25 x 1; 21 in.: (1) 16 x 25 x 1; 24-1/2 in.: (2) 16 x 25 x 1 (per the source table).
Bottom return filter size by cabinet width: 17-1/2 in.: (1) 16 x 25 x 1; 21 in.: (1) 20 x 25 x 1; 24-1/2 in.: (1) 24 x 25 x 1 (per the source table).
Installation Instructions 508247-01, Table 1 – recommended filter sizes (https://www.lennox.com/dA/795a74684b/508247-01a.pdf), last checked 2026-10-26.