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Lennox SL297UHNV filter sizes: 16 x 25 x 1 and 20 x 25 x 1, as listed in the Lennox source document's filter table. Which size fits depends on your cabinet and return. This page is pending human review, so check the source excerpt below.
Auto-extracted · review pending Filter sizes auto-extracted from the manufacturer document.
Last checked against the manufacturer document:
| Sizes found in the source table |
|---|
| 16 x 25 x 1 |
| 20 x 25 x 1 |
Extracted by script from the linked document. Read the excerpt to see which size applies to which cabinet or return.
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.
Manufacturer document for Lennox SL297UHNV
Last checked 2026-11-04. Manufacturers revise documents. If your unit's label disagrees, trust the label.
TABLE 1
Return air can be brought in through the bottom or either
Furnace Filter Size side of the furnace (return air brought into either side of
Cabinet Width Side Return Bottom Return furnace allowed only in upflow applications). If a furnace
17-1/2” 16 X 25 X 1 (1) 16 X 25 X 1 (1) with bottom return air is installed on a platform, make an
airtight seal between the bottom of the furnace and the
21” 16 X 25 X 1 (1) 20 X 25 X 1 (1) platform to ensure that the unit operates properly and
safely. Use fiberglass sealing strips, caulking, or equiva-
Duct System lent sealing method between the plenum and the furnace
Use industry-approved standards to size and install the cabinet to ensure a tight seal. If a filter is installed, size the
supply and return air duct system. FIGURE 14 shows the return air duct to fit the filter frame.
correct supply and return duct installation. Refer to ACCA
Manual D. This will result in a quiet and low-static system
that has uniform air distribution.
SUPPLY
AIR Install self tapping screws
to seal any potential air
leaks
SUPPLYLennox SL297UHNV filter sizes: 16 x 25 x 1 and 20 x 25 x 1, as listed in the Lennox source document's filter table. Which size fits depends on your cabinet and return. This page is pending human review, so check the source excerpt below. 16 x 25 x 1; 20 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.
Every size found in the source table is 1 in. thick: 16 x 25 x 1 and 20 x 25 x 1. Pending human review; check the excerpt.
Manufacturer document for Lennox SL297UHNV (https://www.lennox.com/dA/65549f6864/507760-05c.pdf), last checked 2026-11-04.