The best air filter for a Lennox system is the one that fits its filter slot or cabinet and has the highest MERV rating the equipment can handle. Lennox systems do not all use one standard filter size, and a filter marketed for a Lennox product is not automatically compatible with every Lennox air conditioner.
How to find the right filter size for your Lennox system
Start with the filter already installed. Lennox advises checking the dimensions printed on its frame. If there is no filter to inspect, measure the filter space, then confirm the required size in the equipment manual or with a local Lennox dealer. The brand name alone cannot identify the right size.
Check both the dimensions and thickness. A replacement must fit snugly in the slot without bending or crushing it; the U.S. Environmental Protection Agency (EPA) cautions that fit matters as well as rating. A poorly fitting filter can leave gaps around its edges.
Locate the filter at the return vent or in the air-handler or furnace area. Lennox’s filter guidance applies to systems with a filter in that return-air path; it does not establish that every room, window, or ductless air conditioner uses a replaceable central HVAC filter.
#1 Best Overall
- Price For: Each Item: Filter Fits Brand: Lennox Country of Origin (subject to change): Mexico
Which MERV rating should you choose?
MERV, or Minimum Efficiency Reporting Value, rates a filter’s ability to capture particles in specified size ranges from 0.3 to 10 microns. Higher MERV ratings indicate greater capture efficiency for those particles, but the highest number on a package is not necessarily right for every system.
The EPA recommends choosing MERV 13, or the highest rating the system fan and filter slot can accommodate. Check the equipment manual for the permitted rating. If it is unclear whether the fan and cabinet can handle a higher-efficiency filter, ask a qualified HVAC professional or Lennox dealer before upgrading.
Rank #2
- MERV 11
- High-efficiency alternative to one-inch filters
- Fits the X6660 HCC20-28 Air Cleaner
- Nominal Filter Dimensions: 20x25x5 Actual Dimensions: 19-3/4" x 24-3/4" x 4-3/8"
- Genuine Lennox OEM Furnace Filter
For example, Lennox’s options and accessories document lists a MERV 8 filter sized 16 x 20 x 2 inches (order number 54W20) and a MERV 13 filter sized 16 x 20 x 2 inches (order number 52W37) for specified equipment configurations. These examples are not universal recommendations: verify your system’s size and compatibility before ordering.
How Lennox filter options compare
Compare a candidate filter against your actual equipment on size, supported MERV rating, filter type, and maintenance instructions. Lennox’s Healthy Climate 13 is a MERV 13 media air cleaner with a 5-inch box replacement format; its specifications state up to 12 months of filter life. That deeper replacement format should not be substituted for a thinner filter unless the cabinet is designed for it.
Rank #3
- Nominal Filter Size: 20x20x5 Actual Filter Size: 20" x 19-3/4" x 4-3/8"
| Option | Published details | What to verify |
|---|---|---|
| Lennox 54W20 | MERV 8; 16 x 20 x 2 inches; listed for specified configurations in Lennox’s options and accessories document. | Confirm the equipment configuration and cabinet size match. |
| Lennox 52W37 | MERV 13; 16 x 20 x 2 inches; listed for specified configurations in Lennox’s options and accessories document. | Confirm both the size and that the system can accommodate MERV 13. |
| Healthy Climate 13 replacement | MERV 13; 5-inch box replacement format; Lennox states up to 12 months of filter life. | Confirm the installed media air cleaner accepts this replacement format and follow its instructions. |
Lennox reports that Healthy Climate 13 captures up to 99% of particles down to 3 microns and up to 54% down to 0.3 microns, based on laboratory testing under stated ASHRAE Standard 52.2 conditions. These are manufacturer-reported test figures, not a guarantee of in-home results or an independent ranking against all compatible filters.
How to replace the filter
- Find the filter at the return vent or in the air-handler or furnace area.
- Read the dimensions and thickness on the old filter frame. If there is no filter, measure the opening and check the manual or ask a Lennox dealer.
- Choose a replacement that matches the size and filter type, and confirm that its MERV rating is within the equipment’s limits.
- Insert it with the arrow on the frame pointing toward the furnace or air handler, as Lennox directs.
- Follow the replacement schedule for that filter type and any instructions in the equipment manual.
How often to change a Lennox air filter
Lennox says standard, one-inch disposable filters should be changed every three months. In homes with allergies, pets, or dust buildup, it says changing them about monthly may be appropriate. Those intervals apply to the stated standard disposable-filter guidance; deeper media and advanced filtration systems have their own instructions, so follow the equipment or filter manual rather than applying the one-inch schedule to them.
Quick Recap
Best Value
- X6675 20x25x5 Air Filter Replacement for your furnace, air conditioner, or HVAC system. The filter and is suitable for hospitals, homes, or just about anywhere.
- Easy Replacement - This 20x25x5 furnace filter has the ability to last up to 1 year! Depending on your home's condition, the filter may be replaced every 6-12 months.
- Use the Wholesalehome cloth to clean your furnace or air handler of all dirt before placing your new furnace filter in.
- Highly Efficient - Being Merv 16, the carbon coated fiber matrix this filter will provide extra deep filtration to help you maintain optimal air quality in your home.
- These 5 inch air filters are compatible with HCC20-28 models as well as many Honeywell, Carrier, and Trion Air Bear models that accept a 20x25x5 filter.
Rank #4
- MERV 16 rating. Actual size: 20-3/4 x 24-3/4 x 4-3/8
- Bundle includes a Same Day Supply reminder magnet (1 per filter) so you know when you last changed your filter without having to open your filter cabinet.
- Filter lasts up to 1 year. As with any filtration product, replacement life cycle depends on the individual conditions and needs of the home.
- Removes over 95% of particles ranging in size down to 0.3 micron and more than 90% of particles 0.01 microns and larger.
- Filters are shipped in individual clear plastic bags that can be reused to dispose of your old filter.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
