Description
Lennox LGM120 Roof Top Unit — Washable Pre-Filter Replacement
The correct pre-filter for the Lennox LGM120 Roof Top Unit is the HIA202025 — a washable 5-ply corrugated aluminum mesh filter manufactured by American Metal Filter Company. The LGM120 requires 4 filters at the 20″ x 25″ x 2″ specification (actual: 19.50″ x 24.50″ x 1.75″). Metal Air Filters has verified this specification against the official Lennox product documentation.
The HIA202025 matches the factory filter track dimensions exactly, delivering a rattle-free, bypass-free fit in all filter positions. The washable construction eliminates recurring disposable filter costs — clean with water and return to service, providing 5–10 years of continuous operation from a single purchase.
Lennox LGM092/102/120/150 Packaged Gas/Electric Rooftop Engineering Data (PDF)
Metal Air Filters is an independent manufacturer of aftermarket filters. Lennox® and the Lennox logo are registered trademarks of Lennox International Inc. All OEM part numbers and brand names referenced on this page are used strictly for compatibility identification purposes and do not imply any affiliation with or endorsement by the trademark holder.
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Why the HIA202025 Is the Correct Replacement
- Verified Fit: Dimensionally matched to the Lennox LGM120 factory filter track — no cutting, shimming, or bypass airflow around loose-fitting disposable filters
- Permanent Washable Design: Clean with water and return to service — 5–10 years of service life from a single purchase eliminates recurring disposable filter replacement costs
- Aluminum Alloy Frame: Precision-mitered aluminum frame maintains dimensional accuracy through years of continuous commercial HVAC operation
- Multi-Ply Corrugated Aluminum Mesh Media: Captures large airborne particulates while maintaining low initial resistance — no fan performance penalty
- UL 900 Class 1 Certified: Continuous operation to 275°F (135°C) — compliant with commercial building fire safety codes and insurance requirements
- Made in USA: Manufactured by American Metal Filter Company (AMFCO) using domestic materials — consistent quality and reliable lead times
Specifications
Lennox LGM120 Filter Requirements
| Nominal Size | Actual Size | Filter Type | Qty Required |
|---|---|---|---|
| 20″ x 25″ x 2″ | 19.50″ x 24.50″ x 1.75″ | disposable fiberglass panel filter | 4 |
| Reference Documentation | Lennox LGM092/102/120/150 Packaged Gas/Electric Rooftop Engineering Data (PDF) | ||
Correct Replacement Filters for the Lennox LGM120
The Lennox LGM120 requires 4 filters total. Order the complete set below:
• HIA202025 — HI Series Washable Aluminum Mesh 20x25x2 — Qty: 4 per unit | Recommended replacement
• ECA202025 — EC Series Electrostatic Air Filter 20x25x2 — Qty: 4 per unit | Electrostatic upgrade (MERV 4–6)
• HFA202025 — HF Series Washable Foam Air Filter 20x25x2 — Qty: 4 per unit | Low-resistance foam alternative
Construction Features
Extruded Aluminum Alloy Frame
The precision-mitered .030″ extruded aluminum alloy frame maintains the exact filter track dimensions of the Lennox LGM120 throughout the filter’s full 5–10 year service life. Aluminum construction resists corrosion from moisture exposure during washing and from the humid conditions common in commercial AHU installations, maintaining dimensional stability without rust, scale, or material loss.
5-Ply Corrugated Aluminum Mesh Filtration Media
Five layers of corrugated aluminum mesh are arranged in a cross-pattern, progressively filtering air as it moves through the media depth. This construction achieves effective large-particulate capture with low initial resistance — protecting downstream coils, dampers, and secondary filtration stages without imposing the fan performance penalty that occurs with high-resistance pre-filters.
UL 900 Class 1 Fire Safety Certification
MAF commercial HVAC replacement filters carry UL 900 Class 1 certification for continuous operation to 275°F (135°C). This certification is required by commercial building codes and insurance policies in most jurisdictions. The all-metal construction — aluminum or galvanized steel frame and aluminum mesh media — is non-combustible, ensuring the filter does not contribute to fire spread in the event of a system fault or building emergency.
Made in USA by American Metal Filter Company
All MAF replacement filters are manufactured in the United States by American Metal Filter Company (AMFCO) using domestic materials. US manufacturing provides consistent dimensional tolerances, predictable lead times, and quality control that imported alternatives cannot reliably match. AMFCO can provide country-of-origin documentation for facilities with domestic procurement requirements.
Residential and Commercial Applications
The Lennox LGM120 Roof Top Unit is installed across a broad range of commercial building types. In all of these applications, replacing disposable pre-filters with the MAF permanent washable replacement delivers a measurable operational advantage: one purchase, five to ten years of service, and a straightforward water-based cleaning procedure that restores full filtration performance between washings.
Office Buildings and Corporate Facilities
Commercial office buildings operating Lennox roof top units carry a significant ongoing cost in disposable filter procurement, delivery, and installation when managing multi-unit installations across a building or portfolio. Converting to permanent washable pre-filters eliminates that recurring material cost while reducing maintenance labor to a periodic wash procedure. The MAF replacement delivers consistent pre-filter performance without supply chain exposure to disposable filter availability or price fluctuations.
Retail Centers and High-Traffic Commercial Spaces
Retail facilities operate Lennox equipment under high daily occupancy loads and extended hours, placing elevated demand on pre-filtration. The MAF washable pre-filter handles this loading with a 30–90 day cleaning interval that fits standard maintenance scheduling. The permanent aluminum construction withstands continuous commercial-duty operation without the dimensional degradation and efficiency loss of cardboard-framed disposable filters under high-cycle conditions.
Multi-Family Housing and Apartment Complexes
Centralized roof top unit installations in multi-family and mixed-use properties benefit from the MAF filter’s long service life. Property management teams overseeing filter maintenance across multiple units reduce both material costs and administrative overhead by eliminating disposable filter inventory management. A single MAF filter purchase per position replaces three to six years of recurring disposable replacements at typical commercial filter change intervals.
Healthcare and Institutional Facilities
Hospitals, medical centers, schools, and institutional buildings operating Lennox commercial equipment require pre-filtration that performs consistently without supply chain dependencies. The MAF permanent washable pre-filter provides 5–10 years of service from a single purchase, eliminating the risk of filtration gaps caused by delayed disposable filter shipments or short-term availability issues. The all-aluminum construction is non-toxic, non-shedding, and UL 900 Class 1 certified — meeting the fire safety standards required by healthcare and institutional building codes.
Installation
Fit Verification
Before installation, confirm the filter track dimensions in the Lennox LGM120 match the specifications above. The replacement filters should fit with approximately 1/16″ to 1/8″ clearance on all sides — enough for smooth installation and removal without bypass airflow around the filter edges.
Installation Procedure
Shut down the Lennox LGM120 before accessing the filter section. Open the filter access panel and remove all existing filters. Inspect tracks for debris. Slide the replacement filters into position with media face perpendicular to the airflow direction. Seat fully so frames are flush against track stops and all retaining clips are engaged. Close the access panel and restart the unit. Verify normal supply airflow before returning the unit to full service.
Maintenance and Cleaning
Inspect and clean the filters every 30–90 days depending on outdoor air quality and system operating hours. Remove each filter and spray with water from a garden hose or pressure washer (1500 PSI maximum), directing flow from the clean face toward the dirty face. For units handling air with grease or elevated contamination, apply an aluminum-safe neutral-pH detergent (pH 7–9), allow 10–15 minutes contact time, then rinse until runoff is clear. Air dry completely before reinstalling — approximately 2–3 hours. Never reinstall wet filters.
Related Products
Metal Air Filters manufactures permanently washable pre-filter replacements for the complete Lennox commercial roof top unit product line. All replacements are dimensionally matched to the factory filter track specifications and carry UL 900 Class 1 certification for commercial use.
• HIA202025 — HI Series Washable Aluminum Mesh 20x25x2 (washable, permanent)
• ECA202025 — EC Series Electrostatic Air Filter 20x25x2 (washable, permanent)
• HFA202025 — HF Series Washable Foam Air Filter 20x25x2 (washable, permanent)
Browse all Lennox Roof Top Unit filter replacements at Metal Air Filters
Complementary Products
The MAF washable pre-filter is the correct primary filtration stage for the Lennox LGM120 Roof Top Unit. For facilities requiring multi-stage filtration or alternative filter media strategies, Metal Air Filters offers a complete line of compatible commercial HVAC filtration products.
Media Pad Holding Frames — HP Series
Galvanized steel or aluminum media pad holding frames accept standard disposable filter pad media as a secondary filtration stage downstream of the permanent washable pre-filter. Installing the MAF washable pre-filter upstream of a secondary pad stage extends secondary media service life by 3–5× by intercepting the large particulates that would otherwise load and blind the secondary filter rapidly. Available in the full range of commercial HVAC sizes: HP Series Media Pad Holding Frames.
Electrostatic Filters — EC Series
The EC Series permanently washable MERV 6 electrostatic filter provides enhanced particulate capture through passive electrostatic charging technology. The EC Series is available as an alternative pre-filter in applications where electrostatic attraction of finer particulates is required, or as a secondary filtration stage downstream of a coarser aluminum mesh pre-filter: EC Series Electrostatic Filters.
Washable Foam Air Filters — HF Series
The HF Series polyurethane foam filter is available for applications requiring the lowest possible initial pressure drop, or in secondary filter positions where fine particulate capture is secondary to minimizing resistance across the filter bank. HF Series filters are permanently washable and UL 900 Class 1 certified: HF Series Washable Foam Filters.
Why Choose HIA202025 for the Lennox LGM120?
The HIA202025 is the dimensionally verified, permanently washable pre-filter replacement for the Lennox LGM120 Roof Top Unit. It eliminates the recurring cost and administrative overhead of disposable filter procurement: 4 filters, purchased once, providing 5–10 years of continuous commercial service with periodic water-based cleaning.
The exact-dimension match to the Lennox LGM120 factory filter track delivers a rattle-free, bypass-free fit that protects downstream coils and system components from the particulate loading that occurs when ill-fitting disposable filters allow unfiltered bypass airflow. UL 900 Class 1 certified for 275°F continuous operation. Made in the USA by American Metal Filter Company. Filter specification verified against official Lennox product documentation.
For facilities managing a fleet of Lennox commercial roof top units, converting from disposable to permanent washable pre-filters reduces annual filtration costs substantially while simplifying maintenance scheduling and eliminating supply chain dependencies on disposable filter inventory. Metal Air Filters has been supplying permanent washable commercial HVAC filter replacements for decades — call or contact us online for volume pricing on multi-unit orders.
Frequently Asked Questions
What filter does the Lennox LGM120 use?
The Lennox LGM120 uses 4 filters at the 20″ x 25″ x 2″ specification. The correct washable replacement is the HIA202025 from Metal Air Filters.
How many filters does the Lennox LGM120 require?
4 filters are required for a complete filter replacement. Order 4 units to service this unit in a single visit.
Can washable filters be used in the Lennox LGM120?
Yes. Washable aluminum mesh pre-filters are the correct and preferred replacement type for commercial roof top units in this class. The HIA202025 is dimensionally matched to the Lennox LGM120 filter track and installs without modification.
How often do the filters in a Lennox LGM120 need cleaning?
Inspect and clean every 30–90 days depending on outdoor air quality and system operating hours. Monitor differential pressure across the filter section — increased resistance indicates cleaning is due. In continuous-operation commercial facilities with elevated outdoor particulate loads, 30–45 day intervals are typical.
About Lennox
Lennox International is a major North American manufacturer of residential and commercial HVAC equipment, founded in 1895 in Marshalltown, Iowa. The Lennox commercial product line includes rooftop packaged units, split systems, air handlers, and applied equipment serving commercial buildings from small retail spaces to large office complexes and institutional facilities. Lennox commercial rooftop units are among the most widely installed in the United States, particularly in light commercial applications. For official product documentation and authorized service information, visit Lennox Commercial.
