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The difference between flexible filters and HeavySeal cabinets
Field Controls designs two distinct types of whole‑house air filtration.FlexFilter is a patented, expandable filter cartridge that compresses for shipping and expands to fit multiple HVAC cabinets. Media Air Cleaner cabinets, sometimes called Media Cabinet Filters, are heavy‑duty housings with a built‑in HeavySeal™ to stop air leakage. Both products aim to improve indoor air quality, but they serve different needs. This article explains how each works, compares their features, and answers common questions for homeowners and contractors.
Field Controls FlexFilter: an expandable, high‑efficiency media filter
The FlexFilter line is built around convenience. Each model uses a patented 2‑in‑1 expandable design, meaning the filter is shipped flat then opens like an accordion inside the HVAC cabinet. According to Field Controls’ specification sheet, the design combines several benefits:
- Patented 2‑in‑1 design – the FlexFilter folds flat for shipping and expands when installed. This compact design protects the filter from damage during handling.
- High‑efficiency MERV 11 or MERV 13 media – the filter media meets high‑efficiency standards. MERV 11 filters trap particles down to about 1 µm; MERV 13 filters capture even smaller particles and are often recommended for health‑sensitive homes. Pressure‑drop data show that even at airflow rates of 1,000-1,600 CFM, pressure drop remains below ~0.4 inches of water column for most models, so they provide high filtration without overly restricting airflow.
- Improved inventory management – one FlexFilter model replaces many OEM filters. The company notes that a single FlexFilter can replace over 40 of the most popular models. With nine MERV 11 models to choose from, contractors can stock fewer SKUs and still serve many systems.
- Convenient disposal – each FlexFilter includes a bag so technicians can dispose of the used filter neatly.
FlexFilters are available in sizes that fit popular air cleaner cabinets from brands such as Honeywell, Carrier/Bryant, Aprilaire, Trion and Ultravation. They slide into the existing cabinet, and the flexible frame conforms to the correct dimensions. Because the frame compresses, shipping costs are lower and storing spare filters takes less space. These features make the FlexFilter ideal for contractors or homeowners who replace filters regularly but want to minimize inventory and waste.
FlexFilter Specifications at a Glance
For contractors and distributors, FlexFilter offers a practical replacement solution that simplifies inventory while maintaining high filtration performance.
Available Options:
- MERV 11 and MERV 13 filtration
- Models Flex-1 through Flex-7.5
- Compatible with many popular cabinet systems including Honeywell, Carrier/Bryant, Aprilaire, Trion, Ultravation, GeneralAire, Skuttle, and Field Controls cabinets
- Expandable 2-in-1 design ships flat and expands during installation
- Includes disposal bag for cleaner filter replacement
- UL listed (cULus certified)
Performance Highlights:
- Designed for airflow applications up to 2,000 CFM depending on model
- Low pressure drop helps maintain system efficiency
- One FlexFilter product line can replace more than 40 common OEM replacement filters, reducing distributor inventory requirements and simplifying truck stock management.
Field Controls Media Air Cleaner: a HeavySeal cabinet for whole‑house protection
The Media Air Cleaner is a metal cabinet installed in the return ductwork of a forced‑air system. It contains a replaceable media filter and uses HeavySeal™ technology to prevent air bypass. The specification sheet lists several key features:
- HeavySeal™ construction – the cabinet uses a super‑tight seal that focuses air through the filter. It passes the duct‑blast test at 25 pascals and reduces leakage to as low as 2 CFM. This sealing improves filtration efficiency because unfiltered air can’t bypass the media.
- High‑efficiency MERV 8 or MERV 11 media – the filter captures particles as small as 1.0 micron, including dust, pollen, mold and dander. For even higher efficiency, a MERV 13 filter can be substituted (FlexFilters are often used as replacements).
- Robust metal construction and contractor‑friendly installation – the cabinet is made from heavy‑duty metal and designed for easy installation and media replacement. It meets ANSI/ASHRAE 52.2 standards.
- Whole‑house air cleaning – the cabinet becomes part of the Healthy Home System™, working with system controls to clean the air all year, even when the HVAC equipment isn’t actively heating or cooling. The media filter can trap up to 100 times more contaminants than standard 1‑inch filters while maintaining efficiency.
- Custom colors and sizes – models are available for 16×25 in., 20×20 in., and 20×25 in. media with rated airflows from 600-2,000 CFM. Field Controls also offers custom paint colors to match OEM equipment.
Media Air Cleaner Specifications at a Glance
The Media Air Cleaner cabinet is engineered for contractors who need a durable, high-performance whole-house filtration solution that minimizes air bypass and maximizes filtration efficiency.
Available Cabinet Models:
| Model | Media Size | Airflow Range | MERV Rating |
| FC8-1625HS | 16″ x 25″ x 5″ | 600-1,400 CFM | MERV 8 |
| FC8-2025HS | 20″ x 25″ x 5″ | 600-2,000 CFM | MERV 8 |
| FC11-1625HS | 16″ x 25″ x 5″ | 600-1,400 CFM | MERV 11 |
| FC11-2020HS | 20″ x 20″ x 5″ | 600-1,400 CFM | MERV 11 |
| FC11-2025HS | 20″ x 25″ x 5″ | 600-2,000 CFM | MERV 11 |
Key Construction Features:
- Heavy-duty metal cabinet construction
- HeavySeal™ technology reduces leakage to as low as 2 CFM
- Passes duct blast testing at 25 Pascals
- Meets ANSI/ASHRAE 52.2 standards
- Easy media replacement for ongoing maintenance
- Compatible with MERV 8, MERV 11, and MERV 13 replacement media options
