Intertherm Furnace Filters: Model and Replacement Guide

The right Intertherm furnace filter is the one specified for your furnace and its installed return-air arrangement. The brand name alone does not identify the filter. A thin foam door pad, a larger hog-hair-style pad, a pair of metal A-coil filters and a framed pleated filter are different products with different mounting requirements.

Start with the complete furnace model number, then check the filter location and the replacement part listed in its manual. The options below cover three specific replacement situations. They are not interchangeable recommendations for every Intertherm furnace.

Identify the filter before shopping

Photograph the furnace data label and, if the system has air conditioning, the indoor coil label. Keep the full model and serial numbers. A family name such as M1 or CMF2 helps locate the right literature, but revisions and installed accessories still matter. The manufacturer’s M1 literature library includes current and archived documents so an older furnace can be checked against the appropriate parts list.

• Door-mounted pad: Inspect the pad’s dimensions, thickness and retaining wire or bracket. Do not assume the outside dimensions of the furnace door equal the required filter size.
• A-coil filters: Record the coil model, filter part number, frame shape and number of panels. A furnace model by itself may not identify an added cooling coil’s filters.
• Return grille or separate filter cabinet: Read the rack or cabinet label and installed filter specification. A previous owner’s filter is useful evidence, but it may be the wrong one.
• Unclear or modified installation: Have an HVAC technician identify the intended filter arrangement before buying replacements or adding another filter.

Intertherm furnace filter options by application

Nordyne 669064R for equipment that specifies this replacement part

Nordyne’s archived M1 replacement-parts document 707977D identifies air filter 669064 and filter-retainer wire 669065 for the models in that document. The current replacement listing below is the Nordyne 669064R hog-hair-style filter, advertised as 19-1/2 by 28 by 3/8 inches, one filter. Check the current parts cross-reference for your complete furnace model before ordering the R-suffix replacement.

This is the appropriate starting point when the equipment documentation calls for that part family. It is considerably larger than the 16-by-26-inch foam pad discussed next. Do not trim one into the other or assume a similar-looking pad has the same airflow characteristics. Inspect the retainer too: a correctly specified filter still needs to remain securely positioned. The M1 parts and owner’s manuals should guide the final selection.

Filter Everything F162625-2pk for confirmed 16-by-26-inch foam door applications

This two-pack contains foam door filters measuring 16 by 26 by 1/4 inch. The Amazon listing identifies Filter Everything as the brand and Duraflow Filtration as the manufacturer, with model F162625-2pk. Duraflow’s own catalog lists the same dimensions and two-pack model.

The listing references CMF, CMF2, MOC, MAC and CMH applications. Treat those references as a shortlist to investigate, not a guarantee for every furnace carrying one of those prefixes. Confirm that your existing holder and equipment instructions call for this size and type. A two-pack can be convenient when one washable pad is drying, provided both are the correct replacement. It does not mean two pads should be layered together in the furnace.

Duraflow 917763 replacement mesh filters for specified A-coils

For a cooling coil that specifically uses the 917763 replacement pattern, this listing is a pair of washable aluminum mesh panels measuring 16 by 19 by 1/8 inch. It is an aftermarket Duraflow product, not a claim that every Intertherm A-coil takes a 16-by-19-inch filter.

Nordyne’s C5QA/C5DA coil specifications illustrate why the exact coil suffix matters: their filter table lists 917763 for some configurations and different filter numbers for others. Compare the complete coil designation and original filter shape, including any bends or notches. Do not transfer a retailer’s MERV value from another selected size or assume that a mesh panel is equivalent to a pleated indoor-air-quality filter.

Can you use a pleated filter in an Intertherm furnace?

Only when the particular system’s filter rack and airflow requirements allow it. A standard one-inch pleated filter is not a drop-in replacement for a thin door pad held by wire. Likewise, the fact that a thicker filter can be squeezed behind a door does not establish compatibility. Do not modify the door, obstruct ventilation openings or force the retaining hardware to accommodate an unsuitable filter.

MERV describes particle-capture performance; it does not certify that a filter fits your furnace. The EPA recommends choosing the highest appropriate efficiency your system fan and filter slot can accommodate, with professional advice where needed. A technician can check the equipment’s airflow and pressure requirements before an upgrade. There is no single maximum MERV rating that can responsibly be assigned to every Intertherm model.

If better particle filtration is the goal, ask about a properly specified filter cabinet or a suitable portable air cleaner rather than improvising a restrictive pad arrangement. Keep that decision separate from replacing a missing or damaged original filter.

Cleaning and replacement without changing the system

The M1 owner’s manual calls for monthly filter cleaning or replacement during heating and cooling use. The manufacturer’s CMF2 installation and maintenance manual also recommends monthly attention, with more frequent checks when construction dust is present. Follow your model’s own schedule and the filter maker’s washing instructions.

1. Turn off electrical power as directed by the furnace manual before accessing the filter. Limit the work to the homeowner maintenance the manual permits.
2. Note the filter’s original position and retainers. Remove the filter carefully without disturbing wiring, burners, gas components or the cooling coil.
3. Wash only a filter explicitly identified as washable. Replace disposable media and any pad or mesh panel that is torn, deteriorated or no longer seats correctly.
4. Let a washed filter dry fully according to its instructions. Refit it in the specified orientation with the original retention method secure.
5. Reinstall the access door correctly before restoring operation. Do not bypass a door switch or run the furnace with the filter removed.

A filter change is not a substitute for diagnosing repeated shutdowns, weak airflow or unusual operation. If the correct clean filter is installed and the problem continues, arrange professional service rather than repeatedly resetting the furnace or removing filtration to keep it running.

Buying checklist

Before checkout, match five things: the complete equipment model, replacement part number, filter construction, actual dimensions and package count. For a coil filter, add the coil model and panel shape. Check the selected variant again on the product page; a listing may offer multiple sizes under one product family.

For M1 equipment specifying 669064, start with the documented Nordyne replacement family. For a confirmed 16-by-26-inch foam door application, compare the F162625 two-pack. For a coil specifying the 917763 pattern, compare the exact mesh pair. When none matches the manual, stop shopping by brand name and identify the correct part first.

Image note: Existing category illustration retained from original article.