The Intertherm furnace filter location can vary by model but is commonly found in accessible slots on the return air duct, plenum, or the furnace cabinet. This article explains how to locate, remove, and replace Intertherm furnace filters, highlights common model-specific locations, and offers maintenance tips to improve efficiency and indoor air quality. Knowing the exact filter location reduces maintenance time and prevents damage.
| Intertherm Model | Common Filter Location | Filter Type |
|---|---|---|
| Intertherm Upflow/Downflow Units | Return Plenum Or Side Access Slot | Disposable Panel Filters 1″ Or 4″ |
| Intertherm Mobile Home/Packaged Units | Front Access Panel Or Bottom Return Grille | Flat Panel Or Custom Size |
| Intertherm Horizontal Units | Side Return Or Slide-Out Tray | 1″ Panel Or Extended Media |
How Furnaces And Filters Work: Why Location Matters
The furnace filter protects blower components and heat exchange surfaces by capturing dust, lint, and airborne particles before air circulates through the heat exchanger. Correct filter placement ensures optimal airflow and heating efficiency. A mislocated or missing filter can reduce system performance and increase energy costs.
Intertherm furnace filter location affects maintenance frequency because filters in dusty return locations clog faster. Knowing where the filter sits helps owners perform timely replacements and avoid service calls.
Common Intertherm Filter Locations By Unit Type
Upflow And Downflow Furnace Units
Upflow and downflow Intertherm furnaces typically place the filter at the return plenum or in a side-access slot on the furnace cabinet. Upflow units draw air from the bottom, while downflow units draw from the top, but both often use a removable access that holds a 1-inch or thicker filter.
Horizontal Units
Horizontal Intertherm furnaces used in attics or crawlspaces commonly use a slide-out filter tray on the side of the cabinet. The filter may face a return opening and can be accessed by removing a small panel or unscrewing a cover.
Packaged And Mobile Home Units
Intertherm packaged roof or mobile home furnaces frequently locate the filter behind the front access panel or in the return air grille. Some models use unique flat or custom-sized filters mounted under the control box or at the bottom of the unit.
How To Identify The Filter Location On Your Intertherm Unit
First, locate the model and serial number on the furnace nameplate; this helps when checking manuals or online resources. The nameplate usually appears on the furnace cabinet exterior or inside the access panel. With the model, consult Intertherm documentation or manufacturer cross-reference guides for filter details.
Next, inspect the return air duct, return grille, and the furnace cabinet for removable panels. Look for a small door or slot labeled “filter” or a seam with screws or latches. Filters can hide behind the blower compartment or near the air handler.
Step-By-Step: Safely Accessing And Replacing The Filter
Before service, turn off power to the furnace at the thermostat and the switch at the furnace or breaker. This reduces the risk of injury or damage to components during filter removal.
Open the access panel or grille. If the filter sits in a slide-out tray, gently pull it straight out. Note the airflow direction arrow on the filter frame; install the new filter with the arrow pointing toward the furnace fan.
Measure the old filter to confirm size before buying a replacement. Common sizes include 16x20x1 and 20x25x1, but Intertherm units sometimes use thicker or proprietary sizes. Replace panels and restore power after installing the new filter.
Filter Types And Recommendations For Intertherm Furnaces
Intertherm systems accept several filter types: standard 1-inch disposable fiberglass or pleated filters, 4-inch media filters in a dedicated slot, and washable electrostatic options in some models. Each type balances filtration efficiency and airflow restriction differently.
- 1-inch Disposable Pleated Filters — Good balance of cost and filtration; replace every 1–3 months depending on use.
- 4-inch Media Filters — Capture more particles and last longer (6–12 months); require a compatible slot or pocket.
- Washable Or Electrostatic Filters — Reusable but require cleaning and can restrict airflow if not maintained.
Choose a minimum MERV 8 for better filtration without excessive airflow loss. Higher MERV ratings (11–13) improve particle capture but could strain older blower motors if the filter location or design was not intended for dense media.
Troubleshooting Common Filter Location Issues
No Visible Filter Opening
Some Intertherm units hide the filter behind the furnace blower or inside the return duct. If no access panel is obvious, check under the control panel or behind the kickplate. Consult the user manual using the model number for diagrams showing filter placement.
Filter Holds In Unusual Orientation
If the filter appears sideways or behind a bracket, carefully remove nearby screws and inspect for a slide-out tray or bracket. Take photos for reference before disassembly to ensure proper reassembly.
Proprietary Or Custom Sizes
Mobile home units and older Intertherm models may use nonstandard filter sizes. Measure the filter or opening and search for replacement filters by dimension or cross-reference the model number with aftermarket suppliers.
Maintenance Tips To Extend Furnace Life And Efficiency
Check the filter monthly during heavy use seasons and replace at the first sign of visible dirt. Regular filter changes reduce wear on the blower motor and improve heat exchanger efficiency.
Keep the return grille and surrounding area clean and unobstructed. Ensure the filter is the correct orientation and fully seated to prevent air bypass that deposits dust on internal components.
Schedule professional HVAC inspections annually to check for hidden issues like clogged burners, failing blowers, or duct leaks that simple filter changes do not address.
When To Call A Professional
If the furnace shows restricted airflow after a new filter, produces unusual noises, or the filter location is inaccessible without partial disassembly, contact a licensed HVAC technician. Professionals can verify correct filter type, inspect the blower motor and ductwork, and recommend upgrades such as improved filtration pockets or media filters.
Owners should also seek service if the furnace cycles poorly after filter replacement, which may indicate control issues or a need for duct balancing.
Safety And Warranty Considerations
Always use the correct filter type and size specified by Intertherm. Installing an incompatible filter or modifying the cabinet to fit a different filter can void warranties and create safety hazards.
Follow all manufacturer-recommended safety procedures when accessing the furnace, including disconnecting electrical power and ensuring the gas supply valve is closed if working near gas components.
Resources For Finding Model-Specific Filter Locations
Intertherm user manuals, OEM parts diagrams, and retailer cross-reference tools are the best sources for exact filter location. Many manuals are available online by searching the Intertherm model number plus “manual” or “filter location.”
HVAC forums and YouTube repair channels often show model-specific walkthroughs. When using third-party content, verify alignment with the exact model number to avoid incorrect guidance.
Quick Checklist For Locating And Replacing An Intertherm Filter
- Turn off furnace power at the breaker and switch.
- Find the furnace nameplate and note the model number.
- Inspect return grille, plenum, and cabinet sides for removable panels.
- Remove access panel or slide-out tray to access the filter.
- Note filter size and airflow arrow, then replace with the correct type.
- Restore panels and power, then test furnace airflow and operation.
Key Takeaways About Intertherm Furnace Filter Location
Intertherm furnace filter location commonly includes the return plenum, a side-access slot, slide-out tray, or behind a front panel for packaged units. Correct identification and regular replacement are critical for system efficiency and longevity.
Model numbers determine exact placement and filter sizes; owners should consult manuals or professional HVAC technicians for unusual configurations or custom-sized filters.
Additional Links And Replacement Parts
For replacement filters, owners can use major HVAC parts retailers and online marketplaces by searching the exact filter dimensions or the Intertherm model number. OEM Intertherm parts or certified aftermarket filters ensure proper fit and airflow performance.
Contact local HVAC professionals or the Intertherm customer support line for assistance locating hard-to-find parts or clarifying installation requirements.