Lennox Furnace Filter Size By Model Number

Frequently Asked Questions: Lennox Furnace Filter Sizes by Model Number

Keeping your Lennox furnace running efficiently requires regular filter changes. One of the most common questions homeowners and facility managers have is, "What size filter does my Lennox furnace need?" This FAQ aims to answer that and other related questions to help you maintain your furnace properly.

Question 1: How do I find the correct filter size for my Lennox furnace?

Finding the correct filter size for your Lennox furnace is crucial for optimal performance. Here are the most reliable ways to determine the right size:

Check the existing filter: This is the easiest method. Remove the old filter and look for the size printed on the frame. The dimensions are usually listed in inches (e.g., 16x25x1).
Consult your furnace's owner's manual: The owner's manual will provide detailed specifications, including the recommended filter size. This is often the most accurate source of information.
Look on the furnace cabinet: Sometimes, the filter size is printed on a sticker or label located on the furnace cabinet itself. Look around the area where the filter is installed.
Use a Lennox filter size finder (if available): Some websites offer tools where you can enter your furnace model number and retrieve the correct filter size. Lennox's website might offer this feature, or third-party HVAC parts websites could. However, double-check the results with other sources for accuracy.

If you are unable to find the information using these methods, contacting a qualified HVAC technician is recommended. They can quickly identify your furnace model and provide the correct filter size.

Question 2: Why is using the correct filter size so important?

Using the correct filter size is vital for several reasons:

Airflow: An improperly sized filter can restrict airflow. A filter that is too small leaves gaps, allowing unfiltered air to bypass the filter and enter your furnace, potentially damaging components and reducing efficiency. A filter that is too large may not fit properly, causing it to bend or collapse, also impacting airflow.
Furnace Efficiency: Restricted airflow forces your furnace to work harder to heat your home, leading to increased energy consumption and higher utility bills.
Furnace Lifespan: Overworking your furnace can cause premature wear and tear on components, shortening its lifespan and potentially leading to costly repairs.
Air Quality: A properly sized filter effectively removes dust, pollen, pet dander, and other airborne particles from your home's air. An incorrect size allows contaminants to bypass the filter, reducing air quality.

In short, using the right filter size protects your furnace, saves you money, and improves your indoor air quality.

Question 3: Are there common Lennox furnace model numbers and their corresponding filter sizes?

While it's best to confirm the size using one of the methods mentioned above, here are some *common* Lennox furnace model numbers and their *typically* corresponding filter sizes. Note: This is not an exhaustive list, and it's always best to verify the size on your unit or in the manual.

Lennox EL296E: Often uses a 16x25x1 or 20x25x1 filter, but verify based on your specific unit.
Lennox SLP98V: Can use a variety of sizes depending on the specific configuration. Common sizes include 16x25x1, 20x25x1, or even a larger 20x20x1 or 20x30x1 for some installations. *Always double-check*.
Lennox ML193: Typically requires a 16x25x1 filter, but again, check your unit.
Lennox G61MPV: Often uses a 20x25x1 filter, but configurations can vary, so verify locally.
Lennox EL180E: This unit often takes a 16x25x1 filter, but it is critical to verify.

Important Considerations:

"Nominal" vs. "Actual" Size: Filter sizes are often listed as "nominal" sizes, which are rounded up. The "actual" size may be slightly smaller. For example, a filter listed as 16x25x1 might actually measure 15 3/4 x 24 3/4 x 7/8 inches. This small difference is normal and accounted for.
Filter Thickness: The last number in the filter size (e.g., the "1" in 16x25x1) represents the filter's thickness. While a slightly thicker filter *might* fit, it's generally best to stick with the recommended thickness. Using a significantly thicker filter could restrict airflow.

Never assume a filter size based solely on the model number. Always confirm using the methods mentioned earlier.

Question 4: What type of filter should I use in my Lennox furnace (MERV rating)?

The Minimum Efficiency Reporting Value (MERV) rating indicates a filter's ability to capture particles of different sizes. A higher MERV rating means the filter captures more particles, resulting in cleaner air.

MERV 1-4: These are basic filters that primarily capture large particles like dust and pollen. They offer minimal protection for your furnace and are generally not recommended for modern furnaces.
MERV 5-8: These filters offer a good balance between filtration and airflow. They capture dust, pollen, pet dander, and mold spores. These are suitable for many homes and offer good furnace protection.
MERV 9-12: These filters provide even better filtration, capturing smaller particles like smog and some bacteria. They are a good choice for people with allergies or asthma, but they can slightly reduce airflow.
MERV 13-16: These are high-efficiency filters that capture very small particles, including viruses and smoke. They are often used in hospitals and clean rooms. These filters can significantly restrict airflow and are generally not recommended for residential furnaces unless specifically approved by a qualified HVAC technician. Using too high of a MERV rating without proper system design could damage your furnace.

Recommendation: For most Lennox furnaces, a MERV 8 or MERV 11 filter provides a good balance of air filtration and airflow. However, always consult your owner's manual or a qualified HVAC technician to determine the best MERV rating for your specific furnace model and your home's needs. Consider your family's needs; do allergy sufferers live in your home?

Question 5: How often should I change my Lennox furnace filter?

The frequency of filter changes depends on several factors, including:

Filter type: Thicker, pleated filters generally last longer than thinner, fiberglass filters.
Air quality: Homes with pets, smokers, or high levels of dust require more frequent filter changes.
Furnace usage: If you run your furnace frequently, you'll need to change the filter more often.

General Guidelines:

1-inch filters: Change every 1-3 months.
2-inch filters: Change every 2-4 months.
4-inch filters: Change every 6-12 months.

Best Practice: Check your filter monthly. Hold it up to a light. If you can't see light through it, it's time to change it. It's better to err on the side of changing the filter too often than not often enough.

Setting a reminder on your calendar or using a smart home device can help you remember to change your filter regularly.

Question 6: What happens if I use the wrong MERV rating?

Using the wrong MERV rating, especially a rating that's *too high*, can lead to several problems:

Reduced Airflow: High-MERV filters are denser and restrict airflow more. This forces your furnace to work harder to push air through the system.
Overheating: Restricted airflow can cause your furnace to overheat, potentially damaging components like the heat exchanger.
Increased Energy Bills: A struggling furnace uses more energy, leading to higher heating bills.
Premature Furnace Failure: Overheating and stress can shorten the lifespan of your furnace.
Blower Motor Issues: The blower motor may work harder, leading to premature failure.

Using a MERV rating that's *too low* isn't as immediately damaging, but it results in poorer air filtration. More dust and debris can enter the furnace, potentially damaging components and reducing efficiency over time. Allergy sufferers might also notice a decrease in indoor air quality.

The key is to find the right balance between air filtration and airflow. Follow the manufacturer's recommendations and consult with an HVAC professional if you're unsure.

Question 7: Can I use a washable filter in my Lennox furnace?

While washable filters seem like a cost-effective and environmentally friendly option, they are generally not recommended for most Lennox furnaces, especially newer, high-efficiency models.

Here's why:

Inconsistent Filtration: Washable filters often don't filter as effectively as disposable pleated filters, especially when they start to age. They may not capture smaller particles, leading to poorer indoor air quality and potential damage to your furnace.
Maintenance Requirements: Washable filters require thorough cleaning and drying. If not cleaned and dried properly, they can become breeding grounds for mold and bacteria.
Airflow Restriction: Some washable filters, especially when dirty, can restrict airflow, leading to the same problems as using a high-MERV filter (overheating, increased energy bills, etc.).
Potential for Damage: The cleaning process can damage the filter over time, reducing its effectiveness and potentially allowing debris to enter the furnace.
Voiding Warranty: Using a non-recommended filter type, like a washable filter, may void your furnace's warranty.

Unless your Lennox furnace's owner's manual specifically recommends or approves the use of washable filters, it's best to stick with disposable pleated filters. While they require regular replacement, they offer consistent filtration, are easier to maintain, and are less likely to damage your furnace. You can find disposable filters in bulk to save money and ensure you always have replacements on hand.