How to Change Oil Filter for Furnace?

Changing the oil filter on your furnace is a vital maintenance task that helps ensure the efficient and reliable operation of your heating system. This process involves a few key steps, primarily focusing on safety, cleanliness, and proper installation of the new filter.

Maintaining your oil-fired furnace's efficiency and longevity often comes down to regular tasks like changing the oil filter. This essential component traps impurities in the fuel before they can reach the burner, preventing clogs and costly repairs.

Before you begin, ensure you have the correct replacement filter for your furnace model, typically found on the old filter itself or in your furnace's manual.

Tools and Materials You Might Need

Having the right tools on hand will make the process smoother and safer.

Step-by-Step Guide to Changing Your Furnace Oil Filter

Follow these steps carefully to replace your furnace's oil filter safely and effectively:

1. Turn Off the Electricity and Oil Supply

Safety First: This is the most crucial step. Before touching any part of your furnace or its fuel lines, you must completely cut off both the electrical power and the oil supply.

• Electricity: Locate your furnace's dedicated circuit breaker in your home's electrical panel and switch it to the "OFF" position. Alternatively, many furnaces have a separate kill switch near the unit, often resembling a light switch. Flip this switch off.
• Oil Supply: Find the main oil shut-off valve on the oil line leading to the furnace. It's usually a lever or a knob; turn it to the "OFF" position. This prevents oil from flowing while you're working.

2. Remove the Filter Base

Once power and oil are off, you can proceed to the filter.

• Place a drop cloth or old rags beneath the filter assembly to catch any oil spills.
• Position an oil pan or tray directly under the filter canister.
• Using a wrench or pliers, carefully loosen the nut or clamp holding the filter canister or base in place. There might be some residual oil that drains out, so be prepared.
• Gently detach the filter base or canister from the oil line. Some filters are housed in a re-usable canister, while others are disposable cartridge types.

3. Clean the Filter Canister Base

This step is essential for preventing future issues and ensuring a good seal with the new filter.

• If your filter uses a reusable canister, thoroughly clean the inside of the canister and its base with a wire brush or rag. Remove any sludge, debris, or sediment that has accumulated.
• Inspect the rubber O-ring or gasket on the canister base. If it's cracked, brittle, or damaged, replace it with a new one (often included with the new filter). A compromised O-ring can lead to oil leaks.

4. Add the New Furnace Oil Filter

Install the new filter carefully to ensure proper function and prevent leaks.

• If your system uses a disposable cartridge filter, simply discard the old one and insert the new cartridge into the clean canister base. Ensure it's seated correctly.
• For canister-style filters, ensure the new filter element is oriented as per the manufacturer's instructions (there's often an arrow indicating flow direction).
• Lubricate the new O-ring or gasket with a small amount of clean fuel oil or light grease to help create a good seal.
• Carefully reattach the filter canister or base to the oil line, tightening the nut or clamp by hand first, then a quarter turn more with a wrench. Do not overtighten, as this can crack the housing or damage the gasket.

5. Bleed Air from the Filter and Turn the Oil Supply Back On

After installing the new filter, air can become trapped in the oil line, which will prevent the furnace from firing up. This air must be bled out.

• Turn Oil Supply On: Slowly open the main oil shut-off valve to allow oil to flow back into the system. Check for any immediate leaks around the new filter.
• Bleed Air: Locate the bleeder valve on your oil pump, which is usually a small screw or nut.
  • Place a container or rag under the bleeder valve.
  • Loosen the bleeder valve slightly with a wrench, typically a quarter to half-turn.
  • Go to your thermostat and set it to call for heat. The furnace will attempt to start, and the oil pump will begin to run.
  • As the pump runs, you'll see air bubbles and then a steady stream of oil (without bubbles) coming out of the bleeder valve.
  • Once a steady, bubble-free stream of oil emerges, tighten the bleeder valve securely while the pump is still running. Do not overtighten.
  • If the furnace doesn't fire after a few attempts, you may need to repeat the bleeding process.

6. Clean the Pump Strainer (If You Have One)

Some furnace oil pumps also have a small strainer or screen designed to catch finer particles that bypass the main filter.

• If your pump has one, this is an excellent time to clean it. Refer to your furnace's manual for its exact location and removal instructions.
• Typically, it involves removing a few screws to access the strainer, cleaning it thoroughly, and then replacing it along with any associated gaskets.
• This step is optional but highly recommended for comprehensive fuel system maintenance.

Once these steps are complete, your furnace's oil filter has been successfully changed, and the system is ready for reliable operation.