How To Prime An Oil Furnace

When the cold winter months hit, it’s crucial to ensure your oil furnace is operating efficiently and effectively. One essential step in maintaining your furnace is priming it before use. By priming the furnace, you can remove air from the fuel line, preventing potential issues and ensuring smooth ignition.

Priming an oil furnace is a straightforward process that can be easily accomplished by homeowners with basic tools. However, it’s important to follow the specific instructions provided by the furnace manufacturer. Neglecting this step can lead to operational problems, including difficulty igniting the furnace or even complete failure. In addition, properly primed furnaces are typically more energy-efficient, reducing heating costs and environmental impact.

To begin the priming process, locate the fuel line on your furnace. It typically consists of a flexible hose connecting the oil tank to the furnace. Ensure that the fuel line is securely connected at both ends and that there are no cracks or leaks. Next, open the fuel valve located near the tank. This action allows fuel to flow into the fuel line towards the furnace. Allow the fuel to flow for several seconds to ensure that the line is completely filled.

Understanding the Importance of Priming

To ensure the smooth and efficient operation of an oil furnace, proper priming is crucial. Priming essentially involves filling the fuel line and other components with oil to expel any air and create a continuous path for the oil to flow. This process is necessary to eliminate air pockets that can cause combustion problems and even lead to equipment damage. By priming the furnace, you create a stable operating environment that guarantees optimal performance and extends the lifespan of your system.

Let’s delve into the specific benefits of priming an oil furnace:

Smooth Startup: Proper priming ensures that the furnace starts up without delay or hesitation. Air pockets in the fuel line can create resistance to oil flow, leading to delayed ignition or incomplete combustion.
Stable Combustion: A well-primed furnace ensures a steady and efficient combustion process. Air pockets in the system can cause fluctuations in the air-to-fuel ratio, resulting in incomplete combustion and wasted fuel.
Increased Efficiency: A properly primed furnace operates at optimal efficiency, ensuring maximum heat output with minimal fuel consumption. Air pockets can reduce heat transfer and lower overall system efficiency.
Extended Lifespan: By eliminating air pockets and ensuring proper lubrication, priming helps prevent premature wear and damage to the furnace’s components. This helps extend the lifespan of the equipment and reduces the need for costly repairs or replacements.

Clearing the Fuel Line

If you suspect a blockage in the fuel line, you’ll need to clear it before priming the furnace. Follow these steps:

1. Turn off the furnace and the oil supply.

Locate the oil shutoff valve, typically near the oil tank, and turn it clockwise to close it. Next, go to the furnace and switch off the power at the main electrical panel.

2. Bleed off any pressure in the line.

Connect a fuel line hose to the bleed valve on the oil filter. Open the valve slightly to release any remaining pressure in the line. Close the valve once the pressure has been released.

3. Disconnect the fuel line.

Locate the fuel line connection at the oil filter and use a wrench to loosen the nut holding it in place. Carefully disconnect the fuel line from the filter.

4. Inspect and clean the fuel line.

Thoroughly inspect the fuel line for any kinks, cracks, or blockages. If any blockages are apparent, use a thin wire or pipe cleaner to gently clear them out. You can also blow compressed air through the line to remove any debris.

Blockage	Possible Cause	Solution
Sediment	Dirt or sludge buildup	Flush the line with clean fuel oil
Ice	Condensation freezing in the line	Thaw the line with warm water or a heat gun
Rust	Corrosion from moisture	Replace the affected section of the line

5. Reconnect the fuel line.

Reattach the fuel line to the oil filter and tighten the nut securely. Open the bleed valve again to allow some fuel to flow through the line. Close the valve once the fuel is flowing smoothly.

6. Turn on the oil supply and the furnace.

Open the oil shutoff valve counterclockwise to restore the oil supply. Then, go to the furnace and turn on the power at the main electrical panel. The furnace should now be ready to prime.

Connecting the Primer Pump

To ensure proper priming, follow these detailed steps to connect the primer pump to your oil furnace:

Inspect the Primer Pump: Before connecting the pump, inspect it to ensure it’s clean and free of any obstructions.
Locate the Primer Pump Connection: Identify the connection point on the furnace where the pump will be attached. It’s typically a small hole or port labeled "Oil Primer."
Attach the Primer Pump: Carefully thread the primer pump’s body onto the connection point on the furnace. Tighten the pump securely using a wrench or pliers to prevent leaks.
Connect the Pump Hose: The primer pump will have a rubber hose attached to its outlet. Insert the free end of the hose into a clean, empty container. This container will collect the air and oil that is removed during the priming process.
Prepare the Oil Line: If your furnace has an oil cutoff valve, open it to allow oil flow to the primer pump.

Step	Action
a	Turn off the furnace’s power switch and unplug it.
b	Remove the oil line from the oil filter housing.
c	Insert the primer pump’s flow arrow into the oil filter housing.
d	Reattach the oil line to the primer pump’s flow arrow.
e	Tighten the oil line connections securely.

Restoring the Fuel Line

Restoring the fuel line involves clearing the air from the line and bringing diesel fuel back into the fuel line. Here’s a step-by-step guide on how to do it:

Locate the fuel line bleeder screw: This is usually a small screw located on the fuel line near the fuel filter.
Place a container under the bleeder screw: To catch any fuel that may spill out.
Loosen the bleeder screw: Use a wrench or pliers to turn the screw counterclockwise until diesel fuel starts to flow out.
Tighten the bleeder screw: Once fuel starts to flow, immediately tighten the screw clockwise to stop the flow.
Repeat steps 2-4: Repeat the process until no more air comes out and only diesel fuel flows out.
Tighten all connections: Ensure that all connections along the fuel line are tight to prevent leaks.
Purge the fuel line: Turn on the fuel pump and let it run for a few minutes to purge any remaining air.
Additional Tips for Purging:
- Use a hand pump: A hand pump can be attached to the fuel line to manually pump fuel through the line and remove air.
- Shake the fuel line: Gently shake the fuel line while purging it to help dislodge any trapped air bubbles.
- Tap the fuel line: Tap lightly on the fuel line along its length to help release air pockets.
- Use a fuel line cleaner: Pour a fuel line cleaner into the fuel tank to remove any contaminants that may be causing air leaks.
- Check for leaks: Regularly check for fuel leaks along the fuel line, especially around connections.

Troubleshooting Common Issues

9. No Fuel Flow

If you’ve followed all the priming steps and still don’t have fuel flow, here are some additional tips:

a. Check the fuel line for kinks or blockages. Ensure it’s properly connected to the tank and the furnace.

b. Inspect the fuel filter. It may be clogged, restricting fuel flow. Clean or replace it if necessary.

c. Open the fuel shut-off valve completely to ensure maximum flow.

d. Verify that the oil tank has sufficient fuel. A low fuel level can hinder priming.

e. Manually prime the pump. Disconnect the inlet line from the pump and insert it into a container of fuel. Turn on the pump and check if it draws fuel. This will help identify any issues with the pump itself.

f. Ensure the nozzle is not clogged or damaged. A blocked nozzle can prevent fuel from reaching the combustion chamber.

Maintaining Your Primed Furnace

Once your oil furnace is primed, you need to maintain it properly to ensure it runs efficiently and safely.

1. Inspect the Furnace Regularly

Check the furnace monthly for any leaks, blockages, or loose parts. If you find any issues, fix them promptly to prevent further damage.

2. Change the Oil Filter

Replace the oil filter every month or according to the manufacturer’s instructions. A clogged filter can restrict the flow of oil and cause the furnace to overheat.

3. Clean the Flame Sensor

Use a soft brush or cloth to clean the flame sensor located in the combustion chamber. A dirty sensor can prevent the furnace from detecting a flame and shutting off.

4. Lubricate Moving Parts

Apply lubricant to the moving parts of the furnace, such as the fan motor and blower wheel, according to the manufacturer’s instructions.

5. Check the Flue Pipe

Inspect the flue pipe for blockages or corrosion. A blocked flue can prevent exhaust gases from escaping and create a fire hazard.

6. Test the Oil Line

Disconnect the oil line from the furnace and use a flashlight to check for any cracks or leaks. Replace the line if necessary.

7. Keep the Furnace Clean

Use a vacuum cleaner to remove dust and debris from the furnace and its surroundings. A clean furnace will operate more efficiently and prevent premature breakdowns.

8. Schedule Professional Maintenance

Have your furnace inspected and serviced by a qualified HVAC technician annually. They can perform a thorough inspection, clean and adjust components, and identify any potential issues before they become major problems.

9. Store Your Furnace Properly

If you plan to store your oil furnace for an extended period, take the following steps:

Drain the oil from the tank and lines.
Cover the furnace to protect it from dust and moisture.
Disconnect the electrical power supply.

10. Troubleshooting Common Furnace Problems

If you encounter any issues with your furnace, here are some common problems and their potential solutions:

Problem	Solution
Furnace won’t turn on	Check the power supply, fuse, and circuit breaker.
Furnace makes a banging noise	Inspect the blower motor and fan belt for any loose parts or debris.
Furnace emits a burning smell	Check the flame sensor and clean the combustion chamber.
Furnace doesn’t heat evenly	Adjust the dampers to distribute heat more evenly.
Furnace leaks oil	Inspect the oil line and connections for any cracks or leaks.

Priming an oil furnace is a necessary step to take before starting it up for the first time or after it has run out of oil. The purpose of priming is to fill the fuel lines and pump with oil so that the furnace can start and run properly. This can be done by following these steps:

Turn off the power to the furnace at the circuit breaker or fuse box.
Locate the oil filter and loosen the bleeder screw.
Place a container under the bleeder screw to catch any oil that may leak out.
Open the bleeder screw and allow the oil to flow out until it is free of air bubbles.
Close the bleeder screw and tighten it snugly.
Turn on the power to the furnace.
Start the furnace and allow it to run for a few minutes until the oil lines are primed and the furnace is running smoothly.