Maintaining An Oil furnace

Step 6—Inspecting and Maintaining the Firing Assembly:

The firing assembly if the most important part of the furnace, and is considered the heart of the furnace.  It contains a nozzle, which sprays a fine mist of oil into the combustion chamber, a fan blows air into the chamber, and electrodes produce sparks, which ignites the flame.  If any part of this system does not function properly, a flame can be created and your furnace will not heat. To begin, first remove the oil line, which runs to from the firing assembly to the pump.  Loosen the bolts holding the assembly in place.  Carefully pull the assembly out, turning it as needed to avoid bumping the electrodes against anything.

If there is a housing around the nozzle, remove this.  Some firing assemblies do not have housings around the spray nozzle.  The spay nozzle is designed to shoot/spray a certain pattern and volume of oil per hour.  The volume and spray pattern will vary from furnace and manufacturer.  For this reason it is vital that you read and understand your manufacturer’s instructions on the correct volume and spray patter for your particular furnace.  To remove the spay nozzle, place one wrench on the hex nut located on the oil line and another wrench on the nozzle.  While holding the oil line steady, loosen the nozzle and then remove it. Carefully inspect the nozzle to discover the size and spray angle.  This is usually stamped on the hex end of the nozzle.  If the spray nozzle is rated less than 1.5GHP (gallons per hour), you will have to replace it.  The insert, which comes with the new nozzle, will indicate the size of the nozzle.  Make sure that you replace the old nozzle with the same correct size.  If the nozzle is rated grater than 1.5GPH, then you only need to clean it.

To clean the nozzle, first unscrew the strainer.  This is a tiny basket looking device located on the back of the nozzle.  To take the nozzle apart, you will have to place the screwdriver inside the nozzle and then turn, backing out the locknut.  Once you have the nozzle apart, soak all of the pieces in pain thinner.  Then take an old toothbrush and gently brush the nozzle.  DO NOT USE a metal brush, as this will damage the nozzle.  After you have cleaned all the grooves, all the parts to soak more as you inspect and clean the electrodes.

The electrodes consist of a wire encased in a porcelain sleeve and are what produces the spark that ignites the oil.  To remove the electrode, loosen the screw that holds it in place, then closely examine the sleeve for any cracks.  If you notice any, then replace it with the same model number.  If the sleeve is okay, then clean it with a rag and paint thinner.  Next, examine the electrodes and file the ends into sharp points.

Step 7—Reassembling:

Remove all the nozzle parts from the paint thinner, then rinse them with water and allow then to air dry.  Once they have completely dried, thread the nozzle and finger-tight, then tighten a quarter-turn with the wrench.  Do not over tighten.

Next, tighten the screw just enough so that the electrodes can turn and move slightly back and fourth, but will maintain their position.  Then using calipers, adjust the electrodes and set the distance between then according to your manufacturer’s instructions.  You will also need to adjust he forward and backward alignment.  When the electrodes are correctly set, tighten the screw to firmly hold them in place.  Once this has been accomplished, replace the firing assembly, and then reattach the oil line.  Make sure to double-check all connections before testing the furnace.  Turn on the oil at the cutoff valve located near the filter.  Then TURN ON the power at the circuit breaker.

NOTE: Before you run your finance, you may need to prime the pump.  To do this, place the end of the oil line (that you disconnected to remove the firing assembly) over a bucket.  Turn on the power to the furnace and have a helper turn the thermostat to its highest setting.  Allow the oil to pump through the line for approximately 10 to 15 seconds, and then have your assistant turn the thermostat back down.  Reconnect the oil line.