How to Replace the Combustion Chamber of an Oil Furnace
Shut off the power.,Shut off fuel supply at the bottom of the fuel tank.,Test to verify power is off before continuing., Allow the furnace to cool., Clear cables and power lines that will interfere with the furnace door from opening., Unbolt or...
Step-by-Step Guide
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Step 1: Shut off the power.
Most furnaces have a service switch on or near the boiler itself designed specifically for service personnel to use that ensures the power remains off while they are working on the equipment.
If unable to locate the service switch, shut off power one way or another to prevent furnace from starting.
Place a note on the electrical panel explaining the the circuit is off because the furnace is being serviced. ,,, You risk injury from burns if you do not allow enough time for the furnace cool down before attempting this work., Most modern furnaces have the oil burner supported through an opening in a hinged door.
Take a photo with your cell phone or camera before beginning to help you remember how to reconnect the lines and cables later.
If the fuel line must be removed, be sure also shut off the oil supply valve at or just before the point of disconnect.
Many times, the easiest point and method to disconnect is by unbolting the fuel pump cover from the furnace motor itself.
Gently move it out of the way and try not to move the fuel lines any more than necessary to help minimize the chances of kinking lines or disrupting the mating surfaces between flared ends of the lines and compression fittings.
Remove and (clean or) have a replacement filter ready to install when reassembling later., The door has an important gas-tight seal that is maintained usually by a hex nut or bolt that squeezes the door seal against the furnace opening.
If it is undamaged and you are not interested in replacing it, try not to disturb it., Wear personal protective equipment consisting of safety glasses, long sleeve shirt, protective gloves and mask to prevent inhaling fibers and getting them in your skin.
Wetting the inside of the chamber with water will help prevent fibers from becoming airborne but also reduces the ease with which a vacuum will be able to pick up the debris in the next step., Remove the soot, rust and other debris that has collected or formed on the floor and walls of the chamber.
A soot vacuum or HEPA vacuum is recommended if the inside hasn't been wet down in the previous step.
If it has been wet down, a common shop vacuum will do., Reach in and pull the preformed refractory lining from rear wall and blanket material on the floor out of the chamber.
Use a screw driver to gently break and scrape off the old lining material completely and then use a wisk broom to sweep all pieces into the garbage bag.
Gently clean steel surfaces with a wire brush.
Do not wedge screwdrivers and similar objects between boiler sections.
Wisk broom or vacuum all surfaces once again., There may be small liner blanket behind the preformed refractory liner that should be removed as well.
Clean the area the same as the inside of the chamber and vacuum., If the seal is undamaged and you do not want to replace it
- you can skip this step
- and those appearing later that describe replacement.
Run a screwdriver around the recessed channel to scrape it clean and then wire brush and wisk broom this area clean.,, You may need to tip it to get it into proper position.
Make sure it is all the way back against the rear wall by pressing with palms firmly all the way around., Orient the the blanket as per instructions and lay it inside the chamber.
Butt the blanket up against the bottom edge of the rear wall refractory liner and extend it out of the chamber.
Mark the blanket to indicate where it meets the outside edge of the opening to the chamber.
Arrange the blanket so the sides extend equally up the sides of the boiler wall.
Make a mark on the blanket and chamber floor so you can place it in the same position later., Use a straight edge and razor knife so it fits the chamber as per the instructions., The water glass is wet and sticky and will harden like glue when heated. Pour about 3/4 of the water glass onto the chamber floor and then spread it with gloved fingers.
Save the rest of the water glass to help secure the rope seal into the recess of the door in a later step.
If you are not replacing the rope seal, using more than needed to cover the area needed by the blanket will only drip and leak out the front of the chamber., Hold the blanket inside and above the chamber floor (above the water glass covered surfaces).
Align the marks on the blanket and the chamber floor.
When satisfied with the position, lower and press it into place .,, Some liners come with paper strips to help it slide over rough edges of the cast iron door.
Use them as needed to prevent cracking or breaking of the liner while pressing to fit.
The liner is considered in position when the burner opening is flush with the liner to as much as 1/4" recessed behind the liner
- or as the instructions indicate with your liner kit., This step should be skipped if you did not remove the undamaged rope seal in a previous step.
Remove the paper backing from the rope seal and press the adhesive side into the recess
- starting with the middle of the rope seal at the mid point at the top of the door.
Press the rope seal into the recess all the way around both sides of the door from top to bottom.
Cut the rope seal to allow them to overlap slightly at the bottom middle of the door.,, Try not to move the fuel lines any more than necessary to help minimize the chances of disturbing the mating surfaces between flared ends of the lines and compression fittings.
Wipe away any excess oil from lines, fittings and floor., Visually check for oil leaks at all fittings and correct as needed., If the burner fails to start and locks out, the oil pump may need to primed. The priming procedure can be found here:
Restart-a-Furnace-After-Running-out-of-Oil , Tighten fittings or make the necessary repairs to stop any and all leaks. -
Step 2: Shut off fuel supply at the bottom of the fuel tank.
-
Step 3: Test to verify power is off before continuing.
-
Step 4: Allow the furnace to cool.
-
Step 5: Clear cables and power lines that will interfere with the furnace door from opening.
-
Step 6: Unbolt or otherwise release the door to allow it to open.
-
Step 7: Control airborne fibers.
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Step 8: Vacuum loose particles in the chamber.
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Step 9: Arrange a heavy-duty trash bag with the open end under the opening to the furnace.
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Step 10: Remove the preformed refractory lining from the door.
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Step 11: Remove the rope seal from the inside edge of the door.
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Step 12: Clean up any addition debris and put in the trash bag; close up tightly and remove from the work area.
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Step 13: Locate and install the new preformed rear wall refractory liner as per instructions.
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Step 14: Test fit the blanket on the chamber floor.
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Step 15: Cut the blanket.
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Step 16: Apply water glass.
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Step 17: Ready the blanket for installation on the floor.
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Step 18: Install the door blanket around the burner opening as per instructions.
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Step 19: Install the preformed door refractory liner fully into the recesses of the door by slowly working it into place with hands.
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Step 20: Apply a few drops of water glass every few inches (or less) in the cleaned rope seal recess of the door.
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Step 21: Close the door fully and secure with the bolt or hex nut to re-establish the gas-tight seal.
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Step 22: Reconnect fuel lines / pump and filter / power.
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Step 23: Open all fuel shut off valves.
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Step 24: Turn on power (and adjust thermostat if required) to allow the burner start and allow to run for at least 15 minutes to cure water glass.
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Step 25: Inspect floor and fuel lines for evidence of leaking fuel oil.
Detailed Guide
Most furnaces have a service switch on or near the boiler itself designed specifically for service personnel to use that ensures the power remains off while they are working on the equipment.
If unable to locate the service switch, shut off power one way or another to prevent furnace from starting.
Place a note on the electrical panel explaining the the circuit is off because the furnace is being serviced. ,,, You risk injury from burns if you do not allow enough time for the furnace cool down before attempting this work., Most modern furnaces have the oil burner supported through an opening in a hinged door.
Take a photo with your cell phone or camera before beginning to help you remember how to reconnect the lines and cables later.
If the fuel line must be removed, be sure also shut off the oil supply valve at or just before the point of disconnect.
Many times, the easiest point and method to disconnect is by unbolting the fuel pump cover from the furnace motor itself.
Gently move it out of the way and try not to move the fuel lines any more than necessary to help minimize the chances of kinking lines or disrupting the mating surfaces between flared ends of the lines and compression fittings.
Remove and (clean or) have a replacement filter ready to install when reassembling later., The door has an important gas-tight seal that is maintained usually by a hex nut or bolt that squeezes the door seal against the furnace opening.
If it is undamaged and you are not interested in replacing it, try not to disturb it., Wear personal protective equipment consisting of safety glasses, long sleeve shirt, protective gloves and mask to prevent inhaling fibers and getting them in your skin.
Wetting the inside of the chamber with water will help prevent fibers from becoming airborne but also reduces the ease with which a vacuum will be able to pick up the debris in the next step., Remove the soot, rust and other debris that has collected or formed on the floor and walls of the chamber.
A soot vacuum or HEPA vacuum is recommended if the inside hasn't been wet down in the previous step.
If it has been wet down, a common shop vacuum will do., Reach in and pull the preformed refractory lining from rear wall and blanket material on the floor out of the chamber.
Use a screw driver to gently break and scrape off the old lining material completely and then use a wisk broom to sweep all pieces into the garbage bag.
Gently clean steel surfaces with a wire brush.
Do not wedge screwdrivers and similar objects between boiler sections.
Wisk broom or vacuum all surfaces once again., There may be small liner blanket behind the preformed refractory liner that should be removed as well.
Clean the area the same as the inside of the chamber and vacuum., If the seal is undamaged and you do not want to replace it
- you can skip this step
- and those appearing later that describe replacement.
Run a screwdriver around the recessed channel to scrape it clean and then wire brush and wisk broom this area clean.,, You may need to tip it to get it into proper position.
Make sure it is all the way back against the rear wall by pressing with palms firmly all the way around., Orient the the blanket as per instructions and lay it inside the chamber.
Butt the blanket up against the bottom edge of the rear wall refractory liner and extend it out of the chamber.
Mark the blanket to indicate where it meets the outside edge of the opening to the chamber.
Arrange the blanket so the sides extend equally up the sides of the boiler wall.
Make a mark on the blanket and chamber floor so you can place it in the same position later., Use a straight edge and razor knife so it fits the chamber as per the instructions., The water glass is wet and sticky and will harden like glue when heated. Pour about 3/4 of the water glass onto the chamber floor and then spread it with gloved fingers.
Save the rest of the water glass to help secure the rope seal into the recess of the door in a later step.
If you are not replacing the rope seal, using more than needed to cover the area needed by the blanket will only drip and leak out the front of the chamber., Hold the blanket inside and above the chamber floor (above the water glass covered surfaces).
Align the marks on the blanket and the chamber floor.
When satisfied with the position, lower and press it into place .,, Some liners come with paper strips to help it slide over rough edges of the cast iron door.
Use them as needed to prevent cracking or breaking of the liner while pressing to fit.
The liner is considered in position when the burner opening is flush with the liner to as much as 1/4" recessed behind the liner
- or as the instructions indicate with your liner kit., This step should be skipped if you did not remove the undamaged rope seal in a previous step.
Remove the paper backing from the rope seal and press the adhesive side into the recess
- starting with the middle of the rope seal at the mid point at the top of the door.
Press the rope seal into the recess all the way around both sides of the door from top to bottom.
Cut the rope seal to allow them to overlap slightly at the bottom middle of the door.,, Try not to move the fuel lines any more than necessary to help minimize the chances of disturbing the mating surfaces between flared ends of the lines and compression fittings.
Wipe away any excess oil from lines, fittings and floor., Visually check for oil leaks at all fittings and correct as needed., If the burner fails to start and locks out, the oil pump may need to primed. The priming procedure can be found here:
Restart-a-Furnace-After-Running-out-of-Oil , Tighten fittings or make the necessary repairs to stop any and all leaks.
About the Author
Carol Brooks
Writer and educator with a focus on practical crafts knowledge.
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