How to Troubleshoot an Oil Furnace
Oil-fired burners are used in many parts of the country as the basic heat source for warm air and hot water heating systems. Most of the home oil systems in use today are called pressure burners. In this type of system, oil is sprayed into a combustion chamber at high pressure, propelled by a blower, and ignited by an electric spark.The oil continues to burn as the mist is sprayed. While there aren't many quick fixes you can undertake yourself on these types of furnaces, good regular maintenance can help eliminate many problems. Here are a few oil furnace maintenance tips:
From annoying noise to low heat, there are many problems that can strike your oil furnace. Click here for instructions on how to deal with specific issues. |
- During the heating season, check the smoke from the chimney. If the smoke is black, the furnace is not burning the oil completely and fuel is being wasted. Call a professional service person for adjustments.
- Clean the blower at the beginning of the heating season and again about midway through the season.
- Clean soot from the stack control about midway through the heating season.
- If the blower motor has grease or oil fittings, lubricate the fittings midway through the heating season with cup grease or 10-weight nondetergent motor oil (not all-purpose oil), available at hardware stores.
- Clean the thermostat before each heating season.
�2006 Publications International, Ltd.
Most oil furnaces in use today are called pressure burners. In this type of system,
oil is sprayed into a combustion chamber at high pressure.
To become familiar with your oil furnace, remove the access panel covering the burner blower by removing the retaining screws around the rim of the housing. You can access the air blower and filter through a metal panel on one side of the furnace. The panel is held by either hooks or retaining bolts; slip the panel up and off the hooks or remove the bolts and lift the panel off. Most furnaces have switches and reset buttons located on the motor or in a switch box outside the furnace housing. These are usually identified with stampings or labels, such as DISCONNECT SWITCH, RESET, and so on. The stack control sensor, a safety device that monitors burner operation, is positioned in the stack and held with a series of retaining bolts.
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The oil filter should be changed or cleaned at the start of the heating season and about midway through the season. Here's how to clean or replace the filter:
Step 1: Close oil shutoff valve between fuel tank and filter.
Step 2: Unscrew bottom or cup of filter housing, and remove filter.
Step 3: If filter is disposable, insert new one of same size and type. If furnace has permanent filter, clean filter according to furnace manufacturer's recommendations.
Step 4: Replace old filter gaskets with new ones.
Step 5: Screw in bottom of housing, and open oil shutoff valve.
 �2006 Publications International, Ltd. Clean the pump strainer after cleaning the oil filter. To reach the strainer, unbolt the cover of the pump housing and lift off the cover. |
Step 1: Unbolt cover of pump housing (where oil line enters burner), and lift off cover.
Step 2: Remove thin gasket around rim. Find and remove strainer, which is a cylindrical or cup-shape wire mesh screen.
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Step 4: Inspect strainer. If it's torn or badly bent, replace it with new pump strainer of the same type.
Step 5: Set strainer into place on pump, place new gasket on rim, and bolt cover of pump housing back on.
Switches
Some oil furnaces have two master switches. One is located near the burner unit, and the other is near the furnace housing or even at a distance from the furnace. Make sure these master switches are both turned to the ON position.
Stack Control
The stack control of the oil furnace, located in the stack, is a safety device that monitors the operation of the oil burner. If the burner fails to ignite, the stack control shuts off the motor. Frequently, however, a furnace shutdown is caused by a malfunctioning stack control rather than by the burner.
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The stack control gradually becomes coated with soot during the heating season. To keep it working properly, clean the control every month or as soon as it becomes soot-covered. Here's how to clean the stack control:
Step 1: Remove bolts that hold control in stack. Pull out sensor and its housing.
Step 2: With brush dipped in soapy water, remove all soot from control. Wipe control dry with soft cloth.
Step 3: Before replacing control, clean stack. Spread newspaper to protect floor, then disassemble stack. As you work, remove soot and debris from each section by tapping them firmly on newspaper-covered floor.
Step 4: After cleaning sections, reassemble them in reverse order. Make sure stack sections are properly aligned and firmly connected.
Step 5: Finally, reposition stack control in stack, and reseal connection to chimney with refractory cement.
 �2006 Publications International, Ltd. Clean the stack control every month. To remove the control, turn off the power to the furnace, then back out the bolts that hold it in the stack. |
If the stack control or electric-eye safety switch is especially dirty, the furnace may not be properly set to burn the fuel completely. In this case, call a professional service person for adjustment.
Caution: Do not attempt to replace these controls yourself.
Draft Regulator
The draft regulator, located on the stack, is closed when the burner is off but opens automatically to let air into the chimney when the burner is turned on. Accumulated soot and rattling are signs that the draft regulator needs to be adjusted. Too much air in the chimney wastes heat; too little air wastes fuel by failing to burn it completely. To increase the airflow, screw the counterweight inward. To decrease airflow, turn the counterweight outward. The draft regulator should be adjusted by a professional service person as part of regular annual maintenance.
Limit Switch
The limit switch is a safety control switch and is located on the furnace just below the plenum. If the plenum gets too hot, the limit switch shuts off the burner. It also shuts off the blower when the temperature drops to a certain level after the burner has shut off. If the blower runs continuously, either the blower control on the thermostat has been set to the ON position, or the limit control switch needs adjustment.
To determine the problem, check the thermostat. If the blower control has been set to ON, change it to AUTO; if blower control is already on AUTO, the limit switch needs adjusting. To do this, remove the control's cover and find the toothed dial underneath. One side is marked LIMIT; don't touch this side. The other side is marked FAN. There are two pointers on the fan side; the blower turns on at the upper pointer setting and shuts off at the lower pointer setting. Pointers should be set about 25 degrees apart. Set the upper pointer at about 115 degrees Fahrenheit and the lower one at about 90 degrees Fahrenheit.
Burner Adjustment
Do not try to adjust the burner of an oil furnace; call a professional service person.
Finally, we have electric furnaces and heaters. Electric heat is in some ways much simpler than either gas or oil, but it can still have its fair share of problems. Keep reading to the next section to learn how to maximize the efficiency of your electric furnace.
