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Ideal Building Inspections > Monthly Maintenance > Home Care E-Book > Forced Air Oil Furnace |
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| Oil Fired Forced Air Furnaces | ||||||||
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Oil-fired furnaces are very efficient
and durable, but they are more complicated than gas-fired furnaces. The
basic maintenance procedures described here will go a long way toward
keeping an oil furnace in good operating condition. However, making
repairs and dealing with major operational problems calls for equipment
and skills that few homeowners possess.
Oil-fired furnaces vary with
manufacturer and age, but are generally similar. A pressure or gun-type
burner is the most widely used. Oil is pumped from a storage tank into a
combustion chamber, where it is atomized for ignition by a high-voltage
spark. Just as in a gas-fired forced-air furnace, the flame heats a heat
exchanger that in turn warms the air circulated through the system by a
blower.
One difference among oil furnace
designs is the tank-to-furnace piping. Many systems have only a single
pipe, usually connected to an aboveground tank. If the tank becomes empty,
or if air enters the piping during servicing, the pump must be primed to
resume operation.
When the thermostat calls for heat,
oil is pumped through a nozzle into the combustion chamber. The fuel
emerges as an atomized mist that is ignited by a high-voltage spark. To
produce this spark, an ignition transformer boosts 120-volt house current
to a 10,000-volt impulse that arcs between electrodes located on either
side and slightly above the fuel nozzle. Once ignited, the fuel mist
continuously supplied by the pump burns without further electrical
stimulus. The pump motor also drives a blower that provides air for
combustion. It operates until signaled to shut off by the thermostat. Should the burner fail to ignite, or should the flame go out before the thermostat is satisfied, one of two safety mechanisms will stop the flow of oil, to prevent a buildup of excess fuel in the combustion chamber. One is a stack heat sensor in the combustion exhaust line to the chimney. It opens a safety switch when it senses that no heat is being produced. The second device is a photoelectric cell aimed into the combustion chamber. When the flame goes out, the chamber goes dark, causing the cell to shut the system down. Both devices may have reset switches, but use them cautiously. Never push a reset switch more than twice, as excess fuel pumped into the combustion chamber could explode. Heating System - Inspection These regular inspections are performed after a licensed technician has serviced the furnace and corrected any deficiencies that may be encountered during servicing.
Heating System - Servicing and cleaning An annual service should be performed by licensed heating technician. The following includes some of the tasks performed during this service.
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