HVAC Flashcards
A return grille allows us to modulate the volume of airflow.
a. True b. False
b. Grilles allow us to modulate the direction the air is flowing, but not the volume of airflow.
The vent in a high-efficiency furnace should slope up away from the furnace gently to allow combustion gases to rise more easily.
a. True b. False
b. The reason a vent should slope up away from a high-efficiency furnace is to allow any condensate in the vent to run back to the furnace so it can be collected and carried away.
Monoport burners are popular because they work equally well in any orientation.
a. True b. False
a. Upflow, downflow, and horizontal furnaces can use the same monoport burners.
Backdraft refers to an abnormal flame pattern.
a. True b. False
b. Backdraft, sometimes referred to as spillage, occurs when combustion products flow out of the furnace into the room through the burner or draft hood, rather than up the chimney. This is a life-threatening situation. It’s also an early 90’s movie that my aunt Betsy loves.
Vent connectors other than B-vents require a six-inch clearance from combustibles.
a. True b. False
a. Single-wall vents require a six-inch combustible clearance. B-vents, which are double walled, with an air space between the walls, require only a one-inch clearance.
The fan control switch is a safety device.
a. True b. False
b. The fan control switch is an operating control, not a safety control.
Poor or no heating is the most significant implication of heat exchanger problems.
a. True b. False
b. The most significant implication of heat exchanger problems is the possibility of exhaust products leaking in the house air. This is a life-threatening situation.
The fan control switch is a required operating control on gravity furnaces.
a. True b. False
b. Because gravity furnaces do not have fans, they do not need a fan control switch.
Every oil furnace must have a barometric damper.
a. True b. False
b. Some new, energy-efficient oil burners do not use a draft damper.
Power venters are never allowed on conventional oil furnace vent connectors.
a. True b. False
b. Power venters can be used with oil equipment in some areas to reduce the risk of backdrafting on an excessively long flue.
The vent connector from an oil furnace must connect to the chimney above a vent connector from a water heater.
a. True b. False
b. When multiple vent connectors go into the same chimney, the vent from the smaller input appliance (the water heater) should go above the vent from the bigger appliance (the furnace).
The oil filter is similar to the size and shape of the oil filter on a car.
a. True b. False
a. The oil filter on an oil furnace is similar in size and shape to the one on a car.
Oil burners in conventional oil furnaces are natural draft.
a. True b. False
b. Oil burners in conventional oil furnaces are forced draft.
The typical required combustible clearance between an oil burner and combustibles is 24 inches.
a. True b. False
a. Make sure that combustibles (including drywall) are at least 24 inches from the oil burners.
Aluminum is a commonly used material for exhaust flues on oil furnaces.
a. True b. False
b. Because of the high temperature of oil combustion products (around 500°F) aluminum generally is not allowed. Some areas may permit it if it is very thick.
Oil burners are typically inside the furnace cabinet.
a. True b. False
b. Oil burners typically are outside the furnace cabinet.
Closed systems must have circulators.
a. True b. False
b. A few closed systems do not have pumps (circulators).
If you find a radiator with the balancing valve completely shut off, then there will be no water in the radiator.
a. True b. False
b. Even if the balancing valve is completely shut off, there will still be water in the radiator.
It is possible to have a pressure-relief valve that is too small for the boiler.
a. True b. False
a. Pressure-relief valves come in various sizes, and it is possible to have one that is too small for the boiler. The relief valve setting should always be equal-to-or-greater-than the burner rating.
The pressure-reducing valve on a boiler is a safety control that prevents the pressure in a boiler system from building beyond 30 psi.
a. True b. False
b. The pressure-reducing valve maintains an adequate amount of water in the boiler at the desired pressure (12 psi to 15 psi). It is an operating control. The pressure-relief valve is the safety control that prevents high pressure within the boiler.
Outdoor air thermostats are commonly used with residential hot water boilers.
a. True b. False
b. Outdoor air thermostats are used more in commercial than residential construction, although you may find them in large homes.
Bleed valves on radiators are used to let water out to help balance the heating in individual rooms.
a. True b. False
b. Bleed valves are used to let trapped air out, so the water can circulate properly.
Boilers do not require venting systems
.a. True b. False
b. Boilers, like furnaces, require venting systems to exhaust combustion products out of the house.
A missing automatic air vent is a common problem with hot water boilers.
a. True b. False
b. An air vent is not mandatory, although some boilers come with an integral vent.
You can see the elements on an electric furnace.
a. True b. False
b. The elements in an electric furnace are not visible after removing the cover designed for homeowner access.
When you compress gas, you cool it.
a. True b. False
b. When you compress gas, you heat it.
The evaporator coil is outdoors in a split system.
a. True b. False
b. The evaporator coil is indoors in a split system.
Oversized distribution ductwork is a common problem with central air-conditioning.
a. True b. False
b. Undersized ducts are a common problem; oversized ducts are not common.
An undersized air conditioner is better than an oversized one.
a. True b. False
a. Many air-conditioning manufacturers and installers recommend slightly undersizing an air-conditioning system rather than oversizing it.
The typical temperature drop from outdoors to indoors with a properly operating air-conditioning system would be about 15°F.
a. True b. False
a. The difference in temperature between the conditioned air and the room air is about 15°F to 20°F.
Evaporator coils should be upstream of furnace heat exchangers.
a. True b. False
b. Evaporator coils must be downstream of gas, oil, or propane furnace heat exchangers.
A compressor can be thought of as a pump.
a. True b. False
a. The compressor is the pump that drives the Freon through the system.
Compressors typically are located indoors on an air-to-air, split-system air-conditioning system.
a True b. False
b. On conventional split-system air-conditioning systems, the compressor is located in the condenser cabinet outdoors or in the attic.
The larger refrigerant line contains a liquid.
a. True b. False
b. The larger refrigerant line typically carries a cool gas.
The smaller refrigerant line is called the suction line.
a. True b. False
b. The smaller refrigerant line is called the liquid line.
The larger refrigerant line is called the return line.
a. True b. False
a. The larger refrigerant line is called the return line or the suction line.
Flex ducts have less friction loss than rigid ductwork.
a. True b. False
b. Flexible ducts have far more friction loss than rigid ducts do.
One Btu is the amount of heat required to raise
a. one gallon of water one degree Fahrenheit.
b. one liter of water one degree Centigrade.
c. one pound of water one degree Fahrenheit.
d. one pound of water one degree Centigrade.
c. One Btu is the amount of heat required to raise one pound of water one Fahrenheit degree.
Which of the following is NOT a method of heat transfer?
a. Conduction
b. Induction
c. Radiation
d. Convective loops
b. Induction is not a primary heat transfer method.
For complete combustion, and ignoring dilution air requirements, natural gas requires approximately
a. 1/15 volume ratio of gas/air.
b. 1/100 volume ratio of gas/air.
c. one pound of air for one pound of fuel.
d. 10/1 volume ratio of gas/air.
a. It takes about 15 cubic feet of air to burn one cubic foot of gas.
A conventional gas-fired, forced-air furnace rated at 100,000 Btu input is in a four-foot by four-foot by eight-foot-high furnace room with a door.
a. A single 50-square-inch opening should be provided at roughly the elevation of the draft hood.
b. Two openings should be provided, one near the bottom and one near the top of the room, each 50 square inches.
c. Two openings should be provided, one near the bottom and one near the top of the room, each sized at 100 square inches.
d. One opening should be provided, sized at 500 square inches.
c. A typical furnace room needs two openings, one near the bottom and one near the top. In this case, each one should be 100 square inches (one square inch for every 1,000 Btus).
Natural gas
a. is lighter than air.
b. is piped as a compressed liquid.
c. has a strong natural odor.
d. contains about 2,500 Btu-per-cubic-foot.
a. Natural gas is lighter than air.
Which of the following is NOT a problem with a natural gas burner?
a. Flame lifting
b. Flame rollout
c. Inactive flame
d. Delayed ignition
c. An inactive flame is not a problem.
Flame rollout would NEVER be caused by
a. overfiring of the burner.
b. cracked heat exchanger.
c. lack of combustion air.
d. underfiring of the burner.
b. Flashback or flame rollout is not caused by a cracked heat exchanger.
Heat exchangers
a. separate the combustion air from the house air.
b. can be easily repaired or replaced.
c. are typically made of aluminum.
d. should be completely inspected during a standard home inspection
a. Heat exchangers separate the combustion air from the house air.
The right burner in a two-burner, conventional efficiency furnace ignites from the pilot readily, but the left burner ignition is delayed. When it does ignite, it does so with a flash and pop. What is likely wrong?
a. The pilot is dirty.
b. The flame sensor is malfunctioning.
c. The left burner is damaged.
d. The crossover igniter needs adjustment.
d. When one burner won’t ignite, it is usually a crossover igniter problem.
The flame of the left burner in a two-burner, conventional efficiency furnace touches the heat exchanger when the blower is not running. What is likely to be the problem?
a. The heat exchanger is cracked on the left side.
b. The right burner is dirty.
c. The left burner is dirty.
d. The left burner is misaligned.
d. If the flame touches the heat exchanger, the burner is probably misaligned.
The fan/limit switch will typically tum the blower on at
a. 80°F-110°F.
b. 120°F-150°F.
c. 170°F-200°F.
d. 220°F-250°F.
b. The fan/limit switch typically turns the blower on at 150°F. In some modern systems it can be considerably lower (as low as 120°F).
The high-limit setting for a forced-air, gas furnace is typically
a. 150°F.
b. 200°F.
c. 250°F.
d. 300°F.
b. The high limit setting is typically 200°F.
The anticipator on a thermostat is used to
a. start the furnace, in anticipation of a temperature drop.
b. stop the furnace early to reduce overheating of the house.
c. control current flow to the furnace gas valve.
d. prevent the air conditioner from cycling if it is too cold outside.
b. The anticipator stops the furnace before it is quite heated up to reduce overshoot (overheating of the house).
You can see the elements on an electric furnace.
a. True b. False
b. The elements in an electric furnace are not visible after removing the cover designed for homeowner access.
When you compress gas, you cool it.
a. True b. False
b. When you compress gas, you heat it.
The evaporator coil is outdoors in a split system.
a. True b. False
b. The evaporator coil is indoors in a split system.
Oversized distribution ductwork is a common problem with central air-conditioning.
a. True b. False
b. Undersized ducts are a common problem; oversized ducts are not common.
The anticipator on a thermostat is used to
a. start the furnace, in anticipation of a temperature drop.
b. stop the furnace early to reduce overheating of the house.
c. control current flow to the furnace gas valve.
d. prevent Lhe air conditioner from cycling if it is too cold outside.
b. The anticipator stops the furnace before it is quite heated up to reduce overshoot (overheating of the house).
The right burner in a two-burner, conventional efficiency furnace ignites from the pilot readily, but the left burner ignition is delayed. When it does ignite, it does so with a flash and pop. What is likely wrong?
a. The pilot is dirty.
b. The flame sensor is malfunctioning.
c. The left burner is damaged.
d. The crossover igniter needs adjustment.
d. When one burner won’t ignite, it is usually a crossover igniter problem.
Of the following, which is the best location for the thermostat?
a. In the front vestibule, on an interior wall
b. In the living room across from the fireplace
c. In the second-floor master bedroom, away from all windows
d. On an interior dining room wall by the light switch
d. The best location for a thermostat is on an interior dining room wall close to a light switch. The light switch is not a heat source.
In the operating sequence of a conventional gas-fired, forced-air furnace, which step is out of sequence?
a. The thermocouple verifies that the pilot is on.
b. The house air fan comes on.
c. The gas valve opens.
d. The burners are ignited.
b. The house air fan should not come on before the gas valve opens or the burner ignites.
A conventional gas-fired, forced-air furnace has an input rating of 100,000 Btu. Its output rating is 80,000 Btu. The seasonal efficiency is
a. greater than the steady state efficiency.
b. less than the steady state efficiency.
c. independent of off-cycle losses.
d. minimized by the presence of an induced draft fan.
b. The seasonal efficiency is less than the steady state efficiency.
Corrosion in the draft hood and on the inside of the access cover indicates
a. excess flue gas temperature.
b. inadequate flue gas temperature.
c. backdrafting.
d. excess draft air.
c. Corrosion in the draft hood and on the access cover indicates back drafting.
Heat exchanger failure in a conventional efficiency furnace may lead to all these EXCEPT
a. carbon monoxide in the house.
b. soot buildup on the burner-side of the heat exchanger.
c. high house humidity levels.
d. flame pattern disruption when the house air fan comes on.
b. Heat exchanger failure may lead to spillage but not soot buildup on burner side of heat exchanger.
Which of the following statements, with respect to vent connectors, is FALSE?
a. The temperature of diluted exhaust products from conventional gas-fired furnaces is 500°F to 700°F.
b. The vent connector joins the furnace to the chimney or vent.
c. The vent connector should slope up from the furnace to the chimney at roughly 1/4-inch-per-foot.
d. The implications of vent connector problems are exhaust spillage and condensation.
a. The temperature of exhaust products from conventional gas furnaces is about 300°F to 350°F.
All of the following affect the amount of air delivered to each room EXCEPT
a. duct shape.
b. duct location.
c. duct length.
d. blower size.
b. Duct location does not affect;. the amount of air delivered to each room.
All of the following are problems you’ll commonly find on house air fans EXCEPT
a. dirt.
b. fans poorly secured.
c. a loose fan belt.
d. fans installed backwards.
d. It is not a common problem to find house air fans installed backwards.
All of the following are problems you’ll commonly find on house air fans EXCEPT
a. dirt.
b. fans poorly secured.
c. a loose fan belt.
d. fans installed backwards.
b. Filter problems do not include installing the filter upstream of the blower. That is where the filter should be.
The single cold-air return in a small bungalow is located beside the main supply register to the livingroom. What is the concern with this?
a. The supply and return can be easily blocked with furniture.
b. The living room will get the worst airflow.
c. The return will pull the supply air in.
d. The furnace could overheat with this setup.
c. If the supply and return are too close together, the return will simply pull the supply air back in, short-circuiting the system.
The homeowner has tucked the supply and return plenums up tight along a wood beam. Are there concerns with this?
a. Yes, the ducts are too close to the combustible wood.
b. No, the ceiling is now easier to finish.
c. Yes, the airflow is lowered due to the tight bend.
d. No, duct vibration is less likely to occur.
a. The supply plenum is too close to the wood.
Supply air registers in a forced-air heating system are best located
a. high on interior walls.
b. low on interior walls.
c. low on exterior walls.
d. centrally located on ceilings
c. The best place for supply registers is low on exterior walls.
Poor airflow may be the result of all of the following EXCEPT
a. dirty ducts.
b. obstructed or collapsed ducts.
c. leaking ducts.
d. uninsulated ducts.
d. Uninsulated ducts will not result in poor air flow.
An early generation, mid-efficiency gas furnace has a vent damper. Which of the following list of conditions is NOT a safety concern?
a. The vent damper is stuck open.
b. The vent damper is stuck closed
c. The vent damper motor runs continuously.
d. The vent damper is not interlocked with the burner.
a. A vent damper stuck open is not a life safety problem. The chimney will vent properly.
Off-cycle losses on a conventional gas-fired forced air furnace waste
a. 5 percent of the heat generated.
b. 10 percent of the heat generated.
c. 20 percent of the heat generated.
d. 30 percent of the heat generated.
c. Off-cycle losses are roughly 20 percent.
Which of the following is NOT TRUE?
a. Annual Fuel Utilization Efficiency is the same as seasonal efficiency.
b. Off-cycle losses include chimney losses and standing pilot losses.
c. Induced-draft fans always have standing pilots.
d. Induced-draft fans are used for purging the furnace.
c. Induced draft fans most often do not have standing pilots.
Ignition devices commonly found on mid-efficiency gas furnaces include all these EXCEPT
a. electronic ignition.
b. spark igniters.
c. hot-surface igniters.
d. thermocouples.
d. Thermocouples are not usually found in mid-efficiency gas furnaces.
Natural gas burners can have several different draft mechanisms. All of the following are possible examples EXCEPT
a. natural draft.
b. induced draft.
c. reverse draft.
d. forced draft.
c. Reverse draft is not a draft mechanism.
A mid-efficiency, induced-draft gas furnace is manifolded with a natural-draft water heater. Is this a concern?
a. No, this is always allowed.
b. No, not if the vent is large enough to handle both.
c. Yes, if the furnace vent pressure is positive.
d. Yes, this situation is never allowed.
c. If the furnace vent pressure is positive, the water heater may not be able to draft properly. This may cause backdrafting through the draft hood of the water heater.
Mid-Efficiency, gas-fired furnaces
a. may be vented through the sidewall.
b. never had plastic venting.
c. always have an induced-draft fan.
d. have seasonal efficiencies in the 85 percent to 90 percent range.
a. Mid-Efficiency gas-fired furnaces can be sidewall vented.
Induced-draft fans improve efficiency by doing all of the following EXCEPT
a. using less house air than a natural-draft burner.
b. eliminating off-cycle losses up the chimney.
c. condensing the exhaust gases.
d. eliminating the need for dilution air.
c. Induced draft fans do not condense the exhaust gases.
Mid-Efficiency furnaces with induced-draft fans may have all of the following components EXCEPT
a. an air-proving switch.
b. a draft hood.
c. electronic ignition.
d. a spillage switch.
b. You won’t normally have a draft hood with an induced-draft fan on a mid-efficiency furnace.
High-efficiency gas furnaces improve efficiency by
a. reducing airflow across the heat exchanger.
b. increasing airflow and increasing flue gas exhaust temperature.
c. reducing temperature rise and condensing flue gases.
d. increasing blower speed and evaporating flue gases.
c. High-efficiency furnaces condense exhaust gases and reduce the temperature rise across the heat exchanger.
A common temperature rise across a modern & high-efficiency gas furnace is
a. 10°F to 50°F.
b. 35°F to 65°F.
c. 50°F to 85°F.
d. 70°F to 100°F.
b. A typical temperature rise on a high-efficiency furnace is 35°F to 65°F or 40°F to 70°F.
Corrosion noted inside a high-efficiency, gas-furnace blower compartment may be
a. indicative of humidifier leakage.
b. indicative of condensate line blockage.
c. indicative of induced-draft fan failure.
d. All of the above
d. Corrosion inside a high-efficiency gas furnace blower compartment may indicate humidifier leakage, condensate line blockage, or an induced-draft fan failure.
Direct-vent heating systems
a. take combustion air from outside the dwelling.
b. require 1 square inch of vent space per 1,000 Btu/hour input.
c. usually have standing pilots and forced-draft fans.
d. have their combustion occur outside the building.
a. Direct vent heating systems take combustion air from outside the dwelling. That is the definition.
High-efficiency gas furnaces are designed to condense because
a. of the desire to capture the latent heat of vaporization.
b. the heat exchangers have been made more corrosion-resistant anyway, so condensation doesn’t matter.
c. new technology allows us to collect and dispose of the condensation.
d. the condensation is used to help cool the induced-draft fan.
a. The condensation is the result, not the goal. The goal is to collect the latent heat of vaporization.
Which of the following is NOT a normal installation on a pulse high-efficiency furnace? a. Vibration damping in the duct connections
b. Flexible gas connector
c. Exterior duct insulation
d. A tailpipe
c. Supply and return duct insulation is usually provided for the first few feet moving away from the furnace. However, the insulation is on the interior, not the exterior, of the duct.
The seasonal efficiency of a high-efficiency gas furnace can be
a. 75 percent to 85 percent.
b. 80 percent to 90 percent.
c. 85 percent to 95 percent.
d. 95 percent to 100 percent
c. Efficiencies of over 90 percent have been claimed.
The exhaust gas temperature from a high efficiency furnace is typically
a. 50°F to 100°F.
b. 100°F to l50°F.
c. 150°F to 200°F.
d. 200°F to 250°F.
b. The temperature of the condensate is 100°F to 150°F.
The exhaust from a high-efficiency gas furnace terminates underneath an enclosed deck. Is this a concern?
a. No, the exhaust gases are low-temperature, so there is no combustibility problem.
b. Yes, the wood is combustible
.c. Yes, the exhaust gases will spill into the house.
d. Yes, the exhaust gases will rot the deck.
d. Because the gases are cool, the combustibility of the deck isn’t a problem. Because there is a lot of moisture, rot is the issue.
A pulse furnace has all of the following EXCEPT
a. a purge blower.
b. an air intake vacuum switch.
c. direct spark ignition.
d. an induced-draft fan.
d. A pulse furnace does not have an induced draft fan.
Common problems \With high-efficiency furnaces include all of the following EXCEPT
a. induced-draft fan problems.
b. vent damper problems.
c. heat exchanger problems.
d. clogged condensate systems.
b. Vent damper problems won’t be common with high-efficiency furnaces, because they don’t have vent dampers.
Common heat exchanger problems on mid-efficiency and high-efficiency furnaces include all of the following EXCEPT
a. rust.
b. cracking.
c. vibration.
d. overheating.
c. Vibration is not a common heat exchanger problem.
Common condensate problems on high-efficiency furnaces include all of the following EXCEPT
a. leaking condensate lines.
b. lack of an automatic air vent in condensate lines.
c. poor discharge location.
d. a missing or clogged neutralizer.
c. poor discharge location
Sidewall vents from mid-efficiency or high-efficiency furnaces should be at least
a. 6 feet away from windows and other building openings.
b. 1 foot off the ground.
c. 10 feet from soffits.
d. I0 feet away from gas regulators.
b. Sidewall vents should be at least one foot off the ground.
The implication of improper slope on the exhaust flue from a high-efficiency gas furnace is
a. water damage outside.
b. frost closure at the discharge.
c. moisture being drawn-in through the combustion air intake.
d. corrosion of the vent material.
b. Improper slope on a high-efficiency furnace exhaust flue may result in frost closure at the discharge.
The exhaust flue on a mid-efficiency furnace should have a six-inch combustible clearance. On a high-efficiency furnace exhaust flue, the required clearance is
a. six inches.
b. three inches.
c. two inches.
d. zero inches.
d. No combustible clearances are required for a high-efficiency furnace exhaust flue.
Combustion in a direct-spark ignition, condensing gas furnace is sensed by
a. the primary control.
b. the flame sensor.
c. the thermocouple.
d. the ignition module.
b. Flame sensors are used to detect combustion in a direct-spark ignition furnace.
Combination furnaces
a. use more than one vent
.b. have more than one burner.
c. use one burner to heat space and hot water.
d. always have tempering valves.
c. Combination furnaces use a single burner to heat both the house space and the domestic hot water.
The life expectancy of a conventional gas furnace is
a. 20-25 years.
b. 25-30 years.
c. 30-35 years.
d. 35-40 years.
a. A conventional gas furnace is expected to last 20-25 years.
The heat content of one gallon of No. 2 heating oil is approximately
a. 2,500 Btu.
b. 72,000 Btu.
c. 140,000 Btu.
d. 200,000 Btu.
c. One gallon of #2 heating oil contains approximately 140,000 Btus.
Oil furnaces are like gas furnaces in all of the following respects EXCEPT
a. ducts, registers, and grilles.
b. heat exchangers.
c. fan/limit switches.
d. blast tubes.
d. Oil furnace burners are very different from gas furnace burners as gas burners do not have blast tubes.
You find an oil storage tank in the basement. The entire surface of the tank is rusting. What is the most likely cause?
a. The basement leaks near the tank.
b. The tank leaks.
c. The clothes dryer vents into the tank area.
d. The burner is backdrafting wet combustion gases.
c. If the entire outside of the oil tank is rusting, this could well be the clothes dryer venting into the tank area. The warm, moist air may condense on the coot metal.
When you turn up the thermostat, the oil burner does not operate. You know that the electrical power to the furnace is on. What is NOT a likely concern?
a. A clogged nozzle
b. The firepot having failed
c. Clogging of the combustion air intake
d. An empty fuel tank
b. A failed fire pot will not prevent a burner from operating.
Viewing the flame of an oil burner from the viewport shows a ragged, black-edged, yellow flame. This is
a. normal for a flame-retention head burner.
b. normal for a conventional oil burner.
c. the result of a failed firepot.
d. the result of a failed heat exchanger.
b. A ragged, black-edged, yellow flame is normal on a conventional oil burner. More modern burners have a smoother flame.
The viewport shows that the back wall of the ceramic felt combustion chamber is no longer white. It is browned and stained. What is the likely cause of this discoloration?
a. The ceramic felt is saturated with oil.
b. The felt is covered with soot from a dirty flame.
c. The felt has turned this color with time and use.
d. The heat exchanger has failed and is leaking creosote onto the firepot.
a. A ceramic felt combustion chamber that is brown and stained is probably saturated with oil.
The viewport shows that the back wall of the ceramic felt combustion chamber is no longer white. It is browned and stained. What is the likely cause of this discoloration?
a. The ceramic felt is saturated with oil.
b. The felt is covered with soot from a dirty flame.
c. The felt has turned this color with time and use.
d. The heat exchanger has failed and is leaking creosote onto the firepot.
a. The primary control senses combustion in an oil furnace.
The primary control on a modem flame-retention head oil burner is typically found
a. on the heat exchanger.
b. on the burner.
c. on the exhaust flue.
d. on the furnace cabinet.
b. The primary control is on the burner on a retention head system.
