Heating and Cooling Systems - Set 1

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Closed systems must have circulators. a. True b. False

b. A few closed systems do not have pumps (circulators).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Oil burners in conventional oil furnaces are natural draft. a. True b. False

b. Oil burners in conventional oil furnaces are forced draft.

Oil burners are typically inside the furnace cabinet. a. True b. False

b. Oil burners typically are outside the furnace cabinet.

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.

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.

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.

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.

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.

The evaporator coil is outdoors in a split system. a. True b. False

b. The evaporator coil is indoors in a split system.

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.

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 larger refrigerant line contains a liquid. a. True b. False

b. The larger refrigerant line typically carries a cool gas.

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 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.

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.

The smaller refrigerant line is called the suction line. a. True b. False

b. The smaller refrigerant line is called the liquid line.

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 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).

When you compress gas, you cool it. a. True b. False

b. When you compress gas, you heat it.

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).

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.

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.

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 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.