HVR 110 final exam
With power applied, a voltage measurement across a low-voltage thermostat switch that is closed should read about _____
0 V
With no excess air dilution, the ultimate carbon dioxide content for natural gas is approximately ____.
11.9
With power applied, a voltage measurement across a line-voltage thermostat switch that is open should read about ____.
120 Vac or 240 Vac
Low-voltage thermostats operate at _____, which is supplied by step-down transformers.
24 Vac
A 30 A electric heater is powered by a 240 V circuit. What is the maximum amount of heat energy that can be produced by the heater in Btu/hr?
24,574
An electric furnace's total output should not exceed _____ over the design heat load.
40%
The maximum concentration of carbon monoxide (CO) permitted in furnace flue gas is _____.
400 ppm
Nearly _____ % of all energy used in the home is for heating and cooling.
50
An electric heater is rated at 2200 W. What is its heat output in Btu/hr?
7509
An electric heating system's high-temperature safety cutoff may be in the form of
A bimetal disc switch
Which of the following may be a cause of problems in a gas furnace?
A. A lack of satisfactory combustion air. B. Improperly sized vents and malfunctioning air filters. C. Electrical shorts due to a water leak in the evaporator coils or humidifier. D. All of the above.
Which of the following statements regarding furnace efficiency is false? A Higher efficiency is achieved by keeping more condensation in a system. B. The higher the AFUE rating, the more efficient a furnace is. C. A furnace's AFUE rating is printed on a label attached to the furnace. D. None of the above.
A. Higher efficiency...
Which of the following statements about a heat pump operating in cooling mode is false? A. The compressor pumps high-pressure refrigerant vapor into the indoor coil B. The outdoor coil functions as a condenser. C. The refrigerant vapor gives up its heat to the outside air as it flows through the outdoor D. The indoor coil functions as an evaporator.
A. The compressor...
Which of the following statements regarding rollout switches is true?
A. They are located near the burners. B. They are used to cut off the supply of fuel gas when a flame rollout occurs. C. They must be reset manually. D. All of the above.
Which of the following should be insulated to reduce exfiltration?
A. basement walls B. ceilings C. windows D.All of the above.
Electric radiant floor heating _____.
A. can be used as a primary heating system B. is a type of indirect radiant heat C. produces less temperature variation than convection heating methods D. All of the above.
Electric furnaces can be installed as _____ furnaces.
A. downflow B. upflow C. horizontal D. All of the above.
A device that may be used to detect combustion blower operation is a(n)_____
A. sail switch B. pressure switch C. end switch D. All of the above.
A combination gas valve is used to replace separate furnace components, such as a ______.
A. solenoid valve B. manual shutoff valve C. pressure regulator D. All of the above.
Auxiliary heat for a heat pump _____.
ALL THE ABOVE A. is needed when it is not possible for the heat pump to extract enough heat from the outside air B. is not as efficient as normal system operation C. may use electric heating coils in the supply air ducts
Solar panels used in conjunction with heat pump systems _____.
Absorb heat from the sun
In some furnaces, an opening in the flue, called a(n) _____ helps keep constant pressure in the combustion chamber and prevents ambient air from reaching the furnace flame.
Air break
A heat pump that uses the outside air as a heat source or a heat sink for producing the desired temperature in a conditioned space is a(n) _____ heat pump.
Air-source
Which of the following statements regarding hot-surface ignition (HSI) systems is false? A. An HSI system produces electromagnetic interference. B. The glow coil de-energizes within a few seconds of the gas valve opening. C. Glow coils take longer to ignite a gas burner flame than spark igniters. D. Glow coils are sensitive to shock and vibration.
An HSI system produces electromagnetic interference.
How should you clean the outdoor unit of a residential heat pump?
Apply a non-acidic coil cleaner and rinse with water
To avoid drawing too much current that could result in voltage drops or damage to property, _____ are often wired on their own separate, dedicated circuits.
Baseboard
An air-source heat pump's heating cycle ____ as the outdoor temperature drops.
Becomes less efficient
The primary energy-savings benefit of free cooling is that the _____ does not run.
Blower
To maintain sufficient airflow through an air handler when only some of the zones in a forced-air system are calling for cooling, a(n)_____ is used.
Bypass damper
Which of the following statements regarding radiant heaters is false? A. Radiant heat decreases as the distance increases between the heater and the obiect it is warming. B. Radiant heaters emit infrared light to warm objects in their line of sight. C. An object twice as far from a radiant heater will receive twice as much heat. D. None of the above.
C. An object twice as far...
Which of the following statements about heat pump compressors is false? A. A crankcase heater can help protect a compressor from migrating refrigerant. B. They operate at lower ambient temperatures than most air-conditioning compressors. С. One-way filter-driers protect the compressor from liquid slugging. D. Suction line accumulators are used to protect the compressor from liquid slugging.
C. One-way filters...
Which of the following statements about flow check pistons is false? A. They allow refrigerant to pass freely in one direction. B. Each has a valve assembly and a piston with a hole in its center. C. They meter refrigerant passing through in either direction. D. Two are necessary for a heat pump to operate in cooling and heating modes.
C. They meter refrigerant...
Cooling thermostats use cooling anticipators to compensate for ______.
Chillwave
Thermostats often have automatic maintenance alerts that are typically used for the following reasons, except _____.
Compressor replacement
Which of the following statements about charge compensator tanks is false? A. The liquid line is connected to the tank and fills it with liquid refrigerant. B. It is a canister with the heat pump's gas line running through it. C. The gas line does not open inside the tank. D. During the cooling mode, the gas line cools liquid refrigerant in the tank.
D. During the cooling mode...
The main method of controlling zones in a forced-air HVAC system is through the use of _____.
Dampers
_____ controls are needed to monitor ice buildup on the outdoor coil of an air-to-air system.
Defrost
A ground-source heat pump that circulates refrigerant through an outdoor coil that is placed in direct contact with the earth is a(n) _____ heat pump
Direct-exchange
Class B chimneys are ____.
Double wall metal type
When a heat pump is operating in heating mode, the outdoor coil functions as a(n) _____ by absorbing heat.
Evaporator
T or F: A heating thermostat's temperature switch closes to stop the heater when it senses a rise to cut-off level.
False
T or F: A mid-efficiency furnace has a secondary heat exchanger.
False
T or F: Depending on the type and size of a unit, a drip leg may or may not be installed at the furnace.
False
T or F: Indirect radiant heat produces more room temperature variation than baseboard heating units.
False
T or F: Millivolt thermostats may be used to operate cooling systems.
False
T or F: Solar heating systems help heat pumps provide heating at a significant operating cost.
False
T or F: The price of operating electric heating systems is very cost-effective compared to ground-source heat pumps.
False
T or F: The smaller line in a heat pump system is referred to as the suction line.
False
T or F: Unit heaters should be installed near flammable materials and surfaces.
False
A draft regulator is installed in the ____ to moderate the flow of flue gas.
Flue pipe
A heat pump that uses the earth as a heat source or a heat sink for producing the desired temperature in a conditioned space is a(n) _____ heat pump.
Ground-source
A furnace with an AFUE range of approximately 90% to 97% is a _____ gas furnace.
High-efficiency
The safety device in a furnace's bonnet that is used to protect a heat exchanger from overheating is a(n) _____.
High-limit switch
If a gas furnace's flame characteristics change when the _____ comes on, severe deterioration of the heat exchanger may be indicated.
Indoor blower
A heating element must always be replaced with a heating element that has an identical _____ rating.
Kilowatt
A thermostat that operates using either 120 Vac or 240 Vac is called a _____ thermostat.
Line-voltage
Class A chimneys are ____.
Masonry type
Wireless thermostats _____.
May interface with Wi-Fi to mobile devices
A furnace with an AFUE range of approximately 79% to 83% is a _____ gas furnace.
Mid efficiency
A thermostat that operates a small solenoid valve powered by a thermocouple is a(n) _____ thermostat.
Millivolt
Which of the following thermostats has been generally phased out because it depends on a standing pilot light?
Millivolt thermostat
A heat pump with a 13-SEER rating is _____ a 12-SEER heat pump.
More efficient than
A thermostat that can operate two or three circuits in sequence or vary heat production and cooling capacity is a _____ thermometer.
Multistage
An uninsulated heating element composed of flat strips is referred to as a(n) _____ heating element.
Open ribbon
_____ heating elements are most often formed into coils.
Open wire
Enthalpy control only allows free cooling to run when _____ is low enough.
Outdoor humidity
A reversing valve that uses a solenoid valve to direct high- and low-pressure refrigerant to move the sliding section within the valve body is a _____.
Pilot-operated reversing valve
A disadvantage of electric heating systems is _____.
Possible humidity problems
If a customer is interested in automatic control of an HVAC system during different days and times of the day, recommend installing a _____ thermostat.
Programmable
_____ heats ceramic elements to incandescence.
Radiant heating
If a high-limit switch fails, ____.
Replace the baseboard heating unit
To prevent snow from blocking side airways, install_____
Risers
To confirm airflow through an electric furnace, a ____ may be used.
Sail switch
The primary part of a thermostat that reacts to temperature change is the _____.
Sensing element
Heat anticipators are used to help reduce or eliminate _____.
System overshoot
Which of the following statements about atmospheric gas burners is false?
Those used in older furnaces did not have adjustable air shutters
If the individual voltage measurement across each of the electrical loads powered by a step-down transformer in a forced-air heating and cooling system is less than 24 Vac, then the problem is most likely the _____.
Transformer
T or F: A heat pump is effective only when the ratio of heat pump output to heat loss is at or above the balance point.
True
T or F: A pressure switch can detect airflow through a duct heater by measuring air pressure before and after the duct heater.
True
T or F: Electric crankcase heaters are used to warm a heat pump's compressor dome prior to start-up.
True
T or F: If the time set for trial for ignition (TFI) is exceeded, the ignition control module places the furnace in lockout.
True
T or F: In a solar heating system, a hydronic coil is placed in the air handler plenum.
True
T or F: In electric resistance heating, elements are sized to allow a certain current to flow.
True
T or F: Ultraviolet lights can help eliminate mold or bacteria.
True
An electric heating element enclosed in a heat- and corrosion-resistant steel tube is referred to as a(n) _____.
Tubular cased wire
A(n) _____ draft regulator opens when pulled open by the negative pressure of flue gas suction.
Vacuum
The reduction in pressure that occurs when a fluid flows through a constricted section of pipe is called the _____ effect.
Venture
A heat pump that circulates water through a secondary circuit that is placed underground or underwater is a(n) _____ heat pump.
Water-source
To ensure that a multistage HVAC system is operating at full cooling capacity, measure voltage across terminals R and ____ in the thermostat.
Y2
As excess air increases, ____.
a furnace's stack temperature increases
The most commonly used material for natural gas piping is _____ pipe.
black iron
Flu-like symptoms that subside when a home's inhabitants are away from the house might be an indication of exposure to _____.
carbon monoxide
The chemical process of rapid oxidation in which fuel and oxygen combine to produce heat and light is referred to as _____.
combustion
The rate of flue gas flow primarily affects the amount of ____ entering a furnace or boiler.
combustion air
An ignition system that uses an electric spark to ignite the gas burners is a(n) _____.
direct-spark ignition system
Category IV furnaces _____.
have a flue gas temperature less than 140°F (60°C)
An ignition system that uses a high-resistance heating element to light the gas burners directly is a(n) _____
hot-surface ignition system
An ignition system that burns and monitors its pilot light only while the thermostat is calling for heat is a(n) _____.
intermittent-pilot ignition system
A Category I furnace is a ____ furnace.
negative-pressure, noncondensing
When checking for a gas leak, a technician should use ______.
soap bubbles
