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167 Cards in this Set
- Front
- Back
When servicing a water heater, propane flow downstream of the solenoid valve is determined by
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installing a monometer at the pressure tap.
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Which of his five senses will a technician use to find and verify a leaking propane fitting?
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Sight
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Which test instrument can be used to determine that a gas solenoid is functioning?
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Ohmmeter
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11 inches water column is the
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pressure coming from the second stage of a propane regulator
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What percentage of propane flow is required when setting the system operating pressure (adjusting regulator)?
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50%
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Which two methods are used to determine if a leak in the propane system exists? 1) Timed Pressure Drop 2) Leak Detector Solution 3) Regulator Lockup Test 4) Bubble Leak Tester
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1 and 4
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Which two methods are used to locate a leak in the propane system? 1) Electronic Leak Detector 2) Leak Detector Solution 3) Pressure-drop Test 4) Hearing (hissing sound)
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1 and 2
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It is required that you change the fill valve on a mounted ASME tank. To safely remove propane from the tank you will
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burn off the propane with a suitable torch.
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An opened outage valve is used
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to indicate the maximum liquid level.
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Backup wrenches are used
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to prevent damage to propane connections.
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What propane system fault condition may be present at an appliance in a retracted slideout, yet not seen when the room is extended?
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Low or no gas pressure.
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Automatic changeover regulators are found on
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dual DOT cylinders
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Regarding regulator lockup, which of the following statements is false?
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A timed pressure drop test must be preformed after setting the lockup pressure
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The air conditioner is a 120 VAC, 60 Hz appliance. The proper operation range is
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between ±10% (103.5 and 132 VAC)
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To measure the total amperage drawn by an RV air conditioner you would attach an ammeter to
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the A/C junction box
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The evaporator in an RV air conditioner
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releases heat into the atmosphere
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The rotary switch on a manually controlled air conditioner
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controls the thermostat
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Before testing for an open or shorted capacitor, with an ohmmeter you must first
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discharge the capacitor using a ammeter
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A measurement taken by clamping a test meter around the run (R) or common (C) compressor lead will indicate
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the running amperage
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High side and low side are two types of restrictions found in the sealed refrigerant system. The basic criteria to use in determining a restriction is (are)
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amp draw and pressure
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Used in evaluating air conditioner performance, the delta-temperature relationship is the temperature change between the
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air entering and leaving the evaporator coil
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Normal delta temperature is approximately 20 degrees Fahrenheit. An increase in ____ will decrease the delta temperature.
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humidity
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The pressure of the refrigerant _____ as the ambient air temperature _____ .
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increases / increases
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The water dripping on the roof of an RV from an A/C unit has been removed from the
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moisture inside the RV
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Improper or insufficient air flow through the coils of the evaporator and condenser is the second most common reason why air conditioners stop cooling. What is the main reason?
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Electrical problem
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Liquid refrigerant is vaporized by the absorption of heat and moisture from inside the coach in what component?
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Evaporator
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The high temperature overload switch is directly affected by the current draw at the compressor and also the temperature of the
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windings
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To safely discharge a run capacitor, attach the leads of a VOM set to the
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highest AC scale
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A typical heat strip attachment in working condition will measure about how many Ohms?
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9.5
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The lowest safe operating line voltage for a roof A/C is
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103 VAC
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When installing a roof A/C, it is approximately 21-feet from the mounting location to the breaker box. What size Romex is required?
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12-gauge
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When mounting a wall thermostat be sure it is installed on an inside wall
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about five feet above the floor
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12-VDC is used within a 120-VAC RV air conditioner system
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Both A and B
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The first step in troubleshooting an A/C system that does not work at all is to
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verify the incoming 120-VAC
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BTU stands for
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British Thermal Unit
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Refrigerant changes from liquid to low pressure vapor at the
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evaporator coil
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Refrigerant changes from a low pressure vapor to a high pressure vapor at the
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Compressor
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Refrigerant changes from a high pressure vapor to a high pressure liquid at the
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condenser coil
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In an air conditioner unit, the component in which the heat is absorbed from the living area is
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evaporator coil
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The main difference between the heating and cooling modes of a heat pump is
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the flow of the refrigerant is reversed
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What are the four selector switches used in the manufacture of RV air conditioners?
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10, 8, 6, and 5 position
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You are checking the compressor. When the outside or inside ambient temperature rises, the load conditions change and amperage
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increases
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The 12 VDC operating range for a Dometic air conditioner is
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9 to 16
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For Dometic air conditioner normal operation, AC voltage needs to stay within a range of
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103.5 - 126.5
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Insufficient millivolt output from the thermocouple may be caused by all of the following except
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low battery voltage
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When installing a thermocouple do not over tighten, this is a(n) ____ connection
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electrical
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A fitting on a water heater control valve is provided for a(an)
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propane pressure test port
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On a D.S.I water heater the thermostat is located on
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the outside of the tank
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The initials E.C.O. on a D.S.I. water heater stand for
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Energy Cutoff Switch
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A D.S.I. circuit board controls what function?
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Sending spark to the electrode while powering the propane valve
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What material is used in the construction of an Atwood water heater tank?
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Aluminum
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To bench test an electric thermostat, attach the leads of your VOM to the contacts of the thermostat and test for
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continuity
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An accepted method for testing an electric water heater element is to
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perform a resistance test
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What is the maximum size heating element that can be used on a 15 amp circuit and still meet the NEC (electrical code)?
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1,400 watts
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An open Energy Cutoff will
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shutdown the water heater completely
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A defective electric heating element would be indicated by
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Voltage at the terminals but no amperage draw
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On a pilot model water heater which component does not affect the flow of propane when attempting to light the pilot light?
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Thermocouple
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Which component does not affect the electrode sparking on a DSI water heater?
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Gas valve coil
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Temperature and pressure (T&P) relief valve weeping
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is a natural event
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Excessive sooting in the combustion chamber of water heater can be caused by
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misaligned burner
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A water heater bypass valve that is incorrectly set can cause
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variations in water temperature at the faucet
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A component that protects the water heater tank from corrosion is called a(an)
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anode
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Another way to check the heating element is to check resistance. After the power has been turned off and the wires disconnected from the heating element, you can check the resistance. The water heater is a 120 VAC, 1000-watt heater. What is the correct resistance?
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14.46 ohms
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The pilot model water heater must be supplied with _____ inches nominal water column of propane in order to work
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11
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D.S.I. stands for
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Direct Spark Ignition
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The thermal cut-off device
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opens the electrical circuit
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The same customer has returned three times with the same problem. Each time you replaced the circuit board and the D.S.I. water heater works for a short time. What is probably happening?
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An outside influence is destroying the boards
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Propane valve coils need a minimum of _____ volts to open
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10.5
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When checking propane valve coils for resistance, a good coil should have a resistance of _____ ohms.
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30 – 50
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The process of removing sediment from the bottom of a water tank is called
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flushing
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Weeping or dripping of the P&T relief valve while the water heater is operating usually means
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the air pocket in the water tank needs to be restored
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Replace the anode
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when it has been reduced in size by 25%
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Atwood's newer adjustable DSI thermostat control allows temperature settings between
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None of the above ; 90 - 140 degrees F; 100 - 150 degrees F; 110 - 160 degrees F
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All 120 VAC heating elements for RV water heaters are rated between
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1000 - 1500 watts
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Electric heating element: 1500-watts. Incoming voltage: 120 VAC. What would be the resistance measurement of a good, working element?
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9.6 ohms
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On a water heater with an adjustable main burner assembly, the preliminary setting of the air shutter should be
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1/4 open position
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On a DSI water heater the E.C.O. is typically set to
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180 degrees F
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When its rating is exceeded, the ECO on a DSI unit will immediately shut down the
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gas valve
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The resistance measurement of the coil portion of a good DSI gas valve should read between
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30 to 50 ohms
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On DSI models with three probes at the igniter, one probe is for the spark, one for the sense circuit and one for the
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ground
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For proper operation, the minimum supply voltage coming into an Atwood DSI model is
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10.5 VDC
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To minimize P&T valve weeping, replenish the internal air pocket inside the tank. Which step below is not a part of that process?
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Turn on the water heater
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Which of the following is not a function of the PC board
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Produces the micro-amps for the flame sense circuit
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To remedy a lockout condition on a DSI water heater
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turn off the power switch, then turn it back on
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The main burner orifice size and combustion air volume of a furnace determines the
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BTU rating
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What event causes the blower motor to begin operating?
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Thermostat calls for heat
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Residual gases in the combustion chamber are removed before the burner ignites by
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running the blower motor
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A millivolt meter is used to test a
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thermocouple
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A ohmmeter is used to test a
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thermostat
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The component that moves fresh air into the combustion chamber is the
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combustion air wheel
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An increase in blower speed and decrease in blower motor amp draw is caused by
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air cavitation caused by blocked ducts
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Which component is not in the propane delivery system of a D.S.I. furnace?
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Gas cock
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Primary and secondary air refer to
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air mixed with gas and air use for combustion
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Which component prevents furnace ignition if there is insufficient air to purge the combustion chamber?
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Sail switch
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A high temperature safety device on a furnace is the
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Limit switch
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Which will not affect the operation of the sail switch
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gas control assembly
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Obstructions in the furnace air vent tubes will create
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a restriction in the flow of secondary air
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When voltage is supplied to the DSI circuit board, there is a(an) _____ before ignition.
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approximate 20 second delay
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The coolant level in a hydronic heating system is checked by
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visual inspection of the expansion tank
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The flame sense function on a DSI furnace equipped with a remote sense circuit senses the flame via a separate electrode. On a furnace equipped with a local sense circuit, the flame is actually monitored and sensed via
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the ground electrode
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In any forced air furnace, the resulting products of proper combustion are never mixed with air inside the RV because
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of the design of the sealed combustion chamber coupled with the flow of air through a heat exchanger
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With a proper heat anticipator setting, the furnace should cycle how many times per hour on average once the system has operated for a few hours?
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5 - 6 times
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Another name for a thermopile is
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pilot generator
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A sail switch is also called a(n)
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air prover
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The power source used for the typical modulating gas valve includes
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Neither A or B
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The two types of thermostats used in RV heating systems are
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wall and modulating valve
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The device which controls the furnace operation by reacting to room temperature and opening and closing a set of contact points which allows current to flow to the control valve is the
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thermostat
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The typical furnace pilot assembly consists of the pilot burner and
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pilot orifice
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When troubleshooting a pilot model furnace, if the gas valve does not open and the required voltage is present at the valve contacts,
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replace the gas valve
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If the pilot flame will not stay lit when releasing the manual pilot valve,
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verify the output of the thermocouple
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To test a thermostat on a gravity heater, simply measure for the correct
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continuity
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What type of furnace functions by having the blower engaged prior to the burner lighting?
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Forced air
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The purpose for having the blower start before lighting the burner is to
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purge the combustion chamber of any residual gases
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A furnace "cycling on limit" may have a
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restricted return air path; crushed delivery duct; faulty limit switch
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TDR stands for
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Time Delay Relay
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On a pilot model furnace equipped with a piezo ignition system, the gap between the electrode and burner should be
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3/16-inch
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On a forced air furnace, as the thermostat senses the interior air temperature, the contacts will open removing power from the gas valve. The blower motor will still continue to run until which device cools enough to stop the current flow to the motor?
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TDR
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Since the fan relay circuit is a normally "open" circuit, there should always be voltage from the furnace circuit breaker to the
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fan relay terminal
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On a pilot model forced air furnace, which of the following is NOT a cause for the symptom… blower runs but fails to ignite burner?
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Defective blower relay
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A typical sail switch will close its contacts when the blower wheel reaches what percentage of its rated air flow?
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75%
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If so equipped, the heat anticipator can be found
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in the wall thermostat
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On a DSI furnace, the circuit board will
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allow the blower to purge the combustion chamber for a set period of time; open the gas valve; confirm the presence of a burner flame
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While the furnace is operating, the TDR will draw approximately
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.2-amp
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Which component contains a bimetal disk, a coil, and contacts for the thermostat, ground connection and positive 12-volts DC?
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TDR
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When troubleshooting the redundant gas valve on the DSI forced air furnace, a good coil will measure
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30 - 50 Ohms each
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The voltage range for proper heater operation is
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10.5 to 13.5 VDC
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The thermocouple on a gravity heater creates _____ millivolts.
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20 to 30
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Forced air gravity heaters should have a voltage of between _____ and _____ at the furnace during operation.
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10.5 and 13.5 VDC
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The device that controls the fan causing it to purge the combustion chamber of any residual gases before the furnace attempts to light is called the
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D.S.I. circuit board
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The thermostat has an anticipator which will burn out if the TDR and gas value draw more than _____ amps.
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1.0
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Some manufacturers recommend replacing the gas solenoid valve on a D.S.I. furnace if the coil is defective. One way to know if a coil is defective is when the resistance is not within a range of _____ ohms.
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30 to 50
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The component of a furnace that sends a high voltage spark to the electrode assembly and sends 12 VDC to the gas solenoid valve is the _____.
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D.S.I. circuit board
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The central hot water heating system has an electrical heating element which is _____ watts.
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1650
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The central hot water heating system has a water and antifreeze ratio of
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1 to 1
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To prevent freezing of the water system, adjust the bay thermostat on the central hot water heating system to _____ degrees.
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40 to 50°F (4 to 10°C)
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Normal operating temperature for the central hot water heating system is _____ degrees.
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175 to 200°F (82 to 93°C)
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Only pure ammonia vapor is present after the contents pass through which component?
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Rectifier
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The static pressure of the hydrogen vapor inside the cooling unit
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is 250 PSI
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The purpose of sodium chromate inside the cooling unit is to
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protect the insides of the piping
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Which component is not associated with the electric operation of the RV refrigerator?
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Flue
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In which component does ammonia cool into a liquid?
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Condenser
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What removes heat from the ammonia vapor?
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Air moving through the condenser fins
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During a refrigerator installation, never allow the side clearances to extend beyond
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1/2-inch
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Correct energy source priority for a Norcold automatic refrigerator is
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120-VAC, LP, 12-VDC
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Correct energy source priority for a Dometic automatic refrigerator is
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120-VAC, 12-VDC, LP
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The absorption refrigerator cooling unit consists of the following components:
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boiler, condenser, evaporator and absorber
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Hydrogen Gas has a maximum pressure of _____ PSI when heated.
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600
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An excessive amount of heat in the cooling unit will cause
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both the water and ammonia to vaporize
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_____ requires the refrigerator to be installed in such a manner as to provide complete separation of the combustion system and the interior atmosphere of the RV.
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NFPA 1192 /CSA Z240
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The proper voltage operating range of a 120 VAC, 60 Hz refrigerator is
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108-132 VAC
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For the refrigerator to work properly on propane, the propane pressure should be
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11 " W.C.
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The proper procedure to clean an orifice assembly is to soak it in
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an alcohol based solvent
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If the refrigerator is not running on AC, the first thing to check is the
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incoming Voltage
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To bench test an electric thermostat, attach the leads of your VOM to the contacts of the thermostat and test for
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continuity
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When a capillary tube has lost its charge, it is necessary to
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replace the thermostat
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Where is hydrogen gas combined with liquid ammonia?
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Evaporator
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In an absorption refrigerator the _____ vaporizes in the hydrogen gas atmosphere and absorbs heat from inside the refrigerator.
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ammonia
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Eye-level ranges are no longer produced because of what inherent factor?
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They became too costly to the RV manufacturer
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The pilot flame on an RV range is typically controlled by either a manual on/off valve or by the
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oven thermostat
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The oven safety valve
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contains a thermal bulb which is heated by the standing oven pilot
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A cooking appliance with top burners only is called a
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cooktop
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Care must be taken when replacing burners and orifices to ensure
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matching of Btu/hr ratings
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A thermal bulb performs which function?
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Senses oven temperature
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Which flame sensing device controls the gas flow to the oven standing pilot?
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There is no flame sensing device
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A well adjusted burner flame can be recognized by a
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crisp blue flame with blue inner crown
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Burner orifice rating are identified by
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color
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When trouble shooting a poorly functioning cooktop burner first check the
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propane pressure
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