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167 Cards in this Set

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