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HVAC Practive midterm 56
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Questions in this quiz (56)
1On a standing pilot gas furnace the thermocouple must be replaced when?
- Aits not positioned properly
- BThe millivolt reading is 28 or above
- Cthe millivolt reading is 22 or below
- Dthe tip of the thermocouple is in the tip if the pilot flame is 3/8
2natural gas pressure at the main line is recorded at 7" WC (water column), But at the gas manifold it reads 1.5 WC. What is most likely to be the cause of this?
- AA defective main line regulator
- BToo large of a gas valve
- Cplugged burner orifices
- DA defective pressure regulator on the gas valve
3A technician servicing a gas fired furnace notices that only four out of five ribbon burners are firing simultaneously . What could be the problem with the system?
- AToo much gas pressure
- BToo little gas pressure
- CBurners not aligned correctly
- DA defective gas valve
4Technician A says if a combination gas valve needs to be replaced if there are 24 volts present to the gas valve and it will not open.
Technician B says that if a combination gas valve has a new thermocouple and the pilot will not stay lit the gas valve needs to be replaced.
Which technician is correct?- ATech A
- BTECH B
- CBoth are right
- DBoth are wrong
5What should be the first step that a technician should take if the gas pressure at the manifold is too high?
- Aadjust the pressure regulator clockwise
- Badjust the pressure regulator counter clockwise
- Creplace the pressure regulator
- Dreplace the combination gas valve
6If the glame is lifting off the burner port what should the technician do to correct this problem?
- AAdjust the primary air by closing the air shutter
- Badjust the primary air by opening the air shutter
- Creplace the burner
- Ddecrease the min gas pressure.
7a step down transformer is reading 0 ohms at its secondary winding. what is the possible cause of this problem?
- AAn open primary winding
- Ban open secondary winding
- CA shorted primary winding
- DA shorter secondary winding
8when a fan centre relay needs to be tested for 124 volts, what two terminals are used when measuring for transformer output voltages?
- ATerminals "R" and "W"
- BTerminals "R" and "G"
- CTerminals "R" and "Y"
- DTerminals "R and "C'
9On a call for heat what two terminals should be closed on the thermostat?
- ATerminals "R" and "W"
- BTerminals "R" and "G"
- CTerminals "R" and "Y"
- DTerminals "R" and "C"
10when a thermostat sub base fan selector switch is moved to the fan "ON" postition, what two terminals will close in the thermostat.
- ATerminals "R" and "W"
- BTerminals "R" and "G"
- CTerminals "R" and "Y"
- DTerminals "R" and "C"
11A new thermostat was recently replaced. The technician observes that the burner cycle is not long enough. the most likely cause would be?
- AA defective thermostat
- BLow gas pressure
- Cthe anticipator needs adjusting
- DA defective gas valve
12A customer has replaced a mercury bulb thermostat but complains that the burners will not shut off and the house is getting too hot. The cause would be?
- AA defective limit control
- BA defective gas valve
- CThe thermostat is not properly level
- Dthe anticipator is set too low
13A bimetal fan control will not turn the indoor blower off. As a result cool air passes through the registers between furnace cycles. What is the possible cause of the problem.
- AThe heating circuit is open on limit.
- Bthe fan control contacts are stuck open
- Cthe fan control contacts are stuck closed
- Dthere is a defective gas valve
14residents are complaining of experiencing sumptoms of headaches, watery eyes and nausea.
Tech A says the heat exchanger is cracked
Tech B says the furnace may only need cleaning and the heat exchanger is possibly plugged.
Whos correct?- ATech A
- BTech B
- CBoth are correct
- DBoth are incorrect
15A belt driver motor has recently been replaced but the furnace is shutting off on limit control. the most likely cause is that .
- AA. the motor is running in the wrong direction
- Bthe motor is defective
- Cthe motor is too large
- Dthe motor mount is not correct.
16upon testing a motor winding for continuity the technician records 3 ohms. The winding resistance should be 8 Ohms. The technician concludes that:
- AThe winding is open
- BThe winding is shorted
- Cthe winding is grounded
- Dthe motor is within the satisfactory operating conditions
17A run capacitor is tested with an analog meter. The needle moves towards zero then back to infinity. What is the condition of the capacitor?
- AThe capacitor is open.
- BThe capacitor is good
- CThe capacitor should not be used
- DThe capacitor needs to be of a higher mfd rating
18The temperature rise of a particular furnace states that it should be between 35F and 65F. The furnace is operating at 20F temperature rise with the proper gas pressure at the manifold. What could be done to solve this problem.
- AAdd more outside air to the basement
- Bincrease the indoor blower motor speed
- CDecrease the indoor motor blower speed
- Dreplace the air filter with a more efficient type.
19A belt driven motor has been replaces, but quickly gets hot and stops just short of burning out. Which of the following could cause the problem:
- AA fan belt that is too tightly adjusted
- BA fan belt that has only 1" of slack between the pulleys
- CThe pulley on the motor is too small
- Dnone of the above.
20A combination fan/limit control has been replaced. The indoor blower motor runs too long and the residents complain of cooler airflow. The technician should:
- AReplace the control again
- BAdjust the limit setting
- CLengthen the fan off setting.
- DCheck the readjust the fan-off differential
21A service call is made to a customer who complains that when his furnace ignites, the flame rolls out in front of the head exchanger.
Technician A says that it is due to poor draft possibly a blocked flue or heat exchanger
Technician B says that it has to do with the limit control or the fan switch control circuit.- ATechnician A
- BTechnician B
- CBoth Technician are correct
- DBoth Technicians are incorrect
22A customer complains of headaches, sleepiness and nausea.
Technician A finds a crack in the head exchanger and says that the furnace should be shut down.
Technician B says that the crack isnt too serious and the furnace can operate temporarily but it must be cleaned.- ATech A is correct
- BTech B is correct
- CBoth technicians are correct
- DBoth technicans are incorrect
23A technician is servicing a standing pilot gas-fired furnace. The complaint is that the burners are not lighting. where should the technician start trouble shooting the system?
- AAt the transformer secondary and at the combination gas valve
- BAt the transformer primary only.
- CAt the primary limit control
- Dat the fan limit controls.
24On a spark ignition system, The spark for the ignition continues with no ignition of gas at the burners.
Technician A Concludes that the thermostat is defective.
Technician B Concludes that it is possibly the control module
Which is correct?- ATechnician A
- BTechnician B
- CBoth are correct
- DBoth technicians are incorrect
25Which of the following is the correct test for a faulty cable on a direct spark ignition system?
- AA voltage check
- BA continuity check
- CAn amerpage check
- Dnone of the above
26A customer complains that the burners light on her system, But then immediately shut down. The problem is most likely to be?
- AIn the control module
- Bin the control transformer
- Cin the limit control
- Din the gas valve
27Which of the following would not be a proper procedure to perform on a direct spark ignition system where the spark continues, the burners light and the flames are immediately extinguished?
- ACheck that the sensor is positioned in the flame correctly
- Bcheck for the proper flame rectification
- Ccheck for a proper grounding terminal
- Dcheck that there is proper gas flow to the pilot
28A hot surface ignition system does not ignite the main burner. after measuring voltage to the igniter the technician should:
- APerform a resistance test on the igniter
- BReplace the flame sensor
- CReplace the main gas valve
- DReplace the control module
29The burners of a gas furnace that is equipped with a 115-Volt hot surface igniter lights for approximately 7's and then goes out. what is the problem that could cause this symptom.
- AA faulty igniter
- BA faulty transformer secondary winding
- Cburner shutting off on high limit control
- Da faulty sensor
30The burners on a furnace having a hot surface ignition system light up but quickly shut off.
Technician A states that after testing the gas valve he determined that it has shorter
Technician B Visually checked the flame sensor, cleaned it and performed a continuity test. he faults a dirty sensor.
Whos correct?- ATechnician A
- BTechnician B
- CBoth Technicians are correct
- DBoth technicians are incorrect
31The thermostat on a mid efficiency gas furnace with a hot surface ignition system is placed on a call for heat. The burners do not light, but the igniter does glow. Which of the following would be the next step to take when troubleshooting the system?
- Atest the flame sensor
- Btest the gas valve and the gas manifold pressure
- Ctest the primary limit control and the fan control
- Dtest the thermostat
32The draft pressure switch on a mid effciency gas furnace with a hot surface ignition system is placed on a call for heat. the burners do not light, but the igniter does glow. Which of the following would be the next step to take when troubleshooting the system?
- ATest the flame sensor
- Btest the gas valve and the gas manifold pressure.
- Ca defective inducer draft motor
- Da defective flame roll out sensor
33A high efficiency gas furnace will not stay in operation. The unit runs for approximately 5 min then shuts down by the main furnace controller with an open pressure switch flash code. which of the following is not a proper test to perform in this situation?
- Acheck the inducer draft motor
- BCheck the furnace filter
- CCheck for a restricted flue pipe
- Dboth a and c
34A service call is made on a mid efficiency gas furnace. on a call for heat, the induced draft motor will not operate. what is the proper trouble shooting procedure that should be taken.
- ACheck for control voltage at "G" and "C" terminals at the circuit board.
- Bcheck for control voltage across terminals "W" and "C" at the circuit board.
- Ccheck the control voltage at the induced draft relay
- DBoth B and C
35A high efficiency gas furnace that uses a controller will not energize the blower motor after a pre selected 45sec time on setting. Which of the following would be the most correct trouble shooting procedure?
- Ameasure the resistance across the furnace controller low speed terminal and common.
- Bmeasure the resistance across the furnace controller high speed terminal and common
- Cmeasure the voltage to the motor and test the run capacitor
- Dmeasure the amperage on the blower motor and test the run capacitor.
36when servicing a mid efficiency gas furnace the thermostat has been turned to the off position but the burners remain lit and the induced draft motor continues to operate. which of the following would be the most correct troubleshooting procedure?
- Adetermine if the thermostat is open and check voltage at the gas valve
- Bcheck for voltage at the indoor blower motor.
- Creplace the control module
- Dcheck the ignition system
37on a high efficiency gas furnace that uses a controller the indoor blower motor will not de energize after its pre selected off delay setting. which of the following is a logical repair for the system.
- Areplace the run capacitor
- Breplace the blower motor
- Creplace the control module
- Dchange the speed setting on the control module
38The burners on a gas furnace cycle for approximately 3 to 4 min. during a call for heat. the system does not provide adequate heat for the home.
Technician A has determind that a new thermostat has been installed and that the heat anticipator was incorectly adjusted
Technician B cleans the position of the flame sensor and claim that this was the fault
Whos correct?- Atech A
- BTech B
- Cboth are correct
- Dboth are incorrect
39A gas furnace has recently been converted to LP gas. on a call for heat the furnace is not firing correctly and is starting to soot up. what would be the most likely cause for this problem?
- ALow LPG pressure
- Btoo long of a burner cycle
- Cwrong orifice size installed
- Dall of the above
40when inspecting a gas furnace it is noticed that the burner flames are very small in height. what action should be taken by the technician?
- Areplace the gas valve
- Breplace the orifices
- Ccheck the pressure and adjust the primary air shutters if needed
- Dcontact the utility company to replace the gas meter
41a customer is experiencing a loud delayed ignition from his gas furnace.
Tech A says its possible that the gas valve is not opening or closing properly
Tech B claims that its possible that after the furnace had been cleaned the burner were not properly aligned.
whos correct?- ATech A
- BTech B
- Cboth right
- Dboth wrong
42A customer called in complaining that his indoor blower would not stop running. what is the most possible cause of this problem?
- Aa defective blower motor run capacitor
- Bcontacts stuck open on the fan control
- Ccontacts stuck closed on the fan control
- Dboth A and C
43after diagnosing a no heat call it has been determined that the induced draft motor is not operating.
Tech A says that it is the fault of an induced draft pressure switch
Tech B states that the indoor blower relay module is defective.- ATechnician A
- BTechnician B
- Cboth are right
- Dboth are wrong
44The burners on a gas fired furnace are continously lit and setting the thermostat to the off position doesnt not make any difference. What is a possible problem for this fault ?
- Aa defective gas valve
- Ba defective fan control
- Ca limit control stuck in the closed position
- Da shorted secondary winding on the transformer
45a customer complains that she has no head and that the furnace does nothing at all. she says that it is a mid efficiency gas furnace with an induced draft motor and a direct spark ignition system. which of the following would be likely place to start trouble shooting
- Acheck the fan door switch
- Bcheck for a blown fuse
- Ccheck for a defective furnace switch
- Dall of the above
46on a hot surface ignition system the igniter does not glow. what would be the most likely cause of this fault.
- Aa bad flame sensor
- Ba bad gas valve
- Ca bad closed pressure switch
- Da bad igniter
47on a spark ignition system the spark is occurring but its pilot will not light. which one would you check?
- Aterminals PV and MV/Pv for 24 volts
- Btest for continuity of PV coil
- Ctest for the gas to the pilot line
- Dall of the above
48the thermocouple on a furnace has just been replaced but the pilot light continues to go out. what test should a tech perform?
- Aensure that the pilot flame is engulfing the tip of the thermocouple 3/8"
- Btest continuity of the main valve
- Ctest for voltage to the main gas valve
- Dcheck for open limit control
49an existing thermocouple has been tested with a millitvolt meter and has registered 13 millivolts. which of the following would be the correct action to take?
- Amake sure that the thermostat is calling for heat
- Breplace the thermocouple
- Creplace the pilot gas valve
- Dthere is no problem with the thermocouple and it should be left alone.
50what is an acceptable voltage for a thermocouple?
- A30 milliV
- B20 milliV
- C10 milliV
- D5 milliV
51an indoor blower motor will run but it cycles on a internal overload protector using a digital meter.
Tech A states the meter read zero when placing it across the motors run capacitor.
Tech B states that the meter read OL when placing it across the run capacitor.
whos right?- ATech A
- BTech B
- CBoth right
- Dboth wrong
52a furnace has been operating during the mild winters. during the cold days the 3 year old furnace doesnt provide continuous heat to satisfy the demand. the technician does a Btu input measurement by clocking the gas meter and finds the system within specifcations. the temperature rise is also within system limits which of the following would be the most correct diagnosis.
- Athe furnace was undersized in heating capacity
- Bthe gas pressure needs to be increased
- Cthe duct work needs redesigning
- Dnone
53during furnace operations the thermostat is quickly satisfied. the new furnace heats the entire house very quickly then shuts off on thermostat demand. which would be the most correct statement of this situation
- Athe thermostat needs replacing
- Bthe blower speed should be increased
- Cthe furnace heating capacity is oversized
- Dthe duct system is too large
54Two gas furnaces were installed. Both were 150 MBtu/H (150,000 Btu/H). Both furnaces may operate at the same. when one furnace is running all operations are satisfied. When both furnaces are operating at the same time the burner flames of both furnaces decrease in size. Which procedure is correct.
- AReplace the heating thermostat
- BIncrease the gas pressure regulator of the first furnace
- Creplace both gas valves
- DDetermine if the gas piping layout is properly sized
55On a natural gas to LPG furnace conversation
Tech A states only one burner orifice needs to be changing
Tech B states the orifices gas valve regulator spring and pilot orifice should be changed.- ATech A
- BTech B
- Cboth are right
- Dboth are wrong
56A draft test has been performed and it is indicated that there is an improper draft for the gas furnace that is being used. Whcih of the following would be the correct procedure to preform?
- AIncreases the gas pressure
- Bincrease the inducer draft motor speed
- Ccheck for chimney obstructions
- Dreplace the heat exchanger
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- Description
- This is practice for hell day on tuesday lol
- Author
- Rudy Robertson
- Language
- English
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