Rudy Robertson
Test por , creado hace más de 1 año

This is practice for hell day on tuesday lol

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Rudy Robertson
Creado por Rudy Robertson hace casi 9 años
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HVAC Practive midterm 56

Pregunta 1 de 56

1

On a standing pilot gas furnace the thermocouple must be replaced when?

Selecciona una de las siguientes respuestas posibles:

  • its not positioned properly

  • The millivolt reading is 28 or above

  • the millivolt reading is 22 or below

  • the tip of the thermocouple is in the tip if the pilot flame is 3/8

Explicación

Pregunta 2 de 56

1

natural 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?

Selecciona una de las siguientes respuestas posibles:

  • A defective main line regulator

  • Too large of a gas valve

  • plugged burner orifices

  • A defective pressure regulator on the gas valve

Explicación

Pregunta 3 de 56

1

A 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?

Selecciona una de las siguientes respuestas posibles:

  • Too much gas pressure

  • Too little gas pressure

  • Burners not aligned correctly

  • A defective gas valve

Explicación

Pregunta 4 de 56

1

Technician 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?

Selecciona una de las siguientes respuestas posibles:

  • Tech A

  • TECH B

  • Both are right

  • Both are wrong

Explicación

Pregunta 5 de 56

1

What should be the first step that a technician should take if the gas pressure at the manifold is too high?

Selecciona una de las siguientes respuestas posibles:

  • adjust the pressure regulator clockwise

  • adjust the pressure regulator counter clockwise

  • replace the pressure regulator

  • replace the combination gas valve

Explicación

Pregunta 6 de 56

1

If the glame is lifting off the burner port what should the technician do to correct this problem?

Selecciona una de las siguientes respuestas posibles:

  • Adjust the primary air by closing the air shutter

  • adjust the primary air by opening the air shutter

  • replace the burner

  • decrease the min gas pressure.

Explicación

Pregunta 7 de 56

1

a step down transformer is reading 0 ohms at its secondary winding. what is the possible cause of this problem?

Selecciona una de las siguientes respuestas posibles:

  • An open primary winding

  • an open secondary winding

  • A shorted primary winding

  • A shorter secondary winding

Explicación

Pregunta 8 de 56

1

when a fan centre relay needs to be tested for 124 volts, what two terminals are used when measuring for transformer output voltages?

Selecciona una de las siguientes respuestas posibles:

  • Terminals "R" and "W"

  • Terminals "R" and "G"

  • Terminals "R" and "Y"

  • Terminals "R and "C'

Explicación

Pregunta 9 de 56

1

On a call for heat what two terminals should be closed on the thermostat?

Selecciona una de las siguientes respuestas posibles:

  • Terminals "R" and "W"

  • Terminals "R" and "G"

  • Terminals "R" and "Y"

  • Terminals "R" and "C"

Explicación

Pregunta 10 de 56

1

when a thermostat sub base fan selector switch is moved to the fan "ON" postition, what two terminals will close in the thermostat.

Selecciona una de las siguientes respuestas posibles:

  • Terminals "R" and "W"

  • Terminals "R" and "G"

  • Terminals "R" and "Y"

  • Terminals "R" and "C"

Explicación

Pregunta 11 de 56

1

A new thermostat was recently replaced. The technician observes that the burner cycle is not long enough. the most likely cause would be?

Selecciona una de las siguientes respuestas posibles:

  • A defective thermostat

  • Low gas pressure

  • the anticipator needs adjusting

  • A defective gas valve

Explicación

Pregunta 12 de 56

1

A 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?

Selecciona una de las siguientes respuestas posibles:

  • A defective limit control

  • A defective gas valve

  • The thermostat is not properly level

  • the anticipator is set too low

Explicación

Pregunta 13 de 56

1

A 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.

Selecciona una de las siguientes respuestas posibles:

  • The heating circuit is open on limit.

  • the fan control contacts are stuck open

  • the fan control contacts are stuck closed

  • there is a defective gas valve

Explicación

Pregunta 14 de 56

1

residents 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?

Selecciona una de las siguientes respuestas posibles:

  • Tech A

  • Tech B

  • Both are correct

  • Both are incorrect

Explicación

Pregunta 15 de 56

1

A belt driver motor has recently been replaced but the furnace is shutting off on limit control. the most likely cause is that .

Selecciona una de las siguientes respuestas posibles:

  • A. the motor is running in the wrong direction

  • the motor is defective

  • the motor is too large

  • the motor mount is not correct.

Explicación

Pregunta 16 de 56

1

upon testing a motor winding for continuity the technician records 3 ohms. The winding resistance should be 8 Ohms. The technician concludes that:

Selecciona una de las siguientes respuestas posibles:

  • The winding is open

  • The winding is shorted

  • the winding is grounded

  • the motor is within the satisfactory operating conditions

Explicación

Pregunta 17 de 56

1

A run capacitor is tested with an analog meter. The needle moves towards zero then back to infinity. What is the condition of the capacitor?

Selecciona una de las siguientes respuestas posibles:

  • The capacitor is open.

  • The capacitor is good

  • The capacitor should not be used

  • The capacitor needs to be of a higher mfd rating

Explicación

Pregunta 18 de 56

1

The 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.

Selecciona una de las siguientes respuestas posibles:

  • Add more outside air to the basement

  • increase the indoor blower motor speed

  • Decrease the indoor motor blower speed

  • replace the air filter with a more efficient type.

Explicación

Pregunta 19 de 56

1

A 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:

Selecciona una de las siguientes respuestas posibles:

  • A fan belt that is too tightly adjusted

  • A fan belt that has only 1" of slack between the pulleys

  • The pulley on the motor is too small

  • none of the above.

Explicación

Pregunta 20 de 56

1

A combination fan/limit control has been replaced. The indoor blower motor runs too long and the residents complain of cooler airflow. The technician should:

Selecciona una de las siguientes respuestas posibles:

  • Replace the control again

  • Adjust the limit setting

  • Lengthen the fan off setting.

  • Check the readjust the fan-off differential

Explicación

Pregunta 21 de 56

1

A 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.

Selecciona una de las siguientes respuestas posibles:

  • Technician A

  • Technician B

  • Both Technician are correct

  • Both Technicians are incorrect

Explicación

Pregunta 22 de 56

1

A 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.

Selecciona una de las siguientes respuestas posibles:

  • Tech A is correct

  • Tech B is correct

  • Both technicians are correct

  • Both technicans are incorrect

Explicación

Pregunta 23 de 56

1

A 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?

Selecciona una de las siguientes respuestas posibles:

  • At the transformer secondary and at the combination gas valve

  • At the transformer primary only.

  • At the primary limit control

  • at the fan limit controls.

Explicación

Pregunta 24 de 56

1

On 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?

Selecciona una de las siguientes respuestas posibles:

  • Technician A

  • Technician B

  • Both are correct

  • Both technicians are incorrect

Explicación

Pregunta 25 de 56

1

Which of the following is the correct test for a faulty cable on a direct spark ignition system?

Selecciona una de las siguientes respuestas posibles:

  • A voltage check

  • A continuity check

  • An amerpage check

  • none of the above

Explicación

Pregunta 26 de 56

1

A customer complains that the burners light on her system, But then immediately shut down. The problem is most likely to be?

Selecciona una de las siguientes respuestas posibles:

  • In the control module

  • in the control transformer

  • in the limit control

  • in the gas valve

Explicación

Pregunta 27 de 56

1

Which 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?

Selecciona una de las siguientes respuestas posibles:

  • Check that the sensor is positioned in the flame correctly

  • check for the proper flame rectification

  • check for a proper grounding terminal

  • check that there is proper gas flow to the pilot

Explicación

Pregunta 28 de 56

1

A hot surface ignition system does not ignite the main burner. after measuring voltage to the igniter the technician should:

Selecciona una de las siguientes respuestas posibles:

  • Perform a resistance test on the igniter

  • Replace the flame sensor

  • Replace the main gas valve

  • Replace the control module

Explicación

Pregunta 29 de 56

1

The 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.

Selecciona una de las siguientes respuestas posibles:

  • A faulty igniter

  • A faulty transformer secondary winding

  • burner shutting off on high limit control

  • a faulty sensor

Explicación

Pregunta 30 de 56

1

The 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?

Selecciona una de las siguientes respuestas posibles:

  • Technician A

  • Technician B

  • Both Technicians are correct

  • Both technicians are incorrect

Explicación

Pregunta 31 de 56

1

The 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?

Selecciona una de las siguientes respuestas posibles:

  • test the flame sensor

  • test the gas valve and the gas manifold pressure

  • test the primary limit control and the fan control

  • test the thermostat

Explicación

Pregunta 32 de 56

1

The 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?

Selecciona una de las siguientes respuestas posibles:

  • Test the flame sensor

  • test the gas valve and the gas manifold pressure.

  • a defective inducer draft motor

  • a defective flame roll out sensor

Explicación

Pregunta 33 de 56

1

A 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?

Selecciona una de las siguientes respuestas posibles:

  • check the inducer draft motor

  • Check the furnace filter

  • Check for a restricted flue pipe

  • both a and c

Explicación

Pregunta 34 de 56

1

A 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.

Selecciona una de las siguientes respuestas posibles:

  • Check for control voltage at "G" and "C" terminals at the circuit board.

  • check for control voltage across terminals "W" and "C" at the circuit board.

  • check the control voltage at the induced draft relay

  • Both B and C

Explicación

Pregunta 35 de 56

1

A 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?

Selecciona una de las siguientes respuestas posibles:

  • measure the resistance across the furnace controller low speed terminal and common.

  • measure the resistance across the furnace controller high speed terminal and common

  • measure the voltage to the motor and test the run capacitor

  • measure the amperage on the blower motor and test the run capacitor.

Explicación

Pregunta 36 de 56

1

when 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?

Selecciona una de las siguientes respuestas posibles:

  • determine if the thermostat is open and check voltage at the gas valve

  • check for voltage at the indoor blower motor.

  • replace the control module

  • check the ignition system

Explicación

Pregunta 37 de 56

1

on 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.

Selecciona una de las siguientes respuestas posibles:

  • replace the run capacitor

  • replace the blower motor

  • replace the control module

  • change the speed setting on the control module

Explicación

Pregunta 38 de 56

1

The 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?

Selecciona una de las siguientes respuestas posibles:

  • tech A

  • Tech B

  • both are correct

  • both are incorrect

Explicación

Pregunta 39 de 56

1

A 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?

Selecciona una de las siguientes respuestas posibles:

  • Low LPG pressure

  • too long of a burner cycle

  • wrong orifice size installed

  • all of the above

Explicación

Pregunta 40 de 56

1

when inspecting a gas furnace it is noticed that the burner flames are very small in height. what action should be taken by the technician?

Selecciona una de las siguientes respuestas posibles:

  • replace the gas valve

  • replace the orifices

  • check the pressure and adjust the primary air shutters if needed

  • contact the utility company to replace the gas meter

Explicación

Pregunta 41 de 56

1

a 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?

Selecciona una de las siguientes respuestas posibles:

  • Tech A

  • Tech B

  • both right

  • both wrong

Explicación

Pregunta 42 de 56

1

A customer called in complaining that his indoor blower would not stop running. what is the most possible cause of this problem?

Selecciona una de las siguientes respuestas posibles:

  • a defective blower motor run capacitor

  • contacts stuck open on the fan control

  • contacts stuck closed on the fan control

  • both A and C

Explicación

Pregunta 43 de 56

1

after 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.

Selecciona una de las siguientes respuestas posibles:

  • Technician A

  • Technician B

  • both are right

  • both are wrong

Explicación

Pregunta 44 de 56

1

The 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 ?

Selecciona una de las siguientes respuestas posibles:

  • a defective gas valve

  • a defective fan control

  • a limit control stuck in the closed position

  • a shorted secondary winding on the transformer

Explicación

Pregunta 45 de 56

1

a 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

Selecciona una de las siguientes respuestas posibles:

  • check the fan door switch

  • check for a blown fuse

  • check for a defective furnace switch

  • all of the above

Explicación

Pregunta 46 de 56

1

on a hot surface ignition system the igniter does not glow. what would be the most likely cause of this fault.

Selecciona una de las siguientes respuestas posibles:

  • a bad flame sensor

  • a bad gas valve

  • a bad closed pressure switch

  • a bad igniter

Explicación

Pregunta 47 de 56

1

on a spark ignition system the spark is occurring but its pilot will not light. which one would you check?

Selecciona una de las siguientes respuestas posibles:

  • terminals PV and MV/Pv for 24 volts

  • test for continuity of PV coil

  • test for the gas to the pilot line

  • all of the above

Explicación

Pregunta 48 de 56

1

the thermocouple on a furnace has just been replaced but the pilot light continues to go out. what test should a tech perform?

Selecciona una de las siguientes respuestas posibles:

  • ensure that the pilot flame is engulfing the tip of the thermocouple 3/8"

  • test continuity of the main valve

  • test for voltage to the main gas valve

  • check for open limit control

Explicación

Pregunta 49 de 56

1

an 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?

Selecciona una de las siguientes respuestas posibles:

  • make sure that the thermostat is calling for heat

  • replace the thermocouple

  • replace the pilot gas valve

  • there is no problem with the thermocouple and it should be left alone.

Explicación

Pregunta 50 de 56

1

what is an acceptable voltage for a thermocouple?

Selecciona una de las siguientes respuestas posibles:

  • 30 milliV

  • 20 milliV

  • 10 milliV

  • 5 milliV

Explicación

Pregunta 51 de 56

1

an 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?

Selecciona una de las siguientes respuestas posibles:

  • Tech A

  • Tech B

  • Both right

  • both wrong

Explicación

Pregunta 52 de 56

1

a 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.

Selecciona una de las siguientes respuestas posibles:

  • the furnace was undersized in heating capacity

  • the gas pressure needs to be increased

  • the duct work needs redesigning

  • none

Explicación

Pregunta 53 de 56

1

during 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

Selecciona una de las siguientes respuestas posibles:

  • the thermostat needs replacing

  • the blower speed should be increased

  • the furnace heating capacity is oversized

  • the duct system is too large

Explicación

Pregunta 54 de 56

1

Two 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.

Selecciona una de las siguientes respuestas posibles:

  • Replace the heating thermostat

  • Increase the gas pressure regulator of the first furnace

  • replace both gas valves

  • Determine if the gas piping layout is properly sized

Explicación

Pregunta 55 de 56

1

On 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.

Selecciona una de las siguientes respuestas posibles:

  • Tech A

  • Tech B

  • both are right

  • both are wrong

Explicación

Pregunta 56 de 56

1

A 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?

Selecciona una de las siguientes respuestas posibles:

  • Increases the gas pressure

  • increase the inducer draft motor speed

  • check for chimney obstructions

  • replace the heat exchanger

Explicación

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