Gas Troubleshooting V
Gas Troubleshooting V
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Question 1 |
Which of the following can cause a limit switch to open?
A | A dirty filter |
B | Too high of supply air static pressure |
C | Not enough return air |
D | All of the above |
Question 2 |
A direct short to ground of a primary wire on a transformer would most likely cause
A | A circuit breaker to trip |
B | A transformer to become defective |
C | A gas valve to become defective |
D | A thermostat to become defective |
Question 3 |
To correctly set a heat anticipator, the control amperage reading should be
A | Performed at the gas valve |
B | Performed at the secondary of the transformer |
C | Performed at the thermostat subbase |
D | All of the above |
Question 4 |
When a natural gas furnace has flames that are more yellow than blue what corrective action should a tech take?
A | Replace the gas valve |
B | Increase the gas pressure |
C | Open the primary air ports |
D | Close the primary air ports |
Question 5 |
What are the normally open set of contacts used for on a fan center relay?
A | High speed operation of the blower motor |
B | Low speed operation of blower motor |
C | Humidifier circuit switching |
D | Isolation contacts for the heating circuit |
Question 6 |
A customer complaint is that the furnace is not operating. After inspection of the system, the tech notices a small hairline crack in the ceramic of the sensing probe. What action must the tech take to repair this problem?
A | Repair the probe by sealing the crack with silicone |
B | Replace the sensing probe |
C | No action, sensing probes can handle small cracks |
D | None of the above |
Question 7 |
How should a limit safety check be performed on a gas furnace?
A | Temporarily jump out the limit control for at least 10 min, then remove the jumper |
B | Stop the blower operation for at least 10 min or until the limit control opens |
C | Block off cold air return for 5 min, or until the limit control closes |
D | Jump out the thermostat for 15 min or until the furnace cycles on the limit control |
Question 8 |
How is an induced draft pressure switch tested for proper operation?
A | Jump out the pressure switch after setting the thermostat to the heat position and test the control with a manometer |
B | Decrease the indoor motor speed and test the control with a manometer |
C | De energize the induced draft motor and test the switch with a manometer |
D | Energize the heating system while testing the pressure switch with a manometer |
Question 9 |
Which of the following are input signals to a high efficiency furnace control board?
A | The thermostat, the flame rollout sensor, and the igniter |
B | The pressure switch, the pilot valve, and the limit control |
C | The flame sensor circuit, the main gas valve, and the thermostat |
D | The thermostat, the flame sensor circuit, and the limit control |
Question 10 |
Which of the following are output signals to a high efficiency furnace control board?
A | The thermostat, the main gas valve, and the igniter |
B | The main gas valve, the pilot valve, and the limit control |
C | The flame sensor circuit the main gas valve, and the igniter |
D | The igniter, the pilot gas valve, and the main gas valve |
Question 11 |
Where do high efficiency condensing furnaces get their combustion air?
A | From outside of the home only |
B | From inside of the home only |
C | From inside or outside of the home |
D | None of the above |
Question 12 |
Which of the following is not a cause of insufficient low gas input?
A | Plugged orifice |
B | Faulty regulator |
C | Faulty heat exchanger |
D | Bad gas valve |
Question 13 |
A customer complains that there is not enough supply air coming through the registers. Tech A checked the furnace temperature rise, inspected the air filter and adjusted a loose fan belt. Tech B inspected the air filter, observed the blower motor operation, checked for duct obstructions, and made sure that the balancing dampers were in the correct position. Which tech performed the proper procedures?
A | Tech A |
B | Tech B |
C | Both techs are correct |
D | Both techs are incorrect |
Question 14 |
A tech was called because not enough heat was being generated at the furnace. The tech checked the heat exchanger, flue pipe, and burners. He also tested the inlet and outlet gas pressure to the furnace. His measurement was 4”WC to the main gas valve and 2”WC out of the gas valve. Which of the following could be the problem with the system?
A | Faulty gas valve |
B | Faulty gas meter regulator |
C | Faulty heat exchanger |
D | Faulty gas control circuit |
Question 15 |
Which of the following would not be a cause of a faulty thermostat on a standing pilot furnace?
A | The gas valve will not de energize |
B | The gas valve will not energize |
C | The furnace is short cycling |
D | The pilot will not stay lit |
Question 16 |
A new high efficiency furnace has been installed, and the furnace seems to come on too often.
A | Defective fan control |
B | Improperly adjusted heat anticipator |
C | Defective blower motor |
D | Too much airflow |
Question 17 |
Which of the following would not cause the burners of a gas furnace to shut down?
A | Excessive air flow |
B | Defective gas valve |
C | Faulty thermostat |
D | Defective induced draft motor |
Question 18 |
Which of the following is not a cause for the burners of a gas furnace to short cycle?
A | Dirty air filter |
B | Poor thermostat location |
C | Heat anticipator set too low |
D | Fan control contacts stuck closed |
Question 19 |
A customer complains that her house is too warm. The technician arrives and notices the gas valve is stuck open. The tech taps the side of the valve and gas flow stops. What action should the tech take?
A | Replace the gas valve |
B | Lubricate the sticking valve |
C | Turn the valve on and off several times to free the problem |
D | Any of the above |
Question 20 |
A pilot light has been established, but it is too small and soon goes out. Which of the following procedures would be correct to remedy this condition?
A | Replace the pilot valve |
B | Repair the pilot valve coil |
C | Clean the pilot orifice |
D | Replace the entire gas valve |
Question 21 |
What is the sequence of operation of a mid efficiency furnace using a hot surface indirect ignition system?
A | The thermostat calls for heat, the ignition system lights the pilot, the inducer motor is energized, the pressure switch closes, the main gas valve is energized, and the blower motor is energized |
B | The thermostat closes, the inducer motor is energized, the main burner is lit from the igniter, and the blower motor is energized |
C | The thermostat closes, the inducer motor is energized, the pilot is lit from the igniter, the pilot is proved, the main gas valve is energized, and the blower motor is energized. |
D | The thermostat opens, the inducer motor is energized, the main gas valve is energized, and the blower motor is energized. |
Question 22 |
On an intermittent spark ignition system, the pilot valve is energized, but there is no spark from the igniter. Which of the following could be the problem?
A | Faulty ignition cable |
B | Faulty control module |
C | Bad ground |
D | All of the above |
Question 23 |
On a direct spark ignition system, the igniter is sparking, but the main burner will not light. Which of the following is an incorrect test to perform?
A | Check for 24v across the gas terminals |
B | Check for correct position of spark gap |
C | Check for a cracked insulation on the igniter ceramic |
D | Check from terminals W to C to make sure the thermostat is closed |
Question 24 |
On a direct hot surface ignition system, the igniter is not glowing, but the main gas valve is energized during a trial for ignition. Which of the following is an incorrect test to perform?
A | Measure voltage to the igniter |
B | Measure resistance on the igniter |
C | Measure resistance of the limit control |
D | Measure input voltage to the control module |
Question 25 |
On a direct hot surface ignition system, the igniter is not glowing, but the main gas valve is energized during a trial for ignition. Which of the following is an incorrect test to perform?
A | Measure voltage to the igniter |
B | Measure resistance on the igniter |
C | Measure resistance of the limit control |
D | Measure input voltage to the control module |
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