LEC Heating, Ventilation & AC 2 — Questions and Answers
Question 1: When operating in extremely cold weather, a locomotive engineer notices the cab heater output has dropped significantly. What is the FIRST action to take?
- Increase engine throttle to boost heat output
- Check for blocked or frozen fuel supply lines to the heater (Correct answer)
- Request a helper locomotive for additional heat
- Continue operations and report at the next terminal
Correct answer: Check for blocked or frozen fuel supply lines to the heater
Blocked or frozen fuel supply lines are a common cause of reduced heater output in cold weather and should be checked first.
Question 2: What does the term 'recirculation mode' mean in a locomotive HVAC system?
- Fresh outside air is continuously drawn into the cab
- Cab air is cycled internally without drawing outside air (Correct answer)
- The AC compressor runs in reverse to provide heat
- Outside air is pre-heated before entering the cab
Correct answer: Cab air is cycled internally without drawing outside air
Recirculation mode cycles existing cab air internally, which is useful for rapid temperature changes or when outside air quality is poor.
Question 3: A locomotive engineer detects a strong chemical odor consistent with refrigerant when the AC system is running. What is the correct response?
- Increase AC fan speed to dilute the odor
- Shut down the AC system and notify maintenance of a suspected refrigerant leak (Correct answer)
- Switch to recirculation mode to prevent more refrigerant from entering
- Reduce cab temperature setting to reduce pressure in the system
Correct answer: Shut down the AC system and notify maintenance of a suspected refrigerant leak
A refrigerant odor indicates a leak; the system should be shut down and maintenance notified because refrigerant can be a health hazard.
Question 4: Which regulation governs the required temperature range that must be maintained in a locomotive cab during cold weather operations in the U.S.?
- FRA 49 CFR Part 229 (Correct answer)
- OSHA 29 CFR 1910.94
- EPA 40 CFR Part 82
- AAR Manual of Standards Section 5
Correct answer: FRA 49 CFR Part 229
FRA 49 CFR Part 229 covers locomotive safety standards, including cab environment requirements such as heating during cold weather.
Question 5: What is the primary purpose of the evaporator in a locomotive air conditioning system?
- To compress the refrigerant to a high pressure
- To absorb heat from cab air as refrigerant evaporates through it (Correct answer)
- To release heat absorbed from the cab to the outside air
- To filter dust and particulates from incoming outside air
Correct answer: To absorb heat from cab air as refrigerant evaporates through it
The evaporator absorbs heat from cab air as liquid refrigerant evaporates inside its coils, cooling the air before it is circulated back into the cab.
Question 6: During summer operations, an engineer notices condensation dripping from the overhead AC unit onto the controls. What should be done?
- Increase the temperature set point to reduce condensation
- Report the clogged condensate drain to maintenance and monitor controls for moisture damage (Correct answer)
- Turn off the AC and open windows to ventilate the cab
- Wipe the condensation and continue normal operations without reporting
Correct answer: Report the clogged condensate drain to maintenance and monitor controls for moisture damage
Dripping condensation usually indicates a clogged condensate drain; it must be reported because moisture on controls is a safety hazard.
Question 7: When a locomotive HVAC system has dual-zone capability, what does this feature allow?
- Two separate refrigerant circuits operating simultaneously
- Independent temperature control for the engineer's side and the conductor's side of the cab (Correct answer)
- Heating and cooling to operate at the same time in the cab
- Automatic switching between heating and cooling modes based on outside temperature
Correct answer: Independent temperature control for the engineer's side and the conductor's side of the cab
Dual-zone HVAC allows independent temperature control for different areas of the cab, accommodating crew preferences.
LEC Heating, Ventilation & AC 2
When operating in extremely cold weather, a locomotive engineer notices the cab heater output has dropped significantly.
What is the FIRST action to take?