Heating, Ventilation & AC Flashcards
7 cards from real LEC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Heating, Ventilation & AC flashcards as text
When operating in extremely cold weather, a locomotive engineer notices the cab heater output has dropped significantly. What is the FIRST action to take?
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.
What does the term 'recirculation mode' mean in a locomotive HVAC system?
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.
A locomotive engineer detects a strong chemical odor consistent with refrigerant when the AC system is running. What is the correct response?
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.
Which regulation governs the required temperature range that must be maintained in a locomotive cab during cold weather operations in the U.S.?
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.
What is the primary purpose of the evaporator in a locomotive air conditioning system?
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.
During summer operations, an engineer notices condensation dripping from the overhead AC unit onto the controls. What should be done?
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.
When a locomotive HVAC system has dual-zone capability, what does this feature allow?
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.