HVAC Components

The main components of a train HVAC system include an air handling unit, ductwork, filters, fans and blowers, heating and cooling equipment. The air handling unit houses most of the active equipment and ductwork distributes air throughout the train car. High-efficiency filters remove pollutants and pathogens from incoming and recirculated air. Powerful fans and blowers move air through the ductwork, distributing conditioned air into passenger areas. Heating equipment such as heat exchangers or electric heaters warm incoming air during cold weather. Cooling equipment like refrigerant compressor/condenser units or vapor-cycle machines chill air for hot weather.

Air Distribution

Conditioned air enters the passenger area through vents located above or below seats along the sides of train cars. Return air vents near the floor allow stale air to flow back to the air handling unit for refreshment. Controls in each passenger area allow adjusting vent direction and flow. Distribution aims to maintain an even temperature front to back while accounting for drafts from open windows and doors. Thermostats monitor temperatures to trigger heating or cooling as needed based on setpoints. Temperature sensors provide feedback for control systems.

Outside Air Exchange

For optimal air quality, train heating, ventilation, and air conditioning brings in a mix of outside and recirculated interior air. Outside air intakes prevent a buildup of carbon dioxide and other contaminants from passengers. The ratio of outside to recirculated air determines how much fresh air enters the coach. Train HVAC equipment filters both incoming and reused air before distribution. On some trains, sensors detect carbon dioxide levels and trigger more outside air intake when thresholds are exceeded. This helps ventilate the coach and remove respiratory emissions.

Diesel Locomotive HVAC

For diesel-powered locomotives, an auxiliary power unit (APU) located on the roof powers the HVAC system. The APU runs independently from the main diesel engines that propel the train. It typically uses a small diesel engine or gas turbine generator to produce electricity for HVAC equipment, lighting and other auxiliaries. Locomotive HVAC shares similar components to onboard passenger coaches but must also account for the unique heating needs of engine compartments and operator cabs. Thermal insulation helps maintain safe temperatures for workers and sensitive electrical/mechanical systems.

Electric Train HVAC

Electric trains lacking diesel combustion can still generate heat through braking systems, human bodies, electrical components and solar gain through windows. Electric train heating, ventilation, and air conditioning works similarly to diesel versions but derives power directly from overhead lines or third rails. Some electric train designs utilize heat recovery ventilation, which captures waste heat from traction motors and braking resistors. This captured thermal energy preheats incoming outside air during winter, improving efficiency. All-electric trains eliminate diesel emissions within enclosed coach areas, benefiting air quality for passengers compared to diesel options.

Get more insights on Train HVAC