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Definition: Bus Air Conditioning is the cooling, dehumidification, and filtration of the air within the passenger compartment of your vehicle.
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- The Thermostat, located in the interior of the vehicle, calls for cooling.
- Based on a signal from the thermostat, by means of an inter connecting electrical system, the electromagnetic clutch on the compressor engages.
- Once engaged, the compressor then circulates refrigerant through the system through inter connecting hoses.
- Refrigerant, existing as a gas, and containing the heat from the passenger compartment, is pumped by the compressor, under high pressure, into the condenser coil.
- Fans pull cool air through the condenser coil, which contains refrigerant existing as a hot gas.
- The refrigerant undergoes a change-of-state, from a gas to a liquid, through a process called condensation.
- During condensation, the hot gas rejects its heat load to the outside air, which was transferred from the passenger compartment, into the refrigerant, by the evaporator.
- The refrigerant now exists as a cool liquid, which passes through the filter drier, which removing moisture and impurities, and then the sight glass, which enables visual inspection of the refrigerant.
- The cool liquid is then pumped to the evaporator where an expansion valve meters the refrigerant into the evaporator coil.
- Fans pull passenger compartment air through a filter, which removes particulate matter, then passes the cleaned air through the evaporator coil.
- The refrigerant undergoes a change of pressure from high to low, and a corresponding change-of-state from a liquid to a gas, through a process called evaporation.
- During evaporation, the heat contained in the air in the passenger compartment is absorbed by the gaseous refrigerant.
- A warm air passes through the evaporator coil, moisture condenses, and is collected and drained to the exterior of the vehicle,
- The hot gas is then suctioned back to the compressor and pumped to the condenser.
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Thermostat
- A temperature sensitive device, which when activated, signals the electromagnetic compressor clutch to engage.
- Located in the return air of the evaporator
Inner Connecting Electrical
- Connects air conditioning components through the use of electrical wiring to control system operation
- Electrical System Control Types (General)
- Basic
- Microprocessor
- Multiplex
Electromagnetic Clutch
- A key component of the compressor that controls its operation.
Refrigerant
- A material, which possesses high heat transfer capabilities.
- Acts as the medium for heat transfer, which facilitates the movement of heat from the passenger compartment to the outside air.
- Refrigerant, under varying pressures, exists in different states, and performs different heat absorbing functions
- Under low pressure, refrigerant exists as a gas which can absorb heat
- Under high pressure, refrigerant exists as a liquid which can reject heat.
- The heat transfer properties exhibited when refrigeration changes state is the foundation of the refrigeration cycle.
Inner Connecting Hoses
- Connects air conditioning components by means of hoses and fittings in order to transport refrigerant throughout the system
- Hose / Fitting Types
- Beadlock
- Barb
- O-Ring
- Aeroquip (EZ Clip)
- TA Clip-Loc (Burgaflex)
- Reusable ORS
Filter Drier
- Located within the condenser
- Removes moisture and particulate matter from refrigerant within the liquid line.
- Moisture in the refrigerant of an air conditioning system causes system contamination and eventually could lead to total system failure.
Sight Glass
- Located within the condenser
- Allows for visualization of the filtered liquid refrigerant to assess the level of moisture and/or particle contamination within the system.
Expansion Valve
- Acts as a "spray nozzle" to meter refrigerant into the evaporator coil from the liquid line.
- High pressure created from compressor operation is lowered by the expansion valve.
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© 2010 Trans/Air Manufacturing Corp. • 800-673-2446 • Specializing In World Class Climate Control Products and Services for the Bus and Vehicle Markets.