HVAC Systems

• Fluids absorb heat when changed from a liquid to a gas. 
• Fluids give off heat when changed from a gas to a liquid.

• evaporation
• condensation
• heat transfer.

• Heat always flows from an area of higher temperature to an area of lower temperature. 
• The greater the difference in temperature, the faster heat flows 
• Heat continues to flow until both temperatures are equal.

is the process of changing a liquid into a vapour.

any liquid can be changed into a gas or vapour by adding heat 

is the process of changing a vapour into a liquid. 

any gas or vapour can be changed into a liquid by removing heat

• is the amount of heat required for a change in physical state. 
• The Latent Heat of vaporization is the amount of heat required to change a liquid into a vapour, without changing the temperature of the vapour.

amount of heat removal required to change a vapour into a liquid without changing the temperature of the liquid.

• If the pressure acting on a liquid is increased, the boiling point of the liquid also increases.
• If the pressure acting on a liquid is decreased, the boiling point of the liquid also decreases.

• CFC type refrigerant (dichlorodifluoromethane) 
• non-toxic, non-flammable, non-corrosive and odourless.
• Container Colour: White
• External Threads

• HFC type refrigerant (tetrafluoroethane) 
• does not deplete the ozone layer. 
• non-toxic, non-corrosive, non-flammable and odourless. 
• Container Colour: Light Blue
• Internal Threads - designed to prevent leakage and prevent cross contamination of refrigerants.
• Polyalkylene Glycol (PAG)
• Polyol ester Oil (POE) - good choice for when topping up an A/C system's lubricant level.

Separates the high-pressure side and the low pressure side. 

Primary Purpose: to draw the low-pressure and low-temperature vapour from the evaporator and compress this vapour into high-temperature, high-pressure vapour.

Secondary Purpose: is to circulate or pump the refrigerant through the A/C system under the different pressures required for proper operation.

used in air conditioning cycling clutch systems to control the pressure and temperature at which the refrigerant system operates.

• Clutch not engaged, pulley freewheels meaning refrigerant is not flowing.
• Clutch engaged - power transmitted from the pulley to the compressor shaft by the clutch drive plate - refrigerant is flowing. 

• is to condense or liquify the high-pressure, high-temperature vapour coming from the compressor. 
• having a higher temperature than the surrounding air, the condenser allows the hot refrigerant condense from vapour back to liquid.

• Primary Functions: are to cool, dehumidify and clean the air entering the passenger compartment.   
• refrigerant coil mounted in series of the thin cooling fins. 
• usually located beneath the dash board or instrument panel. 
• the evaporator receives low-pressure, low-temperature refrigerant from either a fixed orifice tube or an expansion valve in the form of an atomized (or droplet) spray. 
• the evaporator serves as a boiler or vaporizer to boil the refrigerant.

• is to separate and trap any liquid droplets of refrigerant that may have passed through the evaporator without evaporating. 
• Contains a Desiccant 
• has an inlet tube -connected to the evap. outlet. The outlet of the accumulator is connected via tubing hoses to the suction side of the compressor.
• found in an air conditioning system equipped w/ an orifice tube metering device.

dries the refrigerant by absorbing any moisture that may have entered the system.

Schrader Type service valve (R12) or Quick Service Valve (R-134a)

• is a storage tank for the liquid refrigerant from the condenser 
• uses a TEV to control refrigerant flow into the exap. 
• as mesh screen helps filter out any debris or contaminants in the refrigerant.

• located in the refrigerant line between the condenser outlet and the evap. inlet.
• separates the high-pressure side and low pressure side of the system. 
• (Operation) the TEV regulates refrigerant flow to the evaporator to prevent evaporator flooding or starving.

• equalizer.
• meter the refrigerant more accurately.

• is used to prevent ice from forming on the evaporator core. 
• this switch cuts off the compressor when the pressure and the temperature of the evaporator reach a predetermined setting below the freezing point of water. 
• also prevents compressor operation when air conditioning system pressure drops too low.

the accumulator assembly mounted on the outlet line of the evaporator.

by receiver-dryer mounted on the outlet line from the condenser.

is used to control the airflow through the heater core. This is a variable-position door.

is used to control which air inlet (outside or recirculation) is used.

• manuel 
• semi-automatic 
• electronic automatic temperature control (EATC)

is the amount of heat required for a change in physical state.

• Ozone Depletion 
• global warming 
• acid rain

heat-trapping gases in the atmosphere.

BTU

Vaporization

thermal expansion valve

Vapour

Polyalkaline Glycol

System Pressure

Circulation & Pressurization

Compressor Control Valve

Absorb Moisture and Store Refrigerant.

Filter, vaporize, and absorb moisture from refrigerant.

change vapour to a liquid

change liquid to a vapour

pressure cycling switch

air & moisture

after doing repairs that involve opening the system.