The Thermax system allows the complete unit charge to be available during heat. Truck units with TherMax have had some components of the standard 3-way valve system removed and other components added.
COMPONENTS REMOVED:
• Bypass check valve
• Bypass line
• Condenser check valve
COMPONENTS ADDED
TherMax (Heat) Solenoid: A normally closed solenoid that opens during the condenser evacuation mode to allow refrigerant flow to bypass the evaporator and flow directly into the accumulator. Located in a line between the suction and liquid lines.
Receiver Outlet Check Valve: Stops refrigerant flow into the receiver tank during the heat/defrost mode.
The Heat Initiation Timer (HIT): Prevents the pilot solenoid from energizing during the condenser evacuation mode (approximately 2 to 4 minutes). May be an individual device or built into the microprocessor controller.
Ambient Switch: This switch is normally used on units with R-502 and other high pressure refrigerants. The switch will prevent the TherMax solenoid from opening, eliminating the condenser evacuation mode, when the ambient temperature is above approximately 0 F (-18 C). The switch is not present in microprocessor controlled units.
MODES OF OPERATION
Cool: Unit operates as normal.
Condenser Evacuation: Discharge pressure forces liquid refrigerant from the condenser and receiver tank into the accumulator for use during the heat/defrost cycle. The 3-way valve remains in the cool position with the TherMax (heat) solenoid open for approximately 2 to 4 minutes.
Heat/Defrost: The 3-way valve shifts to heat and the condenser, receiver tank and liquid line between the receiver tank and receiver outlet check valve are isolated.
