62-11863 2-16
2.5.4 Electric and Electric Hot/Gas Heat
The unit can be equipped with electric heat and electric/hot gas heat. When the microprocessor calls for heat, the
heater contactor will close or valve will open and engage the heat system.
2.5.5 Receiver Pressure Valve (RPV)
The Receiver Pressure Valve is a normally closed valve. In cool mode, this valve is always de−energized or
CLOSED. If the one of the compartments is calling for heat and the other is not calling for cool, the MHV is ener-
gized (CLOSED) and RPV valve will be energized (OPEN). This will allow high pressure refrigerant into the
receiver to pressurize the liquid allowing it to flow through the drier and pass through any liquid solenoid valve
which would be energized.
2.5.6 Main Heat Valve (MHV)
The Main Heat Valve directs flow of the high pressure, high temperature refrigerant leaving the compressor
through the system. The MHV is a normally OPEN valve. During COOL mode, the MHV coil is de−energized, and
the valve is open. The high pressure, high temperature gas leaving the compressor is directed to the condenser.
During HEAT mode when neither remote evaporator is calling for cool, the MHV coil is energized and the valve is
CLOSED. The high temperature, high pressure gas leaving the compressor is now directed towards the hot gas
valves in the remote evaporators.
2.5.7 Remote Evaporator Hot Gas Valve (1HGV and 2HGV)
The Hot Gas Valves are located in the remote evaporators. When the remote evaporator is in COOL mode, the
normally closed valves are de−energized. If one or both compartments are calling for heat and the other is not call-
ing for cool, the corresponding 1HGV or 2HGV is energized and OPEN and the MHV is energized, CLOSED. The
high pressure, high temperature refrigerant leaving the compressor is diverted through the remote evaporator coils.
2.5.8 Liquid Solenoid Valve
The liquid solenoid valve opens or closes depending on the thermostat.
2.5.9 Electric Evaporator Fan Motor
The electric evaporator fan motor moves air over the evaporator coil. See Section 2.7.6 for unit specifications.
Compartment 1:
Cool/Heat - Fans On:
With voltage at the closed N/O contacts of the 1CR pins (30-87) and voltage at the 1J14 connector, there should be
ground at the 1RR coil pin 85 and voltage at 1RR coil pin 86. The N/O contacts of the 1RR (30-87) should close
sending power to the 1EMR coil pin 1 and ground should be at 1EMR coil pin 0. The N/O contacts on the 1EMR (6-
8) and (2-4) should close, sending 230/1/60 A/C voltage to the evaporator fan motors. The fans should be running.
Defrost - Fans Off:
With voltage at the closed N/O contacts of the 1CR pins (30-87) and voltage at the 1J14 connector along with
ground at the 1J11 connector. The ground should be removed from the 1RR coil pin 85. The N/O contacts of the
1RR should be open and the N/O contacts on the 1EMR (6-8) and (2-4) should be open. The fans should be off.
Compartment 2:
Cool/Heat - Fans On:
With voltage at the closed N/O contacts of the 2CR pins (30-87) and voltage at the 1J12 connector, there should be
ground at the 2RR coil pin 85 and voltage at 2RR coil pin 86. The N/O contacts of the 2RR (30-87) should close
sending power to the 2EMR coil pin 1 and ground should be at 2EMR coil pin 0. The N/O contacts on the 2EMR (6-
8) and (2-4) should close, sending 230/1/60 A/C voltage to the evaporator fan motors. The fans should be running.
Defrost - Fans Off:
With voltage at the closed N/O contacts of the 2CR pins (30-87) and voltage at the 1J12 connector along with
ground at the 1J11 connector. The ground should be removed from the 2RR coil pin 85. The N/O contacts of the
2RR should be open and the N/O contacts on the 2EMR (6-8) and (2-4) should be open. The fans should be off.
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