Cooling System Operation

When the thermostat senses the indoor temperature is too hot it will close the contacts from R to Y & G (on a straight cooling condenser). The voltage now flows to the contactor on the outside unit, and the indoor fan control. When the contactor on the outdoor unit pulls in the compressor and outdoor condenser fan will operate. The contacts will remain closed till the thermostat is satisfied. When the thermostat is satisfied the contacts will open and the outdoor contactor and indoor fan control will open causing the units to shut down. The indoor fan is normally on a delay on start up and shut down. If the thermostat is set to the fan only setting the fan will run continuously. In the refrigeration process heat always flows from warmer to a cooler place. When the refrigerant is under a low pressure it will absorb heat and vaporize at a low temperature, the vapors can be drawn off and condensed at a higher pressure and temperature so it can be used again. The evaporator coil referred to as the indoor coil is used to cool and dehumidify the air going across the coil from the conditioned space. When the refrigerant is leaving the outdoor in the liquid line (smaller tube) it travels to the refrigerant metering device of the indoor coil were it continues to pick up heat thru the indoor coil which causes the refrigerant to start boiling, and turning into a vapor called superheat. Superheat is a vapor that absorbs more heat than required to vaporize. With the vapor superheated it is preventing any liquid from entering the compressor and causing damage to it. If liquid refrigerant is returned to the compressor it can cause the valves to break and wash the oil out of the compressor that in turn causing friction on the internal parts to be damaged. The compressor increases the pressure of the refrigerant and sends a high-pressure superheated vapor to the outdoor condenser coil. The high-pressure superheated vapor is hotter than the outdoor ambient temperature allowing a heat transfer from the copper thru the fins and into the cooler outdoor ambient temperature. The refrigerant begins to become saturated (turning back into a liquid) as it goes thru the condenser coil. It will continue to give up heat until it becomes a liquid, and as it goes on thru the circuit it will become a sub-cooled liquid (a liquid temperature is lower than its saturation temperature at that pressure) and it starts it cycle all over again. I hope this provides some basic understanding on the cool system. I tried to explain it were anyone could understand it. Best Regards, Barry Woodard www.newcoolsavings.com