Friedrich R-410A service manual Refrigeration Sequence of Operation

REFRIGERATION SEQUENCE OF OPERATION

A good understanding of the basic operation of the			The refrigerant leaves the condenser Coil through the liquid
refrigeration system is essential for the service technician.			line as a warm high pressure liquid. It next will pass through
Without this understanding, accurate troubleshooting of			the refrigerant drier (if so equipped). It is the function of the
refrigeration system problems will be more difficult and time			drier to trap any moisture present in the system, contaminants,
consuming, if not (in some cases) entirely impossible. The			and large particulate matter.
refrigeration system uses four basic principles (laws) in its			The liquid refrigerant next enters the metering device. The
operation they are as follows:
			metering device is a capillary tube. The purpose of the
1.	“Heat always flows from a warmer body to a cooler
			metering device is to “meter” (i.e. control or measure) the
	body.”		quantity of refrigerant entering the evaporator coil.
2.	“Heat must be added to or removed from a substance		In the case of the capillary tube this is accomplished (by
	before a change in state can occur”		design) through size (and length) of device, and the pressure
3.	“Flow is always from a higher pressure area to a lower		difference present across the device.
	pressure area.”		Since the evaporator coil is under a lower pressure (due to
4.	“The temperature at which a liquid or gas changes state		the suction created by the compressor) than the liquid line,
	is dependent upon the pressure.”		the liquid refrigerant leaves the metering device entering the
			evaporator coil. As it enters the evaporator coil, the larger
The refrigeration cycle begins at the compressor. Starting			area and lower pressure allows the refrigerant to expand
			and lower its temperature (heat intensity). This expansion is
the compressor creates a low pressure in the suction line
			often referred to as “boiling”. Since the unit’s blower is moving
which draws refrigerant gas (vapor) into the compressor.
			indoor air across the finned surface of the evaporator coil,
The compressor then “compresses” this refrigerant, raising
			the expanding refrigerant absorbs some of that heat. This
its pressure and its (heat intensity) temperature.
			results in a lowering of the indoor air temperature, hence the
The refrigerant leaves the compressor through the discharge
			“cooling” effect.
Line as a hot High pressure gas (vapor). The refrigerant			The expansion	and absorbing of heat cause the liquid
enters the condenser coil where it gives up some of its
			refrigerant to evaporate (i.e. change to a gas). Once the
heat. The condenser fan moving air across the coil’s finned
			refrigerant has	been evaporated (changed to a gas), it is
surface facilitates the transfer of heat from the refrigerant to
			heated even further by the air that continues to flow across
the relatively cooler outdoor air.
			the evaporator coil.
When a sufficient quantity of heat has been removed from			The particular system design determines at exactly what
the refrigerant gas (vapor), the refrigerant will “condense”			point (in the evaporator) the change of state (i.e. liquid to a
(i.e. change to a liquid). Once the refrigerant has been			gas) takes place. In all cases, however, the refrigerant must
condensed (changed) to a liquid it is cooled even further by			be totally evaporated (changed) to a gas before leaving the
the air that continues to flow across the condenser coil.			evaporator coil.
The RAC design determines at exactly what point (in the			The low pressure (suction) created by the compressor
condenser) the change of state (i.e. gas to a liquid) takes			causes the refrigerant to leave the evaporator through the
place. In all cases, however, the refrigerant must be			suction line as a cool low pressure vapor. The refrigerant then
totally condensed (changed) to a Liquid before leaving the			returns to the compressor, where the cycle is repeated.
condenser		coil.
		Suction	Discharge
		Line	Line
		Evaporator	Condenser
			Coil
		Coil
		Metering	Compressor
		Device

Refrigerant Drier Liquid

RefrigerantLine

Strainer

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