THEORY OF OPERATION - CONTINUED
AIR CONDITIONING SYSTEM - CONTINUED
Orifice Tube Assembly
N OT E
The orifice tube systems do not have a sight glass for determining whether the system is low on refrigerant.
The orifice tube assembly has a plastic body, two screens, and a small brass tube located in the center of the body. The
O-ring seals are positioned on the body of the orifice tube to seal against leakage. The orifice tube assembly is contained
in the dryer. The orifice tube assembly is used in place of the thermostatic expansion valve.
The orifice tube assembly changes the refrigerant from
a high pressure and high temperature refrigerant into a
low pressure and low temperature liquid. The orifice
tube has a restriction. The restriction in the orifice tube
assembly allows the liquid refrigerant to be reduced
from a high pressure to a low pressure. The flow rate
is controlled by pressure differences across the orifice.
The flow rate is also controlled by the temperature of
the liquid refrigerant in the bottom of the condenser.
The flow rate is sensitive to temperature and pressure
differences. The flow rate is more sensitive to temper-
The accumulator is located at the outlet of the evapo-
rator coil. The accumulator separates the liquid refrig-
erant from the refrigerant vapor that passes through
the evaporator coil. The accumulator retains the liquid
refrigerant that is separated. Also, the accumulator
The oil drain hole is located in the bottom of the accu-
mulator. The oil drain hole will drain refrigerant oil
that is separated. The oil drain hole will also drain
some of the liquid refrigerant. This liquid refrigerant
The flow of refrigerant out of the accumulator to the
small amount of liquid refrigerant. This liquid refrig-
erant comes from the oil drain hole.