Figure 6-22A. Thermostatic expansion valve; B. Automatic expansion valve.
refrigerant to absorb heat from the evaporator.
Second, it applies higher pressure to the bottom of the
diaphragm, forcing it upward, tending to close the
valve. And third, it reduces the degree of superheat by
forcing more refrigerant through the suction line.
Low-Side Float Expansion Valve.The
low-side float expansion valve (fig. 6-23) controls the
liquid refrigerant flow where a flooded evaporator is
used. It consists of a ball float in either a chamber or
the evaporator on the low-pressure side of the svstem.
The float actuates a needle valve through a lever
As the float lowers, refrigerant enters
through the open valve; when it rises, the valve closes.
High-Side Float Expansion Valve.In
high-side float expansion valve (fig. 6-24), the valve
float is in a liquid receiver or in an auxiliary container
on the high-pressure side of the system. Refrigerant
from the condenser flows into the valve and
immediately opens it, allowing refrigerant to expand
and pass into the evaporator. Refrigerant charge is
critical. An overcharge of the system floods back and
damages the compressor. An undercharge results in a
Figure 6-23.A low-side float expansion valve.
Figure 6-24.A high-side float expansion valve.