Bulletin 30-21 – Page 9
Type 180 Solenoid
Pilot Control Valve
FEATURES
The Type 180 Solenoid Pilot
Control offers three outstanding
features for refrigeration applications:
• Costs less, more economical to install.
• Only one size.
• Assures positive shut-off of liquid line.
The 180 Solenoid Pilot Control is available as a supplementary
device to Sporlan Thermostatic Expansion Valves. It is used in
place of large capacity solenoid valves for positive shut-off of
liquid lines. Since only one size is necessary it costs less and is
more economical to install.
The Solenoid Pilot Control does not directly close the liquid
line, but acts on the thermostatic expansion valve causing the
expansion valve to close. The 180 is installed in the external
equalizer line of the thermostatic expansion valve and has a
third 1/4” connection from the liquid line.
OPERATION
To understand the operation of the 180 Solenoid Pilot Control,
it is important to review the principle of operation of a ther-
mostatic expansion valve. There are three fundamental pres-
sures involved in the operation of any thermostatic expansion
valve. They are: Q bulb pressure; W evaporator pressure; and,
E spring pressure, as shown in Figure 8.
The bulb pressure acts on one side of the diaphragm tending
to open the valve. The evaporator pressure acts on the oppo-
site side of the diaphragm tending to close the valve, and the
spring pressure assists in closing the valve. A variation of any
one of the three pressures changes the amount of opening of
the valve. In normal operation of the valve, these pressures
tend to establish a point of equilibrium to maintain a constant
superheat at the outlet of the evaporator. However, when an
abnormal pressure is introduced which upsets the equilibri-
um, another effect may be accomplished. The principle upon
which the 180 Solenoid Pilot Control influences the expansion
valve action is by the creation of a pressure under the valve
diaphragm, which is higher than the bulb pressure. This is
how it is accomplished.
The Type 180 has two ports in the valve body — one high
pressure and one low pressure. When the solenoid coil
is energized, the plunger moves upward sealing off the
high-pressure port. With the high pressure excluded from
the pilot control, true suction pressure acts on the underside
of the expansion valve diaphragm through the equalizer
line and the low pressure port. This is illustrated in Figure 9.
When the solenoid coil is de-energized, the low pressure port
is closed, thereby closing the equalizer line from the valve to
the suction line. The high pressure port is open and liquid
line pressure is applied to the underside of the thermostatic
expansion valve diaphragm. This high-side pressure instantly
overcomes the bulb pressure and supplements of the valve
spring, immediately closing the port of the expansion valve.
See Figure 10.
Bulb Pressure
Spring
Pressure
Head
Pressure
Evaporator
Pressure
120 LBS.
49 LBS.
40 LBS.
40 LBS.
9 LBS.
120 LBS.
Diaphragm
Evaporator
Bulb
External
Equalizer
Connection
Evaporator
Pressure
W
Bulb
Pressure
Q
Spring
Pressure
E
Figure 8
Figure 10
Bulb Pressure
Spring
Pressure
Evaporator
Pressure
Head
Pressure
Evaporator
Pressure
120 LBS.
49 LBS.
40 LBS.
40 LBS.
9 LBS.
Figure 9
Approved
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