Vogt HEC-10, Service Manual

Page: 87 / 114

HEC-Series Service Manual
SERVICE OPERATIONS
10/21/01
9-5
FIGURE 9-2
High-Low Pressure Switch
NOTE: High-low pressure switch contains both high and low voltage circuits. Line numbers 22 and
X6 supply a low voltage signal to the PLC. Line numbers 15 and 30 supply power to the compressor
contactor coil.
If it becomes necessary to install a new high/low pressure switch, the following procedure is
recommended for its adjustment:
Turn the adjusting screws clockwise to raise the pressure setting. Turn counter-clockwise to lower
the setting. Adjust the switch to the indicated pressure settings and test with an accurate gage to be
sure the switch functions properly before installation.
Head Pressure. The head pressure should be maintained at 190-210 psig during the freeze cycle.
This pressure can be checked at the test connection in the high pressure line near the high-low
pressure switch.
Air-Cooled Units. The condenser fan switch (FIGURES 1-2A & 9-4) (CPS) is used to regulate the
head pressure. This is an adjustable pressure switch located on the right-hand front of machine. It
controls the operation of the condenser fan motor(s) through a contactor (FC) located in the control
panel. The switch is set to cycle the fan motor(s) “On” at 210 psig and “Off” at 190 psig.