EPCS - Emergency Pressure Control System
EPCS Overview
The Emergency Pressure Control System (EPCS) continuously monitors refrigerant pressure and
opens a crossover valve if an over-pressure situation is detected. The crossover valve attempts
to relieve the zone's high-pressure refrigerant by transferring the refrigerant from the high-
pressure zone to a low-pressure zone. In addition to the pressure sensors, a digital "trip" input
is provided to remotely trip the zone or test the EPCS functionality.
EPCS Interface
Zone Pressure Analog Sensors
Each EPCS zone is monitored by a pressure sensor. When the zone's pressure exceeds either
the user adjustable setpoint or the fixed setpoint, the zone is tripped, the crossover valve is
opened and the EPCS goes in to an alarm condition.
Zone Crossover Valve Digital Output
Each EPCS zone has a crossover valve control output. When energized, the digital output will
open the crossover valve to transfer the high-pressure refrigerant to a lower pressure vessel.
EPCS Functional Digital Output
When energized, the digital output will indicated the EPCS is functional - even if a zone has
tripped on a high pressure condition. The Functional output will de-energize on loss of control
power, EPCS malfunction, pressure sensor fault or pressure sensor wiring fault.
EPCS Emergency Stop Digital Output
The EPCS Emergency Stop Digital Output is normally de-energized. When energized, the digital
output should be wired to shutdown all associated refrigeration equipment such as
compressors. The EPCS Reset input will reset the Emergency Stop output back to the de-
energized state provided all EPCS zones are in normal condition.
EPCS Alarm Annunciator Digital Output
When energized, the digital output indicates and over-pressure event or sensor malfunction has
occurred. The EPCS Reset input will reset the Alarm Annunciator output back to the de-
energized state as long as all pressure sensors are functional.
EPCS Reset Digital Input
When EPCS Reset input is energized, the EPCS will reset any crossover valves which no longer
have an over-pressure condition. The Alarm Annunciator will also be de-energized as long as all
pressure sensors are functional.
EPCS Test/Trip Digital Input
Each EPCS zone has a Test/Trip input. When a EPCS Zone Test/Trip input is energized the zone
is tripped just as if the pressure exceeded the setpoint (ex. the crossover valve is opened and
the Alarm & Emergency Stop outputs are energized).
