JOHNSON CONTROLS
14
FORM 160.79-O3
ISSUE DATE: 11/09/2018
SECTION 1 – DESCRIPTION OF SYSTEM AND FUNDAMENTALS OF OPERATION
the Discharge Valve is then driven closed. When the
Discharge Valve has fully closed (or 40 seconds have
elapsed, whichever occurs first), the run signal to the
compressor motor starter is de-energized and the com-
pressor enters “Coastdown”. If any Discharge Valve
does not close within 40 seconds, a cycling shutdown
is performed and “Discharge #X – Valve Not Closed”
is displayed.
If the Lag compressor is taken off line due to a Low
Load condition while both compressors are running (as
explained above), a Soft Shutdown is performed on the
Lag compressor.
If one of the following shutdowns is initiated, a Soft
Shutdown is performed simultaneously on all running
compressors:
• Operator Initiated Soft Shutdown at Keypad
• "Remote Stop”
• “Leaving Chilled Liquid temperature – Low Tem-
perature”
• "Discharge Valve X – Valve Not Closed”
• “Multiunit – Contacts Open”
• “System Cycling (1 & 2) – Contacts Open”
• “Control panel – Schedule”
If any faults other than those listed above occur during
a Soft shutdown, the Soft Shutdown is aborted, the run
signal to the compressor motor starter is de-energized
and the compressor(s) immediately enters “Coast-
down”.
If an Operator initiates a “Local Stop” with the Key-
pad Rocker Switch or any fault occurs other than those
listed immediately above, a
Fault Shutdown
is per-
formed on all running compressors. Simultaneously,
the run signal to the compressor motor starter(s) is
de-energized, the compressor(s) enters “Coastdown”,
and the Pre-rotation Vanes and Discharge Valve(s) are
driven closed.
