it, or si
an o
-
ne.
-
e
-
g
-
dresult of any of fife above sa ety
devices, determine and correct the cause before
When power is supplied to control circuit
and control circuit switch is on, unit is ready for
operation providing all safety devices are satisfied,
interlocks are closed and instructions on warning
labels have been followed.
When START-STOP button on control panel is
pressed to START, a white light in button comes on
and step controller and control relays 1 thru 4 are
energized. After a maximum of 1.5 minutes, step
controller cycles back (in the unload direction) to
correct cam position to begin compressor starting
sequence. The compressors start one at a time at
brief intervals until load requirement is satisfied.
After completing starting sequence, controller stops
and starts, unloads and loads compressors to main-
tain capacity control in response to water tempera-
ture controller demand. Factory cam settings on
step controller protect compressors against rapid
cycling.
Complete Unit Stoppage
can be caused by any of
the following conditions: general power failure,
blown fuse in control power feed disconnect, open
control circuit breaker, START-STOP button
pressed to STOP, open contacts in low water tem-
perature cutout, open contacts in any auxiliary
interlock, open contacts in chilled water flow switch.
Single
-
Circuit Stoppage
can be caused by open
contacts in compressor discharge temperature
sensor, open contacts in low-pressure switch, open
contacts in oil safety switch (when used), open
contacts in high-pressure switch.
Stoppage of one circuit by safety device action
does not affect the other circuit. Besides stopping
compressor(s), all devices listed
except the low-
pressure switch
will also close liquid line solenoid
valve for that circuit.
Restart Procedure,
after cause for stoppage is
corrected. (Automatic restarts are under sequence-
starting control.)
GENERAL POWER FAILURE — Unit will
restart automatically when power is restored.
BLOWN FUSE IN POWER FEED DIS-
CONNECT — Replace fuse. Restart is automatic.
LOW WATER TEMPERATURE CUTOUT —
Press the control RESET button on control panel).
Restart is automatic.
AUXILIARY INTERLOCK — Automatic restart
after condition is corrected.
OPEN CONTROL CIRCUIT BREAKER — Close
breaker. Unit will restart automatically.
HIGH-PRESSURE SWITCH — Press unit
START-STOP button to STOP then to START.
Unit will restart under sequence control.
LOW-PRESSURE SWITCH — Compressors will
restart automatically when pressure comes up
sufficiently.
COMPRESSOR DISCHARGE TEMPERA-
TURE SENSOR — After discharge temperature
cools down, press unit START-STOP button to
STOP then to START. Unit will restart under
sequence control.
OIL SAFETY SWITCH — Press RESET button
on the switch and press unit START-STOP button
to STOP then to START. Unit will restart under
sequence control.
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