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4. LWT Freeze Safety: This analog signal is sent by
the Leaving Chilled Water Sensor. If the tempera-
ture drops to < 36°F(factory setpoint), the system
shuts down. For Brine applications, the setpoint can
be varied from 20°F to 40°F on the Analog Board by
R25. An “F11” code will appear for this safety.
5. LEP (Low Evaporator Pressure Cutout): At run
time = 30 sees to 4 min. the micro checks to see that
suction pressure is 80% cut-out. If not, it shuts the
system down. If the analog signal to the Micro Board
tells the system that the Suction Pressure is low on 3
consecutive starts, the system will shut down and
lock out. See Shutdown Safety Controls, Low Pres-
sure Cutout for trip points. Any time the system shuts
down on a Low Pressure (LP Safety) a 90 min. timer
starts and a “count to 3” counter is software is
incremented to “1”. If the system goes down 2 more
times on a LP Shutdown Safety before the 90 min.
timer times out, the system will shut down and lock
out on a LEP Manual Reset Safety. If the 90 min.
timer times out without 2 more LP shutdowns, the
“count to 3” counter will be cancelled and reset to
“0”. This safety operates like all other Manual Reset
Safeties. An “F3” will be displayed for this cutout.
6. FS (Fault Stop): If external High Discharge Pres-
sure Cutout or external Thermal Motor Overload Sen-
sor contacts open, the system will shut down. The
manual reset on the sensor(if equipped) must be re-
set before the system can be restarted. The external
HP cutout is set at 395 PSI. An F1 will be displayed
for this safety. Note: These same codes will also be
displayed for a Motor Current (power) Fault. This oc-
curs because these safeties do not allow the motor
contactor to energize, causing motor current to be
“0”. When the system is to start, the Micro sends the
start signal to the contactor pilot relay on the Relay
Output Board. The pilot relay closes a contact which
applies 115VAC to the motor contactor. If the High
Pressure C.O. or motor protector opens, their con-
tacts which are wired in series with the pilot relay
contacts keep 115VAC from being applied to the
motor contactor. The contactor will not pull in as the
Micro commands or will drop out if pulled in so the
system will shut down on low motor current. When-
ever an “F1” Fault occurs, check discharge pressure
at the time of the fault, motor current at the time of
fault, and also if the H.P. and motor protector con-
tacts are open.
OTHER SAFETY CONTROLS
1. Suction Pressure: If Suction Pressure exceeds 105
PSIG, the Micro Board will unload the compressor. It
will automatically reload when suction pressure drops
below 95 PSIG.
(YCHA100)
2. Flow Switch: To assure that water flow is present in
the evaporator, the Micro Board senses the Flow
Switch input to the R.P. Relay whose contacts con-
nect to J18 & J 19 of the Analog Input Board. If the
Flow Switch opens, the system will shut down and
will not restart until flow is present. An “A” code will
be displayed. The Flow Switch is connected to ter-
minals 3 & 4 of the terminal block at the bottom right
of the Logic Panel. See Fig. 7.
REMOTE START/STOP BY A TIME CLOCK, BUILD-
ING AUTOMATION, OR ENERGY MANAGEMENT
SYSTEM
Remote starting and stopping is accomplished by open-
ing and closing contacts, controlled by a remote source,
connected to the R.P. Relay. These contacts will be wired
in series with the Flow Switch. The Micro Logic Board
looks for the closure of the contacts as a signal to start
the system. Opening the contacts is a signal to stop the
system. See Fig. 7 for connection points.
Since the remote contacts are wired in series with the
Flow Switch, an “A” code will appear on the display when
a REMOTE STOP command is given (contacts open).
If the optional Digital Input Board is used for Remote
Temperature Setpoint Reset, be sure that remote start
and stop is connected in series with the Flow Switch
and not to the Digital Input Board EMS Start and Stop
inputs. These Start and Stop inputs are not active.
“OPTIONAL” REMOTE TEMPERATURE SETPOINT
RESET
Remote Temperature Setpoint Reset capabilities can
be added by adding an optional Digital Input Board and
configuring a jumper/switch on the Micro Logic Board.
J9 must be IN or Switch #4 must be ON. See Fig. 11
and 12 for jumper/switch location.
Temperature Setpoint changes are accomplished by clos-
ing the contacts between terminals 11 and 12 on the Digi-
tal Input Board for a defined period of time. The lowest
temperature desired must be set on the panel via the
“Return Water Temperature Setpoint” rotary switches. To
change the setpoint, the contacts between terminals 11
and 12 must be closed for a period between 1 and 11
seconds. Closure for a period shorter than 1 second will
be ignored by the Micro Logic Board. Closure longer than
11 seconds will be treated as 11 seconds.
The contact closure corresponds to a positive offset
(rise) from the setpoint on the panel. 1 sec = +0° offset
and 11 sec. = +15° or offset = 1.5 (time closed -1 sec.).
For example: A setpoint of 51° on the panel and a con-
tact closure of 4.33 sec. will result in an offset of +5°.
This raises the RWT setpoint to 56°F.