York YCAL Series Installation Operation & Maintenance page 104

SECTION 7 - UNIT CONTROLS
The internal motor protector opens at 185°F to 248°F
(85°C to 120°C) and auto resets. The mechanical HP
switch opens at 405 psig plus or minus 10 psig (27.92
barg plus or minus .69 barg) and closes at 330 psig plus
or minus 25 psig (22.75 barg plus or minus 1.72 barg).
The compressor is also equipped with a discharge
temperature sensor for the purpose of sensing inter-
nal scroll temperature. This sensor protects the scrolls
from overheating due to inadequate cooling that may
occur when refrigerant charge is low, or superheat is
too high.
When the sensor senses a high temperature, it opens
the motor protector circuit in the compressor causing
the compressor to shut down.
During the first two faults an MP/HP INHIBIT message
will be displayed and the system will not be locked out.
Only after the third fault in 90 minutes will the MP/
HPCO FAULT message be displayed.
Whenever the motor protector or discharge sensor
shuts down a compressor and the system, the inter-
nal compressor contacts will open for a period of 30
minutes to ensure that the motor or scroll temperatures
have time to dissipate the heat and cool down.
After 30 minutes, the contacts will close and the sys-
tem will be permitted to restart. The microprocessor
will not try to restart the compressors in a system that
shuts down on this safety for a period of 30 minutes to
allow the internal compressor to time out.
During the 30 minute timeout, the MP/HPCO INHIB
message will be displayed. The MP/HPCO fault will
only be displayed after 3 shutdowns in 90 minutes,
indicating the system is locked out and will not
restart.
S Y S 1 H I G H
S Y S 2 H I G H
When the System Current Feedback option is installed
and selected (Option 11 under OPTIONS key Current
Feedback), this safety will operate as follows. If the
actual feedback voltage of the system proportional to
currents exceeds the programmed trip voltage for 5
seconds, the system will shutdown.
104
M T R C U R R
M T R C U R R
S Y S 1 L O W
S Y S 2 L O W
The Low Evaporator Temperature Cutout is to pro-
tect the evaporator from freeze-up with R-407C. This
safety uses the Cooler Inlet Refrigerant Temp Sensors
to monitor evaporator inlet refrigerant temperature on
each system and will shut down the system if the cut-
out is exceeded. These sensors are only installed on
R-407C units. This safety is ignored for the first 300
seconds of runtime.
After 5 minutes of run time there is a 5 minute Low
Evap Temp Safety Bypass Ramp: anytime the cooler
inlet refrigerant temperature drops below the cutout
will be lowered 6° F and ramped up to the original val-
ue over the next 5 minutes. If the cooler inlet refriger-
ant temperature rises above the original cutout during
the ramp, the cutout will be reset to the original value
and the ramp will be ended.
In water cooling mode, the cutout is fixed at 20°F. In
glycol cooling mode, the cutout is 15° F below the
leaving chilled liquid temperature cutout.
In either cooling mode, if the cooler inlet refrigerant
temp. sensor reads out of range low, the system will
also shut down.
S Y S 1 L O W
S Y S 2 L O W
The Low Superheat Cutout is to protect the
compressor(s) from liquid floodback due to low suc-
tion superheat. This safety is only active when EEV
is selected as the expansion valve in SERVICE Mode.
This safety is ignored for the first 15 seconds of system
runtime.
This safety can be triggered by two events. The first is
when suction superheat less than 2.0°F for 3 seconds.
The second is when the EEV pilot solenoid is closed 10
times in 2 minutes due to low superheat.
S Y S 1 S E N S O R
S Y S 2 S E N S O R
The Sensor Failure Safety prevents the system from
running when the sensors measuring superheat are not
functioning properly. This safety is only active when
EEV is selected as the expansion valve type in SER-
VICE Mode. This safety is ignored for the first 15 sec-
onds of system runtime.
FORM 150.66-NM3
ISSUE DATE: 09/25/2020
E V A P T E M P
E V A P T E M P
S U P E R H E A T
S U P E R H E A T
F A I L U R E
F A I L U R E
JOHNSON CONTROLS