York YCAL0012EC, Installation Operation & Maintenance

Page: 104 / 166

JOHNSON CONTROLS
104
FORM 150.66-NM2
ISSUE DATE: 09/25/2020
SECTION 7 - UNIT CONTROlS
The Low Evaporator Temperature Cutout is to protect
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
cutout 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 value
over the next 5 minutes. If the cooler inlet refrigerant
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.
The Low Superheat Cutout is to protect the compressor(s)
from liquid floodback due to low suction 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 < 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.
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 SERVICE
Mode. This safety is ignored for the first 15 seconds of
system runtime.
The internal motor protector opens at 185°F - 248°F
(85°C - 120°C) and auto resets. The mechanical HP switch
opens at 405 psig +/- 10 psig (27.92 barg +/- .69 barg) and
closes at 330 psig +/- 25 psig (22.75 barg +/- 1.72 barg).
The compressor is also equipped with a discharge
temperature sensor for the purpose of sensing internal
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 internal
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 system
will be permitted to restart. The micro 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.
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.
S Y S 1 H I G H M T R C U R R
S Y S 1 L O W E V A P T E M P
S Y S 1 L O W S U P E R H E A T
S Y S 1 S E N S O R F A I L U R E