York YLAA0041 Installation Operation & Maintenance page 138

Section 7: Unit controls
This fault condition is present when CR1 (SYS 1) or
CR2 (SYS 2) relays de-energize due to the HP switch
or motor protector opening. This causes the respective
CR contacts to open causing 0 VDC to be read on the
inputs to the microboard. The fault condition is cleared
when a 30 VDC signal is restored to the input.
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 585 psig plus or minus 10 psig (27.92
barg plus or minus 0.69 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. The MP/
HP INHIBIT message will be displayed while these
contacts are open or when the HPCO is open. While
this message is displayed, the compressors will not be
permitted to start.
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
138
M T R C U R R
M T R C U R R
This safety will shut down a system if either suction
temperature or suction pressure sensors read out of
range high or low. This condition must be present for 3
seconds to cause a system shutdown. The safety locks
out a system after the first fault and will not allow au-
tomatic restarting.
S Y S 1 L O W
S Y S 2 L O W
System Suction Superheat drops below 2°F and trips
after the programmed trip time has passed. The fault
resets if the superheat rises above 2°F and will lockout
after three shutdowns in 90 minutes. Only active when
EEV is selected.
S Y S 1 L O W
S Y S 2 L O W
System Discharge Superheat drops below 18°F and
trips after 5 minutes have passed. The fault resets if the
superheat rises above 18°F and will lockout after three
shutdowns in 90 minutes. Only active when Discharge
Temperature Sensors are enabled.
S Y S 1 SENSOR
S Y S 2 SENSOR
The Sensor Failure Cutout is to prevent the EEV 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. This Sen-
sor Failure is ignored for the first 15 seconds of system
run time.
If either the suction temperature, or suction pressure
sensors, read out of range high or low for 3 seconds,
the system will shut down. This safety will lock out on
the first time and will not automatically restart.
S Y S 1 A T V
S Y S 2 A T V
If a system is running the system will shut down when
the suction pressure falls below the anti-vacuum low
pressure cut out for more than programmed Anti-Vac-
uum Delay Time. If the system is not running, the sys-
tem is inhibited from starting if the suction pressure is
below the anti-vacuum low pressure cutout.
This fault is a standard system fault (lockout 3 times in
90 minutes and the fault cannot be reset until the fault
condition is resolved.
Form 150.72-ICOM6
Issue date: 12/19/2023
S U C T S H E A T
S U C T S H E A T
D S C H S H E A T
D S C H S H E A T
FAILURE
FAILURE
S U C T P R E S S
S U C T P R E S S
Johnson Controls