Johnson Controls YORK Tempo YLAA Series, Installation Operation & Maintenance

Page: 130 / 192

JOHNSON CONTROLS
130
FORM 150.72-NM1 (1020)
Unit Controls
After 30 minutes, the contacts will close and the system
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.
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.
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
automatic restarting.
S Y S 1 H I G H M T R C U R R
S Y S 2 H I G H M T R C U R R
The internal motor protector opens at 185 °F – 248 °F (85
°C – 120 °C) and auto resets. The mechanical HP switch
opens at 585 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 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 assure 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.