FORM 150.60-NM4
YORK INTERNATIONAL
53
Oil Pressure Safety
The Oil Pressure Safety assures that the compressors
mechanical components receive proper lubrication. The
micro begins monitoring compressor oil pressure after 4
seconds of operation. For operating periods of 4 sec-
onds to 30 seconds, oil pressure must be greater than 5
PSID. From 30 seconds to 240 seconds, oil pressure
must be greater than 20 PSID. After 240 seconds, oil
pressure must be greater than 25 PSID for as long as
the compressor continues to run. If the required oil pres-
sure limits are not met, the system will shut down.
The micro computes differential oil pressure by meas-
uring oil pump pressure and subtracting suction pres-
sure (Oil Suction = Oil PSID).
An example of an oil pressure fault display message is
shown below.
Discharge Pressure Safety
The Discharge Pressure Safety assures that the sys-
tem pressure does not exceed safe working limits which
could open a relief valve or other pressure relief device
causing refrigerant loss.
This safety is a back-up for the mechanical safety in the
system. Anytime the cut-out point is exceeded, the sys-
tem will shut down.
The Discharge Pressure Safety Cut-out is programma-
ble by the user (Page 35). An example of a discharge
pressure fault display message is shown below.
NOTE: This safety is only operable if optional discharge
pressure transducers are installed.
Pumpdown Safety
The Pumpdown Safety assures that a compressor does
not run unless it completes a proper pumpdown. This
prevents operation of a refrigerant system which has a
leaking liquid line solenoid valve.
On start-up, the system must pump down to the suction
pressure cut-out within 300 seconds or the system will
shut down.
An example of the Pump down fault display message is
shown below.
NOTE: LLSV refers to liquid line solenoid valve.
Motor Protector
Three internal temperature sensors are built into the motor
stator. These sensors are wired into the motor protector
module located inside the Motor terminal box. As the
motor windings heat and cool, the resistance of the mo-
tor temperature sensors will change. If the windings over-
heat, the change in resistance in the sensors will be
sensed by the Motor protector module. The module will
open its MP contacts breaking the 115VAC fed to the
motor contactor. When the motor contactor de-energizes,
motor current falls to zero. The low motor current is
sensed by the microprocessor and the system is shut
down. For more information, see MOTOR CURRENT
SAFETY (Page 52).
Auto-restart will be permitted after a shutdown, when
the motor sensors cool and the MP contacts close. A
fault lock-out will result if safety thresholds are exceeded
three times in a 90 minute period.
Mechanical High Pressure Cut-out (HPCO)
A mechanical high pressure cut-out is located on each
compressor discharge or in the compressor head. This
is the primary high pressure safety in the system. Any
microprocessor controls are secondary.
Anytime discharge pressure exceeds 405 PSIG, the con-
tacts in the high pressure cut-out will open which removes
115VAC from the motor protector module. When 115VAC
control power is lost to the module, the modules MP
contacts open breaking the 115VAC fed to the motor con-
tactor. The motor contactor de-energizes and motor cur-
rent falls to zero. The low motor current is sensed by the
microprocessor and the system is shut down. For more
information see MOTOR CURRENT SAFETY (Page 52).
Auto-restart will be permitted after a shutdown when dis-
charge pressure drops to below 330 PSIG which allows
the mechanical high pressure cut-out to reset and its
contacts to close. This re-applies 115VAC to the motor
protector closing the MP contact. A fault lock-out will
result if safety thresholds are exceeded three times in a
90 minute period.
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