York MILLENNIUM YCAS0230, Installation Operation & Maintenance, Page: 13 / 168

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YORK INTERNATIONAL
FORM 201.18-NM1 (102)
The software is stored in non-volatile memory (EPROM)
to eliminate chiller failure due to AC power failure. The
Programmed Setpoint is stored in lithium battery-backed
memory.
Motor Current Protection
The microprocessor motor protection provides high cur-
rent protection to ensure that the motor is not damaged
due to voltage, excess refrigerant, or other problems
that could cause excessive motor current. This is ac-
complished by sending 3-phase current signals propor-
tional to motor current from the Motor Protector mod-
ule to the Power Supply Board, where the signals are
conditioned and routed to the I/O Expansion board to
be multiplexed and sent to the Microprocessor Board.
If the motor current exceeds the 115% FLA trip point
after 3 seconds of operation on either Wye-Delta or
ACL starters, the micro will shut the system down and
lock it out after one fault. A manual reset of the re-
spective system switch is required to clear the fault
and restart the system. A thorough check of the mo-
tor, wiring, and refrigerant system should be done be-
fore restarting a system that has faulted on high motor
current.
The micro also provides low motor current protection
when it senses a motor current less than 10% FLA.
The micro will shut the system down whenever low
motor current is sensed and will lock out a system if
three faults occur in 90 minutes. Low motor current
protection is activated 4 seconds after start on both
Wye-Delta and ACL starters to ensure the motor starts,
the system doesn’t run without refrigerant, the motor
protector is not tripped, and the mechanical high pres-
sure cutout is not tripped. Once the system is locked
out on Low Motor Current, it must be manually reset
with the system switch. See also Motor Protection
Module section following.
The micro senses low motor current whenever a HPCO
or Motor Protector contact opens. This occurs because
the MP and HPCO contacts are in series with the motor
contactor. Whenever either of these devices are open,
the contactor de-energizes and the motor shuts down.
Since the micro is sending a run signal to the contactor,
it senses the low motor current below 10% FLA and
shuts the system down.
Motor Protection Module
The mechanical motor protector is a Texas Instruments
2ACE Three-Phase Protection Module (Fig. 40, page
108) which provides thermal and current motor over-
load protection. This module protects against phase-to-
phase current imbalance, overcurrent, undercurrent, and
phase rotation. The module, mounted in the power panel,
utilizes a 7-segment display which provides operating
status and fault diagnostic information. The 7-segment
display will display either a stationary or a flashing al-
phanumeric value which can be decoded by the opera-
tor. A list of the codes follows:
HAXXX Normal motor OFF display. Sequentially
sweeps through the motor protection dip
switch setting.
0 Normal - no fault detected (Running)
Flashing “0” Motor off or unloaded < 5A (Running)
AC current level.
1 High current fault.
2
Loaded phase-to-phase current
imbalance > 17%.
3
Unloaded phase-to-phase current
imbalance > 25%.
4 Improper incoming phase rotation.
5
High motor temperature. Trip point =
13kW, reset = 3.25kW.
6 Communication error.
7 Unload imbalance ( > 50%)
8 Phase Loss (> 60%)
E Out of range of RLA calibration.
Other symbols Defective module or supply voltage.
Working voltage 18 - 30VAC, 224VAC nominal.
Low voltage trip = 15VAC.
Whenever a motor protector trips, the motor protec-
tor contacts wired in series with the motor contacts
opens and the motor contactor de-energizes, allowing
the motor to stop. The micro senses the low motor
current and shuts the system down. The micro will try
two more starts before locking the system out. The
system locks out because the motor protector is a
manual reset device. After the first start, the modules’
contacts will be open, preventing the motor contactors
from energizing. Power must be removed and reapplied
to reset the module.
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