Quantech QWC4, Installation Operation & Maintenance, Page: 98 / 156

QUANTECH
98
FORM QWC4-NM1 (221)
ISSUE DATE: 02/28/2021
SECTION 6 - OPERATION
TABLE 32 - UNIT SAFETIES FAULTS (CONT'D)
MESSAGE DESCRIPTION
UNIT YYYYYYY
PRE-CHARGE DC BUS
VOLTAGE IMBALANCE
The voltage magnitude of each half of the DC bus shall remain /- 100 VDC of the total
DC bus voltage divided by two. If the magnitude exceeds the +/- 100 volt window the unit
shall initiate a shutdown. This safety will lock out on the first occurrence. YYYYYY will show
LOCKOUT, and will not restart until the operator clears the condition using the keypad
UNIT YYYYYYY
PRE-CHARGE LOW DC
BUS VOLTAGE
Software-Initiated Fault - This fault protects the chiller from conditions outside of the tolerances
required to produce proper output power to the compressor motor. Several conditions must be
met during the pre-charge operation. The DC bus voltage shall reach at least: 41 VDC within
four seconds after the pre-charge signal has been asserted for 50 Hz and 60 Hz VSD, 500 VDC
within 19 seconds after the pre-charge signal has been asserted on the 460V, 60Hz VSD, and
414 VDC within 19 seconds on the 380V 50/60 Hz and 400/415 V, 50 Hz VSD. If the unit fails
to make pre-charge, the signal shall be deasserted for 10 seconds, during which time the units
fans and water pumps shall remain energized. Following this 10-second period, the pre-charge
shall again be initiated. The unit shall attempt to make pre-charge three consecutive times. If the
unit fails to make pre-charge on three consecutive times, the unit shall shut down and lock out.
YYYYYY will show LOCKOUT, and will not restart until the operator clears the condition using
the keypad
UNIT YYYYYYY
SINGLE PHASE INPUT
VOLTAGE
Hardware-Initiated Fault - The VSD’s SCR trigger control board contains circuitry that
checks the three phase mains for the presence of all three-line voltages. If any line voltage is
not present, the unit initiates a shutdown. The unit shall remain in shutdown until all voltage
on all three phases is present. This fault will not cause a lockout. The VSD shutdown type is
immediate. YYYYYYY will show FAULT to indicate a system is in a FAULT condition, and will
restart when the 120 second anti-recycle timer times out.
UNIT YYYYYYY
VSD
COMMUNICATIONS
FAILURE
This fault prevents the unit from trying to run, if the control board never initializes
communications with the VSD logic board. The unit will also shut down with a ramped shutdown,
if the control board loses communications with the VSD logic board while the chiller is operating.
On power-up, the microprocessor board will attempt to initialize communications with the VSD
logic board. The control panel will request data from the VSD, which includes the number of
compressors and the VSD software version. Once these data points have been received by the
control board, and successfully initialized, the control board will not request them again. If the
communications connection fails to occur and a reply from the VSD logic board does take place
in eight seconds, the control board will prevent the chiller from operating, and a fault message
will be displayed. During normal operation, if the control board receives no valid response to
messages for eight seconds, the unit will shut down all compressors. The control board will
continue to send messages to the VSD while faulted. The unit will be inhibited from starting
until communications are established. The fault will automatically reset when the control board
receives a valid response from the VSD for a data request. YYYYYYY will show FAULT to
indicate a system is in a FAULT condition, and will restart when the 120 second anti-recycle timer
times out.
UNIT YYYYYYY
VSD CT PLUG FAULT
Hardware-Initiated Fault - Jumpers are located in each CT plug on the VSD logic board to
feedback a digital signal to indicate if all of the plugs are installed. If a plug is not installed, a low
value is read on the digital input, and the unit will trip. This auto-restart safety will lock out on
the third fault in 90 minutes. The VSD shutdown type is immediate. YYYYYYY will show FAULT
to indicate that a system is in a FAULT condition, and will restart when the condition clears; or
will show LOCKOUT, and the system will not restart until the operator clears the fault using the
keypad.
UNIT YYYYYYY
VSD LOGIC BOARD
FAULT
Upon receipt of the voltage and frequency commands, the VSD PWM generator shall
acknowledge receipt of the command by toggling a port on the system microprocessor. If the
system microprocessor does not receive the handshake within 1.5 seconds of issuing the
command (due to the TEST mode of operation) the unit shall initiate a trip. This auto-restart
safety will lock out on the third fault in 90 minutes. The VSD shutdown type is immediate.
YYYYYYY will show FAULT to indicate a system is in a FAULT condition, and will restart when
the 120 second anti-recycle timer times out; or will show LOCKOUT, and the system will not
restart until the operator clears the fault using the keypad.