JOHNSON CONTROLS
228
FORM 201.23-NM2
ISSUE DATE: 09/25/2020
SECTION 8 - MICROPANEL
run signal is not asserted within the 5-second window,
the system will fault. In addition, if either run signal is
disabled while the VSD is running, the remaining run
signal must be disabled within 5 seconds after the VSD
is shut down or the system will fault. If running, the
unit will fault and shut down with a controlled ramped
shutdown.
Control Panel Info - This is an auto-restart safety that
will autostart after the 120 second anti-recycle timer
times out and will lock out on the 3rd fault in 90 min-
utes. The fault will be a system fault for 2 compressor
units. On 3 and 4 compressor units, the fault is com-
bined as a 1/3 or 2/4 system fault. Below are the fault
messages for all systems.
SYS X YYYYYYYY VSD RUN RELAY
X indicates the system and YYYYYYY indicates the
system is in a “FAULT” condition and will restart when
the fault clears or “LOCKOUT” and will not restart un-
til the operator clears the fault using the keypad.
VSD Logic Board Failure (Software) Fault
Upon receipt of the voltage and frequency commands,
the PWM generator will acknowledge receipt of the
command. If the system microprocessor does not re-
ceive the handshake within 1.5 seconds of issuing the
command, the unit will trip. This safety is only active
during precharge and during running of a compressor.
It is not active when all the compressors are shut down
and the precharge is disabled. If the VSD Logic Board
Fault occurs while the chiller is running, all systems
will immediately shut down on a fault.
This is an auto-restart safety that will auto restart after
the 120 second anti-recycle timer times out and lock
out on the 3rd fault in 90 minutes. The fault is a unit
fault for all units. Following is the fault message.
UNIT YYYYYYYY
VSD LOGIC BOARD FAILURE
VSD CT Plug (Hardware) Fault
Jumpers are installed in each CT plug on the VSD Log-
ic Board to feed back signals to indicate if the plugs
are installed or not. If either plug is not installed, a low
value is read on the digital input and the unit will im-
mediate shutdown on a fault or will not run if off.
This is an auto-restart safety that will restart after the
120 second anti-recycle timer times out and lock out on
the 3rd fault in 90 minutes. The fault is a unit fault for
all units. Following is the fault message.
UNIT YYYYYYYY
VSD CT PLUG FAULT
YYYYYYYY indicates the system is in a “FAULT”
condition and will restart or "LOCKOUT" and will not
restart until the operator clears the fault using the key-
pad.
VSD Fault Data
When a fault has occurred, the VSD Logic Board will
capture fault data. This data will be stored in the on-
board battery backed RAM for safekeeping and trans-
ferred to the panel via the communications link as soon
as possible.
A fault code will be set for the fault that initiated the
system shutdown. This fault will appear as a specific
fault in the Status message.
Any faults that occur after the initial fault, which occur
within the comms transmission time frame following
the inception of the first fault, will be stored and trans-
mitted to the Micro Logic Board together with the first
fault data. These faults will appear in the "All Fault"
display in the History.
A snapshot of the operating parameters of the VSD is
continuously updated in battery-backed memory once
every program loop. Upon receipt of a first fault, the
snapshot of the operating parameters will be stored in
memory and are transmitted to the panel as the fault
data.
Fault Relay/Fault Acknowledge Bit
Control of the Fault Relay is from the VSD Logic
Board. The Fault Relay on the VSD will be closed dur-
ing a non-fault condition.
When a running or pre-charge fault occurs on the VSD,
the fault relay will immediately open. The relay will
not open for non-running faults that occur.
When the Chiller Control Board sees the VSD fault re-
lay open, it will immediately take a snapshot of system
data and save it to the history buffer.
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