Quantech QTC40160, Установка, эксплуатация и обслуживание

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Section 7 - Operation
Quantech
111
Form QTC4-NM2
Issue date: 05/12/2023
7
Low leaving chilled liquid temp fault
The Low Leaving Chilled Liquid Temp Cutout helps
to protect the chiller from an evaporator freeze-up if
the chilled liquid temperature drops below the freeze
point. This situation could occur under low flow condi-
tions or if the Micro Panel setpoint values are improp-
erly programmed. Any time the leaving chilled liquid
temperature (water or brine) drops below the program-
mable cutout point, the chiller will fault and shutdown
with a controlled ramped shutdown. Restart can occur,
if demand allows, when chilled liquid temperature rises
2.2°C (4°F) above the cutout. This fault cannot cause a
lockout. The following is a sample shutdown message:
UNIT YYYYYYYY
LOW LEAVING CHILLED LIQUID TEMP
The unit is inhibited from starting any time the chilled
liquid temperature is below the cutout plus 2.2°C (4°F).
VSD communications failure fault
The VSD Communications Failure is to prevent the
unit from trying to run, if the Chiller Control Board
never initializes communications with the VSD Logic
Board. The unit will also shut down with a controlled
ramped shutdown if the Chiller Control Board loses
communications with the VSD Logic Board while the
chiller is operating.
On power-up, the Chiller 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. After these data points
have been received by the Chiller Control Board,
and have been successfully initialized, the Chiller
Control Board will not request them again. If the
comms connection fails to occur and a reply from the
VSD Logic Board does take place in 8 s, the Chiller
Control Board will prevent the chiller from operating
and a fault message will be displayed.
During normal operation, if the control panel Chiller
Control Board receives no valid response to messages
for 8 s, the unit will shut down all compressors on a
Comms fault. The Chiller Control Board will continue
to send messages to the VSD while faulted. The unit
will be inhibited from starting until communications is
established. The fault will automatically reset when the
Chiller Control Board receives a valid response from
the VSD for a data request. The following is an ex-
ample of a Comms Failure fault message:
UNIT YYYYYYYY
VSD COMMUNICATIONS FAILURE
System safeties, faults
System safety (fault) operation
System safeties are faults that cause individual systems
to be shut down if a safety threshold is exceeded for
3 s. System faults are auto reset faults in that the sys-
tem will be allowed to restart automatically after the
120 s anti-recycle timer times out. The only exception
is after any 3 faults on the same system occur within
90 min, that system will be locked out on the last fault.
The lockout condition requires a manual reset using the
system switch. The respective system switch must be
cycled OFF and ON to clear the lockout fault.
When multiple systems are operating and a system
fault occurs, the running systems will ramp down and
the faulted system will be shut OFF and the previously
operating will restart if required after the fault clears
and/or the 120 s anti-recycle timer times out.
In the descriptions of the fault displays that follow,
the fault message will show a YYYYYYYY to indi-
cate that a system is in a FAULT condition and will
restart when the fault clears, or LOCKOUT and will
not restart until the operator clears the fault using the
keypad. If a system safety is in effect, the message will
be displayed to the operator when the STATUS key is
pressed.
In some cases, a control panel fault will occur after
a VSD fault, possibly during system shutdown or at
some later time. This is known as an “ALL FAULT”
and these faults will be recorded as such under the
HISTORY information stored at the instant of the pri-
mary fault. In some cases, this information may be
valuable in troubleshooting the primary fault. An ex-
ample of the ALL FAULT history message as shown
in the
All fault data on Page 129
under the HISTORY
key. When an ALL FAULT occurs, associated history
information will not be stored. If an additional fault
does not occur, the ALL FAULTS display will indicate
NONE.
In cases where a VSD fault occurs during the ramp-
down of a control panel fault (that is, low suction pres-
sure, low water temp, and so on), the VSD fault will
be stored as a new fault with the associated fault in-
formation stored at the instant the VSD fault occurred
(that is, IGBT Gate Drive, Single Phase Input, VSD CT
Plug, and so on). The control panel fault that occurred