Quantech QWC3050T-200T, Installation Operation & Maintenance

Page: 150 / 186

FORM QWC3-NM1
ISSUE DATE: 11/20/2020
SECTION 8 – UNIT OPERATION
QUANTECH
150
TABLE 17 - COMPRESSOR OPERATION – LOAD
LIMITING
COMPRESSORS
IN UNIT
STAGE 1 STAGE 2
4 50% -
6 66% 33%
COMPRESSOR RUN STATUS
Compressor run status is indicated by closure of con-
tacts at CTB2 – terminals 25 to 26 for system 1 and
CTB2 – terminals 27 to 28 for system 2.
ALARM STATUS
System or unit shutdown is indicated by normally-open
alarm contacts opening whenever the unit shuts down
on a unit fault, locks out on a system fault, or experi-
ences a loss of power to the chiller electronics. System
1 alarm contacts are located at CTB2 – terminals 29
to 30. System 2 alarm contacts are located at CTB2 –
terminals 31 to 32. The alarm contacts will close when
conditions allow the unit to operate, or the fault is reset
during a loss of power, the contacts will remain open
until power is reapplied and no fault conditions exist.
Simultaneous operation of Remote Load
Limiting and EMS-PWM Temperature
Reset (described on following pages)
cannot occur.
EMS-PWM REMOTE TEMPERATURE
RESET
EMS PWM Remote Temperature Reset is a value that
resets the Chilled Liquid Setpoint based on a PWM
input (timed contact closure) to the microboard. This
PWM input would typically be supplied by an Energy
Management System.
A contact closure on the PWM Temp Reset input at
CTB 1 terminals 13 - 20, will reset the chilled liquid
setpoint based on the length of time the contacts remain
closed. The maximum temperature reset is achieved at
a contact closure of 11 seconds. This is the longest con-
tact closure time allowed. One second is the shortest
time allowed and causes the Chilled Liquid Setpoint to
revert back to the Local programmed value. The reset
value is always added to the Chilled Liquid Setpoint,
meaning that this function never lowers the Chilled
Liquid Setpoint below the locally programmed value,
it can only reset to a higher value. The microboard
must be refreshed between 30 seconds and 30 minutes.
Any contact closure occurring sooner than 30 seconds
will be ignored. If more than 30 minutes elapse before
the next contact closure, the setpoint will revert back to
the locally programmed value. The new chilled liquid
setpoint is calculated by the following equations:
setpoint = local chilled liquid se °reset
°reset = (Contact Closure - 1) x (*Max. Reset Value)
10
Example:
Local Chilled Liquid Setpoint = 45°F (7.22°C)
*Max Reset Value = 10°F (5.56°C)
Contact Closure Time = 6 Seconds.