Modulating Water Line Control - Bard Q-TEC Series Literature Assembly

opens, compressor will go into soft lockout mode and
compressor operation will be terminated; red fault
light illuminated. Logic control will then go through
5-minute delay on break plus random start sequence.
If not fault occurs on next run cycle, compressor will
continue operation. If fault reoccurs, hard lockout
occurs and fault signal is sent to L terminal.
NOTE Jumper wire is factory installed.
Over and Under Voltage Protection
When an under or over voltage condition exists, the
controller locks out the unit. When condition clears,
the controller automatically releases the unit to normal
operation and the compressor restarts after the random
start and anti-short cycle timings are met. The under
and over voltage protection starts at plus or minus
20% from nominal voltage and returns to operation at
plus or minus 10% from nominal voltage. All four LED
fault lights will flash when an over or under voltage
conditions occurs.
NOTE The over voltage protection can be disabled by
removing the O/V jumper on the geothermic
logic control board (see Figure 26).
FIGURE 26
Geothermal Compressor Logic Control Board
Jumper Designations
Intelligent Reset
The geothermic logic control has an intelligent
reset feature after a safety control is activated. The
controller locks out the unit for 5 minutes; at the end
of this period, the controller checks to verify that all
faults have been cleared. If faults have been cleared,
the controller restarts the unit. If a second fault
occurs, the controller will lockout the unit until the
control is reset by breaking Y signal from thermostat.
The last fault will be kept in memory after a full
lockout; this is only cleared by cycling the unit power.
Manual 2100-738A
Page 38 of 71

MODULATING WATER LINE CONTROL

On a call for cooling or heat pump (Y signal from
thermostat), the Y terminal has 24 volts applied and
YO output is energized. See Figure 27.
On a call for dehumidification (D signal from
thermostat, with no Y signal from thermostat), the D
terminal (input) is energized. Concurrently, the TWV
(3-way valve) terminal is energized.
When D is energized with no Y signal, the thermistor
connected to the board will start measuring the supply
air temperature at the leaving side of the indoor blower.
The board will modulate the water valve through a
signal sent from the SU and SC terminals to the valve
actuator.
When a cooling/heating call comes while the system
is operating in dehumidification mode, the cooling/
heating call becomes the default state. The
modulating water line board will time delay (75
seconds) the YO signal to allow the modulating valve to
drive to the "full open" position. This process will be
completed prior to allowing the YO signal to travel out
through the control board, simultaneously terminating
the TWV signal.
See TROUBLESHOOTING MODULATING WATER
LINE CONTROL BOARD on page 65 for further
information on modulating water line control.
"WSD"
JUMPER
Modulating Water Line Control Board
"TEST"
JUMPER
MODULATING WATER LINE
"O/V"
CONTROL BOARD
JUMPER
Y
FIGURE 27
SU SC R
C
THERMISTOR
Y0
TWV D R C
MIS-4140
MIS-4140