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

TROUBLESHOOTING MODULATING
WATER LINE CONTROL BOARD
The Bard QW*S3D Series is equipped with a water
line control board. The TACO 3-way valve adjustment,
conducted by the TACO iSeries Smart Actuator, is
generated through the water line control board. The
temperature measurement from the sensor located
in the blower outlet sends the resistance to the
board. The board will forward the resistance reading
through the SU and SC terminals when the unit is in
dehumidification mode, allowing for the appropriate
water flow adjustment to achieve the intended
temperature.
For board troubleshooting, a truth table is suppled
below (see Table 16).
See page 38 for the modulating water line control
sequence of operation.
Full/Part Load Clg or Htg
Dehumidification w/o TWV
Three Way Valve, no Dehumidification
Full/Part Load Clg or Htg with Dehum, no TWV
Full/Part Load Clg or Htg with TWV, no Dehum
Dehumidification
Full/Part Load Clg or Htg with Dehumidification
NOTE When a "Y" signal comes on during a dehumidification cycle, the "Y" signal will have a 75-second
time delay. This allows the iSmart Actuator time to open up valve for operation.
TABLE 16
Modulating Water Line Control Board Logic
R
X
X
X
X
X
X
X
FIGURE 40
Modulating Water Line Control Board
SU SC
MODULATING WATER LINE
CONTROL BOARD
Y Y0
TWV
Inputs from Board
Y D TWV
X
X
X
X X
X X
X X
X X X
R
C
THERMISTOR
D R C
MIS-4140
MIS-4140
Output from Board
Y0
X
X
X
X
Manual 2100-738A
Page 65 of 71