4
Settings
TEMPERATURE SETTING
Move the heating and cooling set point levers to the
desired comfort positions. See Fig. 3.
SWITCH SETTING
T641B—momentary system override switch that in the
ON position will energize a relay that can be used in
building management systems or other application.
The momentary override switch will output a 24 Vac
signal as long as the switch in held in the ON position.
In the OFF position, no output signal will be present.
For use in building management systems, the system
that the T641B interfaces with must be capable of
detecting a contact closure and respond accordingly to
perform a desired action.
T641C—manual heat/cool changeover switch. With this
switch set in the cool position, wire to damper actuator
as shown in Fig. 5. Be sure to determine direction of
damper opening for correct wiring between the T641
and ML6161. See Fig. 7. The changeover switch can
be placed in the heat position to reverse action at
terminals Y and W.
Fig. 7—Determining direction of damper opening
for correct wiring of ML6162 to T641.
IMPORTANT: An incorrectly leveled thermostat will
cause the temperature control to deviate from set
point. It is not a calibration problem.
6. Install two screws in top mounting holes and tighten.
7. Replace the thermostat cover.
WARNING
Because the cooling anticipator operates continu-
ously in the floating band, the T641 incorporates a
factory offset that calibrates the thermostat. The
offset causes the T641 to appear to be switching
10.5
°
F lower when not powered compared to
actual operation. The cooling anticipator is needed
to provide proper thermostat cycling by matching
the current draw of the ML6161 Actuator. To
ensure proper thermostat calibration and operation,
the C terminal must be used.
Fig. 5—ML6161 used with T641 for Type
B
damper applications. Y terminal will energize
counterclockwise winding on call for cooling,
driving motor open.
120
VAC
SYSTEM
TRANSFORMER
24 VAC
T641A THERMOSTAT
R
C
Y
W
PHASE SHIFT CAP.
DRIVE
CCW
WINDING
DRIVE
CW
WINDING
MOTOR ML6161
COMMON
M2257A
COM
CCW
CW
Fig. 6—T641B showing terminals X and C
energizing external relay when momentary
system override switch is pressed to ON
position.
120
VAC
SYSTEM
TRANSFORMER
24
VAC
T641B THERMOSTAT
R
C
Y
W
PHASE SHIFT CAP.
DRIVE
CCW
WINDING
DRIVE
CW
WINDING
MOTOR ML6161
COMMON
M2268
COM
CCW
CW
X
EXTERNAL
RELAY
NOTE: The ML6161 is designed to open a damper by
driving the damper shaft in either the clockwise
(cw)
or counterclockwis
e
(ccw) direction. To wi
re the
T641 correctly to the ML6161, see Figs. 5 and 7.
Cooling
Air Flow
CW TO OPEN, CCW TO CLOSE
CCW TO OPEN, CW TO CLOSE
M2067A
Cooling
Air Flow
TYPE A DAMPER
TYPE B DAMPER