Titus Mixing Box Controls IOM - Manual (Page 14)

Mixing Box Control Installation Manual
IOM-MBC-00 08-30-04
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See Figure 20 for the corresponding control point. The
factory-installed 620 ohm jumper must be in place across
terminals + and S
R.
Single M7415 actuator accepts the thermistor sensor input
from C7150B mounted in discharge or mixed air duct. See
Figure 10.
During the occupied period, on a call for cooling, when
outdoor air temperature or enthalpy conditions are low, the
M7415 economizer actuator will proportion to maintain
between 50-56º Fahrenheit at thermistor sensor.
If the mixed or discharge air temperature is above 56º
Fahrenheit, M7415 actuator will open to admit additional
outdoor air until the temperature returns to the 50 to 56º
Fahrenheit range. During the occupied period, the actuator
will not close past minimum position.
If the fully open M7415 actuator cannot satisfy the space
demand, mechanical cooling is sequenced on.
During the unoccupied period, the M7415 actuator will
override minimum position setting and drive fully closed.
On a loss of power, the actuator will spring return fully
closed.
When in heating operation, or outdoor air temperature or
enthalpy conditions are high, economizer operation is
locked out, and M7415 actuator is held at minimum
position.
Discharge Air Temperature Setpoint
Adjustment
The air temperature sensor – C7150B maintains the
discharge or mixed air duct temperature between 50 and
56º Fahrenheit. If the mixed air discharge temperature is
outside the 50 to 56º Fahrenheit range, the damper motor
will proportion open or closed until the temperature returns
to between 50 and 56º Fahrenheit.
This temperature range can be adjusted either up or down
by wiring a resistor in series or parallel with the C7150B
depending on the application. Refer to Figures 21 and 22
for details.
Figure 21. Increasing the Air Temperature Sensor
Setpoint
Figure 22. Decreasing the Air Temperature Sensor
Setpoint