Titus Mixing Box Controls IOM - Manual (Page 15)

Mixing Box Control Installation Manual
IOM-MBC-00 08-30-04
15 of 15
Verification and Troubleshooting
The following table provides the actions and responses to
verify the installation of W7459A installed on an M7415
Actuator.
DANGER
DISCONNECT POWER SUPPLY BEFORE
CONNECTING WIRING TO PREVENT ELECTRICAL
SHOCK OR EQUIPMENT DAMAGE
Caution: Exercise care when adjusting the
enthalpy changeover and minimum damper
position control. Use a small screwdriver for
these adjustments. Excessive force may damage
the controls.
Perform verification and troubleshooting steps in
order.
Table 16. Modulating Control Verification
and Troubleshooting
e s n o p s e R n o it c A
A.
Power
1. Disconnect power at
terminals TR and TR1.
2. Disconnect jumper
across P and P1.
3. Jumper TR and 1.
4. Jumper T1 to T.
5. If connect, remove
C7400A Enthalpy Sensor
from terminals S
O
and +.
6. Verify Factory-installed
620 ohm resistor is
connected to S
R
and +.
7. Apply 24 Vac power to
terminals TR and TR1
LED should be off.
Motor is in closed
position.
8. Disconnect factory-
installed 620 ohm
resistor from terminals S
R
and +.
LED should be on,
indicating low enthalpy.
Motor drives toward
open.
B. Enthalpy Simulation
1. Reconnect factory-
installed 620-ohm
resistor across terminals
S
R
and +.
2. Connect 1.2k ohm
checkout resistor across
terminals S
O
and +.
e s n o p s e R n o it c A
3. Set enthalpy set point
potentiometer to “A”.
LED should come on,
indicating low enthalpy.
Motor drives toward
open.
4. Set enthalpy set point
potentiometer to “D”.
LED should go off,
indicating high enthalpy.
Motor drives toward
closed.
C. Sensor
1. Reconnect the + lead of
outdoor enthalpy sensor
to the + terminal of
W7459.
2. Connect a DC multi-
meter or voltmeter
between terminals S
O
of
the W7459 and terminal
S of the enthalpy sensor.
(Positive meter lead to
terminal S of enthalpy
sensor.)
Multi-meter or voltmeter
should indicate between
3 and 25 mA, if sensor
is operating properly.
If multi-meter or
voltmeter indicates
zero, the sensor may be
wired backwards.
3. If using differential
enthalpy, the return air
enthalpy sensor may be
checked by connecting a
DC multi-meter or
voltmeter between
terminal S
R
of the W7459
and terminal S of the
return air enthalpy
sensor. (Position meter
lead to terminal S of
return air enthalpy
sensor.
Multi-meter or voltmeter
should indicate between
3 and 25 mA, if sensor
is operating properly.
If multi-meter or
voltmeter indicates
zero, the sensor may be
wired backwards.
Abbreviations
The following table lists the abbreviations found within this
document.
Abbrev. Term
A Ampere
BTU British Thermal Units
DC Direct Current
LED Light Emitting Diode
mA Milliampere
NTC Negative temperature coefficient
RH Relative Humidity
spdt Single-pole, double -throw
spst Single-pole, single-throw
Vac Volts Alternating Current
Vdc Volts Direct Current