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LGH/LCH420, 480, 540, 600
MEASURE ERW PRESSURE DROP
FIGURE 38
RETURN
AIR
POWER
EXHAUST
Measure the static pressure
drop across the ERW
OUTDOOR
AIR
1.9. Economizer Checkout
The following checkout procedures are completed with unit
energized. Confirm proper operation of the heartbeat LED.
Step 1 will determine whether the economizer is allowing
full damper travel. Use step 2 when the damper does not
respond to step 1.
Steps 3, 4, 5, and 6 checkout the operating modes;
checkout only the mode that applies to the unit being
worked on.
CAUTION
Power exhaust fans will be functional. To prevent opera
tion of power exhaust fans, disconnect power to unit and
then PED jack/plug P/J18.:
Step 1. ECONOMIZER OUTPUT VOLTAGE
The M3 Unit Controller monitors P262 (DPOS) and
operates as reference in Section Damper Diagnostics in the
Prodigy 2.0 (M3 Unit Controller) Application Guide
(Advance Features).
A Go to SERVICE > TEST > DAMPER>POSITION >
DAMPER POSITION ACTUAL: 0.0% The motor will
slowly modulate to the closed position.
B Change DAMPER POSITION ACTUAL to 100.0%.The
motor will slowly modulate to the fully opened position.
C If the motor does not respond, go to step 2. If the motor
does respond properly, go to the appropriate mode of
operation checkout.
Step 2. OUTPUT VOLTAGE CHECK
A Go to SERVICE > TEST > DAMPER > POSITION >
DAMPER POSITION ACTUAL: 0.0%
B Adjust the DAMPER POSITION ACTUAL: to 0.0%
position.
C Measure the voltage on P262 between pin 3 (VOT
damper control) and pin 2 (GND) using pin 1 as
common. Voltage should read approximately 2 VDC.
D Adjust the DAMPER POSITION ACTUAL: to 100.0%
position.
NOTE - Allow approximately 90 seconds for actuator to
react.
E Measure the voltage between P262 between pin 3
(VOT damper control) and pin 2 (GND) using pin 1 as
common. Voltage should read approximately 10 volts
DC. If not, check wiring and trouble shoot system.
Step 3. SINGLE ENTHALPY OPERATION (ODE)
In the single enthalpy mode, dampers open for free cooling
when the outdoor enthalpy is less than the enthalpy set
point (Parameter 162 - ECON FREECL ENTH SP);
dampers will try to modulate discharge air temperature
(RT6) to (Parameter 159 - FREE COOL SUPPLY SP) which
has a default setting of 55.0°F (13°C).
A Go to SETUP > INSTALL > press SAVE until you get to
the Configuration ID 1, position 2 needs to be set to S
for Economizer Single Enthalpy and press SAVE.
B To simulate low outdoor enthalpy. Disconnect A7
outdoor enthalpy sensor jack/plugs J/P104. Connect a
750 ohm resistor across plug J104-1 and J104-2. J104
is located in the filter access area.
C Check all connections and wiring between J104 and the
control.
Step 4. DUAL ENTHALPY MODE OF OPERATION
In dual enthalpy mode mode, dampers open for free cooling
when the outdoor air enthalpy is lower than the return air
enthalpy by difference value of (Parameter 163 - ECN
FRCL ENTH OFFST); dampers will modulate discharge air
temperature (RT6) to (Parameter 159 - FREE COOL
SUPPLY SP) which has a default setting of 55.0°F (13°C).
A Go to SETUP > INSTALL > press SAVE until you get to
the Configuration ID 1 position
2 needs to be set to D
for Economizer Dual Enthalpy and press SAVE if
performing an economizer field-install.
B Use two resistors to simulate outdoor air enthalpy
suitable.
Disconnect A62 return air enthalpy sensor
jack/plug J/P105. Place a 1500 ohm resistor
between J105-1 and J105-3. J/P105 is located
in the filter access area.
Disconnect A7 outdoor enthalpy sensor
jack/plugs J/P104. Connect a 750 ohm resistor
across J104-1 and J104-2.
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