RT-SVX34V-EN
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Table 40. Troubleshooting (continued)
Symptom
Probable Cause Recommended Action
M. Evaporator coil freezes up during low
ambient operation.
1. System low on refrigerant charge.
1. Leak check, repair, evacuate, and recharge system as
necessary.
2. System low on air flow.
2. Check return air for obstruction or dirty filters. Check fan
wheels, motors, and belts.
3. Outdoor Air Sensor (OAS) has Failed.
3. Check OAS resistance at connector P15. Refer to the
Resistance versus Temperature chart. Replace sensor if
necessary.
4. Frostat™ has Failed 4. Check Frostat Switch
N. Economizer will not operate.
1. Economizer connector not plugged into unit wiring
harness.
1. Check connector, and connect if necessary.
2. Economizer Actuator (ECA) has failed.
2. Verify that 24 VAC is present between ECA terminals 24
VAC and Common. Place the unit in econ test mode;
economizer actuator should drive open. In any other unit
test mode, economizer actuator should drive to minimum
position. If ECA does not drive as specified, replace ECA.
3. Wiring or terminal failure.
3. Check wiring, Fresh Air Options module, and terminals.
Repair or replace if necessary.
4. ECA is defective.
4. Perform the ECA Test Procedures discussed previously.
O. Minimum position is at zero, cannot be
adjusted. Economizer still modulates.
1. Remote Minimum position potentiometer has failed.
1. With the main power off, check the resistance between
terminals on J8 at the Customer Connection Module by
rotating the remote minimum position potentiometer knob.
Resistance should be 50 to 200 Ohms.
P. Economizer goes to minimum position,
and will not modulate.
1. OAS has failed.
1. Check the OAS at connector P8 by disconnecting P8
from J8 on the RTRM. Check resistance between P8-1 and
P8-2, refer to the Resistance versus Temperature Chart.
Replace sensor if necessary.
2. DAS has failed.
2. Check the DAS at connector P14 of the Symbio™ 700
module. Check for resistance on P14 of the Symbio™ 700
module, refer to the Resistance versus Temperature Chart.
Replace sensor if necessary.
Q. Economizer modulates, but system
does not seem to operate as efficiently as
in the past.
1. Comparative enthalpy setup, RAS or RHS failed. System
is operating using Reference enthalpy.
1. Check the resistance of the return air sensor (RAS) at
connector P9 on the Fresh Air Module. Refer to the
Resistance versus Temperature Chart. Replace the sensor
if necessary. Check the return air humidity sensor (RHS) by
measuring the operating current at terminals P9 of the
Fresh Air Module. Normal operating current is 4 to 20
milliamps mA. Note: The humidity sensors are polarity
sensitive, and will not operate if connected backwards.
2. Reference enthalpy setup, OHS has failed. System is
operating using dry bulb control.
2. Check the outside humidity sensor (OHS) by measuring
the operating current at terminals P9 of the Fresh Air
Module. Normal operating current is 4 to 20 milliamps mA.
3. Comparative enthalpy setup, OHS has failed. System is
operating using dry bulb control.
3. Perform #2 above.
R. Power Exhaust will not operate.
1. Exhaust motor has failed.
1. Check the exhaust fan motor, and replace if necessary.
2. XFR has failed.
2. Check the exhaust fan contactor (XFR). Replace if
necessary
3. ECA has failed.
3. Perform the ECA Test Procedures discussed previously.
S. VFD will not operate properly
1. Symbio™ 700 has Failed
1. See Symbio™ 700 Controller with Voyager 3 Packaged
Rooftop Air Conditioners (BAS-APG048*-EN) for Symbio
700 troubleshooting details.
2. VFD has Failure 2. Check the VFD
T. Power Exhaust Fan cycles ON/OFF
1. Space Pressure Deadband is too narrow 1. Increase the Space Pressure Deadband.
2. Space Pressure Setpoint is too high/low
2. Verify Building Pressure with maximum building exhaust
enabled. Adjust Space Pressure Setpoint accordingly.
For information on component failure diagnostics, see
Symbio™ 700 Controller with Voyager 3 Packaged Rooftop
Air Conditioners (BAS-APG048*-EN).
Troubleshooting
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