Applied Air GAS-FIRED HEATERS, Installation & Operation Instruction

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SECTION VII - TROUBLESHOOTING WITH DDC CONTROLS
continued
Modulating Room Temperature (MRT, MRT-PRO or MRT-EXPERT) Controls
Symptom Possible Cause Field Test Remedy
1. Install properly.
1. Replace modulating gas
valve operator (MT-11) or
transformer.
1. See checkout procedure if
voltage is correct.
2. Consult factory.
1. Adjust to proper minimum
fi re.
1a. Replace Sensors if reading is
incorrect or correct wiring.
1b. Change to correct setpoint.
1c. Change to correct setpoint.
1. Change to correct setpoints.
A. No Gas Flow with
DO-2 on UC-01
energized.
B. Continuous Low
Fire (Electronics
OK).
C. Continuous Low
Fire (Electronics
Problem).
D. Incorrect
Minimum Fire.
E. Continuous
Minimum
Discharge Air
Temperature.
F. Incorrect
Maximum
or Minimum
Discharge Air
Temperature.
Control circuits external to MRT Controls can cause burner malfunction.
Always check manual valve to be certain gas is on, and check limit controls for normal operation.
1. Arrow on side or bottom
of valves should point in
direction of gas fl ow.
1. Inspect wiring (see check out
procedure in Section X).
1. Check for 2-10 VDC at input
terminals.
2. Check 0-10 VDC voltage on
AO-1.
1. See Butterfl y Valve Adjustment.
1a. Check Space Temperature
Sensor (TS-02), use a
BACview 6 to read TS-02
and Discharge Air Sensor
(TS-03) for correct readings.
See Thermistor curve.
1b. Check Space Temperature
Sensor (TS-02) and/or Unit
Enable Potentiometer (MP-15)
setpoint.
1c. Check Heating Occupied
and/or Unoccupied setpoint.
1. Install a BACview 6 or PC.
1. Gas valves improperly
installed.
1. Defective modulating
gas valve operator (MT-
11) and/or burned out
transformer.
1. Incorrect operation of
interface module (IM-02).
2. No output voltage on
UC-01.
1. Incorrect low fi re butterfl y
valve (GP-39) adjustment.
1. Incorrect room
temperature.
1. Maximum or minimum
heating discharge
temperature setpoint
not set correctly.
(Refer to Digital Control System User Manual for additional troubleshooting suggestions)