Applied Air GAS-FIRED HEATERS, Installation & Operation Instruction

Page: 45 / 64

– 45 –
1. Install properly.
1. See checkout procedure if
voltage is correct.
2. Contact Factory.
1. Replace modulating gas
valve operator (MT-11) or
transformer.
1. Adjust to proper minimum fi re.
1. Replace Outside or Inlet Air
Temperature Sensor (TS-01)
and/or Discharge Air
Temperature Sensor (TS-03)
1. Readjust linkage on valve or
replace if necessary.
1. Increase inlet pressure if
possible.
2. See Sequence and Burner
setup in Section X.
1. Change to correct setpoint
setting.
2. If readings are not correct,
replace Discharge Air
Temperature Sensor (TS-03)
or repair wiring.
3. Change to correct setpoint.
See Digital Control System
User Manual.
SECTION VII - TROUBLESHOOTING WITH DDC CONTROLS
continued
Modulating Discharge Temperature (MDT or MDT EXPERT) Controls
Symptom Possible Cause Field Test Remedy
A. No Gas Flow
with DO-2
or UC-01
energized.
B. Continuous Low
Fire (Electronics
Problem).
C. Continuous Low
Fire (Electronics
OK).
D. Incorrect
Minimum Fire.
E. Continuous High
Fire (Electronics
Problem).
F. Continuous High
Fire (Electronics
OK).
G. Incorrect
High
Fire.
H. Incorrect
Discharge Air
Temperature
1. Arrow on side or bottom of
valves should point in direction
of gas fl ow.
1. Check for 2-10 VDC at IM-02
input terminals.
2. Check 0-10 VDC Voltage on AO-1.
1. Inspect wiring (see checkout
procedure in section X).
1. See butterfl y valve adjustment.
1. Check Outside or Inlet Air
Temperature Sensor (TS-01)
and/or Discharge Air Temperature
Sensor (TS-03) for open internal
circuit. See Thermistor curve.
1. Inspect linkage and valve.
1. Read pressure at inlet to
modulating valve using a
manometer with unit operating
at full fi re. Pressure should
be equal to the sum of outlet
pressure setting plus pressure
drop of the valve.
2. Read manifold pressure using
manometer and compare with
the pressure stated on the
specifi cation plate.
1. Check setpoint on Unit Enable
Potentiometer (MP-15)
2. Check Discharge Air
Temperature Sensor (TS-03)
and wiring. See Thermistor
curve.
3. Check setpoint with BACview
or PC.
(Refer to Digital Control System User Manual for additional troubleshooting suggestions)
1. Gas valves improperly
installed.
1. Incorrect operation of
Interface Module (IM-02).
2. No output voltage on UC-01.
1. Defective modulating
gas valve operator (MT-
11) and/or burned out
transformer.
1. Incorrect low-fi re butterfl y
valve (GP-39) adjustment.
1. Open circuit in Outside or
Inlet Air Temperature Sensor
(TS-01) and/or Discharge
Air Temperature Sensor
(TS-03) circuit or wiring.
1. Foreign object holding
butterfl y valve (GP-39)
open.
1. Inlet pressure too low.
2. Incorrect outlet pressure
adjustment of Pressure
Regulator.
1. Unit Enable Potentiometer
(MP-15) not set correctly.
2. Discharge Air
Temperature Sensor (TS-
03) not reading correctly.
3. The Heating Discharge
Air Setpoint on
VDT-EXPERT Control
System is not set
correctly.