Reznor PDH Operation Manual PreevA - Manual (Page 32)

Form O-PreevA, Page 32
4.0 Troubleshooting
(cont'd)
4.2 Troubleshooting - Modulating Control Module used on
Model RDH Sizes 175-400, Model RHH, or Model SHH with
Gas Control Option AG58 or D12G (cont'd)
Gas Heat Section Modulating Control Option AG58 or D12G FUNCTIONAL ALERTS
Code Alert Description Probable Causes Solutions
Failed ignition
attempt (AO1)
Maximum
number of
allowed retries
not met
The flame could not be
established during the trial
for ignition period. This alert
indicates the maximum
number of retries has not
been exceeded and furnace
operation will continue with
another ignition attempt.
See in the
LOCKOUT ERRORS
section, pages 33-34.
See in the LOCKOUT ERRORS section, pages 33-34.
Lost Flame
(AO2)
The flame sensor signal
has been lost after flame is
established during a call for
heat. This alert is displayed
during the RECYCLE period
prior to the next ignition
attempt.
A. Flame sensor coated 1. Clean flame rod sensor.
B. Flame sensor improp-
erly mounted or grounded
1. Check flame sensor wiring integrity and ceramic for cracks.
2. Re-install / replace flame sensor.
C. Unstable flame pattern 1. Verify that the spacing between the burner body and the
burner shield is equal across the entire length of the burner.
2. Check that the seals between the heat exchanger header and
heat exchanger tubes are sound; refer to Paragraph 4.1.1.
3. Ensure that the heat section door gasket is in place and the
doors are properly aligned
D. Insufficient intermediate
gas manifold pressure
through main gas safety
valve
1. Check for faulty gas valve wiring.
2. Check 24 VAC to gas valve assembly.
3. Check inlet pressure to safety gas valve.
4. Check outlet pressure from the safety gas valve.
5. Replace safety gas valve if faulty.
E. Insufficient gas
manifold pressure to
burner through modulating
ball valve assembly
1. Check voltage to gas valve actuator. (2-10 VDC depending on
model)
2. Check alignment and set screw connection between ball valve
and actuator. See Paragraph 4.3.
Insufficient
Combustion
Air (AO3)
Furnace
functional
Furnace cannot achieve
desired combustion air flow
due to blockage or high
altitude operation resulting
in a de-rate of the furnace.
A. High altitude operation 1. Normal operation. Furnace automatically de-rates for high
altitude conditions.
B. Partially blocked vent 1 Check air inlet and outlet for blockage.
2. Check venting configuration for excessive venting length,
improper sizing, etc.
C. Leak in sensing hose 1. Check sensing hose for cracks, crimps, or loose connections.
D. Low Line Voltage 1. Check the line voltage to the control board. Voltage should be
within 10% of nameplate.
E. Faulty venter assembly 1. Verify that the venter assembly is functioning properly by
referring to the sensing pressure chart on page 16..
Limited Low
Fire (AO4)
Automatic adaptive program
is currently limiting the lower
range of modulation to
avoid flame loss at minimum
fire conditions. The alert is
displayed during the run
cycle once a flame-out
condition has triggered the
Limited Low Fire function.
This function is reset by
cycling power to the board.
A. Low gas line pressure 1. Ensure gas supply is connected to furnace and check for
proper line pressure.
B. Insufficient intermediate
gas manifold pressure
through gas safety valve
1. Check for faulty gas valve wiring.
2. Check 24 VAC to gas valve assembly.
3. Check inlet pressure to safety gas valve.
4. Check outlet pressure from the safety gas valve – adjust as
needed.
5. Replace safety gas valve if faulty.
C. Faulty burner operation 1. Check burner orifice for proper size and blockage.
D. Faulty flame sensor 1. Check flame rod wiring and connections.
2. Check for proper alignment of flame rod.
3. Clean flame rod sensor.
E. Improper alignment of
the modulating actuator
and the gas ball valve.
1. Check that the alignment of the actuator to the ball valve is
correct. The valve must be in the fully open position when the
actuator is energized (ACTUATOR DRIVE = 9.6 VDC or greater).
2. Ensure that the setscrew on the actuator is tightened to the
ball valve stem.
F. Blocked or improper
venting
1. Check air inlet and outlet for blockage.
2. Check venting configuration for excessive venting length,
improper sizing, etc.
Weak Flame
Signal (AO5)
The flame signal level is
less than optimal for this
furnace. Maintenance of the
flame sensing components
is advised.
A. Flame sensor coated 1. Clean flame rod sensor.
B. Flame sensor improp-
erly mounted or grounded
1. Check flame sensor wiring integrity and ceramic for cracks.
2. Re-install / replace flame sensor.
C. Unstable flame pattern 1. Verify that the spacing between the burner body and the
burner shield is equal across the entire length of the burner.
2. Check that the seals between the heat exchanger header and
heat exchanger tubes are sound; refer to Paragraph 4.1.1.
3. Ensure that the heat section door gasket is in place and the
door is properly aligned.