Reznor MAPS III, Cabinet D RECB Users Manual User Manual

Page 40

Form O-MAPSIII Cabinet D, P/N 222918R9, Page 40

6.2 Troubleshooting Heat Section (cont'd)

6.2.2.2 Troubleshooting the Modulating Gas Control (cont'd)

Gas Heat Section Modulating Control FUNCTIONAL ALERTS (cont'd)

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 improperly

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 33.

Limited Low

Fire (AO4)

Automatic adaptive program is

currently limiting the lower range

of modulation at 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.

G. Improper jumper connection

on IQ UI-12 causing AO-4 to

show on BacView as alarm and

disables heat sequence.

1. Verify that the IQ heating feedback input is set to receive

the ignition board voltage output of 0-10VDC from terminals

J7 by making sure jumpers are set to receive 0-10VDC signal

on UI-12 of the IQ controller.

Weak Flame

Signal (AO5)

The flame signal level is less

than optimal for this furnace.

Maintenance of the flame sensing

components is advised.