Knight 285, Service Manual

Page: 40 / 44

3
Troubleshooting
40
Service Manual
Combustion Analysis Procedure
1. Turn the main power off to the boiler by placing the
“On/Off ” switch in the OFF position.
2. Remove the flue temperature sensor from the flue pipe
connection.
Note: Combustion measurements will be
made at this point.
3. Turn the main power on to the boiler by placing the
“On/Off ” switch in the ON position.
4. Place the boiler into the active position by pressing the
SHUTDOWN button on the display board (see page 7)
until
BLR:Standby
appears in the display window.
5. Locate the pinhole button above the “T” in the Knight
logo on the display board (see page 7). Press the button
once and hold for 5 seconds to place the boiler into
Service Mode. In Service Mode the boiler will fire at
ignition speed and will then modulate up to full fire.
6. Insert the probe from a combustion analyzer into the hole
left by the removal of the flue temperature sensor.
7. Once the boiler has modulated up to full fire, measure the
combustion. The values should be in the range listed in
Table 11 above.
The CO levels should be less than
150 ppm for a properly installed unit.
If the combustion is not within the specified range,
reference the chart below for possible causes and
corrective actions.
Table 10 Troubleshooting Chart - Combustion Levels
P PO OS SS SIIB BL LE E C CA AU US SE E C CO OR RR RE EC CT TIIV VE E A AC CT TIIO ON N
Vent/Air Intake Length
or Obstruction
• Refer to Section 3 - General Venting of the Knight Boiler Installation and Operation Manual
for the proper venting and air intake methods for the Knight boiler.
• Check for obstructions at the vent/air intake terminals.
Gas Supply Pressure
• Refer to Section 7 - Gas Connections of the Knight Boiler Installation and Operation
Manual for the proper gas supply for the Knight boiler.
Dirty/Damaged Burner
• Refer to page 26 of this manual for burner removal and cleaning procedures.
• Replace burner if necessary.
Gas Valve Adjustment
• Refer to page 41 of this manual for the gas valve adjustment procedure.
Table 11 Flue Products
Natural Gas Propane
CO
2
O
2
CO
2
O
2
8.0% - 10% 3.0% - 6.5% 9.0% - 11% 4.1% - 6.9%
8. Once the combustion analysis is complete, press the
SHUTDOWN button on the display board (see page 7)
to take the boiler out of Service Mode. The boiler will go
to shutdown and the display will show
BLR:OFF
.
9. Turn the main power off to the boiler and replace the flue
temperature sensor into the flue pipe connection.
10. Place the boiler back into normal operation.
You must replace the flue gas temperature
sensor to prevent flue gas spillage into the
room. Failure to comply could result in
severe personal injury,
death, or
substantial property damage.
 
WARNING