LAARS NeoTherm NTV (Sizes 399-850 MBTU/h) - Service Manual - Manual (Page 66)

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Service Manual - NeoTherm 500
The flame sensor is a single-rod system, and is mounted
in the front cover of the heat exchanger. Over time, this
sensor can become tarnished or coated. (This will hap-
pen more quickly if the NT unit has been operating often
at a low firing rate.) The flame sensor has a protective
coating.
Important! Do not use sandpaper, steel wool, or emery
board to clean the flame sensor. These materials will
clean the sensor, but they will also remove the protective
coating. The sensor will work, but only for a short time.
Adjustment Procedure:
1. Shut off the 120V power supply to the unit.
2. Turn off all manual gas valves connecting the unit to
the main gas supply line.
3. Remove the front door of the unit to gain access to
the flame sensor electrode.
4. The end of the flame rod should be 1/4” away from
the burner. See Fig. B36-2.
Cleaning or Replacement Procedure:
1. Shut off the 120V power supply to the unit.
2. Turn off all manual gas valves connecting the unit to
the main gas supply line.
3. Remove the front door of the unit to gain access to
the flame sensor electrode.
4. The best way to clean the flame sensor is to use a
dollar bill, as shown in Fig. B37-1. The paper used
in the bill is just abrasive enough to clean the sensor
correctly, without removing the protective coating.
5. If you need to replace the part, remove the flame
sensor wire from the electrode.
6. Remove the two bolts fastening the electrode to the
burner door. Remove the old flame sensor.
7. Install a new assembly by reversing the instructions
listed above. The end of the flame rod should be
1/4” away from the burner. See Fig. B36-2. Replace
the flame sensor gasket if it is damaged.
Fig. B37-1 - Correct way to clean the flame sensor
B37
Flame Sensor