LAARS NeoTherm NTV (Sizes 399-850 MBTU/h) - Service Manual - Manual (Page 80)

70 Service Manual - NeoTherm 500
Fig. C5-10 - Correct way to clean the flame sensor
Cleaning the Burner and Heat Exchanger (continued)
Fig. C5-11 - Inside of heat exchanger (new unit)
Refractory
material
C5
cont.
Cleaning Procedure:
1. The flame sensor is mounted in the front cover of the
heat exchanger. Over time, this sensor can become
tarnished or coated. (This will happen 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 ma-
terials will clean the sensor, but they will also remove
the protective coating. The sensor will work, but
only for a short time.
The best way to clean the flame sensor is to use a
dollar bill, as shown in Fig. C5-10. The paper used
in the bill is just abrasive enough to clean the sensor
correctly, without removing the protective coating.
2. Figure C5-11 shows the inside of the heat exchanger.
• Black carbon soot can build up on the coils as a
result of poor combustion, combustion air prob-
lems, venting problems, or short-cycling.
• If the unit is operated in a non-condensing
mode, this can cause mineral granules or “coffee
grounds” to build up on the coils. You may also
notice a green build-up.
Any of these conditions can reduce the efficiency of
the unit or plug up the flue passages. Your job is to
get all of this extra material out of the heat exchang-
er so that it can operate properly.