LAARS NeoTherm NTV (Sizes 399-850 MBTU/h) - Service Manual - Manual (Page 70)

60 Service Manual - NeoTherm 500
Combustion Adjustment Procedure -
Units with Original (White) User Interface
WARNING
Improper adjustment may lead to poor combustion quality, increasing
the amount of carbon monoxide produced. Excessive carbon monox-
ide levels may lead to personal injury or death.
Equipment required:
• Combustion analyzer
• 2 mm Allen wrench
Procedure:
1. Measure the CO
2
and O
2
in the flue products at High
Fire. The NeoTherm must be forced to High Fire to
obtain accurate results.
How to get there: From the “Home” screen, press
and hold the Next button for 3 seconds to go to
Diagnostic mode. Press the Next button several
times until you see “Rate” and “100%.” Press the Up
arrow. The NT unit is now forced into high fire for 5
minutes.
The CO
2
readings should be between the values
shown in Table C2-1. If the CO
2
is not within the
range shown, adjustments may be made. To adjust
the high fire CO
2
, locate the high fire adjuster screw
as shown in Fig. C2-1. Slowly make adjustments in
1/16 of a revolution increments until the CO
2
is within
the range identified. For the high fire adjustment,
turning the screw counter-clockwise (CCW) makes
the mixture richer.
Low fire CO
2
adjustment
High fire CO
2
adjustment
Fig. C2-1 - High- and low-fire adjustments on gas valve
Gas Type High Fire CO
2
Low Fire CO
2
Natural 8.8% to 9.0% 0.5% lower than high fire CO
2
Propane 9.8% to 10.0% 0.5% lower than high fire CO
2
Table C2-1 - CO
2
Range
C2