RWB 6104 WMNX Page 13
Set Combustion using Test Instruments
Set the stack or over-fi re draft to the level speci-
fi ed by the appliance manufacturer.
Natural Draft Applications; typically over-fi re
draft is -0.01” or -0.02” w.c.
Direct Venting; typically may not require draft
adjustment.
High Effi ciency/Positive Pressure Appli-
ances; also vary from traditional appliances (see
manufacturer’s recommendations).
Follow these fi ve steps to properly adjust the
burner:
Step 1: Adjust the head/air until a trace of smoke
is achieved. This can be accomplished by turn-
ing the screw on the head/air adjustment plate
assembly to increase air (CCW) or decrease air
(CW).
Step 2: At the trace of smoke level, measure the
CO
2
(or O
2
) . This is the vital reference point
for further adjustments. Example: 13.5% CO
2
(2.6% O
2
)
2.
•
•
•
3.
Step 3: Increase the air to reduce the CO
2
by 1.5
to 2 percentage points. (O
2
will be increased
by approximately 2.0 to 2.7 percentage points.)
Example: Reduce CO
2
from 13.5% to 11.5%
(2.6% to 5.3% O
2
).
Step 4: Recheck smoke level. It should be Zero.
This procedure provides a margin of
reserve air to accommodate variable
conditions.
If the draft level has changed, recheck the
smoke and CO
2
levels and readjust
burner, if necessary.
Step 5: Once the combustion has been set,
tighten the lower acorn nut and splined nut on
the air adjustment assembly. See Figure 9.
Chimney Vent Systems: Install the burner cover
and repeat Steps 2 and 4 above. If CO
2
increas-
es (O
2
decreases), remove the cover and adjust
the air setting so the CO
2
(O
2
) with the cover
installed meets the requirements of Step 3.
Direct Vent Systems with outside air ducted to
burner: Install the burner cover.
Start and stop the burner several times to
ensure satisfactory operation. Test the primary
control and all other appliance safety controls to
verify that they function according to the manu-
facturer’s specifi cations.
4.
5.
6.
Figure 10. – Nozzle Line/Head/Air Tube Assembly (Low fi ring rate shown.)
Retention Head
Head Support Legs
Electrode Tips
Electrode Clamp
Electrode Bracket
Electrode Insulator
Electrode Extension Rods
Nozzle Adapter
Nozzle
Stops in Retention Ring
Retention Ring
Throttle Ring
Throttle Cup
Nozzle Line
Bulkhead Fitting
SK9666A
Throttle Cup Hub
SK9666A
The NX burner has a reduced diameter air tube, preci-
sion-designed air throttle cup and combustion head for
improved performance. This design provides very accu-
rate control of the air/fuel ratio, but the light reaching the
cad cell through small holes in these components is lim-
ited. Because of this, the average cad cell resistance
may be higher than conventional burners with larger
openings.
NOTICE
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