Benchmark 2500 - 3000 Boilers
CHAPTER 4 – INITIAL START-UP
OMM-0094_0E
AERCO International, Inc.
•
100 Oritani Dr.
•
Blauvelt, NY 10913
Page
57
of
204
GF-137
Ph.: 800-526-0288
03/20/2014
BMK 2500 Natural Gas Combustion Calibration
(Cont.)
28. Repeat steps 20 through 27 for valve positions of 50%, 40%, 30% and 16%. The oxygen
(O
2
), nitrogen oxide (NOx) and carbon monoxide (CO) should remain within the same
limits for all valve positions as shown in the following table.
NOTE
If NOx readings exceed the target values shown (<20 ppm),
increase the O
2
level up to 1% higher than the listed calibration
range shown in the table. Record the increased O
2
value on the
Combustion Calibration sheet.
Combustion Calibration Readings
Valve Position
Oxygen (O
2
) %
Nitrogen Oxide (NOx) Carbon Monoxide (CO)
50%
6.0% ± 0.5
<20 ppm
<100 ppm
40%
6.3% ± 0.5
<20 ppm
<100 ppm
30%
6.3% ± 0.5
<20 ppm
<100 ppm
16%
6.0% ± 0.5
<20 ppm
<100 ppm
29. If the oxygen level at the 16% valve position is too high and the Blower voltage is at the
minimum value, you can adjust the idle screw (TAC valve) which is recessed in the top of
the Air/Fuel Valve (see Figure 4-5). Rotate the screw 1/2 turn clockwise (CW) to add fuel
and reduce the O
2
to the specified level. Recalibration MUST be performed again from
50% down to 16% after making a change to the idle screw (TAC valve).
30.
This completes the BMK 2500 Natural Gas combustion calibration procedures.
Figure 4-3: Gas Pressure Adjustment Screw Location
Figure 4-4: TAC Valve Adjust (Idle Screw)
BRASS HEX HEAD
(Remove to access
the Gas Pressure
Adjustment Screw).
TAC VALVE
IDLE SCREW
