AERCO BMK 2.0 LN Nat. Gas - Manual (Page 33)

INITIAL START-UP
It is important to perform the following procedure
as outlined. This will keep readjustments to a
minimum and provide for optimum performance.
1. Open the water supply and return valves to
the unit and ensure that the system pumps
are running.
2. Open the natural gas supply valve to the
unit.
3. Set the ON/OFF switch in the OFF position.
Turn on AC power to the unit. The display
will show LOSS OF POWER and the time
and date.
4. Set the unit to the Manual Mode by pressing
the AUTO/MAN key. A flashing Manual Fire
Rate message will be displayed with the
present rate in %. Also, the MANUAL LED
will light.
5. Adjust the rate to 0% by pressing the ▼
arrow key.
6. Ensure that the 1/4” ball valve downstream
of the SSOV is open.
7. Set the ON/OFF switch to the ON position.
Change the fire rate to 40% using the ▲
arrow key. The unit should begin its start
sequence and fire.
8. Next, gradually increase the firing rate to
100% in 20% increments and verify that the
gas pressure downstream of the SSOV is
4.8” W.C. for both FM and IRI gas trains at
100% firing rate. If not, remove the brass
hex nut on the SSOV using the black plastic
wrench from the Iris Damper. Make the gas
regulator adjustment using a flat-tip
screwdriver to obtain 4.8” W.C (see Figure
4.4). For Benchmark 2.0 Low NOx boilers
configured for De-Rated capacity (see para.
2.4.1), the gas pressure downstream of the
SSOV must be 3.7” W.C. for both FM and
IRI gas trains at a 100% firing rate.
CAUTION:
Turn the gas regulator adjustment screw
very slowly. Unlike ordinary regulators, this
adjustment is very sensitive.
REGULATOR
ADJUSTMENT
SCREW
Figure 4.4
Regulator Adjustment Screw Location
9. Lower the firing rate to 40% using the ▼
arrow key. Insert the combustion analyzer
probe into the exhaust manifold and allow
enough time for the combustion analyzer to
settle. Compare the measured oxygen level
to the oxygen range for inlet air temperature
in Table 1.
10. If needed, adjust the differential regulator
until the oxygen reading is within the
specified range in Table 1.
NOTE:
Adjust only the differential regulator at 40%
control signal. Do not adjust the iris air
damper.
Table 1 - Combustion Oxygen Levels for a
40% Firing Rate
40% Fire Rate
Temp (°F) O2 CO
NOx (corrected to
3% O
2
)
130 4.6 <30ppm <20ppm
120 4.8 <30ppm <20ppm
110 5.0 <30ppm <20ppm
100 5.2 <25ppm <20ppm
90 5.3 <25ppm <20ppm
80 5.5 <25ppm <20ppm
70 5.6 <25ppm <20ppm
60 5.9 <25ppm <20ppm
50 6.2 <25ppm <20ppm
40 6.4 <25ppm <20ppm
30 6.5 <25ppm <20ppm
20 6.5 <25ppm <20ppm
10 6.5 <25ppm <20ppm
0 6.6 <25ppm <20ppm
-10 6.6 <25ppm <20ppm
-20 6.7 <25ppm <20ppm
-30 6.8 <25ppm <20ppm
-40 6.8 <25ppm <20ppm
4-3