Benchmark 750-3000 Boiler Installation & Startup Manual
SECTION 4 – INITIAL START-UP
OMM-0121_D • GF-205 • 5/9/2019 Technical Support • (800) 526-0288 • Mon-Fri, 8 am - 5 pm EST Page 63 of 122
4.4.1 NATURAL GAS Combustion Calibration
NATURAL GAS Combustion Calibration Instructions
These instructions apply only to units running on NATURAL GAS. Instructions for doing
combustion calibration on a unit running PROPANE appear in the next section, 4.4.2.
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 C-More Controller’s ON/OFF switch to the OFF position
4. Turn external AC power to the unit ON. The display will show a description of the unit and
then the time and date.
5. Press the MENU key on the front panel of the C-More Controller and access the Setup
menu, enter the password 6817 and then press the ENTER key.
6. Set the unit to the MANUAL mode by pressing the AUTO/MAN key. A flashing Manual
Valve Position message will be displayed with the present position in % and the MANUAL
LED will light.
7. Adjust the air/fuel valve position to 0% by pressing the ▼ arrow key
ENTER.
8. Ensure that the leak detection ball valve downstream of the SSOV is open
manometer is attached and functioning properly.
9. Set the ON/OFF switch to the ON position.
10. Press the MENU key on the front panel of the C-More Controller until COMBUSTION CAL
MENU appears on the display.
11. Press the Up ▲ arrow key until SET Stdby V Out (Standby Voltage)
Verify that it is set to 2.0 V (the default). AERCO recommends it be kept at 2.0 volts to
prevent flue gas recirculation. Individually vented units
in positive pressure boiler rooms
may set SET Stdby V Out to 0 volts.
12. Press the Down ▼ arrow key until SET Valve Position appears, then press CHANGE.
13. Use the Up ▲ arrow key to change the valve position to 30%. The unit should begin its
start sequence and fire.
14. Next, verify that the gas pressure downstream of the SSOV is set to the value in Table 4-1
for the model you are calibrating. If gas pressure adjustment is required, remove the brass
hex nut on the SSOV actuator to access the gas pressure adjustment screw (Figure 4-3).
Make gas pressure adjustments using a flat-
tip screwdriver to obtain a gas pressure
approximately shown in Table 4-1.
TABLE 4-1: NATURAL GAS Gas Pressure Range @ 100% Fire Rate
Model Single Fuel Dual Fuel
2.0” ± 0.2” W.C. (0.50 ± 0.05 kPa)
2.4” ± 0.4” W.C. (0.60 ± 0.10 kPa)
3.6” ± 0.1” W.C. (0.90 ± 0.02 kPa)
3.6” ± 0.1” W.C. (0.90 ± 0.02 kPa)
3.4” ± 0.2” W.C. (0.85 ± 0.05 kPa)
6.3” ± 0.1” W.C. (1.57 ± 0.02 kPa)
2.0” ± 0.1” W.C. (0.50 ± 0.02 kPa)
5.8” ± 0.1” W.C. (1.44 ± 0.02 kPa)
2.1” ± 0.2” W.C. (0.52 ± 0.05 kPa)
6.0” ± 0.2” W.C. (1.49 ± 0.05 kPa)
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