CHAPTER 4: INITIAL START-UP
PR2: 04/22/13 Page
53
of
158
Benchmark 2.0LN Dual-Fuel Low NOx Boiler
Operation and Maintenance Manual
OMM-0052_0E
GF-127
AERCO International, Inc.
•
100 Oritani Dr.
•
Blauvelt, NY 10913
•
Ph: 800-526-0288
Table 4-12: Combustion Oxygen Level at
21%
Valve Position
Oxygen %
± 0.2
Carbon Monoxide
NOx
8.9 %
<100 ppm
<100 ppm
57.
If the oxygen level is not within the specified range, adjust the level using the ▲ and ▼ arrow
keys. This will adjust the output voltage to the blower motor as indicated on the display.
Pressing the ▲ arrow key increases the oxygen level and pressing the ▼ arrow key
decreases the oxygen level.
58. Once the oxygen level is within the specified range at 21%, press the
ENTER
key to store the
selected blower output voltage for the 21% valve position.
59. This completes the Propane Combustion Calibration procedure.
4.5 UNIT REASSEMBLY
Once the combustion calibration adjustments are properly set, the unit can be reassembled for
service operation.
1. Set the ON/OFF switch in the OFF position.
2. Disconnect AC power from the unit.
3. Shut off the gas supply to the unit.
4. Remove the manometer and barbed fittings and reinstall the NPT plug using a suitable pipe
thread compound.
5. Remove the combustion analyzer probe from the vent hole. Replace the NPT plug in the vent
hole using a suitable pipe joint compound.
6. Replace the unit’s side panels and front door.
4.6 OVER-TEMPERATURE LIMIT SWITCHES
The unit contains three (3) types of over-temperature limit switches. These switches consist of a
manual reset switch, a rotary dial adjustable switch and a digital alarm switch. These switches
are mounted on a plate as shown in Figure 4-6. The switches can be accessed by opening the
front panel door of the unit.
The manual reset switch is not adjustable and is permanently fixed at 210°F. This switch will
shut down and lock out the boiler if the water temperature exceeds 210°F. Following an over-
temperature condition, it must be manually reset by pressing the manual reset button shown in
Figurer 4-6 before the boiler can be restarted.
The rotary dial over-temperature switch is manually adjustable from xxx to yyy ºF. This switch
allows the boiler to restart, once the temperature drops below the selected temperature setting
on the dial. Set the dial on this over-temperature switch to the desired setting.
The digital alarm switch shown in Figures 4-6 and 4-7 is preset at the factory to 210ºF and
should not be changed. If an over-temperature condition is detected, this switch automatically
shuts down the boiler and sounds an audible alarm. If desired, the over-temperature alarm
switch settings can be checked or adjusted using the procedure in paragraph 4.6.1.
