AERCO BMK 2.0 LN October 2012 - Manual (Page 62)

Chapter 4
Benchmark 2.0LN Low NOx Boiler
GF-123
Initial Start-Up Installation, Operation and Maintenance Manual OMM-0046_0F
Page 62 of 172 AERCO International Inc.● 100 Oritani Dr. ● Blauvelt, NY 10913. ● Ph: 800-526-0288 PR1 10/17/12
4.6 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.
4.7 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 temperature limit switch is manually adjustable from 32ºF - 212ºF (0ºC – 100ºC).
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 4.7.1.