AERCO BMK 2.0 LN Natural Gas (SN G-11-1861 and above) - Manual (Page 43)

GF-123
Benchmark 2.0LN Low NOx Boiler
Chapter 3
OMM-0046_0E I nstallation, Operation and Maintenance Manual Operation
PR1 08/20/12 AERCO International Inc.● 100 Oritani Dr. ● Blauvelt, NY 10913. ● Ph: 800-526-0288 Page 43 of 170
3.9 START SEQUENCE
When the Control Box ON/OFF switch is set to the ON position, it checks all pre-purge safety
switches to ensure they are closed. These switches include:
• Safety Shut-Off Valve Proof of Closure (POC) switch
• Low Water Level switch
• High Water Temperature switch
• High Gas Pressure switch
• Low Gas Pressure switch
• Blower Proof switch
• Blocked Inlet switch
If all of the above switches are closed, the READY light above the ON/OFF switch will light and
the unit will be in the Standby mode.
When there is a demand for heat, the following events will occur:
NOTE
If any of the Pre-Purge safety device switches are open, the appropriate fault message will be
displayed. Also, the appropriate fault messages will be displayed throughout the start
sequence, if the required conditions are not observed.
1. The DEMAND LED status indicator will light.
2. The unit checks to ensure that the Proof of Closure (POC) switch in the downstream Safety
Shut-Off Valve (SSOV) is closed. See Figure 3-3 for SSOV location.
3. With all required safety device switches closed, a purge cycle will be initiated and the
following events will occur:
(a) The Blower relay energizes and turns on blower.
(b) The Air/Fuel Valve rotates to the full-open purge position and closes purge position
switch. The dial on the Air/Fuel Valve (Figure 3-4) will read 100 to indicate that it is full-
open (100%).
(c) The VALVE POSITION bargraph will show 100%.