3.4 START SEQUENCE
When the Edge Controller’s Enable/Disable switch is set to the Enable 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
NOTE:
The Blocked Inlet and downstream Blower Proof switches are not checked prior to starting
the pre-purge.
If all 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 hot water, 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, if the required conditions are not observed at any point during the start
sequence, appropriate messages will be displayed and the unit will go into fault mode.
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 3.4-1 for SSOV location.
Figure 3.4-1: SSOV Location (INN 600N–INN 1060N Gas Train shown)
3. With all required safety device switches closed, a purge cycle is initiated and the following
events will occur:
a. The Blower relay energizes and turns on the blower.
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