Aerco Benchmark G-00-711, User Manual

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CONTROL PANEL OPERATING PROCEDURES
8/1/99 3-7
Figure 3.10
Water Level Test and Reset Switch Locations
3.8 ON/OFF SWITCH
The ON/OFF switch is located on the front of the
control panel below the annunciator. (See Fig.
3.1). It is part of the start sequence and must be
in the ON position to enable the unit to fire.
When the switch is in the ON position and
illuminated, it is indicating that the start limit
string, consisting of water temperature, gas
pressure, water level, and the interlock is
satisfied, and that the alarm relay is not
activated. The unit at this point is in standby
mode and ready to run.
Note:
The On/Off switch only interrupts the start
sequence. It does not shut off power to
the boiler’s safety controls.
3.9 STARTING SEQUENCE
When the unit is in the standby mode, and there
is a demand for heating, the following will occur:
1. Upon demand the temperature controller’s
ON status indicator will light.
2. The combustion safeguard’s OPR CTRL
LED lights, and the blower contactor
energizes, starting the blower.
Figure 3.11
Proof of Closure Switch Location
3. The system next checks for proof of closure
of the safety shut-off valve, (see Fig. 3.11),
and the air fuel valve rotates open engaging
the purge position switch (see Fig. 3.12).
4. The LCD display shows PURGE INTLK
OPEN until the above conditions are met.
Once met the LCD display will show LOW
AIR FLOW.
Figure 3.12
Air/Fuel Valve Open and Engaging the Purge
Position Switch
5. The blower proof switch closes, (See Fig.
3.13), and the LCD display will show
PURGING.
SAFETY
SHUT-OFF
VALVE
PROOF OF
CLOSURE
SWITCH