Watts Aerco Benchmark Series Operation And Service Manual page 121

Benchmark Platinum-Edge: Operation-Service Manual
SECTION 9 – AERTRIM OPERATION
Figure 9-3 graphically shows the functional logic of the AERtrim system and how the blower
voltage (BV), O Limits, and air/fuel ratio interact during an AERtrim operation. The limits are
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fixed presets within the controller. The target range is adjustable within these limits to allow the
user to select the optimal air/fuel ratio for a particular boiler or application.
Figure 9-3 shows how the controller would react to an O
controller will reduce the blower voltage (BV) until the O
provided the BV adjustments are within the BV limits for that unit at that fire rate. The control will
then store this as the new BV calibration setting until changed manually or by another cycle of
the AERtrim function.
NOTE:
When the O sensor is off during the 10 hour O
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sends an Oxygen Level of 99 (rather than 0) to the building automation system.
Once the system operational stability conditions are met, the AERtrim system will execute the
following steps:
1. Lock the fire rate at the current position that needs adjustment to the air/fuel ratio.
2. The Demand LED will flash once per second to indicate that the trim function has started.
3. Check the oxygen levels inside the combustion chamber:
•
If oxygen levels are within the set range, AERtrim releases control.
•
If oxygen levels are outside the set range, AERtrim will adjust Blower Voltage to bring
the boiler back to the Target O
This process repeats until the target oxygen range is achieved or the unit reaches the allowable
blower voltage limit.
OMM-0137_D • GF-211 • 7/16/2019
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Sensor OFF periods shown above, Modbus
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Figure 9-3: AERtrim Logic
value.
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% reading above the upper limit. The
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% reading is within the Target Range,
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