Centurion Water Heater- Edge [ii]: Install-Operation-Service
SECTION 9: O2 TRIM OPERATION
OMM-0153_A
• 8/25/2022 Technical Support • (800) 526-0288 • Mon-Fri, 8 am - 5 pm EST Page 94 of 131
SECTION 9:
O
2
TRIM OPERATION
9.1 O
2
TRIM INTRODUCTION
Advanced combustion control systems need to maintain precise air/fuel ratios to maximize
efficiency. Gas Water Heaters often deviate from the ideal air-fuel ratio due to environmental
variations such as humidity, atmospheric pressure, filter dust loading, delivered gas energy
content and other factors. If the Water Heater is operating with fixed blower/damper positions,
the air/fuel ratio will normally vary within an acceptable level but will not be fully optimized for
efficiency and reliability.
The O
2
Trim system is designed to measure and maintain an ideal air-fuel ratio in Centurion
Water Heaters, thus maximizing efficiency and reliability while minimizing emissions.
Figure 9-1: Simplified O
2
Trim Diagram
W A R N I N G :
O
2
Trim and combustion calibration can both alter the voltage sent to the blower and can
thus interfere with each other. If a change is made to any calibration point during combustion
calibration, you must make a corresponding change to the same calibration point in O2 Trim.
If you fail to make the change in O
2
Trim, it may ignore the combustion calibration value and
adjust the O
2
to the O
2
Trim value instead.
NOTE:
For full instructions and menu options, see OMM-0161 Section 6.6.1.
