A.O. Smith Water Heater 520 Direct Vent Indoor Service Manual page 83

NOTE: The dark square is the direction
the dipswitch should be set to.
Figure.1 Left bank of dipswitch settings
For example;
Fan motor for combustion
Fan motor for exhaust
If the combustion fan motor speed is adjusted, the exhaust fan motor speed will also
change proportionally. See the table above.
520 Indoor / 520 Outdoor Service Manual
"MAX" button
"Increase" button
Figure.2 520 models Computer board
Variation for fan motor speed
-10.0 -5.0 -1.0
-6 -3 -0.6
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CONFIDENTIAL
Ver. 1.00
"MIN" button
"Decrease" button
(Unit: %)
0 1.0 5.0
0 0.6 3
10.0
6