520 Indoor / 520 Outdoor Service Manual
Ver. 1.00
27
CONFIDENTIAL
10-10. Flow sensor
Unit Part #
#429
AOS Part #
319143-092
Checkpoint
H2
Function
Detects and measures water flow rate using a spinning impeller and magnetic
pick-up.
Failure event
Unable to detect or measure any water flow rate.
Effects on the water
heater if flow sensor
fails
Ignition sequence does not start
(520 Indoor / 520 Outdoor will not initiate any operation)
Error codes when the
flow sensor fails
441 (Within Easy-link systems only)
Diagnostic
1. Visual inspection: connection/breakage of wires and/or debris on impeller.
2. Check voltages: proper range of values shown below.
Color/Number of wires
Red - Black
4.0 to 5.5 VDC (Input)
White (+)-Black (GND)
1 to 4 VDC (pulse)
1,200 pulse / min (more than 20 Hz)
Water IN
Water OUT
7-7/7” (200mm)
7-1/8” (30mm)
2
”
(5
0
m
m
)
Water
IN
Red
White
Black