Flow Sensor - A.O. Smith T-M50 ASME Service Manual

10-8. Flow sensor

Unit Part #
Function
Failure event
Effects on the water
heater if flow sensor
fails
Error codes when the
flow sensor fails
Diagnostic
Color/Number of wires
Red
White
Black
#421
Detects and measures water flow rate using a spinning impeller and magnetic
pick-up.
Unable to detect or measure any water flow rate.
Ignition sequence does not start (water heater will not initiate any operation)
441 (only within Easy-link and Multi-unit systems)
1. Visual inspection: connection / breakage of wires and/or debris on impeller.
2. Check voltages: proper range of values shown below.
Red - Black
White(+)-Black(GND)
7-7/7" (200mm)
7-1/8" (30mm)
T-M50 / T-M50 ASME Service manual
AOS Part # EKH33
4.0 to 5.5 VDC (Input)
1 to 4 VDC (pulse)
1,200 pulse / min (more than 20 Hz)
Water IN
22
CONFIDENTIAL
Checkpoint
Water OUT
Water IN
Ver. 1.05
H2