A.O. Smith T-H2-DV Service Manual page 50

Error Code
Fan motor fault
611
1 PCB and fan motor fault
V isual inspection of fan motor: connection/breakage of wires or dust
buildup (causing electrical shortage)
Normal: 110 to 160 VDC between red & blue (during operation)
Normal: 13 to 17 VDC between yellow & blue (during operation)
Normal: 2.0 to 6.5 VDC between orange & blue (during operation)
Verify fan motor speed of the water heater using the "diagnostics mode" of
the T-H2-DV/T-H2-OS computer board or the TM-RE30 temperature remote
controller.
See the "12-1. How to diagnose the water heater using the TM-RE30".
V isual inspection of PCB: connection/breakage of wires and/or burn marks
on the computer board.
Error Code
Exhaust fan motor fault (T-H2-DV only)
621
1 PCB and fan motor for exhaust fault
(Refer to section 10-4 & 10-18)
V isual inspection of fan motor: connection/breakage of wires or dust
buildup (causing electrical shortage)
Normal: 110 to 160 VDC between red & blue (during operation)
Normal: 13 to 17 VDC between yellow & blue (during operation)
Normal: 2.0 to 6.5 VDC between orange & blue (during operation)
Just before unit start operation, the signal to operate FM for exhaust is still
OFF. But at that time, if over 1000rpm of FM speed is detected for 20 sec,
621 error code will display.
If under 1000rpm of FM for exhaust speed is detected when the signal to
operate FM is ON, 621 error code will display.
If over 300 rpm of FM for exhasut gas speed difference between the target
speed signal and the actual speed signal from FM is detected, 621 error
code will display.
Malfunction description
(Refer to section 10-3 & 10-18)
Malfunction description
T-H2-DV/T-H2-OS Service Manual
Turn off the power or water supply
Diagnosis
Turn off the power or water supply
Diagnosis
50
CONFIDENTIAL
Ver. 1.01
Cancellation method
Checkpoint
Cancellation method
Checkpoint
G1
G2