Operational Flow Chart - A.O. Smith 710 ASME Service Manual

9. Operational flow chart

Power supply ON
FAV&BV open
Operation SW ON
Pre-check
NORMAL?
Faucet opens
Water Flow
Above 0.5GPM?
BV modulates
Flow&temp
FM speed
(Below
1,000rpm?)
Fan moter start
operation
FM speed
(Above
1,000rpm?)
Flame rod
detects Below
DC0.15 A?
Igniter ON
Hi-limit
Normal?
OHCF
Normal?
MV ON
SV2 ON
GPV ON
Flame rod
detects Above
DC1.0 A?
Burning lamp ON
Igniter OFF
Proportional control
BTU
change over
point?
SV1 SV3 ON
Below water
heat capability?
Below
Max flow rate
restriction?
FAV OPEN
Safety devices
sensed
abnormal condition
NO
False Dipswitch
YES
settings
InTH failure
OuTH failure
MiTH failure
PCB failure
MV circuit failure
NO
SV circuit failure
Fault of Bypass
function in Water
YES
control Valve
Fault of Flow
adjustment function
in Water control
Valve
NO
YES
Fan motor stop
operation
NO
(20sec later)
YES
NO
False flame
YES
NO
YES
YES
NO
Reignition
NO
Success?
YES
Igniter OFF
NO
(5sec later)
YES
(3sec later)
NO
SV1 SV3 OFF
YES
NO
FAV CLOSE
YES
NO
311 blink
YES
OuTH OPEN
or SHORT
YES
NO
Remove cause
Opeartion lamp OFF
Operation stop
031 blink
321 blink
311 blink
331 blink
701 blink
510 blink
551 blink
661 blink
651 blink
Flow sensor OFF
Faucet closes
611 blink
Fan motor
stop operation
FAV ; Flow Adjustment Valve
B V ; Bypass Valve
721 blink
F M ; Fan Motor
OHCF; Over Heat Cut-off Fuse
M V ; Main gas Valve
SV1 ; Solenoid Valve 1 (See the section 6)
SV2 ; Solenoid Valve 2 (See the section 6)
SV3 ; Solenoid Valve 3 (See the section 6)
GPV ; Gas Proportional Valve
InTH; Inlet thermistor
111 blink
OuTH; Output thermistor
MiTH; Mixing thermistor
PCB ; Print Circuit board
121 blink
AFR ; Air Fuel Ratio rod
MV OFF
SV2 OFF
GPV OFF
SV1 SV3 OFF
391 blink 991 blink
OHCF melted
Abnormal
AFR rod failure
burning
(above 430 F)
321 blink 331 blink
InTH OPEN MiTH OPEN
or SHORT or SHORT
(20sec later)
13
CONFIDENTIAL
710 / 710 ASME Service Manual
(Computer board)
121 blink 121 blink
Flame
blows out
611 blink
Fan motor
fault
Ver. 1.00