T-H2-DV/T-H2-OS Service Manual
Ver. 1.01
17
CONFIDENTIAL
9. Operational flow chart
The diagram below refers to both T-H2-DV and T-H2-OS.
FAV ; Flow Adjustment Valve
B V ; Bypass Valve
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
OuTH; Output thermistor
MiTH; Mixing thermistor
PCB ; Print Circuit board
(Computer board)
AFR ; Air Fuel Ratio rod
Power supply ON
Operation activated
FAV&BV open
Pre-check
NORMAL?
Faucet opens
Water Flow
Above 0.5GPM?
FM speed
(Below
1,000rpm?)
Fan moter start
operation
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?
FAV OPEN
Safety devices
sensed
abnormal condition
FAV CLOSE
SV1 SV3 OFF
False Dipswitch settings
InTH failure
PCB failure
MV circuit failure
031 blink
321 blink
701 blink
510 blink
611 blink
Fan motor stop
operation
721 blink
False flame
Igniter OFF
Reignition
Success?
OuTH OPEN
or SHORT
Fan motor
fault
MV OFF
SV2 OFF
GPV OFF
SV1 SV3 OFF
Fan motor
stop operation
Faucet closes
Flow sensor OFF
Remove cause
Operation stop
YES
NO
YES
NO
NO
YES
YES
NO
(20sec later)
YES
NO
NO
YES
YES
NO
YES
NO
(5sec later)
(3sec later)
YES
YES
NO
YES
NO
(20sec later)
YES
NO
NO
NO
YES
FM speed
(Above
1,000rpm?)
Below
Max flow rate
restriction?
111 blink
121 blink
611 blink
311 blink
OuTH failure
311 blink
MiTH failure
331 blink
Flame
blows out
OHCF melted
(above 430 F)
AFR rod failure
Abnormal
burning
121 blink
121 blink
991 blink
391 blink
BV modulates
Flow&temp
321 blink
InTH OPEN
or SHORT
331 blink
MiTH OPEN
or SHORT
SV circuit failure
551 blink
661 blink
Fault of Flow adjustment function
in Water control Valve
Fault of Bypass function in Water
control Valve
651 blink
PCB driving circuit failure
Hi-limit switch failure
OHCF Failure
711 blink
941 blink
Thermistor or HL SW for exhaust gas failure
Exhaust temp.
failure
941 blink
PCB driving
cirsuit failure
HiSW Failure
OHCF Failure
711 blink
NOTE:
The "941" and "621" error codes
are enabled in the T-H2-DV
FM for Exhaust
Failure
621 blink
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