520 Indoor / 520 Outdoor Service Manual
Ver. 1.00
16
CONFIDENTIAL
9. Operational flow chart
The diagram below refers to both the 520 Indoor and 520 Outdoor.
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
P ower sup ply ON
Operation activated
FAV&BV open
Pre-c hec k
NO RMAL?
Faucet o pen s
Wat er Flow
A bove 0.5 GPM ?
FM speed
(Below
1,000rp m?)
Fan mo ter star t
ope ration
Flame ro d
detect s B elow
DC0. 15 A?
Igni ter ON
Hi-li mit
Norma l?
OHCF
Normal ?
MV ON
SV2 ON
GPV ON
Fl ame rod
detects Abo ve
DC1.0
A?
B urn ing lamp ON
Ignit er OFF
P roportio nal control
BTU
cha nge over
p oint?
SV1 SV 3 ON
B elo w water
hea t c apabilit y?
FA V OPEN
S afety devic es
sensed
a bnormal con dition
F AV CLOSE
SV1 SV3 OFF
Fal se Dipsw itc h settin gs
InTH fa ilure
PCB fai lure
M V c ircuit f ail ure
031 blink
321 blink
701 blink
510 blink
611 blink
F an motor st op
operatio n
721 blink
F als e flame
Igni te r OFF
Reigniti on
Success ?
OuTH OPEN
or SHORT
Fan motor
fault
MV OF F
SV2 OFF
GPV OFF
S V1 SV3 OFF
Fan m oto r
stop ope ration
F auc et close s
Flow sensor OFF
R emo ve cause
Op eration sto p
YES
NO
YES
NO
N O
YES
YES
N O
(2 0sec later)
YES
NO
NO
YES
YES
NO
YES
NO
(5sec la ter )
(3sec l ater)
YES
YES
NO
YES
NO
(2 0se c later)
YES
NO
NO
NO
YE S
FM speed
(Above
1,000rp m?)
Below
Ma x flow rate
r estriction?
111 blink
121 blink
611 blink
311 blink
OuTH fa ilure
311 blink
MiTH fa ilure
331 blink
Fl ame
bl ows out
OHCF melte d
(above 430
F)
AFR rod failure
Abnormal
burning
121 blink
121 blink
991 blink
391 blink
BV modulate s
Flow&tem p
321 blink
InTH OPEN
or SHORT
331 blink
MiTH OPEN
or SHORT
SV c irc uit fail ure
551 blink
661 blink
Fault of Flow adjustment function
in Water control Valve
Fault of Bypass function in Water
control Valve
651 bl ink
PCB dri ving cir cui t failur e
Hi-l imi t switch fa ilure
OHCF Fa ilure
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 520 Indoor
FM for Exhaust
Failure
621 blink
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