A.O. Smith Water Heater 520 Direct Vent Indoor User manual

520 Indoor / 520 Outdoor Service Manual
Ver. 1.00
1
CONFIDENTIAL
   
520 Direct Vent Indoor
and Outdoor Models
On-Demand Water Heater
Service Manual
Water Heater
Model 520 Direct Vent Indoor
Water Heater
Model 520 Outdoor
A.O. Smith Water Products Company
500 Tennessee Waltz Parkway
Ashland City, TN 37015
Toll Free: 1
-
877
-
737
-
2840

520 Indoor / 520 Outdoor Service Manual
Ver. 1.00
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CONFIDENTIAL
Table of Contents
1.
Specifications………………………………………...…...………….……………………...…………………………
3
2.
Exteriorview……………………...…….……………………………………………………………………………….
4
3.
Interior view…………………………….………………………………………………………………………………..
6
4.
List of main components in the interior view…….………………………………………………….……
8
5.
Schematic diagram…………………………………………………………………………………………………....
10
6.
Wiring diagram………………………………………………………………………………………………………….
11
7.
Wiring diagram checkpoints for diagnosis………………………..………………….………………….…
12
8.
8.
(A) Resistance valuesof the temperature thermistors……..…………………………………………
(B) Resistance values of the temperature Exhaust thermistors…………………………………..
14
15
9.
Operationalflowchart…………………………………………………………………………………………….…
16
10.
Componentspecifications………………...…………………………………………………………………….…
17
11.
FaultAnalysis & Specifications…………………………………………………………………………………. 41
12.
Controls and settings……………………………………………………………………………………………….…
54
13.
Components diagrams………………………………………………………………..................................
89
14.
Parts list……………………………………………………………………………………………………………………..
92
15.
Revisions……………………………………………………...…………………………………………………………...
97

520 Indoor / 520 Outdoor Service Manual
Ver. 1.00
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CONFIDENTIAL
1. Specifications of the 520 Direct Vent Indoor* and Outdoor
Model 520 Direct Vent Indoor 520 Outdoor
Dimensions H25.6"×W18.5"×D12.4"
Weight 73 lbs. 71 lbs.
Combustion
INPUT
BTU/h Max 199,000
Min 13,000
Combustion System
Power vent
Installation Direct-vent Outdoor
Fan motor PWMturbo fan
Manifold
Pressure**
Max
LP 4.9” WC
Natural 3.6” WC LP 4.6” WC Natural 2.8” WC
Min
LP 1.0” WC
Natural 0.7” WC LP 0.9” WC Natural 0.6” WC
Water control
Flow rate 0.5 GPMto 9.0 GPM
Available set
temperatures 100°F to 185°F default:120°F
Temperatureon
the unitsettings 100°F, 105°F, 110°F, 115°F, 120°F, 125°F, 135°F,140°F, 145°F, 150°F, 155°F, 160°F, 165°F, 170°F, 175°F, 185°F
Bypass valve Yes
Thermistors 4 thermistors
(In, Out, Mixing, Exhaust) 3 thermistors (In, Out, Mixing)
Operation
Remote controller
model 9007603005
PCB model 520
Indicators Red LEDon PCB duringoperation &3-digit7-SEGLED
Power supply
control Surge absorber & Power ON-OFF switch
Features
Freezeprotection
Ceramic heaters and Auto-firing system
Self
-
combustion
improvement
Air-Fuel Ratio Detection System
Easy-Link system
Yes (Up to 4 units)
Multiple-system N/A
* The520 Direct Vent Indoor means the520 Indoor in the text.
**The manifold pressure measurement isbased on conditions without front cover.

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CONFIDENTIAL
2. Exterior view
Top view Bottom view
Side view
Front view
520 Indoor
18-1/2" (470mm)
6-1/4" (162mm)
3-1/2" (90mm)
12-1/2" (320mm)
1/2" (13mm)
GAS 6" (154mm)
HOT 7-1/4" (182mm)
COLD 8-5/8" (221mm) HOT 5-5/8" (142mm)
120VAC 8-1/2" (216mm)
10-1/2" (267mm)
6- 1/ 4" (159mm)
2-3/4" (69.1mm) INTAKE
2-3/4" (71.8mm)EXHAUST
12-1/2" (316mm)
25-1/2" (649mm)
120VAC 2-1/4" (58mm) 4-5/8" (117mm) GAS
Male 4" (101mm) 4" (102mm) Female
3/4" (19mm)
Condensate drain port
Condensate drain port
29-1/2" (751mm)
1-1/4" (29mm) COLD
6-5/8" (168mm)
18-1/2" (470mm)
7-1/4" (184mm)
6-3/8" (162mm)
GAS 4-5/8" (117mm)
120VAC 2-1/4" (58.2mm)
HOT 5-1/2" (142mm)
GAS 6" (154mm)
HOT 7-1/4" (182mm)
120VAC 8-1/2" (216mm)
COLD 8-5/8" (221mm)
COLD 1-1/4" (29.2mm)
10-1/2"(267mm)
6-1/4"(159mm)
Condensate drain port

520 Indoor / 520 Outdoor Service Manual
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CONFIDENTIAL
Side view Frontview
Bottom view
Top view
520 Outdoor
1/2" (12.5mm)
GAS 6" (154mm)
HOT 7-1/4" (182mm)
COLD 8-5/8" (221mm)
12-1/2" (316mm)
120VAC 8-1/2" (216mm)
10-1/2" (267mm)
Condensate drain port
18-1/2" (470mm)
3-1/2" (90mm)
12-1/2" (320mm)
4-1/2" (115mm)
4-1/2" (115mm)
4-5/8" (117mm) GAS120VAC 2-1/4" (58.2mm)
HOT 5-5/8" (142mm) 6-1/4" (159mm)
Condensate drain port
29-1/2" (751mm)
1-1/4" (29.2mm) COLD
25-1/2" (650mm)
1-5/5"(42.6mm)
8"(203mm)
1-5/8"(42mm)
18-1/2" (470mm)
GAS 4-5/8" (117mm)
120VAC 2-1/4" (58.2mm)
HOT 5-1/2" (142mm)
GAS 6" (154mm)
HOT 7-1/4" (182mm)
120VAC 8-1/2" (216mm)
COLD 8-5/8" (221mm)
COLD 1-1/4" (29.2mm)
10-1/2"(267mm)
6-1/4"(159mm)
Condensate drain port

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CONFIDENTIAL
3. Interior view
520 Indoor
20
32
16
10
18
24
11
15
3
19
37
38
17
33
58
27
6
7
21
23
30
31
9
1
13
25
2
22
4
12
14
28
29 26
26
35
35
34
36

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CONFIDENTIAL
520 Outdoor
1
3
4
5
627
7
8
9
2
11
13
15
16
17
19
20
21
22
23 24
25
29
28
10
12
33 37
38
26
18
35
34
35
26
14
36

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CONFIDENTIAL
4. List of main components in the interior view
No.
Description Item# in components
diagram AOS Part# Common parts
Forothermodels
1 Manifold assemblywith
gas valve assembly 118 319143-046 (LP model)
319143-047 (NA model)
2 Computerboard 701 319143-126
3 Igniter 123 319143-052 110, 310,510, 910, 710
4 Transformer 702 319143-127 910
5 Water inlet 411 319143-074 710
6 Water outlet 435 319143-098 710
7 Mixing thermistor 418 319143-081 710
8 Inlet thermistor 422 319143-085 510, 910, 710
9 Output thermistor 433 319143-096 510, 910, 710
10
Overheatcut-off fuse 404 319143-067
11
Burner assembly
(Burners) 101 319143-030
12
Hi-limit switch 432 319143-095 510, 910, 710
13
Fan motor 114 319143-043 310 Indoor, 510 Indoor,
910, 710
14
Freeze protection
thermostat
704
319143
-
129
(
520
Indoor
)
719
319143
-
144
(
520
Outdoor
)
15
Flow sensor 429 319143-092 910, 710
16
Primary heat exchanger
assembly
401
319143
-
064
(
510
Indoor
)
456
319143
-
118
(
510
Outdoor
)
17
Gas inlet 121 319143-050 110, 310, 510
18
Pipe heater 426 319143-089
19
Water control valve 423 319143-086 910, 710
20
Secondary heat
exchanger 446 319143-108

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CONFIDENTIAL
No.
Description Item# in components
diagram AOS Part# Common parts
Forothermodels
21
Outlet drain plug 416 319143-079 710
22
AFR rod 106 319143-035 310, 510, 910, 710
23
Flame rod 106 319143-035 310, 510, 910,710
24
Igniter rod 108 319143-037 310, 510, 910,710
25
Surge box 715 319143-140
26
Heater101 405 319143-068 910, 710
27
Outlet heater 415 319143-078 110,310, 510,710
28
Overheat cutoff fuse
for combustion chamber
008 319143-016 710
29
Secondary heat
exchanger
drain plug 458 319143-120
30
Fan motorfor exhaust 124 319143-053
31
Hi-limit switch for
exhaust 442 319143-104
32
Exhaust thermistor
assembly 706 319143-131
33
Inlet drain plug (water
filter) 409 319143-072 910, 710
34
Flat heater 453 319143-115
35
3 array heater 454 319143-116
36
Case assembly 001
319143
-
009
(
510
Indoor
)
015
319143
-
023
(
510
Outdoor
)
37
Manifold port N/A N/A
38
Gas inlet port N/A N/A

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CONFIDENTIAL
5. Schematic diagram
Thediagram below refersto both the 520 Indoor and 520 Outdoor.
The 520 Outdoor doesn’t have the fan motor for exhaust, exhaust thermistor and hi-limit switch
forexhaust.
1. When a hot water tap is opened,cold water enters the 520 Indoor or520 Outdoor.
2. The water flow sensor detects this waterflowand sends this information tocomputer.
3. The computer initiatesfan motorand sends signal to igniter to create ignition spark.
4. The main, proportional, and solenoid gas valves open to allow gas input.
5. The gas ignitesand flames appear inside the burner chamber.
6. Water circulates through the heatexchanger and isheated up to the set temperature.
7. Using thermistors to measure temperatures, the computer modulates the gas and water valves to
ensureproper output water temperatures.
8. When the tap is closed, the520 Indoor or 520 Outdoor shutsdown.
*520 Indoor controls the fan motor for exhaust and detects the exhaust temperature by using
the exhaust thermistor and hi-limit switch for exhaustduring procedures of #3 to #8.
COLD
HOT GAS
Condensate drain
Flow sensor
Output thermisotor
Inlet thermisotor
Bypasss vavle
Water control valve
Drain pan
Igniter rod
Air-fuel ratio rod
Hi-limit switch
Intake port Primary heat exchanger
Exhaust
AC120V
PCB
ON-OFF-switch
for power supply
Transformer
Surge box
Main gas vavle
Gas proprotional valve
Gas solenoid valve 1
Freeze protection thermostat
Gas solenoid valve 2
Heater
Fan motor
for combustion
Igniter
Gas solenoid valve 3
Flame rod
Mixing thermistor
Secondary heat exchanger
Fan motor
for exhaust
Hi-limit switch
for exhaust
Exhaust thermistor

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CONFIDENTIAL
6. Wiring diagram
The diagrambelow refers to both the520 Indoorand 520 Outdoor.
BK: BLACK R: RED W: WHITE
G: GREEN
BL: BLUE
O: ORANGE Y: YELLOW
P: PURPLE
BR:BROWN LB:LIGHT BLU
E
A
A1
A2
B2
B1
C
C2 C1
D2
D1
E1
E3
E2
K1
F
G1
G2
H1
H2
I
J
K2
Inlet
thermistor
Mixing
thermistor
Output
thermistor
BK
BK
BK
Air-fuel
ratio rod
Ground
Flame rod
MV
SV3
SV1
SV2
BK
BK
BK
O.H.C.F
BL
BL BL
BL
Y
G
O
BL
LB
OR
G
Parent
W
W
BK
BK BL
BL
R
R
Remote
controller
12 3 4 56
OFF
78
1 23 4 5 6
OFF
78
2
1
W
Y
O
R
Gas
Propor-
tional
Valve
W
R
W
R
BK
RW
Flow
Sensor
BK W
R
Hi-limit switch
for exhaust
Exhaust
thermistor
W
W
W
RYGW
BK
BR
ROYGW
BK
BL
Water
Control
valve
Igniter
rod
IG
P P
P
P
BK
BK
G
BK
W
Trans-
former
Ground
BR
BR
120
VAC
G
Ground
BK
W
W
BK
BL
BR
Surge
box
W
BK
BL
W
Y
O
R
BL
W
9
1 0
9
1 0
BL
BL
Hi-limit
switch
O.H.C.F
BL
BL
520 Direct Vent
Indoor Only
MAX button
MIN button
Increase button
Error call button
Decrease button
Alarm
port
Pump port
Burning lamp
7 Seg LED
Number display button
Left bank
of dipswitches
Right bank
of dipswitches
Fan motor for
exhaust
Fan
motor
Heaters
Freeze protection
thermostat
520 Direct Vent
Indoor Only
9007603005

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CONFIDENTIAL
7. Wiring diagram check points for diagnosis
The table below applies to both the 520 Indoor and 520 Outdoor.
Check-
point
Partand Description Color of wires Normal range
A, A1
100V Power supply White – Black (A)
Brown – Brown (A1) 90 to 110 VAC
A2 120V Power supply Black - White 108 to 132 VAC
B1 Heater Black - Black 90 to 110 VAC
B2 Igniter Purple - Purple 90 to 110 VAC
C Gas valves
Light blue -blueat COM (MV)
78 to 100 VDC (during
operation) /0.9 to 1.3 kΩ
Green - blue at COM (SV1) 78 to 100 VDC (during
operation) /1.3 to 1.9 kΩ
Orange - blueat COM (SV2) 78 to 100 VDC (during
operation) /1.3 to 1.9 kΩ
Red - blue atCOM (SV3) 78 to 100 VDC (during
operation) /0.9 to 1.7 kΩ
C1 Hi-limitswitch Blue - Blue Less than 1VDC and
less than 1.0 Ω
C2 Overheatcutoff fuse Blue - Blue Less than 1VDC and
less than 1.0 Ω
D1 Easy-linkconnectors Red – Red
Blue - Blue 15 VDC
(during Easy-link operation)
D2 White -White

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CONFIDENTIAL
Check-
point
Partand Description Color of wires Normal range
E1 Mixing thermistor Black - Black See table on p. 14E2 Output thermistor Black - Black
E3 Inlet thermistor Black - Black
F Remote controller * 11 to25 VDC
G1 Fan motor Red – Blue
Yellow – Blue
Orange - Blue
110 to 160 VDC
13 to17 VDC
2 to 6.5VDC
G2 Fan motor for exhaust
H1 Gas proportional valve White - red
1 to 15 VDC
(during operation)
and
20 to40 Ω
H2 Flow sensor Red - Black 4 to 5.5VDC
White(+) – Black(GND) 1 to 4 VDC
(1,200 pulse /min)
I
Air-fuel ratio rod Yellow - AFR rod (Between AFR rod and
the computer board)
More than 1 μA
(during operation)
Flame rod Orange - Flame rod (Between flame rod and
the computer board)
More than 1 μA
(during operation)
J Water control valve
Blue – Brown
Orange – Brown
Red – Brown
13.0 to16.0 VDC
ON:12.5 to 16.0VDC
OFF:0 to 1 VDC
1 VDC Less ( 0° position)
K1 Exhaustthermistor White -White See table on p. 15
K2 Hi-limit switch for exhaust White -White Less than 1VDC and
less than 1.0 Ω

520 Indoor / 520 Outdoor Service Manual
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CONFIDENTIAL
8. (A) Resistance values of the temperature thermistors
The 520 Indoor and 520 Outdoor use the same thermistors.
Resistance values at different temperatures
ºF 32 41 50 59 68 77 86 95 104 113
ºC 0 5 10 15 20 25 30 35 40 45
Resistance kΩ23.76 19.08 15.43 12.56 10.28 8.47 7.02 5.85 4.90 4.12
Temperature ºF 122 131 140 149 158 167 176 185 194 203 212
ºC 50 55 60 65 70 75 80 85 90 95 100
Resistance kΩ3.49 2.96 2.53 2.16 1.86 1.60 1.39 1.21 1.05 0.92 0.81
Temperature / ºF vs Resistance / kΩ
Temperature / ℃vs Resistance / kΩ
Temperature
0.00
5.00
10.00
15.00
20.00
25.00
20 40 60 80 100 120 140 160 180 200 220
Temperature / ºF
Resisitance / kΩ
0.00
5.00
10.00
15.00
20.00
25.00
0 10 20 30 40 50 60 70 80 90 100
Temperature / ºC
Resisitance / kΩ

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CONFIDENTIAL
8. (B) Resistance values of the temperature Exhaust thermistor
Only the 520 Indoor is equipped with the exhaust thermistor.
Resistance values at different temperatures
ºF 32 41 50 59 68 77 86 95 104 113
ºC 0 5 10 15 20 25 30 35 40 45
Resistance kΩ30.04 24.12 19.50 15.87 13.00 10.71 8.87 7.39 6.19 5.21
Temperature ºF 122 131 140 149 158 167 176 185 194 203 212
ºC 50 55 60 65 70 75 80 85 90 95 100
Resistance kΩ4.41 3.74 3.19 2.73 2.35 2.03 1.76 1.53 1.33 1.16 1.02
Temperature
Temperature(°F) vs. Resistance(kΩ)
Temperature(°Ｃ) vs. Resistance(kΩ)
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
20 40 60 80 100 120 140 160 180 200 220
Temperature / ºF
Resisitance / kΩ
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
0 10 20 30 40 50 60 70 80 90 100
Temperature / ºC
Resisitance / kΩ

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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
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 blinkFalse 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 blink311 blink
OuTH failure 311 blink
MiTH failure 331 blink
Flame
blows out
OHCF melted
(above 430 F)
AFR rod failure
Abnormal
burning
121 blink121 blink991 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 520 Indoor
FM for Exhaust
Failure
621 blink
*
*
*

520 Indoor / 520 Outdoor Service Manual
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CONFIDENTIAL
10. Component specifications
10-1.
Burners……………………..………………………………….………………………………....……….
18
10-2.
Gas manifold………….………………………………………………..…………………………….....
19
10-3.
Fan motor……………………………………………………………………………………….……...…
20
10-4.
Fan motorforexhaust……………………………………………………………………………….
21
10-5.
Gas valve assembly………………..……………………….………………………………..……….
22
10-6.
Flame rod………………………………………………………….……………………………………….
23
10-7.
AFR rod……………………………………………………………………………………………….…….
24
10-8.
Heatexchanger………………………………………………………………………………..………..
25
10-9.
Secondary heatexchanger…………………………………………………………………………
26
10-10.
Flow sensor……………………………………..……………………………………………………..…
27
10-11.
Water controlvalve………………………………………………….………………………………..
28
10-12.
Thermistors……….………………………..…………………………………………..……………..…
30
10-13.
Exhaustthermistor…………………………………………………………………………….……...
31
10-14.
Hi-limit switch…………………..………………………………………………….......................
32
10-15.
Hi-limit switch forexhaust………………………………………………………………………...
33
10-16.
Overheat cutoff fuse…..………………………………………………………….....................
34
10-17.
Freeze protection heaters…………….……………………………………………………………
35
10-18.
Computerboard……………….………………………………………………………………….……
36
10-19.
Transformer. ………...…………………………………………………………………………………..
37
10-20.
Igniter………………………………………………………………………………………………………..
38
10-21.
Freeze protection thermostat………………………………………………………….………..
39
10-22.
Surge box……………………………………………………………………………………………….... 40

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CONFIDENTIAL
10-1. Burners 
Unit Part ##101 AOS Part #319143-030
Checkpoint N/A
Function
There are 2 types of burners in the water heater: the gas-rich burner
stabilizes the flames within the combustion chamber and the air-rich burner
produces moreheat in the combustion chamber. The burners facilitate the
air/gas mixture necessary to produce the proper heat during the
combustion reaction.
Failure events
1. Unable to initialize/sustain combustion
2. Dust or soot deposit on theburner surface.
3. Cracks on the burners.
4. Gas leakage from the burners
Effects on the water
heater if burners fails
1. Unexpected combustion.
2. Unstable flame conditions and/or flame loss.
3. Ignition failure.
4. Back-firing.
Error codes when the
burners fails
101 111 121 991
Diagnostic Visual inspection: excessive dust deposit on the burner surface and/or
unstable flame conditions during operation.
Color/Numberof wires N/A
Theburner forthe 520 Indoor and 520 Outdoor has the “46V” mark as shown below.
The burner damper is not
included in 319143-030.
7-1/2" (189.6mm)5-1/4" (132.3mm)
9" (229mm)
46V
"46V" mark
Burner damper (#111 /319143-040)
7-7/8" (201mm)
1-3/4" (44mm)
46V
"46V" mark

520 Indoor / 520 Outdoor Service Manual
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CONFIDENTIAL
10-2. Gas manifold
Unit Part #Included
in #118 AOS Part #319143-046 (LP)
319143-047 (NG)
Checkpoint N/A
Function
1. The manifold distributes gas from the gas valves to the burners. The
manifold has two types of the nozzles: one type for gas-rich burners (16
nozzles) and the other for air-rich burners (15 nozzles)
2. There are 3 zones within the manifold, to ensure efficient combustion
operation.
Failure events
1. Dust depositon the manifold.
2. Gas leakage from a failed manifold.
3. Ignition failure.
4. Imperfect combustion.
Effects on the water
heater if the manifold
fails
1. The burners cannot receive proper gas flow from the manifold, which can
cause poor combustion in the combustion chamber. In this case, the AFR
rod will detect an improper flame condition and computer will take safety
measures.
2. Gas leakage from the manifold.
Error codes when the
manifold fails 101 111 121 991
Diagnostic 1. Visual inspection: Excessive dust deposit around the nozzles or cracks on
the manifold.
2. Check voltagesand resistance: proper range of values shown below.
Color/Numberof wires Blue-Red 78 to 100 VDC /0.9 to 1.7 kΩ
Nozzles for gas-rich burners
Nozzles for air-rich burners
9-1/8" (232mm)
6-7/8" (175mm)
46V
59J
"46V" mark (LP)
"59J" mark (NA)
319143-046 (for LP model)
and 319143-047 (for NA
model) is an assembly of the
gas manifold with the gas
valve assembly. For safety
reasons, these assemblies
should be installed in the
unit as a whole set.
The gas manifold for the LP
has the “46V” mark, and the
gas manifold for the NA has
the “59J” mark on the
manifold plate.

520 Indoor / 520 Outdoor Service Manual
Ver. 1.00
20
CONFIDENTIAL
10-3. Fan motor
Unit Part ##114 AOS Part #319143-043
Checkpoint G1
Function To provide combustion air into the combustion chamber and to exhaust flue
gas.
Failure events
1. Fan speed failure, causing abnormal sounds with or without combustion
during operation.
2. Unexpected activation caused by the connectors of the fan motor getting
wet.
3. Disconnects from the bottom of the combustion chamber
Effects on the water
heater if fan motor fails
1. The water heater does not function properly
2. Failure to ignite or abnormalignition
3. Unstable combustion conditions
Error codes when the fan
motor fails 101 111 121 611 991
Diagnostic 1. Visual inspection: connection/breakage of wires or dust (causing electrical
shortage)
2. Voltage check: proper range of voltages shown below.
Color/Numberof wires
Red-Blue 110 to 160 VDC (Input)
Yellow-Blue 13 to 17 VDC (Input)
Orange-Blue 2.0 to 6.5 VDC (Input)
White-Blue Verify the fan motor speed using the Diagnostics Mode of
the 520 models computer board or the 9007603005
temperature remotecontroller. See Section 12-1 fordetails.
6-1/2" (165.5mm)
3-3/4"(95.15mm)
Opening 2-1/8"( 54mm)
PWN turbo fan motor