A.O. Smith 710 ASME User manual

710 / 710 ASME Service manual
Ver. 1.00
1
CONFIDENTIAL
710 / 710 ASME
On-demand Water Heater
Service manual
A.O. Smith Water Products Company
500 Tennessee Waltz Parkway
Ashland City, TN 37015
Toll Free: 1
-
877
-
737
-
2840
710 models

710 / 710 ASME Service manual
Ver. 1.00
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CONFIDENTIAL
Table of Contents
1.
Specifications………………………………………...…...………….……………………...…………………………
3
2.
Exterior view…………………………………………………………………………………………………………….. 4
3.
Interior view….………………………………………………………………………………………………………….. 5
4.
List of main components in the interior view………………………………….………………………….
6
5.
Schematic diagram…………………………………………………………………………………………..……….. 8
6.
Wiring diagram…………………….………………………………………………………………………..…………. 9
7.
Wiring diagram checkpoints for diagnosis……………………………………………………………….…
10
8.
Resistance values of the temperature thermistors……………..………………………………………
12
9.
Operational flow chart..……………………………………………………………………………………………..
13
10.
Component specifications…………………………………………………………………………………………. 14
11.
Fault Analysis & Specifications……………………………………………………………........................ 35
12.
Controls and settings………………………………………………………………………………………………….
46
13.
Components diagrams……………………………………………………………….................................. 75
14.
Parts list……………………………………………………………………………………………………………………..
78
15.
Revisions…...................................…………………………...………………………………..…………………
82

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CONFIDENTIAL
1. Specifications
Unit Model 710 / 710 ASME
Unit dimensions H 23.6"×W 18.5"×D 8.9"
Weight 59 lbs.
Max 240,000
INPUT
BTU/h
Min 24,000
Combustion System
Power vent
Installation Indoor, Outdoor, Direct vent
Fan motor PWM Turbo fan
Max LP 3.4”WC
Natural 2.3”W.C
Combustion
Manifold
Pressure*
Min LP 0.7 WC
Natural 0.5”WC
Flow rate 0.5 to 9.0 GPM
Available set temp.
100°F to 185°F
default set 120 °F
Temperature
dipswitch setting
100°F, 115°F, 120°F, 135°F, 145°F, 155°F, 165°F, 185°F
Bypass valve Yes
Water control
Thermistors 3 thermistors (In, Out, Mixing)
Available remote
controller Part # 9007603005
PCB Model T-M32 (Part #319143-279)
Indicators Red LED on PCB during operation & 7-seg LED
Operation
Power supply
control GFI & Surge absorber
Freeze protection
Ceramic heaters and Auto- FM system
Self-combustion
improvement Air Fuel Ratio detection system
Easy-link system
Yes
Future
Multi-unit system
Yes
*The manifold pressure measurement is base on conditions without front cover.

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CONFIDENTIAL
4" ( 1 01mm)
7" (17 9mm)
15-3 /4" (399mm)
18-1 /2" (470mm)
23-5 /8" (600mm)
24-5 /8"(626 mm)
4-1/2" (11 4mm)
1-1/ 8" (27.8mm )
COLD 3- 1/8" (80 .8mm )
HOT 4-5/8 " (1 18.3mm)
GAS 6-1/4" (159mm)
8-7/ 8" (226mm)
120 VAC 5-1/2 "( 142mm )
5-1/ 2"(142mm)
5-3/ 4"(147mm)
COLD 1-5/ 8"(40.9mm)120 VAC 1 -5/8" (42mm)
GAS 5-7/8"(1 47.9mm)HOT 5-7/8"(149mm )
GAS 6-1/4"(159mm )
CO LD 3-1 /8"(80.8mm )
HOT 4-5/8 "(11 8.3mm)
120 VAC 5 -1/2 "(1 41.6mm)
2. Exterior view
Side view Front view
Top view Bottom view

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CONFIDENTIAL
3. Interior view
16
20
1
3
4
5
678
9
10
11
12
13
14
15
17
18
19
21
2
22
23
24 25
26
27
28
29

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CONFIDENTIAL
4. List of main components in the interior view
No. Description
Items# in
components
diagram
AOS
Part #
Common parts
For other models
1 Case assembly 001 319143-287
2 Manifold assembly with gas
valve assembly 120 319143-305 (LP model)
319143-306 (NA model)
3 Computer board 701 319143-279
4 Igniter 125 319143-052 520, 110, 310, 510,
910
5 Transformer 702 319143-309
6 Water inlet 411 319143-074 520
7 Water outlet 435 319143-098
8 Mixing thermistor 418 319143-081 520
9 Inlet thermistor 422 319143-085 520, 510, 910
10 Output thermistor 433 319143-096 520, 510, 910
11 Overheat cut-off fuse 403 319143-286
12 Burner assembly (Burners) 101 319143-299
13 Hi-limit switch 432 319143-095 520, 510, 910
14 Fan motor 115 319143-043 520, 310, 510, 910
15 Freeze protection thermostat
117 319143-185 110, 310, 510
16 Flow sensor 429 319143-092 520, 910
210 319143-302
(Regular model)
17 Heat exchanger
211 319143-314
(ASME model)
18 Gas inlet 123 319143-307
19 Heater 410 319143-068 520, 910
20 Water control valve 423 319143-086 520, 910
21 GFI 712 319143-227 910

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CONFIDENTIAL
No. Description
Items# in
components
diagram
AOS
Part #
Common parts
For other models
22 Outlet drain plug 416 319143-079 520
23 Air-fuel ratio rod (AFR rod) 106 319143-035 520, 310, 510, 910
24 Flame rod 106 319143-035 520, 310, 510, 910
25 Igniter rod 108 319143-037 520, 310, 510, 910
26 Surge box 715 319143-284 910
27 Inlet drain plug (water filter) 408 319143-072 520, 910
28 Manifold port N/A N/A
29 Gas inlet port N/A N/A

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CONFIDENTIAL
5. Schematic diagram
1. When a hot water tap is opened, cold water enters the 710.
2. The water flow sensor detects this water flow and sends this information to computer.
3. The computer initiates fan motor and sends signal to igniter to create ignition spark.
4. The main, proportional, and solenoid gas valves open to allow gas input.
5. The gas ignites and flames appear inside the burner chamber.
6. Water circulates through the heat exchanger and is heated up to the set temperature.
7. Using thermistors to measure temperatures, the computer modulates the gas and water valves to
ensure proper output water temperatures.
8. When the tap is closed, the 710 shuts down.
Output Thermistor
Gas proportional valve
Gas solenoid valve 2
Gas solenoid valve 1
Gas solenoid valve 3
Water control
valve
Mixing Thermistor
Igniter rod
Heat
Exchanger
Gas
Hi-limit switch
Flow sensor
Exhaust
O.H.C.F
Main gas valve
Burner
Igniter
Fan motor
Hot water
Cold water
Inlet
Thermistor
Air-fuel ratio rod
Flame rod
Surge box
PCB GFI
AC120V
Transformer
120 VAC

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6. Wiring diagram
W: WHITE R: RED
BK: BLACK
P: PURPLE
LB:LIGHT BLUE
BL: BLUE
G: GREEN
Y: YELLOW
O: ORANGE
BR:BROWN
GY:GRAY
J
H1
H2
E1
E3
E2
C1
C2
G
B
F
D1
D2
I
A2
A
A1
C
L
C
C
C
K
A3
9007603005
Inlet
thermistor
Output
thermistor
Mixing
thermistor
BK
BK
BK
H i-
li mit
sw itch
Air-fuel
ratio rod
Ground
Flame rod
MV
SV3
SV1
SV2
FM
Igniter rod
IG
RYGW
BK
BR
ROYGW
BK
BL
Water
Control
valve
O.H.C.F
BL
BL B L
BL
Y
G
O
R
BL
YOW
P P
P
P
Gas
Propor-
tional
Valve
Flow
Sensor
W
R
BKW
R
WR
BK
RW
BL
BL
BL
LB
G
O
R
Paren
t
W
W
BK
BK BL
BL
R
R
Remote
controller
W
BK
Heater
Thermostat
Heater
BK
BK
G
W
BK
Trans-
former
Ground
BR
BR
120 VAC
G
Ground
BK
WW
BK
BR
BR
Surge
box
WBK
Heater
1 2 3 4 5 6
OFF
7 8
GFI
12 3 4 5 6
OFF
7 8
BK
W
Pump
Heater
2
1
GY
GY
P
P
O
O
3
4
7 Seg LED
Left bank of
dipswitches
Right bank of
dipswitches
MAX button
MIN button
Increase button
Decrease button
Error call bu tton
Burning lamp
Number display button

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CONFIDENTIAL
7. Wiring diagram check points for diagnosis
Check-
point
Parts and Description
Color of wires Normal Range
A, A1
100 V Power supply White –Black (A)
Brown –Brown (A1) 90 to 110 VAC
A2,A3
120 V Power supply Black - White 108 to 132 VAC
B Igniter Purple –Purple 90 to 110 VAC
Light blue - blue at COM (MV)
78 to 100 VDC (during operation)
/ 0.9 to 1.3kΩ
Green - blue at COM (SV1) 78 to 100 VDC (during operation)
/ 1.3 to 1.9kΩ
Orange - blue at COM (SV2) 78 to 100 VDC (during operation)
/ 1.3 to 1.9kΩ
C Gas valves
Red - blue at COM (SV3) 78 to 100 VDC (during operation)
/ 0.9 to 1.7kΩ
C1 Hi-Limit switch Blue - Blue Less than 1 VDC and less than 1 Ω
C2 Overheat cutoff fuse Blue - Blue Less than 1 VDC and less than 1 Ω
White - White 15 VDC
D1 Easy-link connectors Red –Red
Blue –Blue
15 VDC
(during Easy-link operation)
D2 Multi-unit link
connectors
Purple- Purple
Orange -Orange
15 VDC
(during Multi-unit operation)
E1 Mixing thermistor Black - Black
E2 Output thermistor Black - Black
E3 Inlet thermistor Black - Black
See table on p.12
F Remote controller Black - White 11 to 25 VDC
Red - Blue 110 to 160 VDC
Yellow - Blue 13 to 17 VDC
G Fan motor
Orange - Blue 2 to 6.5 VDC
H1 Gas proportional valve
White - red
1 to 15 VDC (during operation)
and
20 to 40 Ω