A.O. Smith T-H2-DV User manual

T-H2-DV/T-H2-OS Service Manual
Ver. 1.01
1
CONFIDENTIAL
   
T-H2-DV/ T-H2-OS
On-Demand Water Heater
Service Manual
Flash Water Heater
Model T-H2-DV
Flash Water Heater
Model T-H2-OS
A.O. Smith Water Products Company
500 Tennessee Waltz Parkway
Ashland City, TN 37015
Toll Free: 1
-
877
-
737
-
284
0

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Table of Contents
1.
Specifications…………………………………………………..…………………………………………………..……
3
2.
Exterior view……………………...…….……………………………………………………………………………….
4
3.
Interior view…………………………….………………………………………………………………………………..
6
4.
List of main components in the interior view…….………………………………………………….……
8
5.
Schematic diagram…………………………………………………………………………………………………....
11
6.
Wiring diagram………………………………………………………………………………………………………….
12
7.
Wiring diagramcheckpoints for diagnosis………………………..………………….………………….…
13
8.
8.
(A) Resistance valuesof the temperature thermistors……..…………………………………………
(B) Resistance valuesof the temperature Exhaust thermistors…………………………………..
15
16
9.
Operationalflowchart…………………………………………………………………………………………….…
17
10.
Componentspecifications………………...…………………………………………………………………….…
18
11.
FaultAnalysis &Specifications…………………………………………………………………………………. 42
12.
Controls and settings……………………………………………………………………………………………….…
55
13.
Components diagrams………………………………………………………………..................................
90
14.
Parts list……………………………………………………………………………………………………………………..
93
15.
Revisions……………………………………………………...…………………………………………………………...
99

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CONFIDENTIAL
1. Specifications
Model T-H2-DV T-H2-OS
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 TM-RE30
PCB model T-H2
Indicators Red LEDon PCB duringoperation & 3-digit 7-SEG LED
Power supply
control Surge absorber & PowerON-OFF switch
Features
Freeze protection
Ceramicheatersand Auto-firing system
Self
-
combustion
improvement
Air-Fuel Ratio Detection System
Easy-Link system
Yes (Up to 4 units)
Multiple-system N/A
*The manifold pressure measurement is baseon conditions without front cover.

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2. Exterior view
Top view Bottom view
Sideview
Front view
T-H2-DV
GAS 4-5/8" (116.8mm)
120VAC 2-1/4" (58.2mm)
HOT 5-1/2" (142.2mm)
GAS 6" (153.6mm)
HOT 7-1/4" (182.1mm)
120VAC 8-1/2" (216.3mm) COLD 8-5/8" (220.6mm)
COLD 1-1/4" (29.2mm)
18-1/2" (470mm)
7-1/4" (183.8mm)
6-3/8" (161.5mm)
18-1/2" (470mm)
6-1/4" (161.5mm)
3-1/2" (90mm)
12-1/2" (320mm)
1/2" (12.5mm)
GAS 6" (153.6mm)
HOT 7-1/4" (182.1mm)
COLD 8-5/8" (220.6mm) HOT 5-5/8" (142.2mm)
120VAC 8-1/2" (216.3mm)
10-1/2" (266.8mm)
6-1/4" (159.1mm)
2-3/4" (69.1mm) INTAKE
2-3/4" (71.8mm)EXHAUST
12-1/2" (316mm)
25-1/2" (649mm)
120VAC 2-1/4" (58.2mm) 4-5/8" (116.8mm) GAS
Male 4" (100.8mm) 4" (102mm) Female
3/4" (18.8mm)
Condensate drain port
Condensate drain port
29-1/2" (751mm)
1-1/4" (29.2mm) COLD
6-5/8" (168.4mm)

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Side view Frontview
Bottom view
Top view
T-H2-OS
18-1/2" (470mm)
GAS 6" (153.6mm)
COLD 8-5/8" (220.6mm)
HOT 7-1/4" (182.1mm)
120VAC 8-1/2" (216.3mm)
COLD 1-1/4" (29.2mm)120VAC 2-1/4" (58.2mm)
GAS 4-5/8" (116.8mm)HOT 5-1/2" (142.2mm)
25-1/2" (649mm)
1/2" (12.5mm)
GAS 6" (153.6mm)
HOT 7-1/4" (182.1mm)
COLD 8-5/8" (220.6mm)
18-1/2" (470mm)
3-1/2" (90mm)
12-1/2" (320mm)
4-1/2" (115mm)
4-1/2" (115mm)
4-5/8" (116.8mm) GAS120VAC 2-1/4" (58.2mm)
HOT 5-5/8" (142.2mm)
12-1/2" (316mm)
120VAC 8-1/2" (216.3mm)
10-1/2" (266.8mm)
6-1/4" (159.1mm)
Condensate drain port
Condensate drain port
29-1/2" (751mm)
1-1/4" (29.2mm) COLD

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3. Interior view
T-H2-DV
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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T-H2-OS
1
3
4
56 27
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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4. List of main components in the interior view
No.
Description Item# in components
diagram
Takagi
Part # Common parts Forothermodels
1 Manifold assemblywith gas
valve assembly 118 EKH6T (LP model)
T-K4-IN/OS, T-D2-IN/OS
EKH6U (NA model)
2 Computerboard 701 EKH4E
3 Igniter 123 EKN74 T-K3, T-K3-Pro, T-K3-SP/OS, T-KJr2-IN/OS, T-K4-IN/OS,
T-D2-IN/OS, T-M50,T-M32
4 Transformer 702 EM296 T-M50
5 Waterinlet 411 EM404 T-M32
6 Water outlet 435 EKJ02 T-M32
7 Mixing thermistor 418 EX00H T-M32
8 Inletthermistor 422 EKK38 T-K3, T-K3-Pro, T-D2-IN/OS,
T-M50, T-M32
9 Output thermistor 433 EKK2T T-K3, T-K3-Pro,T-D2-IN/OS,
T-M50, T-M32
10
Overheatcut-off fuse 404 EX02A
11
Burner assembly (Burners) 101 EKH5W T-K4-IN/OS, T-D2-IN/OS
12
Hi-limit switch 432 EKN34 T-K3, T-K3-Pro, T-K3-SP/OS,
T-D2-IN/OS, T-M50,T-M32
13
Fan motor 114 EKK25 T-K3, T-K3-Pro,T-K3-SP, T-K4-IN, T-D2-IN, T-M50,
T-M32
14
Freeze protection
thermostat
704 EKH79 (T-H2-DV)
719 EKH7A (T-H2-OS)
15
Flow sensor 429 EKH33 T-M50, T-M32
16
Primary heat exchanger
assembly
401 EKH5P (T-H2-DV)
456 EKH63 (T-H2-OS)

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CONFIDENTIAL
No.
Description Item# in components
diagram
Takagi
Part # Common parts Forothermodels
17
Gas inlet 121 EKK1E T-K3, T-K3-Pro, T-K3-SP/OS, T-KJr2-IN/OS, T-K4-IN/OS,
T-D2-IN/OS
18
Pipe heater 426 EKJ47
19
Water control valve 423 EKH32 T-M50, T-M32
20
Secondary heat exchanger 446 EKH6X
21
Outlet drain plug 416 EK239 T-M32
22
AFR rod 106 EKK0E T-K3, T-K3-Pro, T-K3-SP/OS, T-K4-IN/OS, T-D2-IN/OS,
T-M50, T-M32
23
Flame rod 106 EKK0E T-K3, T-K3-Pro, T-K3-SP/OS, T-K4-IN/OS, T-D2-IN/OS,
T-M50, T-M32
24
Igniterrod 108 EKK0F T-K3, T-K3-Pro, T-K3-SP/OS, T-K4-IN/OS, T-D2-IN/OS,
T-M50, T-M32
25
Fuse box 715 EKH67
26
Heater 101 405 EX002 T-M50, T-M32
27
Outlet heater 415 EKK2P T-K3, T-K3-Pro, T-K3-SP/OS, T-KJr2-IN/OS, T-K4-IN/OS,
T-D2-IN/OS, T-M32
28
Over heatcutoff fuse for
combustion chamber 008 EM484 T-M32
29
Secondary heat exchanger
drain plug 458 EX13A
30
Fan motorfor exhaust 124 EKH5T
31
Hi-limit switch forexhaust 442 EKH6G

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CONFIDENTIAL
No.
Description Item# in components
diagram
Takagi
Part # Common parts Forothermodels
32
Exhaustthermistorassembly
706 EKH6E
33
Inlet drain plug (water filter)
409 EX006 T-M50, T-M32
34
Flat heater 453 EX13P
35
3 array heater 454 EX13R
36
Case assembly 001 EKH5B (T-H2-DV)
015 EKH5C (T-H2-OS)
37
Manifold port N/A N/A
38
Gas inlet port N/A N/A

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5. Schematic diagram
Thediagram below refers to both the T-H2-DV and T-H2-OS.
The T-H2-OS doesn’t have fan motor for exhaust, exhaust thermistor and hi-limit switch for
exhaust.
1. When a hot water tap is opened,cold water enters the T-H2-DV or T-H2-OS.
2. The water flowsensor detects this water flowand sends this information to computer.
3. The computer initiates fan motorand sends signal to igniterto createignition 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. Watercirculates through the heat exchangerand is heated up to theset temperature.
7. Using thermistors to measure temperatures, the computer modulates the gas and water valves to
ensureproper outputwatertemperatures.
8. When the tap is closed, the T- H2-DV or T- H2-OS shuts down.
*T-H2-DV controls fan motor for exhaust and detects the exhaust temperature by using exhaust
thermistorand hi-limitswitch for exhaustduring procedures of3 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
Fuse 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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6. Wiring diagram
The diagram below refers to both the T-H2-DV and T-H2-OS.
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
B2B1
C
C2 C1
D2
D1
E1
E3
E2
K1
F
G1
G2
H1
H2
I
J
K2
TM-RE30
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
1 2 34 5 6
OFF
78
1 2 34 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
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
Fan motor for
exhaust
Fan
motor
Heaters
Freeze protection
thermostat
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
T-H2-DV
Only
T-H2-DV
only
120
VAC
Remote
controller

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CONFIDENTIAL
7. Wiring diagram check points for diagnosis
The table below applies to both the T-H2-DV and the T-H2-OS.
Check-
point
Partand Description Color of wires Normal range
A, A1
100V Powersupply White – Black (A)
Brown – Brown (A1) 90 to110 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 - blue atCOM (SV2) 78 to 100 VDC (during
operation) /1.3 to 1.9 kΩ
Red - blue at COM (SV3) 78 to 100 VDC (during
operation) /0.9 to 1.7 kΩ
C1 Hi-limit switch Blue - Blue Less than 1 VDC and
less than 1.0 Ω
C2 Overheat cutoff fuse Blue - Blue Less than 1 VDC 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 Remotecontroller * 11 to25 VDC
G1 Fan motor Red – Blue
Yellow – Blue
Orange - Blue
110 to 160VDC
13 to 17 VDC
2 to 6.5 VDC
G2 Fan motor forexhaust
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
(1,200pulse / min)
I
Air-fuelratio flame 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 controlvalve
Blue – Brown
Orange – Brown
Red – Brown
13.0 to 16.0 VDC
ON:12.5 to 16.0VDC
OFF: 0 to1 VDC
1 VDC Less ( 0° position)
K1 Exhaust thermistor White - White See table on p. 15
K2 Hi-limit switch for exhaust White - White Less than 1 VDC and
less than 1.0 Ω

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CONFIDENTIAL
8. (A) Resistance values of the temperature thermistors
TheT-H2-DV and the T-H2-OS 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 T-H2-DV 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
Thediagram 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 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 T-H2-DV
FM for Exhaust
Failure
621 blink
*
*
*

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CONFIDENTIAL
10. Component specifications
10-1.
Burners……………………..………………………………….………………………………....……….
19
10-2.
Gas manifold………….………………………………………………..…………………………….....
20
10-3.
Fan motor……………………………………………………………………………………….……...…
21
10-4.
Fan motorforexhaust……………………………………………………………………………….
22
10-5.
Gas valve assembly………………..……………………….………………………………..……….
23
10-6.
Flame rod………………………………………………………….……………………………………….
24
10-7.
AFR rod……………………………………………………………………………………………….…….
25
10-8.
Heatexchanger………………………………………………………………………………..………..
26
10-9.
Secondary heatexchanger…………………………………………………………………………
27
10-10.
Flow sensor……………………………………..……………………………………………………..…
28
10-11.
Watercontrol valve………………………………………………….………………………………..
30
10-12.
Thermistors……….………………………..…………………………………………..……………..…
31
10-13.
Exhaust thermistor…………………………………………………………………………….……...
32
10-14.
Hi-limit switch…………………..………………………………………………….......................
33
10-15.
Hi-limit switch for exhaust………………………………………………………………………...
34
10-16.
Overheat cutoff fuse…..………………………………………………………….....................
35
10-17.
Freeze protection heaters…………….……………………………………………………………
36
10-18.
Computerboard……………….………………………………………………………………….……
37
10-19.
Transformer. ………...…………………………………………………………………………………..
38
10-20.
Igniter………………………………………………………………………………………………………..
39
10-21.
Freeze protection thermostat………………………………………………………….………..
40
10-22.
Fusebox…………………………………………………………………………………………………....
41

T-H2-DV/T-H2-OS Service Manual
Ver. 1.01
19
CONFIDENTIAL
10-1. Burners 
Unit Part ##101 Takagi Part #EKH5W Checkpoint N/A
Function
There are 2 types of burners in the water heater: the gas-rich burner
stabilizes the flames within the combustion chamberand the air-rich burner
produces more heat 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
7-1/2" (189.6mm)5-1/4" (132.3mm)
9" (229mm)
46V
"46V" mark
The burner forthe T-H2-DV and T-H2-OS has the“46V” mark as shown below.
Burner damper (#111 / EKH5G)
The burner damper is
not included in EKH5W.
7-7/8" (201mm)
1-3/4" (44mm)
46V
"46V" mark

T-H2-DV/T-H2-OS Service Manual
Ver. 1.01
20
CONFIDENTIAL
10-2. Gas manifold
Unit Part #Included
in #118 Takagi Part #EKH6T (LP model)
EKH6U (NA model)
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 deposit on the manifold.
2. Gas leakage froma 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)
EKH6T (for LP model) and
EKH6U (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.