A.O. Smith T-D2-OS User manual

T-D2-IN/T-D2-OS Service Manual
Ver. 1.00
1
CONFIDENTIAL
   
T-D2-IN / T-D2-OS
On-Demand Water Heater
Service Manual
T-D2-IN
A.O. Smith Water Products Company
500 Tennessee Waltz Parkway
Ashland City, TN 37015
Toll Free: 1
-
877
-
737
-
2840
T-D2-OS

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CONFIDENTIAL
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…………………………………………………………………………………………………….
10
6.
Wiring diagram………………………………………………………………………………………………………….
11
7.
Wiring diagram checkpoints for diagnosis………………………..………………….………………….…
12
8.
Resistance values of the temperature thermistors…………..…………………………………………
14
9.
Operational flow chart…………………………………………………………………………………………….…
15
10.
Component specifications………………...…………………………………………………………………….…
16
11.
FaultAnalysis &Specifications…………………………………………………………………………………..
36
12.
Controls and settings……………………………………………………………………………………………….…
46
13.
Components diagrams………………………………………………………………..................................
70
14.
Parts list……………………………………………………………………………………………………………………..
73
15.
Revisions……………………………………………………...………………………………………………………......
78

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CONFIDENTIAL
1. Specifications
Model T-D2-IN T-D2-OS
Dimensions H20.5"×W13.8"×D8.5"
Weight 39 lbs.
Combustion
INPUT
BTU/h Max 199,000
Min 11,000
Combustion System
Power vent
Installation Indoor & Direct-vent Outdoor
Fan motor PWMturbo fan PWN multi blade fan motor
Manifold
Pressure*
Max LP 3.5” WC
Natural 2.0” WC LP 4.4” WC Natural 2.8” WC
Min LP 0.7” WC
Natural 0.4” WC LP 0.9” WC Natural 0.5” WC
Water control
Flow rate 0.75 to 10.0 GPM
Available set
temperatures 99 to 185°F default: 122°F
Temperature
dipswitch settings
104°F, 113°F, 122°F, 131°F, 140°F, 158°F, 176°F,185°F
Bypass valve Yes
Thermistors 3 thermistors (In, Out, Mixing)
Operation
Remote controller
model TM-RE30
PCB model T-D2
Indicators Red LED on PCB during operation & 7-SEG LED
Power supply
control Surge absorber & Power ON-OFF switch
Features
Freezeprotection
Ceramic heaters and Auto-firing system
Self-combustion
improvement Air-FuelRatio Detection System
Easy-Link system
Yes (Up to 4 units)
Multiple-system
N/A
*The manifold pressuremeasurement is based on conditions without front cover.

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CONFIDENTIAL
2. Exterior view
Top view Bottom view
Side view Front view
COLD 2-7/8" (71mm)
HOT 6-1/2" (164mm)
HOT 5-1/4" (133mm) GAS 4-7/8" (124mm)
GAS 5-1/4" (135mm)
120VAC 3-7/8" (99mm)
120VAC 1-3/8" (36mm)COLD 3-1/4" (84mm)
13-1/8" (334mm)
4-3/8" (113mm)
5-1/8" (130mm)
T-D2-IN
13-3/4" (350mm)
10" (254mm)
1-3/4" (45mm) 1-3/4" (45mm)
1-3/8" (36mm)
3-9/8 ( 101mm)
21-3/8" (544mm) 20-1/4" (520mm)
1-7/8" (47mm)
HOT 5-1/4" (133mm)
120V 1-3/8" (36mm)
GAS 4-7/8" (124mm)
COLD 3-1/4" (84mm)
4-3/8" (113mm)
19-3/8" (493mm)
COLD 2-7/8" (71mm)
1" (26mm)
HOT 6-1/2" (164mm)
9-1/2" (241mm)
120VAC 3-7/8" (99mm)
GAS 5-1/4" (135mm)
2-1/4" (58mm)

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CONFIDENTIAL
Sideview Frontview
Bottom view
Top view
T-D2-OS
13-3/4" (350mm)
10" (254mm)
1-3/4" (45mm) 1-3/4" (45mm)
21-3/8" (544mm) 20-1/4" (520mm)
1-7/8" (47mm)
HOT 5-1/4" (133mm)
120V 1-3/8" (36mm)
GAS 4-7/8" (124mm)
COLD 3-1/4" (84mm)
4-3/8" (113mm)
19-3/8" (493mm)
COLD 2-7/8" (71mm)
1" (26mm)
HOT 6-1/2" (164mm)
9-1/2" (241mm)
120VAC 3-7/8" (99mm)
GAS 5-1/4" (135mm)
1-5/8" (43mm)
5" (128mm)
7-7/8" (203mm)
13-1/8" (334mm)
COLD 2-7/8" (71mm)
HOT 6-1/2" (164mm)
HOT 5-1/4" (133mm) GAS 4-7/8" (124mm)
GAS 5-1/4" (135mm)
120VAC 3-7/8" (99mm)
120VAC 1-3/8" (36mm)COLD 3-1/4" (84mm)

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CONFIDENTIAL
3. Interior view
T-D2-IN
1
3
4
5
67
9
8
31
10
11
13
14
15
16
17
18
18
19
2
21
12
23
24
32
25
22
28
29
27
30
20
26

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T
-
D2
-
OS
1
3
4
5
67
9
8
31
10
11
13
14
15
16
17
18
18
19
2
21
12
23
24
32
25
22
28
29
27
30
20
26

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4. List of main components in the interior view
No.
Description Items# in components
diagram
Takagi
Part# Common parts forothermodels
1 Case assembly 001 EK402 (T-D2-IN)
EKK41 (T-D2-OS) T-K3OS
2 Manifold assembly with
gas valve assembly 102 EKH6T (LP model)
T-H2-DV/OS
EKK5K (NA model)
3 Computerboard 701 EK439
4 Igniter 711 EKN74 T-K3, T-K3-Pro, T-K3-SP/OS, T-H2-DV/OS , T-KJr2-IN/OS,
T-K4-IN/OS, T-M50, T-M32
5 Transformer 702 EKH09 T-K3, T-K3-Pro, T-K3-SP/OS,
6 Waterinlet 404 EKK1U T-K3,T-K3-Pro, T-K3-SP/OS,
T-KJr2-IN/OS, T-K4-IN/OS
7 Water outlet 409 EKK1V T-K3, T-K3-Pro, T-K3-SP/OS,
T-KJr2-IN/OS, T-K4-IN/OS
8 Inletthermistor 407 EKK38 T-K3, T-K3-Pro, T-H2-DV/OS ,
T-M50, T-M32
9 Mixing thermistor 408 EKK1A T-K3, Pro, T-M50
10
Overheatcut-off fuse 413 EK333 T-K3, T-K3-Pro, T-K3-SP/OS, T-KJr2-IN/OS, T-K4-IN/OS,
T-M50
11
Burnerassembly
(Burners)
101 EKH5W T-H2-DV/OS
12
Hi-limit switch 412 EKN34 T-K3,T-K3-Pro, T-K3-SP/OS,
T-H2-DV/OS , T-M50, T-M32
13
Fan motor 103 EKK25 (T-D2-IN) T-K3, T-K3-Pro, T-K3-SP,
T-H2-DV/OS , T-M50, T-M32
EKK54 (T-D2-OS) T-K3-OS, T-K4-OS
14
Freeze protection
thermostat 713 EKJ59 (T-D2-IN) T-K3, T-K3-Pro, T-K3-SP,
T-M32
710 EKK40 (T-D2-OS) T-K3-OS, T-KJr2-OS, T-K4-OS

T-D2-IN / T-D2-OS Service Manual
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CONFIDENTIAL
No.
Description Items# in components
diagram
Takagi
Part# Common parts forother models
15
Flow sensor 402 EK438
16
Heatexchanger assembly
401 TU002 (T-D2-IN)
EK437 (T-D2-OS)
17
Gas inlet 118 EKK1E T-K3,T-K3-Pro, T-K3-SP/OS, T-KJr2-IN/OS,T-K4-IN/OS,
T-H2-DV/OS
18
Heater 414 EKK2R T-K3, T-K3-Pro,T-K3-SP/OS,
T-KJr2-IN/OS, T-K4-IN/OS
19
Flow adjustmentvalve 402 EK438
20
Surge box 703 EK428 T-KJr2-IN/OS, T-K4-IN/OS
21
Outlet drain plug 410 EKK2E T-K3,T-K3-Pro, T-K3-SP/OS,
T-KJr2-IN/OS,T-K4-IN/OS,
T
-
M50
22
Air-fuel ratio rod
(AFR rod) 108 EKK0E T-K3, T-K3-Pro, T-K3-SP/OS, T-H2-DV/OS, T-M50,T-M32
23
Flame rod 108 EKK0E T-K3,T-K3-Pro, T-K3-SP/OS,
T-H2-DV/OS, T-M50,T-M32
24
Igniterrod 109 EKK0F T-K3, T-K3-Pro, T-K3-SP/OS,
T-H2-DV/OS, T-M50,T-M32
25
Inletdrain plug (water
filter) 405 EKK2B T-K3, T-K3-Pro,T-K3-SP/OS, T-KJr2-IN/OS, T-K4-IN/OS
26
120 VAC PowerON-OFF
switch 706 EKK4V T-K3-SP/OS, T-KJr2-IN/OS, T-K4-IN/OS,T-H2-DV/OS
27
Gas valve assembly Included in #102
EKH6T (LP model)
T-H2-DV/OS
EKK5K (NA model)
28
Manifold port N/A N/A
29
Gas inlet port N/A N/A
30
Exhaust chamber Included in #401
TU002 (T-D2-IN) T-H2-DV/OS
EK437 (T-D2-OS)
31
Output thermistor 411 EKK2T
32
Bypass valve 403 EKK0U

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CONFIDENTIAL
5. Schematic diagram
The diagram below refers to both the T-D2-IN and T-D2-OS.
1. When a hot water tap is opened,cold water entersthe T-D2-INor T-D2-OS.
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 ignites and flames appear inside the burner chamber.
6. Watercirculates through the heat exchanger and isheated up tothe settemperature.
7. Using thermistors to measure temperatures, the computer modulates the gas and water valves to
ensureproperoutput water temperatures.
8. When the tap is closed, the T-D2-IN or T-D2-OS shuts down.
H
O
T
C
O
L
D
G
A
S
PCB
Hi-limit SW
Inlet drain
plug filter
Mixing
Thermistor
Drain plug
Main gas valve
Gas solenoid valve 2
Fan motor
Flame rod
Igniter rod
Igniter
O.H.C.F
Heater
Flow adjustment valve
with Flow sensor
Gas proportional valve
Gas solenoid valve 1
Air-fuel ratio rod
Gas solenoid valve 3
Output
Thermistor
Bypass valve
Inlet
Thermistor Transformer

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CONFIDENTIAL
6. Wiring diagram
The diagram below refers to both the T-D2-IN and T-D2-OS.
Gas
Propor-
tional
Valve
3
9
53
73
G
BK
W
Trans-
former
IG
Igniter rod
Heater
Freeze
protection
thermostat
Heater
Ground
BK
BK
MV
SV3
SV2
SV1
LB
G
O
R
O.H.C.F
Hi-
limit
switch
BL
BL BL
BL
BL
BL
BL
W
YBL
O
R
FM
W White
R Red
BK Black
P Purple
LB Light blue
BL Blue
G Green
Y Yellow
O Orange
BR Brown
BKW
R
BK
WR
W
R
R
Flow
Sensor
W
Bypass
Valve
Flame rod
Ground
AFR rod
Y
G
O
Inlet
thermistor
Output
thermistor
Mixing
thermistor
Remote
controller
Pump
connectors
Parent
BK
W
BK W
654321
BK
BK
BK
BK
BK
BK
BK
BK
W
Flow
Adjust
ment
Valve
RR
RR
BKBK
BKBK
Multi-system
On line LED
7 Seg LED
33
7
7
OFF
1 2 3 4 5 6
OFF
PP
PP
BRBR
BRBR
MAX button
MIN button
Increase button
Decrease button
Red LED
Dipswitches
Error call button
BK
W
SW
BK
W
Surge
box
BK
W
120 VAC
G
Ground
2
1
W
W
BK
PCB
A2
A3
A A1
G
H1
H2
B1
B
C
I
J
J1
K D1
D2
F E1
E2
E3
C1
C2
TM-RE30

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CONFIDENTIAL
7. Wiring diagram check points for diagnosis
The table below applies to both the T-D2-IN and T-D2-OS.
Check-
point
Partand Description Colorof wires Normalrange
A, A1
100V Power supply White – Black (A)
Brown – Brown (A1) 90 to 110 VAC
A2,A3
120V Power supply Black - White 108 to 132 VAC
B Igniter Purple - Purple 90 to 110 VAC
B1 Heater Black - Black 90 to 110VAC
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 - blueatCOM (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-limit switch Blue - Blue Less than 1VDC and
less than 1.0 Ω
C2 Overheat cutoff fuse Blue - Blue Less than 1VDC and
less than 1.0 Ω
D1,D2
Easy-link connectors Black - White 15 VDC
(during Easy-link operation)
E1 Mixing thermistor Black - Black See table on p. 11E2 Output thermistor Black - Black
E3 Inlet thermistor Black - Black
F Remote controller * 11 to 25 VDC
G Fan motor Red - Blue 110 to 160 VDC Yellow - Blue 13 to17 VDC
Orange - Blue 2 to 6.5 VDC

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CONFIDENTIAL
Check-
point
Partand Description Colorof wires Normalrange
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 1 to 4 VDC (pulse) 1,080 pulse / min
(more than 18 Hz)
I
Air-fuel ratio rod Yellow - AFR rod (Between AFR rod and
the computer board)
More than 0.5 μA
(during operation)
Flame rod Orange - Flame rod (Between flame rod and
the computer board)
More than 1 μA
(during operation)
J Flow adjustment valve Red - Black 7 to 16 VDC and
0.09 to 0.2 kΩ
J1 Bypass valve Red - Black 7 to16 VDC and
0.09 to 0.2 kΩ
K Pump connectorport White -Black Lessthan 1.3 Ω

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CONFIDENTIAL
8. Resistance values of the temperature thermistors
The T-D2-IN and T-D2-OSuse 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
9. Operational flow chart
The diagram below refers to both the T-D2-IN and T-D2-OS.
Power supply ON
Operation SW ON
FAV&BV open
Pre-check
NORMAL?
Faucet opens
Water Flow
Above 0.75GPM?
FM speed
(Below
1,000rpm?)
Fan moter start
operation
Flame rod
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
SV 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
Opeartion lamp OFF
Operation stop
YES
NO
YES
NO
NO
YES
YES
NO
(20sec later)
YES
NO
NO
YES
YES
NO
YES
NO
(5sec 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 blink
121 blink
991 blink391 blink
BV modulates
Flow&temp
321 blink
InTH OPEN
or SHORT
331 blink
MiTH OPEN
or SHORT
detects Below
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

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CONFIDENTIAL
10. Component specifications
10-1.
Burners……………………..………………………………………………………………………....……….
17
10-2.
Gas manifold………….………………………………………………………………………………….....
18
10-3.
Fan motor………………………………………………………………………...……………………………
19
10-4.
Gas valve assembly………………..……………………….……………………………………………..
20
10-5.
Flame rod………………………………………………………….…………………………………………..
21
10-6.
AFR rod………………………………………………………………………………………………………….
22
10-7.
Heatexchanger………………………………………………………………………………………………
23
10-8.
Flow adjustment valve…………….……………………………………….....………………………..
24
10-9.
Flow sensor……………………………………..…………………………………………………………….
25
10-10.
Bypass valve…………………………………………………………………………………………………..
26
10-11.
Thermistors……….………………………..……………………………………..………………………….
27
10-12.
Hi-limit switch…………………..…………………………………………………...........................
28
10-13.
Overheat cutoff fuse…..………………………………………………………….........................
29
10-14.
Freeze protection heaters…………….………………………………………………………………..
30
10-15.
Computerboard……………….……………………………………………………………………………
31
10-16.
Transformer. ………...……………………………………………………………………………………….
32
10-17.
Igniter………………………………………………………………………………...............................
33
10-18.
Freeze protection thermostat…………………………………………………….....................
34
10-19.
Surge box……………………………………………………………………………………………………….
35

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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 chamber and theair-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 theburners.
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/Number of wires N/A
The burner for the T-D2-IN and T-D2-OS has the “46V” mark as shown below.
7-1/2" (189.6mm)5-1/4" (132.3mm)
9" (229mm)
46V
"46V" mark
Burner damper (#112 /EK412)
The burner damper is
not included in EKH5W.
59K
7-7/8" (201mm)
1-3/4" (44mm)
"59K" mark

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CONFIDENTIAL
10-2. Gas manifold
Unit Part #Included
in #102 Takagi Part #EKH6T (LP model) EKK5K (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 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 voltages and resistance: proper range of values shown below.
Color/Number of wires Blue-Red 78 to 100 VDC /0.9 to 1.7kΩ
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
EKK5K (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.

T-D2-IN / T-D2-OS Service Manual
Ver. 1.00
19
CONFIDENTIAL
10-3. Fan motor
Unit Part ##103 Takagi Part #EKK25 (T-D2-IN)
EKK54 (T-D2-OS)
Checkpoint
G
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 doesnot 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/Number ofwires
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 TM-RE30 temperature remote controller. See Section
12-1 for details.
5-3/8" (137.4mm)
Opening 2-1/4" ( 60mm)
T-D2-OS
PWN multi blade fan motor
PWN turbo fan motor
T-D2-IN
6-1/2" (165.5mm)
3-3/4"(95.15mm)
Opening 2-1/8"( 54mm)
Fan damper (#115 / TU001)
1-5/8" ( 40mm)
40
The fan damper
is not included in
EKK25.

T-D2-IN / T-D2-OS Service Manual
Ver. 1.00
20
CONFIDENTIAL
10-4. Gas valve assembly
Unit Part #Included
in #102 Takagi Part #
EKH6T (LP model)
EKK5K (NA model)
Checkpoint C,H1
Function Opens and closes the gas pathways of the water heater (main and solenoid
gas valves)
Modulates the gas flow from the gas inlet (proportional gas valve)
Failure events 1. Gas leak from the valves.
2.Unable to open/close (main and solenoid gas valves)
3.Unable to modulate the gas flow (proportional gas valve)
Effects on the water
heater if valves fails
1. Gas leak from the unit.
2. Excess carbon monoxide emissions. / No flames.
3.Lack of water temperature control.
Error codes when the
valves fails 111 121 510 701
Diagnostic
1.Visual inspection: connection/breakageof wires.
2. Listen for "clunk" sounds from the gas valves opening right after fan motor
initiates.
3. Check voltages and resistance of coils; proper range of values shown
below.
Color/Number ofwires
Blue - Light blue (MV) 78 to 100 VDC (duringoperation) / 0.9 to1.3 kΩ
Blue - Green (SV1) 78 to 100 VDC (duringoperation) / 1.3 to1.9 kΩ
Blue - Orange (SV2) 78 to 100 VDC (during operation) /1.3 to 1.9 kΩ
Blue - Red (SV3) 78 to 100 VDC (duringoperation) / 0.9 to1.7 kΩ
White -Red
(Proportional valve) 1.0 to 15 VDC (during operation) /20 to 40 Ω
Proportional Valve
Proportional valve
Main gas valve
4-1/4" (108mm) 7/8" (22.2mm)
4-5/8" (119mm)
Solenoid valve
Gas
valve
3-5/8" (91.5mm)
1-3/8" (34mm)
2-5/8" (67mm)
EKH6T (for LP model) and EKK5K (for NA model)
is an assembly of the gas manifold with gas valve
assembly. For safety reasons, these assemblies
should be installed in the unit as a whole set. The
diagram below shows the gas valve assembly.