Maintenance Sheet

ManualsBrandsTakagi ManualsPlumbingTK110U-I-NG Indoor Natural Gas Tankless Water Heater with 140000 BTU, Non Condensing, Ultra-Low NOx

987654321 10

OFF

Bank of DIP switches

Decrease buon

Increase buon

MIN buon

MAX buon

Flow

Sensor

PCB

120 VAC

Ground

Igniter rod

O.H.C.F.

Gas

Propor-

onal

Valve

O.H.C.F.

Outlet

thermistor

Inlet

thermistor

Surge

box

Green LED

Hi-

limit

Switch

Flow

Adjust-

ment

Valve

SV3

SV2

SV1

Thermostat

Temperature

remote controller

Heater

Ground

Flame rod

AFR rod

Built-in controller

Maintenance sheet

110U, 310U 200 series

B. Error codes

031: Incorrect DIP switch setting

• Check the DIP switch settings on the PCB. Refer to Section D.

101: Warning for the “991” error code

• Check the gas type of the house (and/or the building). This model comes from the factory

set for natural gas. This model can be converted to propane by a qualified agent with the LP

Conversion Kit (100270585) that comes with the heater.

• Check for and remove any blockage in the venting system. Refer to “Venting instructions” in

the Installation manual.

• Check for proper distance between the intake air and exhaust terminals and other exhaust

gas terminals. Refer to “Venting instructions” in the Installation manual.

• Verify that the vent length is within max. limit. Refer to "Venting instructions" in the

Installation manual. Make sure the DIP switches are set for the correct vent length and

installation. Refer to section D.

• Check the altitude/elevation where the water heater is installed. Refer to the “High-altitude

function” in Section D for correct DIP switch settings.

• Check for any grease and/or dirt in the burner (Part #101) and the fan motor (Part #103),

especially if the water heater has been installed in a contaminated area.

• Check if there is dust and lint in the heat exchanger.

• Check the manifold pressure of the water heater. Refer to the rating plate or LP Conversion

label.

111: Ignition failure*

• Check the gas supply and inlet gas pressure.

• Check if the Hi-limit switch (Part #412) is functioning properly.

• Check for connection/breakage of wires (Part #008, 413, 708, 709), and/or soot on the flame

rod (Part #107). And then if the O.H.C.F (Part #008, or 413) has a breakage, consult the

manufacturer.

• Check if there is a buzzing spark ignition sound coming from the burner (Part #101) when

water heater prepares for combustion.

• Listen for the double “clunk” sound coming from the gas valve assembly (Part #102) when

water heater goes into combustion.

• (Only if no sparking and/or clunk sound) Check the voltage on each wire to gas valve

assembly (Part #102) and/or the igniter assembly (Part #711). Refer to “Appendix A” in

Section C.

*No sparking sound >>>>> Refer to #1 of “Appendix A” in Section C.

*No clunk sound >>>>> Refer to #2 of “Appendix A” in Section C.

• Check if there is water leaking from the heat exchanger (Part #401).

• Check if there is dust and lint in nozzles of the manifold (Part #102).

• Check the current on the flame rod (Part #107). Refer to #3 of “Appendix A” in Section C.

121: Loss of flame*

• Check the gas supply and inlet gas pressure.

• Check if the Hi-limit switch (Part #412) is functioning properly.

• Check for connection/breakage of wires (Part #008, 413, 708, 709), burn marks on the

computer board (Part #701), and/or soot on the flame rod (Part #107). And then if the O.H.C.F

(Part #008 or 413) has a breakage, consult the manufacturer.

• Check if there is water leaking from the heat exchanger (Part #401).

• Check if there is dust and lint in the nozzles of the manifold (Part #102).

• Check the current on the flame rod (Part #107). Refer to #3 of “Appendix A” in Section C.

311,321: Disconnected/short-circuited thermistor*

• Check for connection/breakage of wires and/or debris on the thermistor (Part #407, 408).

• Check the thermistor resistance. Refer to “Appendix D” in Section C.

391: Air-fuel ratio rod failure*

• Check for connection/breakage of wires (Part #709) and/or soot on the flame rod (Part #107).

510,551: Abnormal main gas solenoid valve and gas solenoid valve

• Check for connection/breakage of wires (Part #708) and/or burn marks on the computer board (Part #701).

• Reset power supply of the water heater.

• Check the voltage of each valve on the gas valve assembly (Part #102). Refer to “Appendix C” in Section C.

611: Fan motor fault*

• Check for connection/breakage of wires, dust buildup in the fan motor (Part #103) and/or burn

marks on the computer board (Part #701).

• Check to see if the fan motor connectors are frozen or corroded (Part #103).

• Check the voltage between the blue wire and each wire of the fan motor (Part #103). Refer to

“Appendix B” in Section C.

701: Computer board fault*

• Check for connection/breakage of wires (Part #714), and check the resistance between the white

wire and red wire. Refer to #2 in Appendix A of Section C.

• Check the outlet thermistor (Part #408) for proper readings as it may need to be cleaned.

711: Gas solenoid valve drive circuit failure*

• Refer to the “111” and “121” error codes in this section.

721: False flame detection*

• Clean the flame rod (Part #107).

• Check if a vertical condensation drain is installed on the vent collar of the water heater, if there is

more than 5 ft. (1.5 m) of straight pipe.

• Check if there is water leaking from the heat exchanger (Part #401).

741: Miscommunication between water heater and remote controller

• This error code will appear if the remote controller is disconnected from the PCB while power is still on.

• Check the model type of the remote controller. Model No. 100209924 (TM-RE42)

• Inspect the connections between the water heater and remote controller. Refer to the

“Temperature Remote Controller” in the Installation manual.

• Check the power supply to the water heater.

• If this error code appears only on the green LED on the PCB (Part #701), check the voltage on the

remote controller terminal on the PCB. Refer to “Appendix E” in Section C.

• If this error code appears only on the remote controller, replace the PCB (Part #701).

• If this error code appears on both the PCB (Part #701) and the remote controller, replace the

remote controller.

751: Miscommunication between water heater and built-in controller

• Check the power supply of the water heater.

• If this error code appears only on the green LED on the PCB (Part #701), check the voltage on the

buit-in controller terminal on the PCB. Refer to “Appendix E” in Section C.

• If this error code appears only on the buit-in controller, replace the PCB (Part #701).

• If this error code appears on both the PCB (Part #701) and the built-in controller,replace the

built-in controller.

991: Imperfect combustion*

• Refer to the “101” error code in this section.

*These error codes will be cleared when water flow stops.

C. Wiring diagram and check points on the water heater

Appendix A (For error code 111)

Check the following points during ignition stage.

# 1. Refer to check point “B” on the wiring diagram above.

Check the voltage between purple wires during the ignition process.

(Normal: 108 to 132 VAC)

Is the voltage within normal range?

Yes >> Replace the igniter assembly (Part #711).

No >> Go back to error code.

# 2. Refer to check points “C” and “H1” on the wiring diagram above.

Check the voltages below during the ignition process:

C: Between blue wire and light blue wire (#3).

(Normal: 93 to 120 VDC)

C: Between blue wire and orange wire (#9).

(Normal: 93 to 120 VDC)

H1: Check the voltage between white wire and red wire.

(Normal: 1 to 15 VDC)

Are these voltages within normal range?

Yes >> Replace the gas valve assembly (Part #102).

No >> Replace the PCB (Part #701).

# 3. Check the current through the orange flame rod wire (Part #709).

(Normal:morethan5μAwhenthereisaflame.)

Is the current normal when there is a flame?

Yes >> Replace the PCB (Part #701).

No >> Replace the flame rod (Part #107).

Appendix B (For error code 611)

Refer to check point “G” in the diagram to the left and the following:

• Check the voltage between red wire and blue wire.

(Normal: 132 to 192 VDC)

• Check the voltage between yellow wire and blue wire.

(Normal: 13 to 17 VDC)

• Check the voltage between orange wire and blue wire.

(Normal: 2.0 to 6.5 VDC)

Are all of the voltages within normal range?

Yes >> Replace the fan motor (Part #103).

No >> Replace the PCB (Part #701).

Appendix C (For error code 510 and 551)

Refer to check point “C” in the diagram to the left and the following.

Check the voltage on the each valve on the gas valve assembly.

• Between blue wire and light blue wire (#3) (Normal: 93 to 120 VDC).

• Between blue wire and green wire (#73) (Normal: 93 to 120 VDC).

• Between blue wire and orange wire (#9) (Normal: 93 to 120 VDC).

• Between blue wire and red wire (#53) (Normal: 93 to 120 VDC).

Are all of the check points normal?

Yes >> Replace the gas valve assembly (Part #102).

No >> Replace the PCB (Part #701).

Appendix D (For error code 311, 321)

• Outlet thermistor (Find the connector with No.113 stamped on it.)

Check point “E1” on the wiring diagram.

• Inlet thermistor (Find the connector with No.42 stamped on it.)

Check point “E2”on the wiring diagram.

Check the resistance between black wire and black wire.

Temperature

°F 50 59 68 77 86 95

°C 10 15 20 25 30 35

Resistance kΩ 15.4 12.6 10.3 8.5 7.0 5.9

Are all of the check points normal?

Yes >> Replace the PCB (Part #701).

No >> Replace the thermistor (Part #407, 408).

If the error code is displayed on the built-in controller and/or the remote controller, refer to Section B.

<< It takes a long time to get hot water at the fixtures >>

• The time it takes to deliver hot water from the water heater to your fixtures depends on the

length of piping between the two. The longer the distance or the bigger the pipes, the longer

it will take to get hot water.

• If you would like to receive hot water to your fixtures more quickly, you may want to consider

a hot water recirculation system.

<< The water is not hot enough or turns cold and stays cold >>

• Compare the flow and temperature. Refer to the “Output temperature chart” in the

Installation manual.

• Check cross plumbing between cold water lines and hot water lines.

• Check if the gas supply valve is open fully, the gas line is sized properly, and the gas supply

pressure is within specified limits. Refer to the “Gas supply and gas pipe sizing” in the

Installation manual.

• Check the set temperature on the built-in controller (the remote controller, if it is installed*)

or the DIP switch setting. Refer to Section D.

• Refer to the “Water circuit” in this section.

<<The water is too hot>>

• Check the set temperature and lower.

<<The hot water is not available when a fixture is opened>>

• Refer to “Power supply circuit” and “Water circuit” in this section.

• Check if the gas supply valve is open fully, the gas line is sized properly, and the gas supply

pressure is within specified limits.

<<Fluctuation of hot water temperature>>

• Check if the filter on the cold water inlet is clogged (Part #406).

• Check if the gas line is sized properly and the supply gas pressure is within specified limits.

• Check for cross connection between cold water lines and hot water lines.

• Refer to “Water circuit” in this section.

<<Unit does not ignite when water goes through the water heater>>

• Refer to “Power supply circuit” and “Water circuit” in this section.

• Check if the inlet water temperature is too high. If it is too close to the set temperature, the

water heater won't activate.

• Is the gas supply turned on?

A. Troubleshooting

<<The fan motor is still spinning after operation has stopped>>

• This is normal. After operation has stopped, the fan motor keeps running for 15 to 70 seconds in

order to re-ignite quickly, as well as purge all the exhaust gas out of the flue.

<<Abnormal sound from water heater>>

• An abnormal sound from the water heater is caused by insufficient air supply or incorrect installation.

The water heater needs more combustion air. Refer to the “101” error code in the section B.

<<Power supply circuit>>

• Check the power supply, and make sure that the water heater has 120 VAC.

• Is the power switch inside water heater turned on? (Part #706)

• Press the “ON/OFF” button of the built-in controller (the remote controller, if it is installed*) and

make sure that the STAND BY LED on the controller is lit. Run the water.

• Check if the green LED on the PCB (Part #701) of the water heater is lit. If so, the power supply circuit of

the water heater is under normal condition. Next, refer to “Water circuit” in this section.

• Check the fuse on the surge box (Part #703), and if it has a brown spot, need to replace it.

• If the green LED on the PCB (Part #701) isn’t lit, some electrical parts may be broken. Consult the

manufacturer.

<<Water circuit>>

• Turn on the power button on the built-in controller (the remote controller if it is installed*), and

then check if the STAND BY LED will light up.

• Open all hot water faucets, and make sure that there is enough water flow. This water heater

needs at least 0.5 GPM (1.9 L/m) water flow (at the default set temperature) to operate.

• Check for reverse connection and cross connection.

• Check to see if the filter on the cold water inlet is clogged or if there is sediment buildup in the

filter. (Part #406).

• Check if water ways in the water heater are frozen. If so, thaw them. Refer to the Installation

manual to protect your water heater from freezing.

• Check if the inlet water pressure is higher than 40 psi. If it’s lower than 40 psi, increase the pressure.

• Check for connections and breakage of wires (Part #402).

• Check if the motor drive of the flow adjustment valve (Part #402) is locked due to scale buildup,

and/or water leakage. If so, consult the manufacturer.

*If a remote controller is installed, it will take priority over the built-in controller.

1W3010-1

W: WHITE

R: RED

BK: BLACK

P: PURPLE

LB: LIGHT BLUE

BL: BLUE

G: GREEN

Y: YELLOW

O: ORANGE

BR: BROWN

D. DIP switch settings on the computer board of the water heater

Locate the bank of DIP switches at the bottom left of the computer board of the unit. Change the DIP switch settings when the

power supply is turned off. The dark squares indicate the correct DIP switch positions. DEFAULT is the factory setting.

Gas type

Natural

(DEFAULT)

OFF

1 2 3 4 5 6 7 8 9 10

Propane

OFF

1 2 3 4 5 6 7 8 9 10

Temperature set

120 °F (50 °C)

(DEFAULT)

OFF

1 2 3 4 5 6

7 8 9

140 °F (60 °C)

OFF

1 2 3 4 5 6 7 8 9 10

Appendix E (For error code 741 and 751)

Error code 741: Refer to check point “F” on the wiring diagram above.

Error code 751 : Refer to check point “L” on the wiring diagram above.

Check the voltage on the remote controller and/or built-in controller

on the PCB.

•

Between black wire and white wire. (Normal: 11 to 25 VDC)

Is this check point normal?

Yes >> Replace the remote controller and/or built-in controller.

No >> Replace the PCB (Part #701).

Outdoor

installation

OFF

1 2 3 4 5 6 7 8 9 10

Vent length

Two pipe direct

vent installation

0 to 20 ft

(0 to 6.1 m)

OFF

1 2 3 4 5 6 7 8 9 10

21 to 40 ft

(DEFAULT)

(6.2 to 12.2 m)

OFF

1 2 3 4 5 6 7 8 9 10

41 to 60 ft

(12.3 to 18.3 m)

OFF

1 2 3 4 5 6 7 8 9 10

Vent length

Vent kit

100187154

0 to 55 ft

(12.3 to 16.8 m)

OFF

1 2 3 4 5 6 7 8 9 10

Vent length

Single pipe with

room air intake

0 to 60 ft

(0 to 18.3 m)

OFF

1 2 3 4 5 6 7 8 9 10

Vent Length and Installation

Indoor model

0 to 2,000 ft

(0 to 610 m)

DEFAULT

OFF

1 2 3 4 5 6 7 8 9 10

2,001 to 3,000 ft

(611 to 914 m)

OFF

1 2 3 4 5 6 7 8 9 10

3,001 to 5,000 ft

(915 to 1,524 m)

OFF

1 2 3 4 5 6 7 8 9 10

5,001 to 7,500 ft

(1,525 to 2,286 m)

OFF

1 2 3 4 5 6 7 8 9 10

7,501 to 10,100 ft

(2,287 to 3,078 m)

OFF

1 2 3 4 5 6 7 8 9 10

Outdoor model

0 to 2,000 ft

(0 to 610 m)

DEFAULT

OFF

1 2 3 4 5 6 7 8 9 10

2,001 to 4,000 ft

(611 to 1,219 m)

OFF

1 2 3 4 5 6 7 8 9 10

4,001 to 6,000 ft

(1,220 to 1,829 m)

OFF

1 2 3 4 5 6 7 8 9 10

High Altitude Function

DIP switches

The tech should power the heater off and then on to reset the

error code.