Takagi T-KJr User manual

T-KJr. Instantaneous Water Heater
Installation Manual and Owner’s Guide
Flash Water Heater
Model T-KJr.
Suitable for potable water heating and/or space heating
FEATURING
•ENDLESS HOT WATER
•ON DEMAND
•COMPACT, SPACE SAVING
•ENERGY CONSERVING
•COMPUTER CONTROLS
•COMPUTERIZED SAFETY
•NO PILOT LIGHT
Takagi Industrial Co. USA Inc.
3-B Goodyear
Irvine, CA 92618
Toll Free [phone]
www.takagi-usa.com
FOR YOUR SAFETY
- This product
must be installed and serviced by a
professional service technician or licensed
plumber or gas fitter when installed in the
Commonwealth of Massachusetts and/or
any other State. Warning
Operation creates carbon monoxide gas
and flue gases, which can cause serious
injury or death. Improper installation
and/or operation, or installation by an
unqualified person, will void warranty.
WARNING
: If the information in this
manual is not followed exactly, a fire or
explosion may result, causing property
damage, personal injury or death.
•Do not store or use gasoline or other
flammable vapors or liquids in the
vicinity of this or any other appliance.
•WHAT TO DO IF YOU SMELL GAS
•Do not use any appliance.
•Do not touch any electrical
switch; do not use any phone in
your building.
•Immediately contact your gas
supplier from another location.
Follow the gas supplier’s
instructions.
•If you cannot reach your gas
supplier, call the fire
department.
•Installation and service must be
performed by a qualified installer,
service agency or the gas supplier.

1
Table of Contents
Specifications…………………………….. 1
For Your Safety…………………………... 2
Operation…………………………………. 3
General…………………………… 3
Turning It On……………………… 3
Turning It Off……………………… 3
Temperature……………………… 3
Flow……………………………….. 4
Freeze Protection………………... 4
Installation………………………………… 5
General…………………………… 5
Accessories………………………. 5
Electrical Connections…………... 5
Wiring Diagram…………………… 6
Temperature Settings……………. 6
Gas Supply Plumbing…………… 7
Water Plumbing…………………. 8
Pressure Relief Valve……………. 8
Wall Hanging Installation………...9
Outdoor Installation………………. 9-10
Indoor Installation………………... 10-11
Combustible Air Supply…. 10
Exhaust Venting…………. 10-11
Manufactured Home (Mobile Home)
Installation……………….………... 11
Indoor……………………… 11
Outdoor……………………. 11
Initiating the Appliance…………... 11
Initial Operation…………………...... 12
Space Heating Application……….. 13
Dual Purpose Heating……………. 14
Applications………………………… 15
TKJr with Storage Tank…………... 15
TKJr with Recirculation…………... 15
Before Operating………………….. 16
Danger……………………………… 17
Maintenance…………………………………. 18
Troubleshooting / Errors Codes…………... 18-19
Optional Items……………………………… 20
TK-RE01………………………….. 20
TK-BK01………………………….. 20
TK-TV01…………………………... 20
TK-TV03…………………………... 20
Parts Diagram………………………………. 21-22
Parts Lists………………………….. 23
Flow Chart…………………………………… 24
Specifications
Natural Gas Input Min. 19,500 Btu
Max. 140,000 Btu
LPG Input Min. 17,000 Btu
Max. 140,000 Btu
Gas Connection ¾” NPT
Water Connections ¾” NPT
Water Pressure Min. 15 psi
Max. 150 psi
Natural Gas Pressure Inlet Min. 5” WC
Max. 10.5” WC
LP Gas Pressure Inlet Min. 11” WC
Max. 14” WC
Manifold Pressure Natural 2.9” WC
Propane 3.2” WC
Weight 30 lbs.
Dimensions 20”x14”x6”
Ignition Electronic Ignition
Electrical Supply AC 120 V
***
•Inlet gas pressure must not exceed the
above maximum values.
•For gas pressures lower than 5” WC for
natural gas, call the manufacturer.
•Before installing in areas over 4,500 feet
above sea level, contact the manufacturer
for high altitude adjustment instructions.
•Check the rating plate to insure this
product matches your specifications.
•Takagi - USA is constantly improving our
products; therefore specifications are
subject to change without prior notice.

2
For Your Safety
PLEASE READ THIS MANUAL CAREFULLY
AND FOLLOW IT EXACTLY FOR YOUR
SAFETY.
1. Follow all local codes, or in the absence of
local codes, follow the most recent edition of
the National Fuel Gas Code, ANSI
Z223.1/NFPA 54 in USA or the CGA standard,
CAN/CGA B149.1 or .2 Installation Codes for
Gas Burning Appliances in Canada.
2. Properly ground the unit in accordance with all
local codes, or in the absence of local codes,
with the National Electrical Codes, ANSI/NFPA
70 in the USA or CSA standard C22.1 Canada
Electrical Code Part 1 in Canada.
3. Carefully plan where to install your Flash
Water Heater. Insure that your heater will have
enough combustible air, proper ventilation, and
locate your heater where water leakage will not
do damage to surrounding areas. If there is a
possibility of water damage, install a suitable
drain pan under the unit, which will not restrict
combustible airflow.
4. Check the rating plate for the correct gas type,
gas pressure, water pressure, and electrical
rating. Do not install this unit if these
requirements can’t be met.
5. If a problem should occur, turn off all hot water
taps and turn off the gas. Call a trained
technician, the Gas Company, or the
manufacturer.
WARNING: Do not disconnect the electrical
supply if the temperatures will be near freezing.
The Freeze Prevention Device will only work if the
unit has proper electrical power. The Freeze
Prevention Device is rated for temperatures down
to 5º F (-15º C) in a wind free environment. The
wind chill factor will cause the Flash Water Heater
to freeze and be damaged at temperatures above
5º F (-15º C). Refer to the sections on Winterizing
and the Freeze Prevention Device for more
information.
6. WARNING: Before bathing or showering
always check the water temperature. Do not
leave children or the infirm unsupervised in the
shower or bath. The water temperature is set
at 120º F (50º C) from the factory to maximize
the amount of hot water you can use. Water
temperature over 125º F can cause severe
burns instantly or death from scalds.
7. WARNING: Do not use this appliance if any
part has been underwater. Immediately call a
certified and trained technician to inspect and
service the unit if necessary.
8. WARNING: Do not store or use gasoline or
other flammable vapors or liquids in the vicinity
of this or any other appliance.
9. WARNING: Do not reverse the water and gas
connections, this will damage your heater and
can cause severe injury or death from scalds.
Follow the diagram below when installing your
Flash water heater.
Rating plate
Cold In
Hot Out
Gas

3
Operation
General
The Flash Water Heater is an instantaneous,
tankless water heater designed to efficiently supply
domestic or commercial hot water. The principle
behind the Flash water heater is simple: Once a
hot water tap is opened, the Flash’s flow sensor
detects that hot water is needed, and automatically
commands the computer to electronically ignite the
burners, and heat water. During operation, the
computer monitors the water temperature and flow
rate, and controls the gas flow and fan speed to
maintain a constant output temperature. After the
burners are ignited the “fire on” lamp will be lit.
0.75 gallons per minute is required to turn the
burners on, but after the burners are ignited, the
flow rate can drop to 0.60 gallons per minute
without the burners turning off.
As long as water, gas and electricity are
connected, there will be an endless supply of hot
water. To turn on your water heater, just open a
tap. To turn the heater off, just close the tap.
Turning It On
To turn on the Flash water heater
1. Open a hot water tap, or turn on water
demanding appliance.
2. Unit will detect flow, burners will ignite, and
“Fire On” lamp will light up on computer board.
3. If necessary, mix in cold water to get a
comfortable temperature.
Turning It Off
To turn off the Flash water heater
1. Close the hot water tap, or turn appliance off.
2. Flow will diminish and unit will shut off.
3. “Fire On” lamp will go out.
Temperature
The output temperature of the T-KJr. has been
factory set to maintain a maximum of 120°F (50°
C). This is electronically controlled by the
computer and can be adjusted with a TK-RE01
temperature controller. Further adjustment may be
made by mixing in cold water with the hot to obtain
the ideal water temperature.
The maximum possible flow rate out of the unit is
dependent on ground water temperature and the
temperature setting chosen. Consult the flow
charts on the last page of this unit to determine the
possible outlet temperature and flow rate
combinations.
WARNING: Temperatures above 125º F (52º C)
can cause severe burns or death from scalding.
Children, the disabled and the elderly are at a high
risk of being injured. Feel the water temperature
before bathing or showering. Do not leave
children, disabled persons, or the elderly
unsupervised.
Lamp is lit
Lamp is lit
extinguished

4
Flow
The flow rate through the T-KJr. is limited to a
maximum of 5.8 GPM. The temperature setting,
along with the supply temperature of the water will
determine the flow rate the unit puts out. Consult
the flow charts on the last page of this manual to
determine the possible outlet temperature and flow
rate combinations. Based on the United States
Department of Energy method of testing water
heater output, the T-KJr. is rated for 180 gallons
per hour, or 3.0 GPM, at a 77°F rise above the
inlet temperature. Refer to the following chart of
typical household flow rates to determine what the
T-KJr. can do in a household application.
Remember that for bathing, cold water will be
mixed for a comfortable temperature, increasing
the flow output rate.
Freeze Prevention
This unit comes equipped with heaters that
discourage the unit from freezing. For this freeze
prevention system to operate there has to be
electrical power to the unit.
The freeze prevention devices will not work if the
electrical power source is disconnected.
The unit has been rated for temperatures down to
5º F (-15º C) in a wind free environment. The wind
chill factor will cause the unit to freeze at
temperatures above 5º F (-15º C), even if the unit
is installed indoors.
For indoor installation in areas where the
temperature will be well below freezing for
extended periods of time, use the included
“thermostat extension cable” to relocate the
internal thermostat located on the fan motor to the
outdoors. This will sense the ambient air
temperature and turn on the internal heater blocks
on to prevent the heat exchanger from freezing.
Install a TK-TV03 backflow prevention kit so that
cold air will not backflow into the flue and cause
the unit to freeze. Do not install the water heater in
an area with extremely cold weather. This will void
your warranty and Takagi Industrial Co. USA Inc.
will not be responsible for any damage that occurs.
WARNING: The pipe heaters are located on the
Flash Water Heater. Any hot or cold water pipes
located outside of the unit will not be protected.
Properly protect and insulate these pipes from
freezing.
If the heater will not be in use for a long period of
time or if the temperatures will drop below 5º F (-
15º C) with the wind chill factor, turn off heater and
drain the unit of water. This applies to indoor and
outdoor installations. This will keep the unit from
freezing and being damaged. Frozen heat
exchangers are not covered under warranty.
Follow these instructions carefully:
1. Turn off the power supply to the Flash Water
Heater.
2. Close manual gas control valve.
3. Close manual water shut off valve.
4. Open all hot water taps in the house.
(Bathroom, kitchen, laundry room, etc.). When
the water flow has ceased, close all hot water
taps.
5. Have a bucket to catch the water from the
unit’s drain plugs. Remove the drain plugs to
drain the water out of the unit.
6. Let drain for 5 minutes.
7. Securely screw the drain plugs back into place.
Follow these steps when it is again safe to use the
water heater:
1. Make sure all hot water taps are closed and
the drain plugs are securely attached.
2. Purge the water line of debris.
3. Open manual water control valve located on
the water supply line.
4. Open all the hot water taps to verify water
flows to the taps. Close hot water taps.
5. Open manual gas control valve located on the
gas supply line.
6. Turn on the power supply to the Flash Water
Heater.
Household Flow Rates
Appliance / Use Flow Rate
(GPM)
Lavatory Faucet 1.0
Bath Tub 4.0
Shower 2.0
Kitchen Sink 1.5
Dishwasher 1.5
Washing Machine 2.0
Taken from UPC 1997

5
Installation
General
All gas water heaters require careful and correct
installation to ensure safe and efficient operation.
This manual must be followed exactly.
1. Read the For Your Safety section in the
beginning of this manual.
2. This unit is not capable of being used as a pool
or spa heater.
3. The Manifold gas pressure is preset at the
factory. It is computer controlled and should
not need adjusted.
4. Suitable for potable water heating only. Well
water or hard water may cause scale problems
that will not be covered by the manufacturer’s
warranty.
5. Maintain proper space for servicing. Install the
unit so that it can be connected or removed
easily.
6. Install so that the electrical power can be
switched off if necessary.
7. Avoid installing in an area with high levels of
dust, sand or debris. Particles may clog the air
vent, reduce fan function, or cause improper
combustion.
8. Do not install the unit where the exhaust vent
is pointing into any opening to a building and
should be at least 3’Ft. from a property fence
or where the noise may disturb your neighbors.
Accessories
Check that all the parts listed below were included
with the unit.
Electrical Connections
The T-KJr. requires a 60 Hz 120 VAC electrical
power supply, and it should be properly grounded
in accordance with the most recent edition of the
National Electrical Code, ANSI/NFPA 70 and any
local codes. In Canada, all electrical wiring to the
heater should be installed in accordance with the
Canadian Electrical Code, CSA C22.1 Part 1, and
any local codes. Do not rely on the gas or water
piping to ground the metal parts of the heater.
CAUTION: Label all wires prior to disconnection
when servicing controls. Wiring error can cause
improper and dangerous operation. Verify proper
operation after servicing.
•A means for switching off the 120 VAC power
to the water heater must be provided.
•Wire the heater as shown in the wiring
diagram.
•A green screw is provided in the junction box
for the grounding connection.
Please keep this owner’s manual in a safe
place for future reference. Copies of this
manual are available from TAKAGI-USA
This section is for the installer. The
installer is responsible for the correct
installation of your Flash Water Heater.
For Your Safety:
Only a certified and trained service
technician or qualified plumber may
service or install your product.

6
Wiring Diagram

7
Gas Supply Piping
Check the rating plate to make sure that the unit
was built for the type of gas available in the area.
The gas supply piping should be sized according
to the Applicable Plumbing Code for a maximum
draw of 140,000 BTUH. First determine the
effective length of the gas supply line by
measuring the actual length of piping, and then
adding 5 ft. for every elbow or “Tee” to the actual
length. Use the charts below to determine the pipe
diameter necessary to accommodate the BTU
demand of the unit. If there are more than one gas
drawing appliances on the line, size according to
the maximum amount of BTU demand.
The gas supply pressures must be within the
ranges of the following chart:
Natural Gas
Supply Pressure Min. 5” WC Max. 10.5” WC
Propane Gas
Supply Pressure Min. 11” WC Max. 14” WC
Insufficient gas supply pressure can cause the
Flash Water Heater to lose efficiency or not work
at all.
WARNING: Fire or explosion may result if the
maximum supply pressures are exceeded. The
manifold gas pressure should be at maximum 2.9”
WC for natural gas, and 3.3” WC for propane.
Always use approved connectors to connect the
unit to the gas line. Always purge the gas line of
any debris before connecting to the water heater.
WARNING: Conversion of this unit from natural
gas to propane or propane to natural gas cannot
be done in the field. Contact your local retailer or
distributor to get the correct unit for your gas type.
Always install a manual shutoff valve on the gas
supply line in case of an emergency, or if service
or maintenance is necessary.
This appliance and its individual shut-off valve
must be isolated from the gas supply piping
system by unplugging the unit and turning off the
main gas valve during any pressure testing of the
gas supply piping system at test pressures equal
to or less than ½ PSI.
When all of the connections have been made,
check the gas line for leaks. Apply soapy water to
all gas fittings and connections, if bubbles form,
there may be a leak.
Natural Gas Supply Piping
Based on 0.60 specific gravity for natural gas at .5” WC pressure drop
DOE standard is 1100 BTU per cubic ft. of natural gas
Pipe
Size Cubic Feet of Natural Gas
Length 10’ 20’ 30’ 40’ 50’ 60’ 70’ 80’ 90’ 100’ 125’ 150’ 200’
¾” 363 249 200 171 152 138 127 118 111 104 93 84 72
1” 684 470 377 323 286 259 239 222 208 197 174 158 135
1 ¼” 1404 965 775 663 588 532 490 456 428 404 358 324 278
1 ½” 2103 1445 1161 993 880 798 734 683 641 605 536 486 416
2” 4050 2784 2235 1913 1696 1536 1413 1315 1234 1165 1033 936 801
Propane Supply Piping
Based on 11” WC supply pressure
Pipe
Size kBTU of Propane
Length 10’ 20’ 30’ 40’ 50’ 60’ 70’ 80’ 90’ 100’ 125’ 150’ 200’
¾” 567 393 315 267 237 217 196 185 173 162 146 132 112
1” 1071 732 590 504 448 409 378 346 322 307 275 252 213
1 ¼” 2205 1496 1212 1039 913 834 771 724 677 630 567 511 440
1 ½” 3307 2299 1858 1559 1417 1275 1181 1086 1023 976 866 787 675
2” 6221 4331 3465 2992 2646 2394 2205 2047 1921 1811 1606 1496 1260

8
Water Plumbing
Follow local guidelines for the length of the
plumbing line in order to ensure that there is
enough water pressure for all the fixtures on the
line. First, calculate the effective length of the
plumbing line by measuring the total length of pipe,
and then adding to this 5’ for each elbow or tee in
the line. Use the following chart to determine the
total number of fixture units on the line, and then
compare with the chart at the bottom of this page
to find the pipe diameter and water pressure
necessary.
Install with control valves on the inlet and outlet,
and use removable unions or connectors to
facilitate maintenance or service if necessary.
If the water heater is installed in a closed water
system, means shall be provided to control thermal
expansion. Contact the water supplier or a local
plumbing contractor on how to control this
situation.
Purge the water line of air, and clean the filter
before initial operation.
WARNING: Do not reverse the hot outlet and cold
supply line connections to the Flash Water Heater.
Make sure the hot and cold lines are connected as
in the “FOR YOUR SAFETY” section at the front of
this manual.
Pressure Relief Valve
An approved pressure relief valve must be
installed in any installation with this unit. The
pressure relief valve must be installed on the hot
line out of the unit, with no check valves or control
valves between the unit and the relief valve. It is
recommended that the Pressure only relief valve
be installed 6” inches away from water flow to
prolong the life of the Pressure relief valve.
The Pressure only Relief Valve must be rated for
150 PSI. and 140,000 BTU or higher. Connect the
discharge opening of the relief valve to a suitable
drain outdoors to prevent water damage should
discharge occur.
If the pressure relief valve discharges periodically,
this may be due to thermal expansion in a closed
water supply system. Contact the water supplier or
local plumber on how to correct this situation.
Do not plug the pressure relief valve. The line
should have no reduced fittings or other
restrictions and should allow for complete drainage
of valve and line. The pressure relief valve should
be manually operated once a year to check for
correct operation.
Should overheating occur or the gas supply fail to
shut off, turn off the manual gas control valve to
the appliance.
Length to the End of Hot Water Line and Recommended Fixture UnitsPipe
Size Pressure Range 30 to 45 PSI Pressure Range 46 to 60 PSI Pressure Range 60+ PSI
Length 100'200'300'400'100'200'300'400'100'200'300'400'
3/4"3-12 1-6 1-5 0-4 5-17 3-11 2-8 1-6 6-20 4-13 3-10 2-8
1"12-25 6-17 5-13 4-12 17-36 11-25 8-20 6-18 20-39 13-32 10-26 8-22
1-1/4"25-48 17-32 13-25 12-21 36-78 25-52 20-39 18-33 39-78 32-74 26-54 22-43
Fixture Unit Per Fixture (from UPC)
Plumbing Fixture
Description Fixture Unit
Combination Bath /
Shower 4
Whirlpool Bath 4
Shower 2
Lavatory 1
Clothes Washer 4
Dishwasher 1.5
Valve
HOT
6’’
Hot T-Fitting

9
Wall Hanging Installation
The TKJr is built for wall mount installations only.
Use proper screws to secure the unit in place.
Locate the heater as desired, but follow all
applicable local codes, as well as the indoor or
outdoor clearances that apply to the installation.
Outdoor Installation
Follow all local codes, or in the absence of local
codes, follow the codes for Installation of Gas
Burning Appliances; National Fuel Gas Code ANSI
Z221.23 in USA or CAN/CGA B149.1 or .2 in
Canada.
For outdoor installation, purchase a TK-TV04 and
install on the top of the unit.
Locate the water heater in an open, unroofed area,
and maintain the following minimum clearances
from combustible and noncombustible materials.
Outdoor Clearances
Bottom (Piping side) 6”
Front (Maintenance space) Min. 6”
Back of heater 1”
Non piping side (in enclosed closet) 2”
Non Piping side (open area) 12”
Top of heater 36” from
overhang
If this unit is installed under an overhang, there
must be a 36” clearance from the top of the unit to
the overhang, and the surrounding area must be
open in front and on the sides of the unit.
WARNING: Do not have the flue terminal pointing
toward any opening into a building. Do not locate
your heater in a pit or any location where gas and
water can accumulate.
WARNING: Do not install the heater where water,
debris, or flammable vapors may get into the flue
terminal. This may cause damage to the heater.

10
WARNING: United States regulations forbid
installing the unit within 4’ of any opening into a
building. Similar Canadian regulations forbid the
unit from being installed within 10’ of any opening
into any building.
WARNING: Improper installation can cause
nausea or asphyxiation from carbon monoxide and
flue gases which could result in severe injury or
death.
For installation in altitudes above 4,500 feet,
contact the manufacturer for instructions only if
you are experiencing difficulties with the unit.
Indoor Installation
Follow all local codes, or in the absence of local
codes, follow the codes for Installation of Gas
Burning Appliances; National Fuel Gas Code ANSI
Z221.23 in USA or CAN/CGA B149.1 or .2 in
Canada.
WARNING: In an indoor installation, the T-KJr.
must be connected to a Category III gas vent in
order to direct the dangerous exhaust byproducts
to the outdoors.
Connect the 4” Category III vent pipe to the 4”
round collar on the top of the unit.
WARNING: Do not install the unit directly on a
combustible surface such as wood floors, etc.
Install with clearance in mind keeping at least 6”
between the unit and the surface/floor.
Combustible Air Supply
The T-KJr. must be installed in a location where
the proper amount of combustible air will be
available to it at all times. If the unit is installed in
a confined space, there must be permanent
openings supplying air to the unit. One of these
openings should be within 12” from the ceiling, and
the other should be within 12” from the floor.
Exhaust Venting
This water heater must be vented in accordance
with the section on venting of equipment in the
latest edition of the National Fuel Gas Code.
This is a Category III appliance, and must be
vented accordingly. The following are UL listed
manufacturers: ProTech Systems FasNSeal, Z-
Flex Inc. Z-Vent II, Heat-Fab Inc. Saf-T Vent and
Flex-L. This unit requires 4” vent pipe. Connect
the vent pipe to the unit so that it is sealed airtight.
Follow the vent pipe manufacturer’s instructions

11
when installing the vent pipe. Do not common
vent this appliance with any other vented
appliance.
The venting system must not exceed a length of
35 ft. minus 5 ft. for every elbow. Do not use more
than 3 elbows.
No. of Elbows Max. Vertical or
Horizontal Length
035 ft.
130 ft.
225 ft.
320 ft.
If the horizontal vent run exceeds 5 ft., the
following criteria must be observed:
•There must be a 2” inch vertical run off the
top of the heater before the horizontal run
begins.
•The horizontal run must be supported at 3’
intervals.
•The vent run should be pitched up towards
the termination at ¼” per foot.
The unit can be vented either up and out the roof,
or directly through a wall. If the unit will be vented
through a wall, use Takagi USA Inc. optional part,
the TK-TV01 vent terminator, or an equal Category
III vent part. Locate the vent terminator according
to ANSI Z223.1/NFPA 54 and applicable local
codes.
Maintain the following clearances to any
combustible surface in an indoor installation:
Indoor Clearances
Non Piping Side (in Enclosed Closet) 2”
Non Piping Side (Open Area) 12”
Front (Maintenance space) Suggested 24”
Min. 4”
Piping Side 6” Minimum
Back of heater 1”
Top of heater 12”
Manufactured Home (Mobile Home)
Installation
This appliance must be installed in accordance
with the Manufactured Home Construction and
Safety Standard, (Title 24, CFR; Part 3280) and
ANSI A119.5/NFPA 501D. In addition, install in
accordance with the following instructions, the
instructions supplied with any venting, local codes,
utility company requirements for the installation of
water heaters in manufactured homes (mobile
homes), and the latest edition of the National Fuel
Gas Code, ANSI Z221.3/NFPA 50.
Locate the heater in an enclosure separating the
unit from the internal atmosphere of the
manufactured home or trailer. All combustion air
must be obtained from the outside atmosphere,
and the flue gases must be discharged directly
outdoors through a gas vent. There must be no
opening from the interior of the home or trailer into
the water heater enclosure.
Indoor Installation
Follow indoor installation instructions as set out in
an earlier section of this manual, except that
combustion air must not be taken from the inside
of the home or trailer.
Initiating the Appliance
For your safety, read before operating.
WARNING: If you do not follow these instructions
exactly, a fire or explosion may result causing
property damage, personal injury or loss of life.
a) This appliance does not have a pilot. It is
equipped with an electronic ignition device,
which automatically lights the burner. Do not
try to light the burner by hand.
b) Before operating, check for gas accumulation
in the area around the appliance. Pay special
attention near the floor, because gas is often
heavier than air, and it may accumulate near
the floor.
c) Do not attempt to open the manual gas shutoff
valve with anything but by hand. Never use
tools. If the valve will not open by hand, do not
try to repair it. Instead, call a qualified service
technician. Force or attempted repair may
result in a gas leak, fire or explosion.
d) Do not use this appliance if any part has been
under water. Immediately call a qualified
service technician to inspect the appliance and
to replace any part that may have been
damaged by being under water.

12
WARNING: IF YOU SMELL GAS:
•Do not use any appliance.
•Do not touch any electric switch; do not use
any phone in your building.
•Immediately call your gas supplier from a
neighbor’s phone. Follow the gas supplier’s
instructions.
•If you cannot reach your gas supplier, call the
fire department.
Initial Operation
1. STOP! Do not operate without reading the
safety information first!
2. Switch off the electrical power supply to the
heater.
3. Do not attempt to light the burner manually.
4. Turn the manual gas control valve located on
the outside of the unit counterclockwise to the
OFF position.
5. Wait five (5) minutes to clear out any gas. If
you then smell gas, STOP! Follow “b” in the
“Initiating the Appliance” section above. If you
do not detect gas, proceed to the next step.
6. Turn the manual gas control valve located on
the outside of the unit clockwise to the ON
position.
7. Turn on the electrical power to the appliance.
8. Turn on any tap, and the T-KJr. will initiate
itself.
9. If the appliance will not operate, follow the
instructions in the “Turning Off the Gas Supply
to the Appliance” section following, and call a
service technician or gas supplier.
TURNING OFF THE GAS SUPPLY TO
THE APPLIANCE
Close the manual valve on the gas inlet line. Turn
off the power supply.
Manifold pressure tap.

13
Space Heating Application
The FLASH T-KJr. can be used for space heating as well as potable heating of hot water
applications.
WARNING
•Toxic chemicals such as used for boiler treatments chemical, alcohol,
glycerol and glycol group will not be introduced into the system when used
for potable water and space heating.
•The FLASH T-KJr. can be used to supply potable water and space heating and
shall not be connected to any heating system or component(s) previously
used with non-potable water where any chemicals were added to the water
heating appliances.
•When the system requires water for space heating at temperatures higher
than required for other used, a means such as a mixing valve shall be
installed to temper the water for those uses in order to reduce scald hazard
potential.
•Water temperature over 125 °°F can cause severe burns instantly or death from
scalds.
•Chemicals such as diluted Glycol can be used for radiant floor, Hydro-warm
air or Baseboard heating only.
Basic system drawings and Schematics.
Heating application only:
Warning: This illustration is for concept only. There are a wide variety of variations to the
application of controls and equipment presented applications. Designers must add all
necessary safety and auxiliary equipment to conform to code requirements and design
practice.
For more details, contact Technical Department at [phone].

14
Dual-purpose hot water heating (Domestic and Heating):
Priority Control Devices: It has a capability to make priority system that can be used as a flow
sensor, Aquastat, or electronic controller to control radiant, Hydro or baseboard heating
equipments. A maximum allowable distance of 6’ Ft. between water heater and heat exchange
panel.
Warning: Follow all local codes, or in the absence of local codes, follow the most recent edition of
the National Standard Code, ANSI Z21. 10.3.
Warning: This illustration is for concept only. There are a wide variety of variations to the
application of controls and equipment presented applications. Designers must add all necessary
safety and auxiliary equipment to conform to code requirements and design practice.
Diagrammatic Layout of Radiant
Heating and Domestic Water Heater

15
Applications
The T-KJr. can be installed in a variety of plumbing applications, which will provide more
comfortable domestic hot water.
T-KJr. with Storage Tank:
The maximum flow rate through the T-KJr. is 5.8 GPM. If it is necessary to achieve higher flow
rates for longer periods of time, then it can be installed in conjunction with a storage tank. A pump
will be necessary to keep the water hot. We suggest a pump of 1/12 hp or greater depending on
the system.
Recirculation:

16
This system will also need a pump of 1/12 hp or greater, depending on the application situation.

17
OPERATING INSTRUCTIONS
1. STOP!Read the safety information above or in the Owners Manual.
2. Turn off all electric power to the water heater.
3. Do not attempt to light the burner by hand.
4. Turn the gas manual gas valve located on the outside of the unit clockwise to the
off position.
5. Wait five (5) minutes to clear out any gas. If you then smell gas. STOP! Follow "B"
in the safety information above on this label. If you don't smell gas, go to next step.
6. Turn the manual gas valve located on the outside of the unit counter clockwise 
to the ON position.
7. Turn on all electrical power to the water heater.
8. If the water heater will not operate, follow the instructions “to Turn Off Gas to water
heater" and Call your service technician or gas supplier.
FOR YOUR SAFETY READ BEFORE OPERATING
WARNING: If you do not follow these i
nstructions exactly, a fire or
explosion may result causing property damage, personal injury or loss of
life.
A. This water heater does not have a pilot. It is equipped with an ignition device that
automatically lights the burner. Do not try to light the burner by hand.
B. BEFORE OPERATING smell all around the water heater area for evidence of
leaking gas. Be sure to smell next to the floor because some gas is heavier than air
and will settle on the floor.
WHAT TO DO IF YOU SMELL GAS.
•Do not try to light any appliance.
•Do not touch any electric switch, do not use any phone in your building
•Immediately call your gas supplier from a neighbor's phone. Follow the gas
supplier's instructions.
•If you cannot reach your gas supplier, call the fire department.
C.
Use only your hand to turn the gas valve knob. Never use tools. If the knob will not
turn by hand, don't try to repair it. Call a qualified service technician. Force or
attempted repair may result in a fire of explosion.
D. Do not use this water heater if any part has been under water. Immediately call a
qualified service technician to inspect the water heater and to replace any damaged
parts.
TO TURN OFF GAS TO APPLIANCE
1. Turn off all electric power to the water heater if service is to be performed.
2. Turn the manual gas valve located on the outside of the unit clockwise  to the off
position.

18
Vapors from flammable liquids will explode and catch fire causing death or severe burns.
Do not use or store flammable products such as gasoline, solvents or adhesives in the
same room or area near the water heater.
WARNING: Do not install water heater where flammable products will be stored.
Read and follow water heater warnings and instructions. If owner's manual is
missing, contact the retailer or manufacturer.
WARNING
The outlet hot water temperature of the T-KJr.. water heater is factory set at 120°F.
WARNING: Use this heater at your own risk. The set outlet water temperature can cause
severe burns instantly or death from scalds. Test the water before bathing or showering.
Do not leave children or the infirm without supervised.
DANGER
Hot Water Heater temperature over 125 °F can cause
severe burns instantly or death from scalding.
Children, disabled and elderly are at the highest risk of
being scalded. Feel water temperature before bathing or
showering. Temperature limiting valves are available, ask
professional person.
WARNING: California Proposition 65 lists chemical substances known to the state to
cause cancer, birth defects, death, serious illness or other reproductive harm. This product
may contain such substances, be their origin from fuel combustion (gas, oil) or
components of the product itself.
DANGERDANGER
Keep flammable products:
1. Far away from heater.
2. In approved containers.
3. Tightly closed
4. Out of children's reach
Vapors:
1. Cannot be seen
2. Vapors are heavier than air
3. Go a long way on the floor
4. Can be carried from other rooms
to the main burner by air currents.

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Maintenance
WARNING: Turn off the electrical power
supply, the manual gas control valve, and
the manual water control valve before
servicing.
The unit should be checked once a year or as
necessary by a certified and trained technician. If
repairs are needed, the repairs should be done by
a certified and trained technician.
The following systems and parts should be
checked at least once a year:
1. Venting systems
2. Manual operation of the pressure relief valve to
ensure correct operation.
3. Periodic cleaning of the water filter, refer to
figure below.
4. Heat exchanger. Remove the thermistor and
check for a mineral coating. A mineral coating
on the thermistor requires flushing the heat
exchanger with a descaling solution. Scale
build up will shorten the life of your water
heater and is not covered under your warranty.
This procedure is highly recommended.
Troubleshooting
Water Isn’t Hot Enough
The T-KJr. can burn gas at a maximum input rate
of 140,000 BTUH. This puts a limit on the possible
output temperature and flow capabilities (See flow
chart on the last page of this manual). If the water
doesn’t seem hot enough, compare the flow and
temperature that is being attained to the T-KJr.
flow vs. temperature chart. If the unit is not
performing according to the chart, first check that
the gas supply line is sized properly, and that the
gas pressure is within the required range. If the
gas line is okay, check the plumbing for mixing
valves, thermostatic valves, scald protection,
single handled valves or crossed connections. If
the unit is performing in accordance with the flow
chart, then it may be undersized for the
application. If the unit is performing according to
the chart, the output temperature can be adjusted
using the T-KJr.
It Takes Too Long to Get Hot Water
The T-KJr. takes a second to ignite, and three
more to get up to temperature. The rest of the
time needed for hot water to get to a fixture is due
to the length of piping between the water heater
and the fixture. If the unit seems to be taking
longer than six seconds to initiate, check the filter
and flow sensor for any debris or damage.
The T-KJr. Will Not Initiate
First check the flow rate through the unit. If the
flow is not .75 GPM or greater, the unit will not
initiate. Check the filter and the flow sensor for
any debris or damage.
Press the lower green button on the GFCI inside
the unit. If the red light above it does not come on,
then there is a problem with the electrical supply to
the unit. If that light does come on, hit the green
reset button above the light, and look for the green
light on the circuit plate at the top left of the unit. If
this light is not lit, there is a problem with the
electrical connection between the GFCI and the
circuit plate. Contact Takagi Industrial Company
for Instructions.
CLOSE