| The following
Requirements must be adhered to when planning for and installing a
Takagi tankless water heater. Failure to do so could result in improper
operation, shortened unit life, voiding the warranty and/ or a compromise
Information and Guidelines such as water connections, temperature
settings, recirculation systems, and initial cleaning of the water
filter are also included.
| Requirement #1: Gas Supply
Gas Meter Size:
The larger BTU input of a tankless water heater may
necessitate the installation of a larger meter. Check
with the local utility.
Gas Line Size:
All Takagi heaters have ¾ inch NPT connections.
Gas line sizing shall be a minimum of ¾ inch inside
diameter pipe. Gas lines shall be sized to allow for maximum
BTU/hr input of said heater at the specified inlet pressure.
These specifications can be found in the installation
manual or on the rating plate located on the front cover
of the heater. Please use the follow the standard set
forth by the “American Gas Association.”
Pressure: The minimum
natural gas pressure at the unit should be 5.5
inches of water column, with a maximum of 10.5 inches.
For liquid propane, the minimum is 11 inches and 14 inches
maximum. Refer to the installation manual for proper specification
or list the specs for every heater.
Connection to the Heater: This can be
done with hard pipe or with flexible line that is made
specifically for gas. Please check your local codes. This
piping MUST be no smaller than ¾ inch INSIDE Diameter.
Just because a flex line uses ¾ inch connections
doesn’t mean that it actually measure ¾ inch
on the inside. In fact, most are ½ inch to 5/8
inch I.D. and will not supply enough gas to operate a
tankless heater properly.
Valve: High quality full port gas shutoff
valve shall be installed per National/Local codes. Note:
Some ball valves significantly reduce the diameter of
the pipe and should therefore be avoided if possible.
Requirement #2: Venting
Supply (Combustion Air): On the direct
vent models, which draw the combustion air they need
“directly” from the outside, the pipe diameter
is 3 inches. This material is usually made of PVC, although
galvanized steel (B-vent) and aluminum may also be used.
Do not install a non-direct vent model, such as the
T-M1 where there is an inadequate supply of combustion
air to the heater area. Sizing for combustion air indoors
shall follow the NFPA 54 code.
Vent: All Takagi water heaters are Category
III appliances, and therefore MUST be vented with Category
III stainless steel, four inch diameter, exhaust gas vent
pipe made especially for Category III appliances (the
exception is the T-H1, which is a Category IV unit and
uses a vent pipe approved for Category III appliances).
The Category III pipe, which is available from several
manufacturers, is called a “BH” vent pipe
in Canada. Using another material, such as common B-vent,
will damage the heater, possibly resulting in carbon monoxide
poisoning. The entire exhaust vent must be sealed –
from the top of the heater to the terminator. This is
done by the high-temperature seals and locking devices
built into the Category III approved vent pipe.
Rules for Venting:
best results, try to keep the vent system as short
and straight as possible.
vent pipe should be removable from the top of the
heater for inspection and possible servicing of
heater MUST NOT be common-vented with any other
gas appliance or vent stack.
not upsize (oversize) the vent pipe. It must be
4 inches in diameter for the entire run.
horizontal runs, either a) slope the pipe upwards
from the heater at a rate of ¼ inch per foot
and install a condensation drain; or b) slope it
down and away from the heater at the same rate (25),
so that the condensate will drain out.
any runs that are at a significant slope up to vertical
and over 5 feet in length, always use a condensation
drain to protect the heat exchanger, especially
in cold weather. Refer to the manufacturers instructions
for proper installation.
Connections – Pipe Sizing: The
connections on the heater are ¾ inch NPT. Takagi
specifies minimum ¾ inch piping to and from the
heater. Using pipe smaller that ¾ inch will create
flow and temperature fluctuations.
Currently the T-K3, T-H2-DV, T-H2-OS, T-K3-Pro, T-M32, and
T-M50are the only
heaters that should be connected in parallel to increase
flow rate. Installing any other model in parallel will
result in unsatisfactory performance in most cases.
When connecting multiple T-K3, T-H2-DV, T-H2-OS, T-K3-Pro, T-M32, and
T-M50 units together,
install a check valve on each hot-water-out pipe. High
quality, full port ball valves should be used on the hot
and cold lines for servicing purposes. You may also want
to install isolation valves for future servicing purposes.
You must also determine the correct header size, based
on the number of tankless units installed. A general rule
of thumb to use 1¼ inch pipe for 1 to 4 heaters;
1½ inch pipe for 5 to 10 heaters; and 2 inch pipe
for up to 20 heaters.
Electrical Supply: All units run on 120
VAC 60 Hz, and draw no more power than about 92 watts
or 0.92 amps. A dedicated circuit or GFCI is not needed
unless dictated by local code. Units can be simply plugged
into an outlet with an AC power cord (not suggested) or
hard-wired. We suggest using and off/on switch in the
latter case. A simple light switch will work.
Mounting the Units:
All of Takagi’s current water heaters shall be
wall mounted. The wall mounting brackets are attached
to the heaters at the factory. Takagi water heaters
are typically wall-mounted to save floor space for the
end-user. Wall-mounting also makes it easier for the
contractor to install and service. From the back of
the unit, there is a 1-inch clearance to combustible
surfaces and a zero-inch clearance for non-combustible
- All Takagi models come
with a factory-installed mounting bracket.
Requirements: Each Takagi unit has different
clearance requirements. Refer to the Takagi installation
Protection: Takagi has installed freeze-protection
devices to help guard against permanent damage to the
heat exchanger in the event of below-freezing temperatures.
Although these devices will attempt to protect the unit,
there is no guarantee that they always will, such as in
the case of power loss to the unit. This type of damage
is not covered under warranty, so great care should be
taken to avoid freezing conditions.
Each unit has a freeze-protection sensor mounted to the
fan. It senses the incoming or ambient temperature. When
the temperature drops below 37°F, the unit will turn
on ceramic heaters located around the heat exchanger and
water lines. Again – any type of power failure would
cause this system not to work.
In freezing climates where the unit is installed inside,
Takagi recommends that the freeze protection sensor be
relocated outside if possible or at least attached to
a surface that more accurately reflects the temperature
of the incoming air. An extension cable is provided with
each unit for this purpose.
In addition to the sensor, the backflow preventer (Part
No. TV-TV03) MUST be installed wherever air at below-freezing
temperatures may be drawn down the exhaust pipe into the
heater a backflow preventer used by the venting manufacturer
is acceptable. This device shall be installed on top of
the heater. Although the backflow preventer helps to limit
the flow of freezing air, it does not block all of it.
In very cold climates, care must be taken to insure power
to the unit, and to eliminate any negative air pressure
conditions in the building that would promote cold-air
flow in the heater. If this cannot be avoided, the unit
should be thoroughly drained to prevent damage.
Relief Valve: A “pressure only”
relief valve shall be installed according to national/state/local
codes. A temperature & pressure relief valve is not
required unless required by applicable codes.
Settings: All heaters come preset with
a default setting of 122°F (Our T-K3 has a total of
8 settings). This temperature may be changed to three
other settings via dipswitches located on the computer
boards. Please see service manuals or the Takagi Tankless
Translator for these settings.
Please note that studies have found that 122°F is
the ideal temperature for most residential and many commercial
applications. Try to avoid the old “tank habit”
of raising the temperature to “get more hot water.”
This will, in fact, produce a lesser volume of hot water
than leaving it at its default setting.
The heaters may also be set to 17 different temperatures,
using the appropriate Remote Control, depending on the
heater model. See the Product Descriptions or Accessories
page to find out the right Controller for your specific
Switch: Make sure this switch is set correctly
for your heater’s location. The default setting
for every Takagi unit is “indoor”.
Systems: Tankless water heaters may be
used with hot water recirculation systems. Tankless water
heaters provide a continuous flow of water at a consistent
temperature. They do not provide “instant”
hot water, despite “aggressive advertising”
and wishful thinking. Just as a conventional water heating
system must move the hot water from the tank to the fixture
or appliance – which takes time – so does
a tankless system. In fact, a tankless system may take
a few seconds more to turn on and heat the water. This,
however, is a small price to pay for its benefits.
| There are wrong ways to install a “recirc”
Way No. 1: Install a pump that is either
too small, such as what was used on the previous tank-type
heater; or one that is too large, such as what may have
been recommended to “cover all the bases.”
“ Generally, if the pump is sized too small, it
will not provide enough flow to activate a Takagi tankless
heater. This is especially true if the return piping is
small or is an extended line with several elbows.”
Takagi requires a minimum high head 1/12 hp pump.
Wrong Way No. 2:
“Install a high head pump that is too large.”
such as a We specify a minimum 1/12 hp pump.
This will provide enough flow to turn the heater on, but
may also cause unnecessary wear on all the pipes, valves
and heat exchanger. It will also waste energy. This size
pump would be required, however, in a large house with
long runs or with a small return pipe.
The Right Way: Use
engineering formulas to estimate – as closely as possible
– the approximate dynamic head loss through the recirculation
loop. Then choose the correct pump from manufacturer’s data,
based on flow rate at a certain head.
If these formulas are not practical, try to estimate the size of
your return line run. How long and how large of a pipe run is it?
In general, a long run with many elbows and a small diameter (½
inch, for example) will require a larger pump to draw the water
back to the unit.
You should be looking for approximately 2 to 4 GPM of flow for most
domestic hot water recirculation systems. This should be enough
to turn the unit on reliably and not cause premature wear or energy
waste. Use a Takagi remote to determine the flow rate, which can
be adjusted using a ball valve on the first pump or the three-speed
switch on the second.
Comparable pumps by other manufacturers would be a Taco 003-BC-1
for the 15-42, or a Taco 009-BF5 for the 26-96, or equal.
Having “instant hot water” at the faucet is a wonderful
benefit, bit it can also be a costly one and actually defeat the
purpose of tankless water heating, which is to save energy and money.
Make sure you install an aquastat (a thermostat for water) and a
timer on the pump to limit activation frequency and duration.
For example, the timer may be set to early morning (before showers)
and afternoon/evening hours. Also, if at all possible, install insulation
on the supply and return lines to avoid heat loss.
One system that performs well with tankless is a Metlund D’MAND
System: the S-70T-PF-R, for small homes and the S-02T-PF-R for larger
residences. Neither model needs a separate return line, because
they use the existing cold-water line to return the water from the
farthest fixture. Consult the manufacturer for more details.
Clean Water Filter After Initial
Run: There is a small screen filter on the cold-water
input connector of each heater. After running the heater for five
minutes during setup, turn off the water supply and remove this
screen to check for debris. Some screens may be removed easily with
a half-inch copper pipe wire brush. You may choose to install an
extra cartridge filter on the heater’s cold supply to avoid
problems with small filter clogging prematurely.