| Takagi tankless
heaters have proven themselves to be highly reliable over the years,
requiring little maintenance or repair. However, a few minor service
requirements should be performed at least once a year to insure trouble-free
performance. These are outlined in your Service and Installation Manual
under “Maintenance and Service.”|
A very high percentage of service problems requiring troubleshooting
can usually be traced to causes external to the unit. These problems
in order of occurrence are:
Venting: The most common error is the
use of normal B-vent, which can quickly destroy the heat
exchanger due to acidic condensation. Improper venting
is also unsafe. All Takagi tankless water heaters must
use sealed stainless steel vent pipe approved for use
in Category III appliances.
Supply Line Problems: Undersized Line:
There is a great tendency to just “hook up to the
existing gas line,” which is usually only ½
inch diameter. As stated in the installation manual and
in this guide, the minimum size is ¾ inch, but
this size is good only for certain lengths from the source.
Strict attention must be paid to the gas-line requirements
section in the installation manual. Make sure that you
size for the maximum BTU per hour rating and not the minimum.
Gas Pressure: The working pressure should
be from 5 to 10½ inches WC for Natural Gas and
9½ to 14 inches for Liquid Propane, depending on
Type of Gas: Make
sure that you order the correct heater for the type of
gas you will be using, Natural Gas or Liquid Propane.
There is no modification available to change the unit.
Water Flow/Temperature Fluctuation
Problems: If there is a low flow from
the heater, the first thing to check would be the input
filter. Turn off the cold supply, relieve the hot pressure
and remove the filter to check for debris. Clean or replace
the filter and then check the flow again. If there is
inadequate hot water or variations in temperature, check
for plumbing “cross flow,” which means there
is a connection somewhere between hot and cold. This may
be as inconspicuous as a worn seal in a one-handle faucet.
To check for this, shut off the cold supply to the heater
and open either the pressure relief valve or any hot-water
faucet. If there is a steady flow of water from the hot
output after the pipe has drained, there is a cross flow
somewhere that must be fixed.
causes of temperature fluctuations can be missing or
incorrectly installed check valve, especially on multiple
systems. The gas line may be too small, or the heater
temperature may be set too high in an effort to “get
more hot water.” This can cause a shower to be
turned too far to the cold side, which doesn’t
allow enough hot-water flow to keep the heater on steadily.
In most circumstances, the heater should be set to its
default of 122°F.
In areas where the water is very hard with high
levels of calcium and magnesium (about 9+ grains per
gallon or 70 to 140 parts per million), Takagi recommends
that the water be treated with a water softener or some
other de-scaling device. Do not use a reverse osmosis
process! It will destroy the heat exchanger. Removing
minerals or keeping them in suspension will greatly
lengthen the life of the heater and reduce service problems.
Issues: The heaters should be installed
in relatively clean areas with access to combustion air
that is free from dust, lint, grease, or chemicals. If
any of these conditions are present, a direct vent model
should be installed. For this reason, restaurant, beauty
salon and industrial applications should always get a
direct vent unit, which draws it combustion air from the
Internal Troubleshooting and Repair
Internal troubleshooting should be done only after all of the above
external criteria have been thoroughly checked and repaired. If the
heater still does not work correctly, here are some basic steps to
take with all Takagi models. A more in-depth troubleshooting guide
is available in the Service and Installation Manual provided with
the front cover.
sure there is AC power to the unit by pressing the test
button on the black GFCI panel
red LED should turn on. If it does not, check for power
to the unit or blown fuses. Push the reset button. The
LED will turn off and the unit should be ready to fire.
sure that there is gas supply to the unit. This should
be done using a pressure gauge or by verification from
the gas company.
sure there is good water flow. If there is not, check
the filter, as described above under water flow problems.
Check for reversed hot and cold lines. (Oops! Even licensed
professional plumbers can make an occasional mistake.)
Do you have adequate water pressure and flow? All units
need 0.75 gallons per minute to activate, except the T-K3,
which needs 0.5 GPM.
the following sequence of events after turning a hot water
fan turns on.
igniter starts sparking or clicking.
gas valves “clunk” as they open up.
flame appears in the viewing window and the red
“burner on” lamp lights up.
hot water starts flowing out of the unit in about
6 to 10 seconds. This timing applies to all Takagi
models except the T-M1, which may take a few seconds
one of the above does not happen, use one of the following
methods to determine the cause of the problem:
the hi-limit switch at the upper-left-hand corner
of the heat exchanger. It is a small, black, round
switch that may have a center button popped out
slightly. This may have happened randomly, or it
may be a sign that your heat exchanger is clogging
up with deposits and needs to be flushed out. If
resetting this switch causes the heater to run temporarily
before the button pops out again, a service call
your service manual’s “Common Troubleshooting”
section to determine what is causing the problem.
This section explains the meaning of the error codes,
which are shown as flashing LED’s on the computer
board or as numeric codes on a remote control. These
error codes are also available on the Takagi Translator,
a tool for selecting the proper Takagi model for
any hot-water application.