TROUBLESHOOTING
TROUBLESHOOTING
On-Demand Water Heater Service Handbook for 240, 340 & 540 Condensing Models •
reading correctly. Refer to error
codes 311 and 321 in Table 2:
Error and Flash Codes, page 11.
• The flow adjustment valve could
be obstructed due to hard water
scale or debris, causing lower than
expected water flow. Verify water
flow with a graduated container or
with the temperature controller.
NOTE: Indoor models have a built-in
temperature controller. However,
outdoor models require a remote
temperature controller in order to
view the flow rate.
Make sure that the unit is installed properly.
• Test whether the problem is
within the unit or external to the
unit (i.e., plumbing system).
• Plumbing connections:
1. Check for a crossed
connection. See “Checking
for a Crossed Connection,”
page 33.
2. Problems with the
recirculation system:
◦ Make sure that a check
valve is installed between
the pump discharge and
the connection to the
cold water supply.
◦ Check to see if the pump
is operating properly.
◦ Check for air cavitation.
If present, the pump will
be very hot or chattering.
◦ Check the directional
indicator on the pump
flange.
◦ Check the sizing of the
pump. A minimum flow
of 2 gpm is required.
3. If the unit is installed in a
multi-unit system, verify
that the Easy-Link system
or Multi-Link system is set
up correctly. Refer to the
installation manual.
• Check gas supply:
◦
Verify that the gas meter
is capable of supplying
sufficient gas supply to all
gas appliances. Determine
the sum of all gas appliances’
maximum energy input (in
cubic feet per hour). This
number must be less than the
maximum ratings shown on
the gas meter’s rating plate.
If the maximum energy input
of all appliances exceeds the
maximum rating of the gas
meter, consult your local gas
utility.
◦
For LP models, there may not
be enough propane left in the
tank.
◦
Verify that the supply
gas pressure is within
specification, not only when
the heater is in standby,
but also while the heater is
running on maximum fire.
(See “Checking the Inlet Gas
Pressure and Pressure Drop,”
page 33.)
◦
The gas supply pressure
may be too low. This may be
caused by a malfunctioning
gas supply regulator or
incorrect gas line sizing.
◦
Check the pressure difference
between static and maximum
operating pressure. If the
drop is more than 1 inch W.C.,
there may be insufficient gas
supply. NOTE: In Canada, do
not exceed the maximum
allowable pressure drop
permitted by B149.1.
• Venting:
◦ Verify that the venting is
installed to manufacturer’s
specifications.
◦ Verify that the vent run
does not exceed the
allowable limit. Refer to
the installation manual.
◦ Verify that the DIP switch
settings for vent length
match the installation’s
equivalent vent length and
diameter.
• The filter on the cold water inlet
should be clean. Look for signs of hard
water scaling. See “Unit Draining and
Filter Cleaning,” page 32.
• If the clear tube from the
proportional gas valve to the
bottom of the combustion
chamber is disconnected,
fluctuations in temperature and/
or very low flow to the fixtures
may occur.
• On well systems or even on
some city water systems, water
pressure fluctuations (especially
on low flow) of 8 to 10 psi will
result in flow rate fluctuations.
This may result in minor
temperature fluctuations.
• Flow sensor or water control valve
may be compromised. Inspect
both parts for blockages or debris.
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