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10 • On-Demand Water Heater Service Handbook for 240, 340 & 540 Condensing Models
Unit does not ignite when
water goes through it.
•
If you have an indoor model, is
the power button on the built-in
controller turned on?
•
If you use a remote controller, is
the remote power button turned
on?
•
Check to see if the Computer
board is receiving power. This can
be verified by observing the green
LED on the computer board or the
amber LED on the temperature/
remote controller.
If it is not lit, the computer board
is not being powered. Check to
see if the ON/OFF switch below
the fuse box is set to the on
position, or if the fuse in the fuse
box assembly is blown.
•
Is the flow rate over 0.5 gpm?
See if the unit initiates when you
increase demand of water being
drawn through the unit (e.g.,
opening up more hot fixtures).
You can verify the flow rate by
pressing the info button on the
front of the unit until the arrow
lights up beside “flow.”
•
Check that the filter on the cold
water inlet is clean (page 32).
•
If the unit is in a recirculation
system, the return water
temperature may be too close
to the set point temperature to
activate the water heater. You
can verify the incoming water
temperature by using the INFO
button on the front of the unit.
Simply press the INFO button until
the arrow on the display points
toward IN. Refer to “error code
indicator” in Figure 3 (p. 11).
•
Check that the gas line is open
and is purged of air
•
Are the hot and cold water
connections to the water heater
reversed (hooked up backwards)?
Water flowing in reverse through the
heater will not be detected by the
flow sensor and the water heater
will not operate. See page 33 for
details on checking for a reversed
connection.
•
Check both ends of the clear
hose that runs between the
proportional gas valve and the
combustion chamber. If this hose
is disconnected, the unit may fail
to light.
•
Check for 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. A
malfunctioning or missing
check valve will cause a cross
connection, allowing cold water
to back-feed into the system.
•
If the fan does not initiate at all
and it is verified that there is
power to the unit, the flow sensor
may not be working properly.
Check the flow sensor for proper
impeller functionality. See
“Checking the Flow Sensor,” page
Abnormal sounds come from
the unit.
•
Check the fan for debris.
•
Check for blockages in the
exhaust vent and intake air line.
•
Check for proper gas supply
pressure.
•
Check the rating plate to ensure
that the correct gas type is
applied to the unit.
•
Check the DIP switch settings.
•
Check flame quality.
•
Check vent termination
clearances.
•
If you cannot identify the source
of this issue, contact the technical
service department.
