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Code 721: False Flame
Detec on
A false flame was detected by the
system during start up. No flames
should have been present, so the
system stopped the ignition process.
1. WARNING! Shut off all gas and
power to the unit. Failure to do
so could lead to fire, explosion,
personal injury or death.
2. Inspect the flame sensor to
see if it is dirty. Also, check the
ceramic housing for cracks. Clean
the assembly, if necessary. See
Cleaning the Flame Sensor and
Igniter Rod, p. 33. Contact the
technical service department for
further assistance.
Code 741: Remote Control
Problem
This code indicates a
miscommunication between the
temperature remote controller and
the water heater. This code is not
associated with the built-in controller
for indoor models.
NOTICE:
If you disconnect the remote from
the heater with the power supply
on, this error code will result. Turn
off power before disconnecting the
remote from the heater.
1. Verify that the remote is compatible
with the water heater. Refer to the
remote's instruction sheet and the
heater's installation manual.
2. Verify that only a single remote
is installed. Only one remote
may be used in addition to the
built-in temperature controller.
An incorrect remote or multiple
remotes will result in this error
code.
22
•
On-Demand Water Heater Service Handbook for X3P Models
3. Make sure that all wiring is
connected to the remote controller
properly.
4. Power surges can cause this fault. If
frequent power surges occur, install
adequate surge protection to prevent
nuisance faults.
5. Check the voltage across the wires
coming to the remote. Normal
voltage should be 11-17 VDC. If
within normal range, replace the
remote. If the voltage is out of
range, replace the computer board
(PCB).
Code 751: Temperature
Controller Problem
This code indicates a
miscommunication between the water
heater and the built-in temperature
controller. NOTE: This code is not
associated with the remote controller.
1. Check that all wiring is properly
connected to the built-in
temperature controller.
2. Power surges can cause this fault. If
frequent power surges occur, install
adequate surge protection to prevent
nuisance faults.
3. Check the voltage across the
wires that are connected to the
remote. Normal voltage should
be 11 VDC and 17 VDC. If within
normal range, replace the built-
in temperature controller. If the
voltage is out of range, replace the
computer board (PCB).
Code 761: Communica on Error
in Easy-Link System
A 761 error code means that the parent
unit in the Easy-Link system has lost
communication with at least one heater.
This code will display on the parent
heater in an Easy-Link system.
To reset the code, either reconnect
the easy-link wires or cycle the parent
heater's power off and then back on.
To address this error, do the following:
1. Inspect the wiring between the
Parent heater and the heater
identified by the code.
2. Verify that the heater in question
has power to the computer board.
•
Make sure the switch above the
computer board is on.
•
Make sure that a fuse or surge
absorber in the fuse box has not
blown.
•
Verify proper supply power to the
water heater in question.
If the error appeared when you
disconnected the easy-link wire to a
heater to troubleshoot, then cycle the
parent heater's power off and then on
to remove this heater from the easy-
link system.
Code 991: Combus on Air and/
or Exhaust Gas Blockage (also
Code 051 and 101)
These codes are related and appear
during different phases of operation.
•
Code 051: This error code will
appear if there are combustion
air and/or exhaust vent issues
during the post purge sequence.
This check occurs once in a 24-
hour time period.
•
Code 101: This error code will
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