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Code 391: Flame Rod Failure
1. Ensure that the unit is plugged into
a socket that is properly grounded.
A floating ground can cause this
error.
2. Check that the wire connections are
secure and free of burns or cuts.
Verify that the green ground wire is
installed properly and is making an
electrical connection. This ground
wire is part of the connector to the
PCB. The green wire is secured to
the metal plate to the right of the
surge box.
3. Clean the flame rod. See "Cleaning
the Rod Assembly (Flame Sensor
and Igniter Rod)" on page 33.
Code 441: Flow Sensor Failure
This code is displayed when the
computer doesn't detect a signal from
the flow sensor when the pump is
running or when a heater in the Easy-
Link System is running.
1. If the code appears when the pump
should be operating, then:
•
Inspect the filter on the
return connection and clean
as necessary.
•
Inspect the pump for
any debris in the pump
connections and clean as
needed.
•
If using a crossover valve,
check to make sure the
crossover valve DIP switch
setting is in the ON position
(DIP switch #5, top bank).
2. Disconnect the water heater
from the linked system before
you advance to step 2. The water
heater must be tested as an
individual unit.
3. Ensure that the water supply is
turned on.
4. Check the flow sensor/control valve
wires to see if they are broken or
disconnected.
5. Verify the flow rate using the water
heater's controller. To do so, select
Flow Rate by pushing the INFO
button until the arrow on the left
side of the display points toward
"Flow." Ensure that the controller
displays a flow rate during
operation. If a flow rate is not
indicated, proceed to the next step.
6. Check the inline water filter for
debris.
7. Turn off the gas supply and
electrical power to the heater, then
remove the flow sensor/control
valve (p. 61). Check the flow
sensor as described in "Checking
the Flow Sensor," page 32. Clean
or replace as necessary.
Code 511: Abnormal Main Gas
Valve (MV)
This code indicates a fault in the main
gas valve (MV) circuit.
1. If the hot water is shut off, but
flames are still visible through the
burner sight window, immediately
shut off gas and power to the unit
and contact the technical service
department.
2. Check the wire connections to the
main gas valve for burns or cuts.
3. If the unit was serviced recently
and the gas valve had to be
removed, make sure that each gas
valve wire is fully plugged into the
connector.
4. Verify that the gas supply pressure
is within the specified limits. An
inlet gas pressure that is too high
can jam or damage the main gas
valve.
5. With the power off, check the
On-Demand Water Heater Service Handbook for X3P Models
resistance of the valve. Normal
resistance reading is 1.15-1.65 kΩ.
If the resistance is out of range,
replace the gas valve.
6. Check the voltage across the main
gas valve wires (blue - light blue
#3) during operation. The voltage
reading should be 93-120 VDC. If
the voltage is not within normal
range, replace the computer board.
Code 521: Air Damper Failure
1. Verify the DIP switches are set for
the proper installation altitude.
If adjustment is needed, turn off
power to the heater and adjust.
Then go to step 4 for the error
code reset and test heater. If this
doesn't fix it, go to steps 2-4.
2. Visual inspection of the air damper
for blockage and/or loose fit.
Remove any debris or blockage
that would keep the damper from
rotating.
3. Normal: 3 to 11 VDC between
COM (white) & brown (during
operation) Visual inspection of PCB:
connection/breakage of wires and/
or burn marks on the computer
board.
4. To reset this error code, go to Reset
Procedure, step 10 of 991 error
code on page 24.
Code 551: Abnormal Solenoid
Gas Valve (SV1, SV2, and/or
SV3)
This code indicates a driving circuit
fault for one or more of the solenoid
gas valves (SV1, SV2, or SV3).
1. Check the wire connections to the
gas solenoid valves for burns or
cuts.
2. If the unit was serviced recently
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