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13 Troubleshooting
Table 13E (continued from previous page) Troubleshooting Chart - Fault Messages Displayed on Water Heater
Interface
FAULT DESCRIPTION CORRECTIVE ACTION
Manual Reset
High Limit
(will require a manual
reset once the condition
has been corrected. Press
the RESET button on the
display to reset.)
The outlet water temperature has exceeded
the fixed setting of the manual reset high
limit.
• Verify that the system is full of water and that all air
has been properly purged from the system.
• Verify that the water heater is piped properly into the
heating system. Refer to Section 6 - System Piping
for the proper piping methods for the Shield water
heater.
• Check 120 VAC to water heater pump motor on a call
for heat. If voltage is not present, check wiring back
to the main control board.
• Replace the main control board if necessary.
• If 120 VAC is present on a call for heat and the water
heater pump is not operating, replace the pump.
• Check resistance of water sensors and compare to
Table 13B on page 60 of this manual. Replace
sensor if necessary.
Fan Low
OR
Fan Speed Low
(will require a manual
reset once the condition
has been corrected. Press
the RESET button on the
display to reset.)
The actual fan RPM is 30% lower than what
is being called for.
• Vent/air intake lengths exceed the maximum allowed
lengths. Refer to Section 2 - General Venting for
proper lengths.
• Check for obstruction or blockage in the vent/air
intake pipes or at terminations.
• Check the wiring connections at the fan and at the
main control board.
• Replace the fan.
• Replace the main control board.
Blown fuse.
• Replace fuse F4 on the control board, see page 58
of this manual.
APS
Open
(will require a manual
reset once the condition
has been corrected. Press
the RESET button on the
display to reset.)
Air pressure switch contacts are open.
• Check the wiring connections to switch. Wires
should be connected to the common and normally
closed terminals.
• Air intake lengths exceed the maximum allowed
lengths. Refer to Section 2 - General Venting for
proper lengths.
• Check for obstruction or blockage in the air
intake pipes or at terminations.
• Check reference hoses connected to the air pressure
switch for blockage or obstruction.
• Inspect the burner. Reference page 56 of this
manual for removal and cleaning procedures.
Replace if necessary.
• Inspect the heat exchanger. Reference page 57 of
this manual for removal and cleaning procedures.
Replace if necessary.
• Faulty air pressure switch. Replace switch.
Installation & Service Manual
TM