Rheem 96P series Installation Instructions Manual page 90

TABLE 20 (continued)
90P 2 STAGE FAULT CODES WITH DESCRIPTIONS AND SOLUTIONS
STATUS: Up to three failed ignitions will not constitute a critical condition. Critical condition (with no heating operation) is only
noted when the furnace has failed to ignite four or more times consecutively. After four failed ignition attempts, the IFC enters
one-hour lockout and the dual faults "11" and "10" are alternately displayed at the IFC's seven-segment display.
DESCRIPTION: This fault is displayed at the furnace control after the first failed ignition attempt. It continues to be displayed
until successful ignition or the furnace control has failed to ignite four consecutive times. After four attempts, the status of the
fault is elevated to "10" and the furnace control (or I.F.C.) reacts as described under description for the fault code "10".
Note: This fault will not be displayed to the homeowner on communicating systems unless it occurs at least three times within a
single heat call. It will not be displayed to the homeowner after the first or even second failure. However, it will be displayed in
the active fault screen of thermostat immediately after the first failure (and all subsequent failures) during a single heat call.
Further, this fault (11) will only be logged into the fault buffer one time. It will not log more than once in the buffer.
EXPECTED OPERATION: After the first failed ignition attempt, the fault ("11") is displayed and the inducer will complete a 20
second post-purge followed by a second ignition attempt. This cycle will be repeated until gas heat is established or until the
fourth failed ignition attempt. After the fourth failed attempt, the furnace control (IFC) will proceed to one-hour lockout.
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CAUSE: There can be several causes for a failed ignition attempt(s). The most common are:
(1) The flame sense rod is unable to sense flame. It may need cleaning or may not be properly connected.
(2) The gas valve may be turned off.
(3) The igniter is not working properly. It may not be properly connected or the spark location may not be correct.
(4) The furnace control may not be working properly and may need to be replaced.
(5) The flame may not be properly spreading from the first burner to the last.
SOLUTION: The solution will depend on the cause. Solutions to noted causes (1) through (5) above are:
(1) Clean or replace the flame sense rod or check all connections and wire between the rod and the furnace control (or I.F.C.).
Make sure furnace ground is properly connected.
(2) Turn the valve on.
(3) Replace or reposition the igniter or check all connections and wire between the igniter and the furnace control (or I.F.C.).
(4) Replace the furnace control.
(5) Check the manifold pressure during ignition. For natural gas it should be approx. 3.5" w.c. and for LP gas it should be
approx. 10" w.c.. If manifold pressure is good, watch the burner during ignition. If the first burner lights, but the second, third
and so on do not light, the burner may need to be replaced.
STATUS: The status of this fault is non-critical and furnace operation will continue as normal in heating (and all other) mode(s).
If flame sense is low, the furnace control (or I.F.C.) may soon no longer be able to properly sense the flame and status of the
problem may be elevated to the level of fault code "13" or fault "11" (if flame can not be sensed at all).
DESCRIPTION: The flame sense current from the flame sense rod at the furnace control (or I.F.C.) is weak or marginal at best.
EXPECTED OPERATION: All operation (including gas heat) will proceed as normal with only the fault code ("12") displayed at
the furnace control (I.F.C.) and "LO FLAME SENSE" displayed in the fault area of a communicating thermostat.
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CAUSE:
(1) The most common cause for low flame sense during heat operation is that the flame sense rod may need cleaning or may
not be properly connected or wiring between the rod and the furnace control may be shorted or opened.
(2) Another cause for low flame may be an improperly mounted or poorly grounded flame sensor.
SOLUTION:
(1) Clean or replace the flame sense rod or check all connections and wire between the rod and the furnace control (or I.F.C.).
(2) Reinstall or replace flame sensor and check wiring and connections. Also make sure the furnace is properly grounded.
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FAILED IGNITION
LOW FLAME SENSE