Rheem 96P series Installation Instructions Manual page 93

TABLE 20 (continued)
90P 2 STAGE FAULT CODES WITH DESCRIPTIONS AND SOLUTIONS
STATUS: This is a critical fault. The furnace will not operate in gas heat or any other modes.
DESCRIPTION: This fault code is an indication that line voltage and neutral are reversed to the furnace control or may also be
an indication of a grounding issue. No operation is not allowed to proceed until the problem is corrected.
EXPECTED OPERATION: No heating or cooling operation will take place.
CAUSE:
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(1) Line and neutral to the furnace have been interchanged at the furnace.
(2) Line voltage and neutral have been interchanged at the disconnect or at the breaker box.
(3) Furnace control cannot properly sense ground.
SOLUTION:
(1) Check voltage with meter and reverse line and neutral if necessary.
(2) Check voltage with meter and reverse line and neutral if necessary.
(3) Check ground wire inside furnace cabinet is attached to sheet metal, verify ground to furnace cabinet and at breaker box.
STATUS: This is a critical fault. The furnace will not operate in gas heat modes but all other modes (e.g. cooling) should
function.
DESCRIPTION: The Manually Reset Limit Control (M.R.L.C.) is also known by the name "Rollout Limit". There can be several
on any given furnace. When one or more of these limits open, they must be manually pushed back to the closed position (hence
the name; Manually Reset) to force the acknowledgement of a critical fault. This fault will occur when flames have rolled out of
the normal area in the heat exchanger and into the burner compartment. This fault should rarely (if ever) be seen in the field and
indicates a very serious problem that must be repaired before furnace operation can continue.
EXPECTED OPERATION: When the MRLC (Manually Reset Limit Control) circuit has been opened, the IBM (Indoor Blower
Motor) is energized at maximum heating speed. The gas valve circuit is de-energized (if it was energized) and the IDM (Induced
Draft Motor) is energized at high speed. Response to thermostat cooling calls will take place as normal with IBM energizing at
the higher of the two blower speeds (high heat or cool) when a call for cooling is also present. When the fault is cleared, the IDM
will remain energized for a 20 second post-purge and the IBM will remain energized for the user-selected blower off-delay
period.
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CAUSE:
(1) Insufficient venting through either the inlet or exhaust.
(2) Loose or faulty wiring.
(3) Unstable flame pattern.
SOLUTION:
(1) Check that the pressure switch(es) have not been welded closed or bypassed. Check that the inducer is operating at the
proper rpm. Insure that the venting does not exceed the maximum specified lengths. Check for obstructions in combustion
venting. Check that all gaskets between the inducer and center panel / heat exchanger are properly installed and sealed.
(2) Check wiring and connections. Replace and/or repair as necessary.
(3) Check that all burner assembly components are properly installed. Check that all seals between the burner and blower
compartments are tight. Insure that the door seals are in place and that the burner door is properly installed and does not leak.
Check to make sure that the heat exchanger has not been damaged; i.e.: crushed tubes, breached collector box and etc.
LINE AND NEUTRAL REVERSED OR POOR GROUND
OVER-TEMPERATURE SWITCH (ROLL-OUT) OPEN
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