A033_F: Roll-Out Switch Alarm
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 physically reset back to the closed position (hence the name; Manually Reset) to force the acknowledgement of a critical fault. This fault will occur when flames or higher than expected heat has rolled out of the normal area in the heat exchanger and into the burner compartment. This fault indicates a very serious problem either in the heat exchanger or flue that must be repaired before furnace operation can continue.
Expected Operation
If an open roll-out limit is sensed during a heat call or post-purge, the furnace control will immediately de-energize the igniter and gas valve (if energized), and energize the inducer and indoor blower at the highest heat speed. Alarm “A033_F Roll-Out Switch Alarm” will be declared. These conditions will remain until the limit control resets.
Once the roll-out limit resets, alarm "A033_F Roll-Out Switch Alarm" is cleared. The inducer does a post-purge of 10 seconds and the blower runs through a user-defined blower off delay. Once the blower off delay is completed, the control returns to normal operation.
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.
