HVAC Code Lookup

Rheem Furnace Code 33

Safety fault

Over-temperature switch (roll-out) open. A manually reset rollout limit has tripped, which means flames rolled out of the heat exchanger into the burner compartment. The manual describes this as a very serious problem that must be repaired before the furnace runs again.

Manual wording: “OVER-TEMPERATURE SWITCH (ROLL-OUT) OPEN ... 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.”

Documented for: (-)97V, (-)96V, (-)801S/(-)801P

Likely causes, most common first

  1. Insufficient venting through either the inlet or exhaust
  2. Loose or faulty wiring
  3. Unstable flame pattern

What you can safely check yourself

  • Turn the furnace off at its switch and leave it off.
  • If you smell gas or see soot, leave the building and call your gas utility from outside.

When to call a technician

Call a technician. Rollout means combustion products left the heat exchanger; the vent system, inducer, gaskets and heat exchanger all have to be inspected. Never push the rollout reset button and put the furnace back in service without a diagnosis.

A Rheem furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.

Sources

Other Rheem codes