Furnace Flame Rollout: What It Means on Your Home Inspection Report

In a gas furnace, the burners fire into the heat exchanger, and a small fan, the inducer motor, draws the exhaust gases away from inside the heat exchanger, as Goodman explains. Flame rollout is what it sounds like: flames rolling out of the burner area instead of being drawn into the heat exchanger. Rheem's instructions describe the flame rollout switch as the part that checks that the burner flames are drawn into the heat exchanger tubes, and opens if they aren't.

The switch is a heat-sensing, manual-reset control on the burner box. When it opens, it shuts off the gas to the burners, so the furnace stops heating; on some models the blower keeps running. Your report may say the switch had tripped or been bypassed, or describe scorching or soot around the burners. A trip means the switch did its job; either way, the question is why.

Why It Matters

The hazard is fire. In a 2002 safety release, the CPSC said that all gas-fired furnaces made since 1987 have flame rollout protection "that prevents flames from spilling out of the furnace's combustion chamber and starting a fire."

Some causes are carbon monoxide problems too. The makers' manuals name these:

• Blocked or restricted venting. Rheem says the rollout switch opens if the furnace runs with blocked or restricted venting. Carrier lists a restricted flue gas passageway, inadequate combustion air, and component failure.
• Burner and gas problems. Goodman's service manual lists flame impingement, an orifice plate out of position, over-firing, improper orifices, and improper gas pressure.
• A leaking heat exchanger. Goodman also lists air leaking around the heat exchanger into the burner compartment, or through the heat exchanger itself (see cracked heat exchanger).

Blocked vents and leaking heat exchangers are the same faults that can send exhaust into the house, and the CPSC calls carbon monoxide "a deadly, colorless, odorless, poisonous gas." Soot is a warning in its own right: Payne's owner's manual puts soot at the burners under a carbon monoxide poisoning hazard warning and says, "Do not operate your furnace."

What makes it more urgent: a CO alarm that sounds, or anyone with headaches, dizziness, nausea, fatigue, or shortness of breath (get everyone outside and call 911; see CO alarm going off); a switch that trips again after a reset, or one that's been jumpered or bypassed, which Rheem says defeats its function; heavy soot; or burner flames that aren't clear blue, which Payne says is a reason to call your dealer.

What to Do Before Closing

• Ask the inspector what they found: a tripped switch, scorching, or soot, where, and whether the furnace ran. Ask for photos.
• Don't reset it yourself. It's the seller's furnace, and the fault behind it hasn't been found.
• Have a licensed HVAC contractor find the cause and put it in writing: venting, combustion air, burners, gas pressure, and the heat exchanger. Goodman's service manual is blunt: if a rollout switch has tripped, "it is important to find out why."
• Talk to your real estate agent about asking the seller to repair it or offer a credit within your inspection contingency. The scope depends on the cause, from a vent fix to a heat exchanger or furnace replacement.

What to Do After You Move In

If it wasn't resolved before closing, have the contractor correct the cause before you rely on the furnace. If the switch itself needs replacing, Rheem says to use only factory-approved parts.

Resetting. The makers' instructions differ. Payne's lets the owner push the reset button once and says, "If it trips again, shut down the furnace and call for service." Rheem's 2004 instructions include a similar troubleshooting reset followed by a call to a qualified serviceman, but also say not to reset the switch "without identifying and correcting the fault condition which caused the switch to trip," and Carrier's 2000 instructions say to correct the combustion air, component, or flue problem first. With a rollout already on your report, leave the reset to the technician. Never jumper or bypass the switch: Carrier says "DO NOT bypass the switch," and Rheem says not to install a jumper wire across it.

• Put CO alarms on every level and outside sleeping areas, as the CPSC recommends; see our CO alarm guide.
• Book a yearly inspection. The CPSC says to have the heating system, including chimneys and vents, inspected and serviced every year by a trained service technician.

Can You Fix It Yourself?

No. Finding the cause means working on burners, gas pressure, venting, and the heat exchanger. Payne's manual says only trained and qualified personnel should repair or service heating equipment, and the CPSC warns never to service combustion appliances without the proper knowledge, skills, and tools. What you can do, per Payne: keep the air openings on the furnace and in the furnace room unblocked, and check the outside vent pipe for blockage.

Frequently Asked Questions

Can I reset a furnace rollout switch?

If the inspector found a trip or scorching, let an HVAC contractor reset it after finding the cause. A trip always has a cause, and Carrier's instructions and Rheem's venting section say to correct it before resetting. Some owner's manuals, like Payne's, allow one owner reset and say to call for service if it trips again.

What causes flame rollout?

The manuals list blocked or restricted venting, inadequate combustion air, burner, orifice, or gas pressure problems, over-firing, and air leaking through or around the heat exchanger. Only a technician can tell which.

Is flame rollout a deal breaker?

It depends on the cause, so get the contractor's written diagnosis before your contingency ends. If the cause is the heat exchanger, note that Trane calls heat exchanger replacement one of the most expensive furnace repairs.

The Bottom Line

The rollout switch shuts the burners off when flames escape the burner area, a fire hazard, and some of the faults that trip it, like a blocked vent or a leaking heat exchanger, can also send carbon monoxide into the house. Don't reset or bypass it; have a licensed HVAC contractor find and fix the cause, and put CO alarms on every level. See more findings in our inspection report decoder.

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