I have an older natural gas furnace that has a manifold and 4 burners. I clean & inspect it myself every year. This fall I removed & cleaned each burner as usual. I'm now experiencing something I don't see in any of the troubleshooting articles....occasionally a burner or sometimes 2 burners will have a flame inside the burner as well as on the top (where it is supposed to be). This abnormal flame causes a noticeable increase in the sound that the furnace makes. Sometimes it makes a popping sound for a few minutes. This flame stays there for as long as 5 minutes then always goes out and burns just fine....have you ever experienced this? What would you suggest? My inclination is that maybe I misaligned the burners when I put them back in, but I fail to see how this could cause the phenomenon. Do I need to reclean and try again?

Remove the cover over the burners so an inspection of the heat exchanger is a bit easier. Take an LED flashlight and a small telescoping mirror and inspect the heat exchangers front section above the burners giving special attention to the two sections of the chamber on either side of the pilot light. Many times there will be a hole in the chamber or a crack that will allow the blower that circulates the air into the duct blow out the pilot light.

If you are handy enough, consider turning off the gas and remove the ribbon burners prior to performing your inspection. The pilot assembly is probably attached to one of the burners. Lay them on the floor in the order in which they install in the furnace as some furnaces have dedicated left and right end burners and most older standing pilot furnaces have the one burner with the pilot mounting bracket.

To remove, many times you gently pull backwards towards the gas manifold while raising up on the front of the burners. Once elevated enough, the burner then slips off the brass spud (orifice) and forward and out.

The next reason the pilot can go out is because the safety 'holding' coil in the gas valve is defective. Its responsibility is to hold open electrically a safety circuit proving the pilot gas is burning so that main gas can flow. The thermocouple generates just enough electricity to hold the safety coil open. Coil bad = pilot out.

If your furnace is over 25 years old, there is a good chance there is a hole or crack.

If the burners are inshot burners (look like little jets), Shut the furnace and gas off. Take a 5/16 nutdriver and remove the four screws that hold the gas manifold and the gas orifice's. This should pull back, and each of the inshot burners will also have the same size screws...one per burner. Remove each burner individually and look @ the front of the burners where the "wings" are. With a flat head screwdriver, slightly open the wings which act as flame runners. This will allow the gas to run across evenly so the flame will hit each burner and not build up gas and blow like you are experiencing. Reassemble and run test with gas & power on. Good luck

Hello, A roll out is a switch that senses the temp near the burners. If the the flame pattern in the burners is abnormal that roll out switch will open and turn off the furnace for safety. You can try cleaning the burners yourself and see if that will fix the problem, make sure you turn off the power and gas to the Furnace when working on it. However, if that does not fix the problem Iw ould call a HVAC technician to inspect the furnace, sometimes it could be low combustion air or a problem with the gas input to the burners.

First of all try cleaning all the components inside the burner assembly, including the ignitor and the flame sensor.Try cleaning flame sensor well with steel wool or sandpaper. after cleaning check out.if the problem is same then, check out whether the manual gas shut-off valve is on and not off, and the gas lines leading up to and inside the unit all seem unmoved and undamaged. If everything is proper then remove cover from burner compartment and re-try. If ignition is successful, check for leaky ignitor gasket, or look CLOSELY for webbing inside far-right burner. It can also be caused if there is low gas presure, or a bad gas valve. That has to be checked.
To remove and replace/check the burner .follow this instructions

(These instructions apply to an upflow installation. Turn 90* in appropriate direction for horizontal orientation. Only perform these steps if you are sufficiently qualified.) Turn off power & gas supply, loosen nearest union BETWEEN gas **** & furnace. Remove wires from gas control, noting where each one belongs. Remove cover from burner enclosure & remove 2 screws securing manifold to enclosure. Lift upward/outward to disengage manifold from enclosure & carefully move aside. Remove screws securing burner set, remove burners. Inspect burners for debris in passage and runner slots. Check manifold orifices for blockage (ants?), particularly the one facing burner nearest to ignitor. If debris is present inside burner enclosure, CAREFULLY remove with vacuum cleaner. AVOID ANY CONTACT WITH IGNITOR. Re-install burner set and manifold, assuring that manifold brackets engage correctly in slots AND all orifices engage fully into burner entrance, replace manifold screws. Reconnect wires to gas control, reconnect gas supply & turn gas on. Apply liquid soap to union, check for bubbles (indicates leakage - correct before proceeding). Re-install cover on burner enclosure. Turn on power supply and check unit operation. Pay particular attention when re-installing manifold to assure proper alignment of orifices into burners.
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The way it lights is that the gas is spread from one burner to the next by either a flame tray or small holes drilled in the burner tubes. If the flame does not get all the way across the burner tubes within a few seconds, the unit goes out on failure. Clean and inspect each burner tube, not just the orifice. Clean any tray that connects the burners. You can use a small wire brush or tooth brush but be careful near the glow igniter as it is very fragile.

You may have a dirty/rusty burner that is clogged or your gas valve
manifold pressure setting may be too low. Normal manifold pressure
is 3.5 inches water column on natural gas furnaces. ( 1 psig is equivalent to 28 inches water column). Pull and clean burner. Also
check and clean pilot assy. including flame sensor (if present).
Please let me know.

the orifice that comes with the unit has a starter hole only needs to be drilled out, in the instructions is a chart for altitude de-rating.

I have had problems like this before. Most of the time it is the connection between the burners. There are small slots that the gas runs thru to lite. Clean those with a brush and then try it. Rus

A few years back I helped a neighbor with this same problem in a forced air, gas fired, "horizontal" furnace in his attic.

After having him cycle the thermostat a couple dozen times while I watched through the opening in the side of the furnace, I finally figured out what was happening.

First, there were about 6 cast iron burners [about 14 inches long with two rows of gas holes along the length]. These burners were parallel to each other and oriented perpendicular to the long axis of the furnace.

The gas was fed to the ends of the burners with a pipe manifold. The standing pilot light was at the center between burners 3 and 4. Due to the spacing distance between the burners, the pilot light was too far from even burners 3 and 4, the flame could not "jump" to ignite them, or any of the other burners. The manufacturer had installed a thin sheet metal "tent" which ran from the gas entrance end of burner 1 to burner 6, and was about 2 inches above the burner, AND the pilot light.

The standing pilot was on all the time. When the gas control valve turned on, gas began to come out of all the burners at the same time. Naturally it came out of the gas supply manifold ends of all the burners.

The "tent" captured that gas coming from the burners and "filled" up to over the pilot light which ignited the gas at that point, and the flame would propagate along the tent to ignite the gas coming out of all of the burners.

In my neighbors case, the tent had somehow become dislodged so that it did not cover all of the burner ends. For those burners which it did cover [including the pilot light] it caused the burners to light properly.

For those burners who's ends were not covered, and who's gas could not be captured, they would NOT ignite simultaneously with the others.

As these burners WERE feeding gas into the combustion chamber, the gas "envelope" would spread until it reached the nearest flame ignition source, at which time the entire "bubble" of gas would ignite with a minor boom [actually a low energy explosion]. Flame would momentarily shoot out of the burner chamber opening, and from that point the furnace would operate normally until the next restart cycle.

Although there could be several causes, I suspect that the symptoms you describe are the result of DELAYED IGNITION of some or all of the main burners.

IF this is the problem, then the solution is to clean all the burners [including the burner outlet holes in the ignition ends of the burners], clean out the burner compartment, AND properly adjust the orientation of whatever system [you have to evaluate how it works from analysis of YOUR furnace] your furnace has to ensure all burners ignite as close to the same time as possible.

When operating properly, the ignition should be a smooth transition, burner by burner, from the pilot to the farthest burners. In other words. the ignition will "flow" from the pilot outward to each adjacent burner until the farthermost ends ignite last. This usually doesn't take more than one or two seconds at the most.

Unless you are an experienced handyman, and understand this analysis and instructions, I strongly suggest that you engage the services of a professional furnace technician.

Take the orfice out and clean it sounds like something in it