Suburban furnace - yellow flame

[Pat]

This is the "Suburban furnace won't heat" topic, but there is a new issue.? Yesterday I was able to get a new igniter plus igniter and burner door gaskets.? Turned out the no-start problem was the igniter, but now I'm checking the flame for the first time, and it's the dreaded "high yellow."? I have the manual and am reading how to adjust the flame, but could anybody say it in other words or give any suggestions what to do.?

--Later

Back with a modification.  The manual says to clean the burner assembly with a wire brush and blow out any dust, which I did.  I noted a hairline crack that goes over the top half of the tube.  I reassembled the furnace, and for a second there, I thought the flame was blue, but it turned into the big yellow flame.  I'm going to buy a new burner assembly. 

Is there some kind of gas adjustment?  I have to assume that was set correctly.  Since I've never looked at the little flame window before, who knows how long this has been burning yellow.

If this turns out to be a simple replacement of the igniter and burner assembly and gaskets, it sure was an easy task.  Well, not counting the learning curve.  And two 90-mile round trips to Springfield for parts.

Thanks.

--pat

 

[Jim Dick]

Pat,

CRS has struck. Is this a furnace or hot water heater? If it's the hot water heater, try moving the metal cylinder that is on the burner tube a little. Loosen the set screw and slide it one way and then the other. That usually fixes the problem. It's a matter of air/fuel mixture. DO NOT use your hands! I move them with a screw driver. You may not have to move it much at all to make a difference.

 

[Pat]

Jim:  Furnace, as noted in the title.  What might CRS be?

Thanks.

--pat

 

[Jim Dick]

Pat,

CRS=can't remember stuff. There was a discussion on hot water heaters and I couldn't remember who started it.

I'm not familiar enough with furnaces to tell you what might be wrong. If you don't get the answer in the next day or so, let me know and I'll ask the techs at the dealership.

 

[Karl]

Pat,

Don't go out and buy a new burner assembly quite yet; they are almost bullet-proof. First, make sure the gas orifice is clean of any debris. Don't stick anything in the little hole that's any harder than a toothbrush bristle. Suburban furnaces use a small squirrel-cage blower connected to the same motor shaft as the hot air blower to provide combustion air. Make sure nothing is obstructing it (dirt, leaves, insect hives, dead birds) and that it turns freely. Anything that reduces the combusdtion air flow will cause the yellow flame. Couldn't find any mention of an air/fuel mixture control sleeve like there is on the water heater, but if there is you could try opening it up a bit (give the flame more air). Another possibility is that the gas pressure regulator on the main tank or the gas valve on the furnace is not working properly, but I would check the other things first. 

 

[John From Detroit]

Yellow indicates not enough air, clean everything, involved, visually isnpect looking for spider nests and the like, and

Well, I'm sure Bob will tell you prayer never hurts

 

[Pat]

I cleaned the burner assembly today, which is when I discovered the small crack in the tube.  I will also look for the other parts to clean.  Another thing I want to try is to use the onboard propane.  I'm using an auxiliary tank, which is easier to fill.  Maybe the auxiliary doesn't have a proper pressure regulator. 

If I get this flame down to the little blue that it's supposed to have I will be SO pleased to have fixed this thing myself.  Then I'll know how to maintain it within reason.

I have been looking for bugs, birds, mice, etc.  'Course, I'm not overly fond of bugs, so I don't mind in the least if they're vaporizing in that wild yellow flame.

--pat

 

[Jim Dick]

Pat,

I was called into work today (Yeaaah) and I asked one of the techs if there was an air/fuel adjustment on a furnace. He said no and a yellow flame is usually rust debri. If you have a crack in the assembly that might be the problem.

 

[Pat]

Jim:  Thanks for that info on the rust debris.  It's quite helpful.  There is a thin coating of rust around the inside of the burn chamber that I have been cleaning, but I will work at it some more.  Is there some cleaner that removes rust?  This box is a little difficult to wire brush inside.

--pat

 

[Karl]

Pat,

There is an easy (not fast) way to remove rust - use a product like CLR or some other bathroom cleaner that says it removes rust from tubs or sinks. They contain hydrochloric acid which will remove it, but it's very dilute and may take several applications to work completely. An old toothbrush will help. When done, rinse several times with plain water and dry thoroughly.
 

 

[Gary RV_Wizard]

You don't need to make the burner tube bright and shiny - just remove any loose scale and get the debris out.

 

[Lee Pilon]

A crack in the heat exchanger can also cause a yellow flame.  Be certain to check for Carbon Monoxide.  Carbon monoxide is ordorless, colorless and deadly. 

 

[Pat]

I got the burner tube fairly clean, but I'll use my new bottle of CLR bathroom cleaner and on the rust.  Rinse well.  I think I'll replace the cracked burner tube.  Probably a manufacturing defect.  I should contact Suburban to ask how serious it is and how frequently this happens. 

--pat

 

[Pat]

Karl:  The gas pressure regulator (assuming there is one) on my auxiliary LP tank seems to have been the cause of the yellow flame.  After I used CLR to clean the last of the rust out and  replaced the burner assembly (I just wasn't comfortable with the cracked one), I turned on the auxiliary tank.  This is a 7 gallon tank I carry around.  CampingWorld installed a Y valve next to my main tank, and I hook up a hose to the Y valve under the RV with the other end to the auxiliary tank.  Then when I need more LP, all I have to do is unscrew the hose and take the aux tank in the car for a refill. 

I got yellow flame with the aux tank, so I turned it off and turned on the onboard 19 gallon tank.  It worked fine, except the igniter was giving off yellow flame.  It probably has some coating on it from being new that will burn off. 

So now I'm wondering if there's a regulator I can put on the aux tank to, uh, regulate it. 

--pat

 

[Pat]

Fired up my furnace this morning to check the flame, and I got lovely blue dots. 

I'm going to try it one more time, but I think my auxiliary LP tank needs a regulator or something.  The furnace burned big yellow flames when I had the aux. tank hooked up.  The flames are fine on the internal tank, but I have to unhook and drive someplace for refills, so I prefer to use the aux tank.  Anybody know of a regulator for it?  Or is it a bad gas supply?  Somebody suggested the LP in the aux tank might contain air.

--pat