Rust on burner box. Serious?


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Old 11-12-14, 01:40 PM
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Rust on burner box. Serious?

I'm not familiar with all the terminology of furnaces, but I call the silver chamber where the burners are located the "burner box". My furnace is 12 years old and I noticed that there's a ring of rust on the top portion of the outside, and even some on the inside if I look through the little window in front. The rust on the outside (I thought it was made of stainless, or rust-free, steel) around a pipe. Here is a picture. Should I be concerned about this? Is there a remedy? I sprayed some oil on the rust part last year thinking it would halt the rusting, but it looks no better now than it did then.

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Old 11-12-14, 03:16 PM
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Yes that's the burner box. I wouldn't expect to see rust there. What's the make and model number of the furnace?
 
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Old 11-13-14, 05:43 AM
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I've most commonly seen this on 2 pipe vent systems. It seems to be caused by a natural draft thru the furnace. Another place I've seen it is on furnaces with A/C when installed in an unconditioned space.
 
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Old 11-13-14, 12:55 PM
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I'm not home right now to check the specifics, but the make is UPG or York. Don't know the model number, but I do know it's a high efficiency type, with condensation pumps.

I've most commonly seen this on 2 pipe vent systems. It seems to be caused by a natural draft thru the furnace. Another place I've seen it is on furnaces with A/C when installed in an unconditioned space.
Mine does have 2 pipes. One brings in air from outside for combustion, and the other vents it back outside. Now, what is this "natural draft" you refer to? Is there a way of avoiding it? Would blocking those pipes that lead outside reduce this draft? Also, I don't have A/C (I'm assuming your mean air conditioner). But the furnace is located in an unconditioned space--my basement.
 
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Old 11-13-14, 02:48 PM
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Yes, by "A/C" I did mean air conditioning.
Please keep in mind, without being able to actually see what's going on, I'm speculating about the natural draft thru the furnace.

I wonder if the incoming air gets cold enough in the winter to cause condensation on the furnace & burner box. Also is the basement cool enough in the summer to cause condensation? If it is a summer occurance, maybe blocking the pipes after the heating season would help. The big downfall to this is remembering to unblock them when the heating season comes.
 
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Old 11-14-14, 11:57 AM
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Yes, by "A/C" I did mean air conditioning.
Please keep in mind, without being able to actually see what's going on, I'm speculating about the natural draft thru the furnace.

I wonder if the incoming air gets cold enough in the winter to cause condensation on the furnace & burner box. Also is the basement cool enough in the summer to cause condensation? If it is a summer occurance, maybe blocking the pipes after the heating season would help. The big downfall to this is remembering to unblock them when the heating season comes.

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I suppose I could open it up after it's been running awhile to see if there's condensation forming where the rust is. The incoming air is pretty cold, coming from outside. The basement is cooler than the rest of the house in the Summer and condensation does form on things down there, but I keep the door to upstairs open in order to let most of the moisture out of the basement (it's an older "trap-door" style door).

If this burner box ends up rusting all the way through, is it a simple thing to replace it? Is it something I should be able to do myself, or something a professional would need to do? Worse yet, is it one of those really expensive type of things (like replacing the transmission on an old car) that signals the need to just get a new furnace? I haven't had any real problems with it up to this point, except for replacing a capacitor last year (which I did myself!) so I'd hate to do a complete replacement.

BTW, this model has an electronic ignition which my Dad thought was a bad idea because he always thought a pilot light would reduce the chances of rust. He may have been proven right.
 
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Old 11-14-14, 04:22 PM
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I always liked a standing pilot for just that reason. You can't even buy a furnace with a standing pilot anymore. I suspect your condensation issue, if that is really the cause of the rust, is a summer thing. Maybe, maybe not. The best I can suggest is check it once in a while, summer & winter. How difficult & expensive it would be to replace the burner box, I don't know. Most are fairly easy & shouldn't be expensive, but it does make me question what the heat exchanger looks like.
 
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Old 11-15-14, 01:25 PM
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I always liked a standing pilot for just that reason. You can't even buy a furnace with a standing pilot anymore. I suspect your condensation issue, if that is really the cause of the rust, is a summer thing. Maybe, maybe not. The best I can suggest is check it once in a while, summer & winter. How difficult & expensive it would be to replace the burner box, I don't know. Most are fairly easy & shouldn't be expensive, but it does make me question what the heat exchanger looks like.
The heat exchanger--is that inside the burner box? Looking in the little window with a flashlight, I can see some rust in there too. Maybe I could take those 4 bolts off the front and remove the front cover and take a picture and post it here. If I can see rust when looking in the window, I shudder at what I might see if I took the whole front cover off. If it's that easy to remove the front cover of the box, it's worth it to see what problems I may have to deal with. I imagine the heat exchanger is a much more expensive thing to replace than just the burner box.
 
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Old 11-15-14, 02:50 PM
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For what it's worth, I would expect the heat exchanger to still be under warranty. Only a service person could tell for sure if the heat exchanger is still intact.
 
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Old 11-16-14, 12:24 PM
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Grady:
It was a bit of a struggle, but I got the front cover off the front of the burner box. The inside wasn't as bad as I had expected. There was what appeared to be some surface rust or corrosion in there, but nothing serious. Here are 2 pictures. One of them shows what it looks like around the pipe from my original photo, except from the inside. I couldn't get very close to it, but it seems that there's less rust around the pipe on the inside than on the outside. Also, I ran the furnace for awhile and checked for condensation in that area while it ran, but there was none, so I have no idea why this ring of rust formed on the outside of the box.

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Old 11-16-14, 06:36 PM
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There's a good possibility it is summer condensation.
 
 

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