Atwood Furnace - Faint Exhaust Smell

Kevin H · January 17, 2016

I have an Atwood Hydro Flame furnace in my '13 Montana. We've had the rig since new, two years this past October. Just recently I'm noticing a faint exhaust smell inside when the furnace is running. I do NOT smell propane, just the exhaust smell of burnt propane - like a propane fueled forklift. All appears to be working fine, just the smell. My propane detector tests fine and is not alarming.

I looked into the exhaust outlet and it is clean, no evidence of mud daubers or other critters. The boss says she does not smell it. She ordinarily has a pretty sensitive sniffer.

I can smell exhaust pretty good outside when it is running, which I would expect. No windows near the furnace. Wind is pretty calm here.

Furnace is in basement. Mounted upright rather than horizontal.

Any ideas?

Yarome · January 17, 2016

Any ideas?

Are you sure you're not getting a little exhaust intake in from an open roof vent? If there is little to no wind to help dissipate the external exhaust, it "might" be possible that an open vent and window might be causing a cross draw of air flow into your coach, or when the door is opened, it "might" create a little suction in through your roof vent or even your stove top fan exhaust (if vented).

Just spit balling... but if you're taller than the boss... you might be closer to an open roof vent where the exhaust might linger at ceiling level? I would think it would be 'very' obvious and accompanied by light smoke if it was a cracked heat exchanger.

Kirk W · January 17, 2016

We've had the rig since new, two years this past October. Just recently I'm noticing a faint exhaust smell inside when the furnace is running. I do NOT smell propane, just the exhaust smell of burnt propane - like a propane fueled forklift. All appears to be working fine, just the smell.

Part of the question is to define how much odor? Since you have owned the RV for two years I'd guess it is safe to assume that you have used the furnace in the past and didn't notice any odor. There is a noticeable odor the first time or two you use a furnace that has sat all summer, but I suspect that you have experienced that before. But there are still some possibilities that I can think of. If you have both a working CO detector and a working propane detector and neither is alarming you most likely do not have a safety issue. If in doubt, you can test the propane detector by getting a butane lighter and with the valve open but no flame, point it into the opening of the propane detector and it should alarm after a few seconds. Propane detectors do not actually detect propane but actually detect hydrocarbons, such as methane and similar combustibles. If it detects the butane of the lighter it will detect any propane that may leak.

My question is, where are you in the propane bottle supply level? It your propane bottle is nearly empty, it is not unusual for there to be a much higher concentration of the odorant from the propane in the last of the propane and so the smell will get much stronger and sometimes be detectable inside of the RV with nothing wrong. If you are nearing the bottom of the bottle, the first thing that I'd try is switching to a full bottle to see if that changes anything.

If it should prove to be just an excess of odorant, do not be concerned as it won't harm you, just smells bad and the propane detector can't detector don't sense smells.

SCClockDr · January 17, 2016

I have an Atwood Hydro Flame furnace in my '13 Montana. We've had the rig since new, two years this past October. Just recently I'm noticing a faint exhaust smell inside when the furnace is running. I do NOT smell propane, just the exhaust smell of burnt propane - like a propane fueled forklift. All appears to be working fine, just the smell. My propane detector tests fine and is not alarming.

I looked into the exhaust outlet and it is clean, no evidence of mud daubers or other critters. The boss says she does not smell it. She ordinarily has a pretty sensitive sniffer.

I can smell exhaust pretty good outside when it is running, which I would expect. No windows near the furnace. Wind is pretty calm here.

Furnace is in basement. Mounted upright rather than horizontal.

Any ideas?

I would confirm all the outside cover screws are tight. We had an odor last year from our furnace and discovered the screws loose with the upper right one missing. This was causing exhaust to deflect back into the burner area. Glad I caught it before any heat/fire damage.

Kevin H · January 18, 2016

Thanks for the replies. All screws are in and tight. Everything looks good. We had a breeze today. I did not smell anything. I think it is an issue of calm winds and exhaust accumulating close by. Although not right over the furnace opening, the cooktop fan/MW vent is somewhat close. Not going to worry about it unless it gets stronger.

Kirk - you could be onto something with an accumulation of odorant. I have been going through a bit of propane lately. That equates to more frequent tank fills. Perhaps something is up with that too.

Thanks to all for your input. Always a great help