Hot air out the side

Both. It is exhaust, but the heat is wasted. RV furnace efficiency is still very low, not likely toget much better unless we are willing to pay a lot more and give up a lot of space to much larger heat exchangers and ducting to handle larger volumes of lower temperature air.

It's the combustion air. Full of CO! Yeah it would be nice if RV furnaces were just a little more efficient wouldn't it?

I don't think it's wasted at all. On a cool morning, I love to sit outside with my coffee and enjoy the warm air that the vent puts out. Kind of like a clean campfire.

It's water vapor and deadly carbon monoxide...resulting from the combustion of propane.

A typical 40 k input furnace has an output of only 30 k. That means that 25% of heat
is going outside. Such is life

I would also think it's full of water vapor.

RV furnaces are running about 80% efficient. Check your stand home non high efficient furnace and they sent just as much heat up the chimney. Your RV furnace are not the BTU or have the blower motor size of the average small home so they don't heat as well. Most RV furnaces are around 35,000 and to heat real good should be up around 60,000 for most RVs 34' and longer.

TucsonJim wrote:
I don't think it's wasted at all. On a cool morning, I love to sit outside with my coffee and enjoy the warm air that the vent puts out. Kind of like a clean campfire.

IF you call breathing CO gas "clean". There are several deaths per year from camping too near neighbors furnace exhause and contaminating the air inside a neighbors RV. Happens most often at events like NASCAR events or DRAGS where RVs are parked very close together. Please don't think of it as "clean" anything.

I wish they could redirect that exhaust to the tubes and tanks that are exposed to the cold. You'd think they could wrap the exhaust tube around important stuff and have it go out somewhere else. I doubt I'm the first person to think this and I'm sure there's a perfectly good reason why it's like it is.

Hi Ed,

It is waste heat, and combustion by products. Such things are often corrosive. I would not want a leak in a pipe which was intended to attempt to keep the battery box a bit warmer.

It, to me, is surprising that they are 80% efficient. Like any hydrocarbon, propane when completely burned produces carbon dioxide and water; these are not too bad, although you could use up enough oxygen and produce enough carbon dioxide to suffocate anyone in the building. Complete combustion never happens in the real world, and so you end up with partial combustion products of which the worst is carbon monoxide, which combines readily with the hemoglobin in the blood, displacing oxygen and suffocating the victim.

When I have enough shore power I can heat totally electrically down to -27 C (-16.6 f).