Condensation/Temp Control

way2roll wrote:

wallynm wrote:
So please explain why the RV furnace has a hot exhaust vent on the outside. Some RV furnaces also has an antisale switch to keep the furnace from coming on if an obstruction does not allow the combustion gasses from exhausting.

way2roll wrote:

msturtz wrote:

way2roll wrote:

msturtz wrote:

way2roll wrote:
I had a similar issue once in our first class A. A literal waterfall was running down my windshield. A by-product of burning LP is water. So if you have an LP furnace you are not only creating condensation by differing temperatures, you are pumping H20 into the air via your furnace. Showers and cooking exacerbate the issue. The best way I have found to combat this is to open your roof vents and run the vent fans. I know it seems like you will be pulling your heated air out of the coach - and you are - but you will also be pulling out the moisture. A dehumidifier is always helpful as well.

You are technically correct burning propane does create a lot of water vapor, however per code RV furnaces must have an external air intake and external exhaust for combustion. All you get inside the coach is hot dry air. This is not true with small portable heaters. So no running your RV furnace will not put water vapor into the air.

A lot of folks disagree;

http://www.irv2.com/forums/f93/engineering-help-water-from-propane-104216.html

The confusion is coming from the use of ventless heaters. Installed propane heaters are prohibited from venting exhaust gas (including water vapor) inside the coach.

I am not going to get into a pi$$ing match with you over it. If you tell me that RV furnaces are designed to mitigate water vapor induction into the coach when it's well known that burning lp generates 1-2 gals of water per gal of LP - sorry but that's a hard sell. I tend to believe that your LP furnace - vented or not - pumps a good amount of water vapor into the RV. It's certainly not going through any sophisticated air scrubber as you can smell the additives in the LP when it burns. And if you can smell that, it's a good bet you are getting exhaust gasses - not just the heat. LP furnaces are not complicated and the vents are passive. Moving on.

Please explain how my humidity monitor would spike in my coach prepping for a trip in the winter running only the LP furnace and no one was in the coach. Not just condensation, the ambient humidity. Outside humidity 40%, coach almost 70%.

The humidity monitor may be incorrectly reading the humidity near the wall due to the lower ambient temperature, there is also an effect where building materials, clothes, and other porous materials will give off stored humidity as the humidity in the room drops. There is another possibility that could be that your furnace is defective and has a leaking heat exchanger which would be extremely important to correct immediately due to the issue of carbon monoxide poisoning. A properly designed, functioning and installed furnace cannot leak ANY exhaust gas into a coach.