Sources of humidity

[tinglett]

Last time we dry camped in the cold we had a lot of condensation issues that I expected. No big deal, but this led me to wonder about how RV furnaces work so....I have a dumb question. Do RV furnaces typically produce humidity in the rig? I was thinking no.

Obviously people produce humidity from our breath, we get humidity from the shower, from steam from cooking, and from the stove cooktop/oven burning propane. But I would think the furnace, absorption fridge, and water heater would all be designed to burn outside air and return the exhaust (including water vapor) to the outside. I doubt these are hermetically sealed, but I'd think that would be the design point.

Just asking in case my world view is totally off .

[creativepart]

The product of combustion contains gases that are not healthy for humans. So, yes, the propane appliances - hot water heater, floor heater and RV gas absorbtion fridge are vented outside. Your propane stove and oven, if you have one, are not.

The condensation you see inside your RV is simply from the poorly insulated walls of the RV. The air in an RV is at least as humid as the outside air and probably more so due to the people breathing inside. When the walls of RV are colder than the dew point the humidity in the air falls out and collects as water droplets on all cold surfaces.

It's just like a the water condensation you'll find on a cold glass of water, soda or beer. Or your bathroom mirror after a shower.

[tinglett]

Ok, that's good to confirm. We use our stove pretty heavily and crack a window for some air, but I wouldn't think to do this for the furnace. I know we have a CO/gas detector, but I'm not sure if it detects low oxygen. Bad to learn that the hard way!

I'll just mop up the condensation best we can. If it's super cold, I'd rather do that instead of heating the outside. But I do run the fan on low while cooking and showering even if it is cold.

[Markgel]

What if you run a/c for a while won't that de-humidify interior somewhat?

[creativepart]

Originally Posted by Markgel

What if you run a/c for a while won't that de-humidify interior somewhat?

Running a heat pump A/C will both heat and dehumidify at the same time. But in weather cold enough to run the heater I doubt folks would want to run the A/C. Burrrrrr.

[Elkman]

A product of a propane stove is water that is released into the air. I bought a small electric dehumidifier for the RV for $80 and it removes a surprising amount of water from the air inside. Need shorepower of course but it gets the job done. First had bought a larger one for my house and after 60 minutes there were 2 quarts of water in its holding tank.

Moisture is going to cause far more problems with organic materials and do plastic or synthetic material draps and coverings are far less likely to develop mold. Important to keep surfaces clean of dirt as well so as not to provide a media for the mold spores.

[Wyatt]

Originally Posted by creativepart

Running a heat pump A/C will both heat and dehumidify at the same time. But in weather cold enough to run the heater I doubt folks would want to run the A/C. Burrrrrr.

Not only that, but running an A/C unit in temps less than ~65 degrees, (depends on your model), will hurt the unit, and it can freeze up.

[Phil G.]

Originally Posted by creativepart

The product of combustion contains gases that are not healthy for humans. So, yes, the propane appliances - hot water heater, floor heater and RV gas absorbtion fridge are vented outside. Your propane stove and oven, if you have one, are not.

The condensation you see inside your RV is simply from the poorly insulated walls of the RV. The air in an RV is at least as humid as the outside air and probably more so due to the people breathing inside. When the walls of RV are colder than the dew point the humidity in the air falls out and collects as water droplets on all cold surfaces.

It's just like a the water condensation you'll find on a cold glass of water, soda or beer. Or your bathroom mirror after a shower.

That brings a question to mind:

Our 2005 Itasca Class C has an outlet in the coach wall (to the outside) above the cooktop burners. There is also a fan above the cooktop, plus an outlet at the back of cooktop that has hot air from the oven (below the cooktop), or the oven burner, coming out of it whenever we use the oven.

If I turn on the fan above the cooktop air is drawn out above the cooktop (and/or any hot air rising from the oven if it's being used) and expelled out the outlet in the coach wall to the outside.

This means that the propane cooktop and oven do not add moisture to the inside air if I have the cooktop fan running. Aren't all motorhome galley areas set up this way?