All for nothing?

[truxpin]

So I had this idea.........

Once the "cold" sets in, here in Central Kansas, in an effort to heel the use of propane we were wanting to use electric heat and circulate with the furnace fan . Currently we are using the heat pumps on the Dometic A/C units, which suffice during the day, but will soon struggle in the evenings.
I spent the morning outside with my meter and finally figured out how to keep the fan motor running without the burner firing up. Then it dawned on me......

This heating system in our rig doesn't use return air. It simply pulls in fresh air from outside, heats it, and send it on in. Running the fan without the burner in the winter simply turns the furnace into a " cold air machine"

Unless I'm missing something ? Can someone confirm I'm on the right track here?

If nothing else, I have a bunch of clean electrical contacts and a spider web free heater access area!

[truxpin]

Apparently, (after further research here in the forums) there is "return air". Makes me wonder where it's pulling it from however. One would assume from the opening in the bottom of the cabinet below the stovetop. What made me think we were using fresh air to heat with was that I cannot feel any "pull" of air from this area while the fan is running. When I disable the burner and run the fan only, it really feels pretty chilly ( like it's pulling air in from outside) Maybe I'll have to do some further investigating......

[Aage]

It's my belief that the two vents on the outside of your TT where the furnace is are only to do with the intake and exhaust for the combustion section of your furnace. Cold air is not taken in and pumped into the cabin; it supplies O2 so the LP gas can burn, and provides an exit for the furnace's exhaust.

Did you really look into LP gas and electricity costs in your area? I would have thought that the gas would be less money over a cold winter than electricity, but I didn't do the numbers either.

[eubank]

Todd, I don't know how cold it gets in southern Kansas, but if it gets really cold, then turn on that propane furnace. The problem is that while machines like heat pumps and small electric heaters do a fine job of heating the interior of the rig, they do not provide any heat at all down to the tanks and associated piping. Indeed, there's an inverse effect: The electric heaters also heat up the thermostat that runs the propane furnace, so even if the propane furnace is set to provide some heat, it'll incorrectly think that there's enough heat and fail to turn on.

Lynn

[mandolindave]

I'm pulling from my experiences in an effort to help you come up with a game plan.

#1 Thirty some odd years ago ( dunno if economics have changed ) When my High School went on break for ten days, they left the heat on. It was cheaper for the boilers to maintain 70 degree temps than to warm up a freezing building.

#2 I have an 1500 watt oil filled electric radiator that heats up an 18X22 room with a 16 foot ceiling. It takes all day to heat it up though. I used a fan to circulate. Fantastic fan has a table top model that uses very little 12 volt power.

#3 I use a wood stove to heat my basement. My friend has a gas furnace in his basement. Both of our pipes in our basements were freezing. He solved his problem by installing an air supply to his furnace. I stopped using the wood stove to stop my pipes from freezing. The problem was that cold air was being sucked in from cracks to displace the hot air that was going up our chimneys. ( yeah I know that Airstreams are pretty air tight )

#4 Electric heat is very efficient ( maybe not cheap ) because most of the heat remains in the area, and no heat is going up the chimney.

#5 Many of the folks from this forum that winter in trailers, put an insulated skirt around the bottom of their trailers, and use incandescent light bulbs to heat their "basement ". Some get a few big propane tanks.

Don't know if this helps your particular situation, and I realize it is somewhat random information

[idroba]

The propane furnace only recirculates air from the trailer and pushes it out the heat vents. It does not take outside air and heat it. You cannot feel the air move into the furnace, but it is happening.

The combustion air for the burner itself is taken directly from outside, burned with propane, and then exhausted back to the outside. There is no mixture of inside and outside air.

I doubt that trying to circulate air with the furnace fan will increase your comfort any in your Airstream. It will probably just feel drafty, even though it is not bringing outside air into the trailer. It will circulate the colder air near the floor only, and that is why it will feel drafty.

[Pitou49]

If the water tank is heated with forced air. Circulating the air with the furnace fan, will push the cold air around fresh water tank in the trailer.

[carl2591]

I believe a RV furnace system is much like a home system. If the fan is running it is moving the air inside the RV around the tanks be it cold or heated.. If the temp outside is in the low teens you might need to "run" the furnace with heat but in most cases if you have a vent-less heater the air temp will be above freezing and by running just the furnace fan you can prevent tank from freezing..

Originally Posted by Pitou49

If the water tank is heated with forced air. Circulating the air with the furnace fan, will push the cold air around fresh water tank in the trailer.

[eubank]

Ah, the black and gray tanks are below the floor in most (?) rigs. In order for heat to reach them, it'll have to be forced down there by a vent.

Lynn

[Aage]

Maybe I'm missing your point, Lynn, but most AS have that vent to the tanks below the floor. In fact, my '74 31-footer has two, one midships for the white water, and a second one at the rear for the waste tanks.

The AS LP gas furnaces have at least one difference between them and home types: there is no prevision to run the fan without having the heating function active.

So, if we want to use the fan and ductwork to equalize the temperature in the TT by just running the fan, a modification will have to be made to its circuitry.

[eubank]

Could very well MY misunderstanding! I understood that one of the posters was saying that just providing heat to the interior of the rig would suffice to keep the tanks warm, too.

Chaulk one one to low levels of caffeine intake.


Lynn

[Pitou49]

Truxpin said :
"while the fan is running. When I disable the burner and run the fan only, it really feels pretty chilly ( like it's pulling air in from outside)"

The fan push the cold air around the tanks in the coutch

[truxpin]

Did you really look into LP gas and electricity costs in your area? I would have thought that the gas would be less money over a cold winter than electricity, but I didn't do the numbers either.

Aage- Didn't actually run any numbers. Cost wasn't a factor. Ideally we were wanting to run (heat) with electricity during the daytime hours and when we're home, to quell the noise of the furnace fan ( or the heat pump fan) Then use the furnace fan to circulate that heat throughout the night while we slept. (therefore keeping a supply of air to the black/grey tanks)
Nighttime is really the only time we need to worry about freezing here in South KS. I guess I'll have to actually give it a try one of these evenings and just see if it will work. The temps during the day are in the 60's , but the evenings are running to the upper 30's.
What I'm wondering is whether or not I can heat with electric ( radiant, ceramic, oil, quartz, FANS, whatever....) then in the evenings engage the furnace fan to help circulate that heat to keep important bits from freezing, without creating a huge temp drop in the entire trailer itself.
I know I can heat the cabin itself. One good electric heater and a few small fans do that job easy. It's the tanks I worry about, and whether or not the electric heat source can keep up with moving air throughout the trailer and still maintain a "comfortable " sleeping temp in the evenings.
I'm sure when it does get cold enough we'll have to break down and engage the propane..... I'm just trying to find a way to put it off as long as possible.

[dwightdi]

Run the LP furnace when the outside night temperature gets lower than 27F. The inlet water system and output pipes will freeze at 28F, You need to protect them too. Putting a skirt on it made from 2 inch Styenefoam (extruded) or PE foam is a big help, if you are staying in one place. Hay bales are cheap but not as effective. Airstreams were really not designed for winter living. The interior walls will get very cold and damp. The one pain windows are even worse. Renting a mobile home is a better way to go. The best way to winterize an Airstream is hook it to a TV and move 1,000 miles to the south.

[A W Warn]

Originally Posted by dwightdi

The best way to winterize an Airstream is hook it to a TV and move 1,000 miles to the south.

That would put me just south of Key West, so I would have to stop a little short of 1,000. But, I could not agree more with your theory!

[Aage]

Personally, I don't understand why you feel a need to make it so complex. I would just set the thermostat to come on at 55 degrees during the time you aren't there, and whatever you like when you are there.

The gas system will make sure nothing freezes, day or night. Check that issue 'done' and go on to the next.

Oh, and the fan noise? You get used to it surprisingly quickly. Yes, really.

[truxpin]

Check that issue 'done' and go on to the next.

Done! Moving on.

[pgr32e]

One small note about running the fan without flame from the burner, you are then sucking cold outside air over the heat exchanger in the combustion chamber and cooling the cabin air in the heat exchanger. So the air you heat with the electric heater is being cooled going through the furnace......Phil.

[HiHoAgRV]

I have done exactly what you are asking. If the inside of the camper is 70 degrees and the fan is running...it's sucking in 70 degree air from inside the camper and swirling it thru the unlit furnace and out to the tanks. VOLIA! 70 degree air to the tanks with out burning propane...

[Jim Foster]

Originally Posted by HiHoAgRV

I have done exactly what you are asking. If the inside of the camper is 70 degrees and the fan is running...it's sucking in 70 degree air from inside the camper and swirling it thru the unlit furnace and out to the tanks. VOLIA! 70 degree air to the tanks with out burning propane...

Exactly.