Furnace with NO blower ???

[Billy Bob]

Way back in the 70's I had a 15 ft TT until a tornado took it away. But that trailer had a furnace that was gravity feed, meaning NO blower it just ran on propane and it worked great. Used the trailer many times deer hunting and kept warm and cozy even in below zero weather. So my question is why do the PU's now all have furnaces with a blower that eats up the battery power and can the blower be disconnected and still run the furnace on a gravity fed mode.

[brainpause]

I'm not sure how a gravity fed propane heater would work, but it sounds like an easy recipe for the burner to not get enough air, thus creating higher concentrations of carbon monoxide from incomplete combustion.

Larry

[Gone-Camping]

Ummm, Gravity fed may not be the proper teminology here, but it's close and descriptive! I believe the correct terminology would be that the system works on convection...heat rises! And as such, it sucks in colder air via the lower vent, and expells heat from the main vent (and as such worked opposite of gravity). I had one of them in my 78 Starcraft PU, worked very well actually, and believe it was made by Atwood.
 
However, I wouldn't try disconnecting the fan on the one in your unit without some kind of guidance from the manufacturer. The current units are likely designed differently and not sure what the heat would do without the fan to help move it along.

[CAPEd CODger]

First off, I am not an HVAC tech. But they usually don't put things in appliances for no reason.

My old home furnace heat exchanger worked as you described; gas lights, burns, when the exchanger reached it's optimal temp, the blower came on.

My new home furnace has a fan to help with the combustion process; if there isn't a positive airflow, the burner will not light.

I believe that most modern camper furnaces use the same style system; it is supposed to give more energy from the same amount of propane, and, I'm thinking here, if a blockage in the outside air inlet/exhaust port is present, should not allow the furnace to run and possibly overheat or cause some other bad thing to happen.

I guess the best thing to do is get an extra battery.

Bob

[flyfisherman]

The concept of no blower I can understand - as per a radiant heater -
(some examples):

http://www.heatershop.com/propane_radiant_heaters.html

But I can't get a handle on "gravity fed", especially with propane, which is under pressure. My thinking for a gravity fed heater would be one of those old time fuel oil (or kerosene) heaters where the fuel simply fell down by gravity force (of course going through a  regulator) into a burning chamber.


Fly

[dthurk]

The gravity concept is not referring to the fuel, it's referring to the heated air.  Probably easiest to understand would be pre 1960 (thereabouts) homes.  Huge furnace in the basement, ducts go to the second floor, grates in the 2nd floor floors to first floor ceilings, cold air returns on the first floor to the basement.  Furnace heats the air, air rises in ducts to second floor, displaces cooler air which falls to first floor, through cold air returns into basement to be heated, and thus the air in the house circulates, warming the home.  Well, kind of.  Today's systems are much more efficient.

[AustinBoston]

The gravity concept is not referring to the fuel, it's referring to the heated air.  Probably easiest to understand would be pre 1960 (thereabouts) homes.  Huge furnace in the basement, ducts go to the second floor, grates in the 2nd floor floors to first floor ceilings, cold air returns on the first floor to the basement.  Furnace heats the air, air rises in ducts to second floor, displaces cooler air which falls to first floor, through cold air returns into basement to be heated, and thus the air in the house circulates, warming the home.  Well, kind of.  Today's systems are much more efficient.

This is an excellent description.  The reason such systems are called "gravity fed" is because gravity is the driving force.  Hot air is lighter than cold, so gravity pulls the cold air down, forcing the hot air up.

In weightless situations (microgravity), hot air doesn't rise.

Austin

[hoppy]

My 1978 19 foot Palomino had a 9 K BTU propane convection furnace built into it. It was made by Hydra-Flame, it it did a decent job keeping this little camper comfortable during the winter month camping trips.

  Just like today's models, it pulled outside the PU air into the combustion chamber, and an exhaust tube went to the outside of the PU. The combustion chamber was like a big ol' coffee can, with a gas grill style burner inside it. It was very quiet. The only sound it would make is when the mechanical style thermostat signaled the burner to light up, and that was only a slight poping noise of the burner lighting.

  I gave this camper to my daughter and SIL about four years ago, and the furnace still works great.

[tlhdoc]

I don't think I would try and disconnect the blower in your furnace, but why not get a portable propane heater, like the Mr. Heater Buddy and let that heat the camper.