Extended Stay Propane Tanks and Furance Problems

The ability of liquid propane to vaporize (boil) to a gas is dictated by the wetted area of your tank. In simple terms that means the square inches of steel touching the liquid is the determining factor.

This is reduced even more as the liquid level in a tank drops since there is less liquid touching the metal surface thereby reducing the vaporization rate. Ambient temperature is the second major factor to consider since the tanks ability to transfer heat to the liquid is reduced by the temperature also.

Part of the OP's problem nay very well be from flow restrictions in his supply system from the 20# cylinder through the hose and added fittings, as well as ambient temperatures being lower at this higher elevation. A complete series of factors that when combined create the problem he is experiencing.

In cooler weather a 20# cylinder will struggle to keep up with a significant BTU demand which a furnace would be. Add in the other possible flow restrictions and the results are evident.

The newer style OPD valves are not required in cylinders over 40# capicity and would provide full flow from cylinders of any size larger than that.

I would do one of several things to cure the problem. Connect two 20# cylinders together, similar to a trailer setup without the regulator, or go to a single cylinder of a larger size. Absolute minimum of 30# and as large as 100#. Since the problem didn't seem to be there when he was at a lower elevation, and I'm guessing a somewhat higher ambient temperature, I believe the problem is not as much flow restriction as it is adequate size of the supply.

RaenMark wrote:
enrays - part of the problem may be what you described. Part of it may be the combination of altitude and temperature. When the ambient temp gets too low, propane does not want to vaporize.

First I'm going to address this point.. PROPANE the vapor temp (At 1 atmosphere of pressure) is roughly minus 40 degrees, your choice of F or C on that one (-40 is crossover point)

Butane, however.... Closer to the freezing point of water (0C 32F)

Are you sure your luggable tank is propane and not cheaper Butane sold as Propane to maxamize profit for a fraudlant dealer?

Second: I have the Extend a Stay, one of the very first things I added to this motor home. Never had the kind of problelms cited. But then my Luggable was filled in Michigan, where Propane is Propane cause the freezing point of water is often... Much warmer than the air outside the house.

A 30# or larger propane tank may solve the problem. I have a propane generator, 8 KW, that will not run on a 20 lb tank. Pulling that much vapor off the liquid propane cools the liquid which causes less vapor to form. Larger tank, less problem with the over cooling. The higher altitude and probably lower outside air temp will make the situation worse. On our last Class A I installed an Extend A Stay and used 30 lb tanks without a problem.

Let us know what the outcome is.....inquiring minds would like to know.

I'm a first timer to the RV.net forum. I'll start with a Thank You! I've spent hours in on-line searches trying to understand the problem and to come up with a solution. In just a few hours I've received more usable information than in all of the searches I did before. Thanks again to each of you for sharing your expertise. ernrays

Hi,

The altitude is lowering the boiling point of the propane. Warm the tank.

I have used an ex tenda stay to -11 f with no problems ken

Just about every spud in your propane system (and your "Extend-A-Stay) has a flow limiter in it and they can be drilled out, which will eliminate that problem, but your 20# tank may also have a limiter in the OPD valve. I had similar problems and when I talked to the engineers at Manchester Tank they told me the following:

When the OPD valves were designed, a by-product of the new valve design was that some valves also gave them a flow limiting capability. They recommended that I search for tanks that had the word "Italy" cast into the valve body just under the tank valve shutoff handle. These tanks had a different valve that did not give flow limiting actions, but are still completely legal under our law. I bought 3 of these tanks in Lowes and have never had a shutdown problem since. Of course, you can't just trade bottles when you need a refill if you get this type tank.

enrays - part of the problem may be what you described. Part of it may be the combination of altitude and temperature. When the ambient temp gets too low, propane does not want to vaporize. Another potential problem may not be with the fuel, but the air, at 9800ft your oxygen concentration may be too low for the furnace to light properly on the fuel flow you have from the extended stay tank. JMHO.