Propane only has ~ 96,000 BTUs/gallon and yes the Westy tank is only 2.5 gallons at best. That is why LPG is lousy as a motor fuel. As the tank empties and the surface area of the liquid is reduced the LPG will vaporize slower, especially at low temperatures making the last 1/4 or so difficult to use for running a heater.

Dennis

----- Original Message -----
From: "Mike \"Rocket J Squirrel\" Elliott"
Date: Thursday, January 18, 2007 5:09 pm
Subject: LPG > BTUs, check my math
To: vanagon@GERRY.VANAGON.COM

> The lack of a gauge on the LPG tank causes me to be very, very frugal
> with my LPG. For example, though we were having record low
> temperaturestwo weeks ago when I was camping along the west
> coast of California, I
> didn't run the Olympia 3100a catalytic heater in the evening
> because I
> didn't want to find I could not easily boil water for coffee in the
> morning. As a result, I was pretty uncomfortable once the sun
> went down.*
>
> So that got me thinking: what is the rate of consumption of this
> heater?I could not find any real specifications for it, except
> that it puts out
> 2800 BTU on max, and 1600 BTU on min. They don't say, but I
> presume that
> BTU's per hour. A gallon of LPG (propane) has about 140,000
> btu/gallon.The tank on the Westy is -- what? 2 gallons?
>
> So . . . if the heater is on max (2800BTU/hr) then 2 gallons of LPG
> (280,000 btu) should last 100 hours, assuming 100% efficiency?
> (And if
> it is not 100% efficiency, wouldn't it be releasing LPG into the van?)
>
> *Yeah, yeah, it dropped to about 30F, which is tinkertoys to
> people who
> don't live in our sunny clime, but we San Diegans are unprepared for
> temps that low, and let's face it: the Westfalia is not a
> paragon of
> insulation.
>
> --
>
> Mike "Rocket J Squirrel" Elliott
> 71 Type 2: the Wonderbus
> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
> 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
> KG6RCR
>