On Wed, 2007-03-07 at 20:17 -0700, Bob Cunnings wrote:
> I know this is only anecdotal, but here goes -
>
> years ago, when I lived in Michigan, I drove a propane powered pickup
> truck. That darn thing would *not* start at temperatures below 0
> degrees F or so. I would always need to drive my gasoline powered car
> on a morning colder than that!
>
> Yes 0 F is pretty cold, but overnight lows fell below that point more
> than a few times each winter (in those days), and I still had to go to
> work.
>
> After 3 years I sold it because refueling was a hassle, with propane
> stations set up to refuel vehicles few and far between out in my neck
> of the woods. The upside was that it was economical, at least at that
> point in time.
>
> Bob NW8L
>
Pickups, cars, tractors, and buses use a different fuel system than the
small generator. They can't carry a large enough tank to get the
evaporation from the environment, so run on liquid. That liquid has to
be evaporated with a water heated vaporizer on its way to the
carburetor, so they run poorly on the minimal fumes from their liquid
tank until they get the radiator water hot enough to boil the liquid in
the vaporizer.
Reducing pressure, e.g. expanding gas from tank pressure to intake
pressure does take heat. But the process is done in three stages on the
standby generator propane system, using mostly the same regulators that
run the house furnace in all kinds of weather, though when running an
engine, it may be necessary to use regulators rated for adequate volume
to keep them from freezing up. The second conventional regulator feeds
fuel to the generator system at about 12" water column. The regulator at
the engine drops that to a vacuum and opens when the engine pulls a
vacuum on the manifold.
An engine with a oil pressure switch for protection should have that
switch out o the circuit for starting, else starts are going to be
uncommon. I suspect that switch was added after the factory controls
were built and it needs a relay hooked to the starter solenoid to give
the engine a chance to start.
--
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer
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