[TenTec] emergency power via generator

[Gary Hoffman]

Not what I was talking about.   Sure, the tanks will also freeze if they are
too small.  I was assuming they were large enough and would not freeze.

I am talking about the propane feed into the engine itself.  The rapid
expansion of the propane causes sub-zero temps inside the engine, unless the
ambient supplies enough heat to compensate.  That is why they won't start up
if it is too cold unless they are in a warm enough ambient.

My neighbor for example, has his in an insulated, heated cabinet.  That is
the way the manufacturer (Coleman) sells their propane models (at least the
ones I've see).  He feeds it with a 250 gallon tank - so no problem there.

Gary

By the way....all sized tanks have exactly the same vapor pressure at the
same temperature.  Why the size of the tank can matter (if it is too small
which most are not) is that when you evaporate the liquid to gas (inside the
tank now) it uses up heat.  This chills the tank itself, and if it is too
small, its temperature will also drop.  Then the vapor pressure will drop -
but only because the temperature is now colder.   A large tank stores enough
heat in its liquid mass that this is usually not an issue.


----- Original Message ----- 
From: "Dr. Gerald N. Johnson" <geraldj at storm.weather.net>
To: <tentec at contesting.com>
Sent: Wednesday, March 07, 2007 2:58 PM
Subject: Re: [TenTec] emergency power via generator


> On Wed, 2007-03-07 at 14:47 -0500, Gary Hoffman wrote:
> > Propane powered generators will not start in freezing cold weather.
They
> > must be insulated and heated.  Keep that in mind.
>
> Not true. But the propane tank must be large enough. Too small a tank
> won't have enough vapor at low ambient temperatures. My 5 KW Onan needs
> at least a pair of 100 pound tanks. They typical house 500 or 1000
> gallon tank WILL supply adequate propane at all temperatures for the
> propane fired generator.
> >
> > Buy a little extra capacity, not the surge capacity, but the continuous
> > capacity.
> >
> > Be sure your generator puts out 240 VAC to power home stuff.  Then you
can
> > (through proper, code-compliant, wiring) backfeed the house wiring from
the
> > generator.  Then you can power anything anywhere in the house - provided
of
> > course that you limit the total load to what the generator can deal
with.
>
> The transfer switch is essential for convenience and safety. Any other
> scheme is hazardous to the health of the generator, family, and linemen.
> >
> > Have lots and lots of gasoline  (or propane) on hand.  You can't run
> > anything without fuel.  You generally cannot get fuel during an outage,
> > cause the gas station has no power to run its pumps.
>
> So true.
> >
> > Any modern AC generator makes a nice clean sine wave.  You won't have
any
> > worries there.  Check the voltage (under load) the first time you use it
to
> > make sure it was regulated right at the factory.
> >
> > Gary
> >
>
> -- 
> 73, Jerry, K0CQ,
> All content copyright Dr. Gerald N. Johnson, electrical engineer
>
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