Date: Sun, 8 Jul 2007 23:04:51 -0500
Reply-To: Matt Roberds <mattroberds@COX.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Matt Roberds <mattroberds@COX.NET>
Subject: Re: An AC idea for driving and camping
In-Reply-To: <20070709011921.GYR17907.fed1rmmtai105.cox.net@fed1rmimpi01.cox.net>
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
> From: Edward Maglott <emaglott@BUNCOMBE.MAIN.NC.US>
> Date: Sun, 8 Jul 2007 17:55:58 -0400
>
> So here's my idea. Use one of those freestanding rolling AC units
> that has air exchange hoses to connect to a window.
Cheaper yet: in a few weeks, all of the big-box stores will start to
discount the heck out of their remaining window air conditioners. Some
of them offer refurbished air conditioners cheap, as well. Get one and
fangle some dryer vent hose from the warm-air inlet and cold-air outlet
to a piece of cardboard taped in one of the door windows that is rolled
down a little. Park outside your place with as much glass facing south
as you can, pop the top, fire up the window A/C, and see what happens.
If the A/C can't produce the needed temperature drop while sitting
outside the van, it'll never do it inside the van. :)
> Questions/Ideas: Is 1200 watts enough to power an AC unit big enough
> to cool a vanagon going down the road on a hot day?
If you want to get more scientific, I did work out how many Btu it would
take to heat up (or cool down) the back of a Bus:
http://www.type2.com/archive/vintagebus/043445.html
http://www.type2.com/archive/vintagebus/063342.html
Most alternators have an output somewhere in the 13 to 14 V range,
making the actual output of a 100 A unit somewhere between 1300 and
1400 W. 1200 W needs at least 1.6 hp from your engine; 1400 W needs
at least 1.9 hp. It will take more than this, because alternators are
not 100% efficient.
> For driving it runs off an inverter connected to aux battery. Here's
> my concept breakthrough: replace the AC compressor on the engine with
> another alternator.
If I wanted to do this, I'd get the inverter as close as humanly possible
to the second alternator, and run long wires for the the 120 V AC
instead of the 12 V DC. Two 14-gauge wires would be enough to carry
10 A at 120 V; you'd need a couple of 6 gauge or better battery cables
to carry 100 A at 12 V.
Another option, not as cheap: replace the second 12 V DC alternator and
inverter with a 120 V AC alternator. This does avoid one conversion
step between the engine and the air conditioner, saving some energy.
If you wanted to be able to charge the aux battery with this, you could
add a regular 120 V battery charger - put the conversion step in the
lower-power side of the system instead of the high-power side.
Matt Roberds
