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Old 08-17-2011, 03:03 PM   #21
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Re: Alternatives to cooling an SMB

Another update on Danhard usage in this hot SW weather: Its imperative to start the unit while the can is cool. That means get it on, leave the fan speed at medium and switched to ON rather than AUTO, get the thermostat at an intercept/on temp not more than 80 or so, all windows and windscreen covered using an interior reflective sunshade as well. An additional interior fan for circulation and closing the curtain behind the driver compartment also makes a big difference.

With all those steps its possible to hold an 84/5 interior temp at 105+ ambient at 4pm by which time the exterior has been sitting in direct sun for 8 hours. Starting the motor and idling it for 30 mins with the a/c on high will arrest or stabilize the temp at a lower level but the heat soak and heat load on the exterior surfaces is so high that as soon as you switch off the engine the heat bakes through the limited insulation. If you can find a way to park under cover the system performs much better and will hold the temperature at 80 because although the air temp remains 100 plus, you are avoiding the radiant heat of the sun on the exterior which increases the surface temp to 150 deg as tested with an IR gun. This applies to a silver exterior. A dark color will raise all these numbers by several degrees I suspect.

I have toyed with designing a retractable shade that would extend from the rear bumper, run over the back doors and clip on top of the windscreen. Perhaps making this from mylar or some other reflective material, I believe it would take a considerable heat load off the roof surface and reduce that oven effect. However its install would be clumsy and any sort of wind would or could destroy it. But without something like that, its a losing battle to expect a mere 12000 btu to manage these temperatures.

The Honda drive this system acceptably but I have read of some who say they can drive it using their Inverter and battery for a period of several hours. Mine hammers the battery so heavily when the Honda is off line that I am at a loss to understand how this is possible unless my 4D battery is smaller than the ones they use though AFAIK the 4D is the largest single unit generally installed. I also have not tried to run the Danhard without the Honda but using the alternator as the charge source.

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Old 08-17-2011, 03:04 PM   #22
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Re: Alternatives to cooling an SMB

BTW Vlamgat is the nick name for Mirage F1 drivers who were prone to light their rear ends in a vertical climb showing just that: a "vlamgat" ! A vestige of days gone by in another world and another hemispere.
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Old 08-17-2011, 03:09 PM   #23
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Re: Alternatives to cooling an SMB

Quote:
Originally Posted by vlamgat
With all those steps its possible to hold an 84/5 interior temp at 105+ ambient at 4pm by which time the exterior has been sitting in direct sun for 8 hours. Starting the motor and idling it for 30 mins with the a/c on high will arrest or stabilize the temp at a lower level but the heat soak and heat load on the exterior surfaces is so high that as soon as you switch off the engine the heat bakes through the limited insulation.
If you open the hood, it will not only release the engine heat, but the updraft will pull cooler air past the firewall/doghouse and virtually stop the heat from coming into the interior. I do this most of the time when I set up camp for the day.

Mike
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Old 08-18-2011, 02:17 PM   #24
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Re: Alternatives to cooling an SMB

Great idea. Thanks
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Old 05-06-2012, 09:04 PM   #25
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Re: Alternatives to cooling an SMB

The inverse square law: More BTU's from the engine than from the sun.
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