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Old 08-01-2021, 10:04 AM   #1
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Using supplemental A/C unit with Basement A/C??

I have the Coleman basement a/c which works great, always has. On a very hot day, say 105+ degrees with no shade, it will maintain the normal 20 degree variance of about 85 degrees which is fine, I understand the temp variant. At night, it cools down fine for sleeping.

We will be a week or so in Las Vegas in 2 weeks and I'm predicting very hot weather with no shade. I was thinking of setting up one of those stand alone portable a/c units for an additional cooling during the day. The unit has to be exhausted to the outside with a duct which brings up my question for you all.

By running this type of a/c, when it exhausts the hot air to the outside, is it robbing some of my cool air already provided by the onboard a/c unit? Am I decreasing the effectiveness of the on-board a/c unit?

I will have an external power source to run the portable unit, so I'm not taxing my house power.

I'd appreciate your thoughts, thank you!
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Old 08-01-2021, 10:19 AM   #2
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Any of the ones I’ve seen like at HD or Lowe’s rob air from the conditioned space.

Just looked at the 8k BtuH unit from HD - it has a single exhaust duct which is a sure sign that the conditioned air is robbed.

Also noted that it said something about a feature that reduces the need to empty the condensate pan “quite as often” - you can’t air condition air without condensing the moisture in the air. Some parts of the country are less humid than others, and that controls how much condensate is produced.

The key to air conditioning is moisture removal - it takes ~1000 times more energy to remove 1 lb of water out of the air than it takes to cool 1 lb of air.
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Old 08-01-2021, 03:12 PM   #3
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If you are going to use one of the portable models, look for a "dual hose" one that doesn't suck the air from your coach.
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Old 08-01-2021, 03:28 PM   #4
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Any of the ones I’ve seen like at HD or Lowe’s rob air from the conditioned space.

......
I agree! Looked at those last summer when in the Vegas area. At temps there those portable A/C units will not work.
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Old 08-08-2021, 05:16 PM   #5
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I read all your inputs and I agree with you all. I didn't know there were units with the two duct system, but they are considerably more expensive for the week we will need it. I will be parked at my sisters house and we won't be spending any time inside during the daylight hours. Our experience has been that once the sun goes down, the on board a/c drops the inside temp nicely so we can sleep at night.

Thank you for our inputs, that was a big help!
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Old 08-09-2021, 06:40 PM   #6
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There is a slight misconception. The temperature difference/Delta has nothing to do with outside air temperature. The Delta/temperature difference is between inside air and chilled air exiting the duct vents.
This means as the inside air cools the chilled air from the vent remains approx. 20° cooler until set temperature is reached.


The single biggest difference you can make is to completely block out the windshield, even with a blanket supported by cardboard.



BTW, for that one week consider renting the stand-alone A/C unit instead of buying.
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Old 08-09-2021, 06:49 PM   #7
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Originally Posted by Ray,IN View Post
There is a slight misconception. The temperature difference/Delta has nothing to do with outside air temperature. The Delta/temperature difference is between inside air and chilled air exiting the duct vents.
This means as the inside air cools the chilled air from the vent remains approx. 20° cooler until set temperature is reached.


The single biggest difference you can make is to completely block out the windshield, even with a blanket supported by cardboard.



BTW, for that one week consider renting the stand-alone A/C unit instead of buying.

And use a thermometer to measure the units performance. A infrared will not measure air temperature. It measures heat radiated from a solid surface. Measure the air temperature at the inlet duct and the first outlet closest to the unit. Expect 18 to 20 degF colder air out than the inlet.

As noted, nothing to do with outside temperature. I wish this misinformation could disappear from the internet.

Ken
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Old 08-09-2021, 07:40 PM   #8
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I have a basement air I use in Mexico. Very hot in October. Make sure you have a full windshield sunscreen. Since I keep my front blinds closed, I also use that closed cell reflective insulation. Put it on the outside of the windshield, the pull your sunscreen over it to hold it in place. Lowers the temp in the drivers/passenger area 20 degrees. I also keep my window awnings down, and I do have pieces of insulation cut to put in the windows if it get really hot coming through. It keeps up. Plus fans help.
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