gmcase Loc: Galt's Gulch

I bought a portable AC that uses two hoses. One is exhaust which obviously has to exhaust out of the room being conditioned but the other is the subject of my inquiry. In the description regarding the intake hose, it says it draws in warm/hot outside air through the intake hose and mixes it with air from other intake vents pulling from inside air though it does not give the ratio.

My question is why does it require outside air for intake at all? It seems it would be better to be drawing in 100% inside air (cooler and drier) and exhausting it 100% to the outside getting rid of heat and moisture. What am I missing or simply don't understand? Is it more efficient to use hotter intake air somehow?

It is interesting that in the installation instructions it only stresses the need to make sure the exhaust port is connected to the outside bound hose and says nothing about the intake port.

I have little humidity inside or out as I live in the desert with a typical daytime humidity of zero to 3%.

PS - the model is a Whynter.

IowaDave Loc: North Iowa

think of a window AC...it sits outside the window and uses outside air to cool the hot coils.
Your unit is indoors so it is more efficient at cost effective to bring uncooled outside air in to bring down the temp of the hot side of your indoor unit.

If you didnt use outside air, your portable unit would have to use indoor air for cooling the coils and the room temp would take forever to cool. Cause you would be heating up the indoor air to cool the unit that is trying to cool your room.

the high efficient furnaces do the same thing....they bring outdoor air for the combustion chamber that is exhausted out. Its better then using air from the dwelling that is already heated to burn and exhaust away.
I hope this helps...kind of hard for me to explain.

gmcase Loc: Galt's Gulch

Thank you. I did some other searching and it basically mirrors what you said. Seems counterintuitive but I will go with the experts!

rgrenaderphoto Loc: Hollywood, CA

It's called makeup air. Constantly recycling interior air is bad, and inefficient for the A/C system. It is easier to pull air from the outside than the room.

OBTW, in the trade, you floor mounted unit with two hoses is called A White Elephant, for obvious reasons.

dlmorris Loc: Loma Linda, Ca

Looking at a picture of the unit.... One hose brings in the outside air to blow across the condinser, cooling it, and then the air is exhausted back outside. Kind of like a split system, where the condinser is outside, the fan brings the air across the coils and out the top. Does that make sense? Just make sure that the hoses are far enough apart that the intake hose doesn't suck air in from the output hose.
The *cooling* part of the unit pulls indoor air through some grill somewhere (Usually in the back or side) and then across the cooling coil and out the front vents. Yeah, both of those large hoses MUST go outside, but as I said, keep them far enough apart. And just wondering, if it is that dry, why not use a good swamp cooler? They can work really well in those conditions, and if it gets too hot, that portable unit will have trouble anyway...

gmcase Loc: Galt's Gulch

I do wood working (also auto mechanics) and introducing moisture with a swamp cooler then removing it when the swamp cooler is off would be disastrous for the wood I have in the garage. Some of it is exotic, hard to find and very expensive. If it wasn't for that I would have gone the swamp cooler route.

I have it hooked up and it has dropped the temperature 5 degrees in two hours in an extremely we'll insulated shop that is roughly 1,100 sq ft. It is about 100 right now. It was 85 when I turned it on and just hot 80. I realize it is undersized but I am not looking for office type temps just something to knock off the extremes some.

HOHIMER

this might help. see download pdf image.

Attached file:
(Download)

Attached file:
(Download)

dlmorris Loc: Loma Linda, Ca

Loved the drawings!

gmcase Loc: Galt's Gulch

No doubt and thank you Hohimer!