Portable A/C Efficiency Improvements

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Old 08-11-16, 02:18 PM
J
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Portable A/C Efficiency Improvements

Hi everyone,

First of all, I own two portable, single hose A/C units- a DeLonghi 1400BTU 3-in-1 and an Insignia 1200BTU unit. As I grew up in an area where A/C really wasn't necessary, I wasn't privy to the inefficiencies or problems of portable A/C units, and they just seemed convenient to me. Despite insulating the exhaust tubing for the unit, I'm still not quite happy with their performance- and moreover, due to significant negative pressure problems, I'm unable to run both units simultaneously to any benefit. The tape I use to seal around the wind installation adapter will literally pull itself off to let air in from the outside

Searching for a low cost solution or modification, I discovered this video online:

Indoor Portable Air Conditioner Efficiency Improvement: single hose to dual hose conversion

Now, I tried to look up any information about similar modifications elsewhere on the internet, but this seems to be the only source- so I'm not sure if this is a trustworthy, effective, or safe modification.

Furthermore, if this is an effective modification, I have another question. Doing the modification for the Delonghi 14000 BTU unit would be trivially easy- like the one from the video, there is a filtered intake for recirculated air, and an unfiltered intake that cools the compressor before being exhausted. Unfortunately the design of the Insignia unit differs significantly. There are 3 filtered vents on the unit that all lead to a shared open air compartment containing the condenser and the intake fan. I would assume that makes the mod described in the video impossible to perform. To that end, do I have any alternatives? Would there be any sense in adding an intake tube to that compartment? If I understand negative pressure correctly, it will suck the air in from wherever it can anyway, so why not make sure that air goes directly into the A/C?

In the future I intend to get window units or at least dual hose portables, but if this works it could save me a bit of cash.
 
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Old 08-11-16, 04:11 PM
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Welcome to the forums.

Even with modifications.... those portable units are a compromise.
You will never approach the efficiency of a window unit.

If you have a place for a window unit. Get it and sell the portable.
 
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Old 08-11-16, 04:42 PM
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First I not sure running two units is creating that much negative pressure. A bath and kitchen fan both exhaust air and don't create an extreme negative pressure when running at the same time.

Isolating the two air paths would be difficult and a pain to create. While the weather is super hot, selling those two as PJ suggests should be easy. Then you upgrade to more efficient window units and enjoy. Even if you were successful with the modification, you would most likely not achieve the necessary airflow and efficiency would drop offsetting part of what you might gain.

Bud
 
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Old 08-11-16, 05:01 PM
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First, thanks for welcoming me to the forum.

As for window A/C: I absolutely agree with both of you, and I would never purchase a portable A/C again (much less a single hose version). Unfortunately window air conditioners aren't really a possibility at the moment for a number of reasons, but might be if I move. Hence my investigation of this bandaid solution- even a slight increase in efficiency would be sufficient to get me through the season comfortably.

As for negative pressure being an issue- I have had to seal a number of leaks with very noticeable breezes. If you crack a window with both A/Cs running it's like a wind-tunnel.
 
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Old 08-11-16, 05:03 PM
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http://www.doityourself.com/forum/ai...ml#post2415623
Pilot Dane wrote:
I used aluminum trim stock, you could also use aluminum flashing stock, to make a box that fits over the air intake that brings the air in that gets blown out the tube. If you are lucky you might even find a box that fits. Screw, rivet or duct tape it to the unit and attach a large hose. I used 6" duct and ran it to the outside. Keep the ducting as short as possible and as smooth and straight as possible to minimize resistance. This separates the air being re-circulated and cooled in the room from the air used to cool the coils. For $20 you can convert a single hose unit into a much more efficient dual hose.
 
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Old 08-11-16, 05:21 PM
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That's great- basically the same idea as the video I posted. So it looks like it's a safe modification in theory- but my second question remains a little unanswered. You'll note the second part of his post reads:

"Just make sure you understand what's going on with the unit. The one hose blowing out is easy as is the vent blowing cold air into the room. You need to look at it and determine which air intake takes the air that gets recirculated back into the room and which takes in the air that get's blown outside through the hose. Build your box and intake plenum around the intake for the air that gets blown outside."

The Insignia unit I mentioned has a shared intake for condenser cooling and the air that eventually gets recirculated. There is only a single set of intake vents, and the air gets separated inside.

Here's a picture of the unit disassembled for clarification. The intake fan for the recirculated air pulls air over the condenser. That black and blue fan is open on the other side too, facing the right hand vent

Here's what the unit looks like from the back, assembled.
 

Last edited by JVNO106; 08-11-16 at 05:41 PM.
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Old 08-15-16, 01:45 AM
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For anyone interested, I've done the mod Pilot Dane mentioned on the delonghi A/C. It was a little awkward since the back is rounded, but with some duct tape and a few attempts to fit it I managed to get it done. Used a cardboard box (covered in packing tape as cardboard is air permeable), and ran a flexible aluminum 6" dryer hose out the window.

So far, so good. The room is a few degrees cooler than normal, and the negative pressure problem has been ameliorated (though still exists to a minor extent. I am at last able to run both A/C's now without the negative pressure pushing the plastic window fittings off. All in all, I'd recommend the conversion.

Still wondering if any sort of equivalent mod would work for the single vent, single fan Insignia unit.
 
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