I bought a couple EdgeStar AP14001HS portable air conditioners in April 2020, since I expect to spend most of the Summer at home. I'm not able to use window A/Cs here, though that would be the obvious choice for efficiency because all the hot parts remain outside.

Similar models

From looking at Internet photos, these A/Cs appear to follow the same general desgin:

I can't say to what extent they are identical, but the stuff on this page might apply to all of them.

Air Gaps

I wanted a dual-hose air conditioner because single-hose models are thermodynamically suboptimal. Blowing hot air out the window creates negative pressure in the room, which sucks outdoor air back inside through various cracks. In theory, dual-hose models avoid this problem by cooling the condenser with outdoor air, which is then re-exhausted.

However, when I feel the intake and exhaust hoses on the AP14001HS, the volume of air moving through the intake is considerably smaller, so air must be leaking from the room into the condenser compartment, and also between the room and outside while the blower is off. There are two major locations where this happens:

  1. Where the bottom meets the front:

bottom gap

I sealed this one using tape:

bottom gap taped

  1. On the back, below the air filter:

filter gap

To block this one, I cut a 436mm x 98mm rectangle from a sheet of 1/16" (1.5mm) ABS plastic. A cereal box also works for prototyping purposes... in general, the material needs to be pretty thin, but rigid enough to keep itself flat.

The plastic gets pulled toward the rear while the compressor is running, and toward the front otherwise, so a piece of tape can help hold it in place.

Finally, if you decide to open the unit (a 12-inch #2 Philips screwdriver is helpful), it's possible to tape over some internal hose/wiring gaps, but I'm not sure how important these are.

Am I going to fry this thing?

These modifications are intended to make the condenser compartment run hotter, which may shorten the life of some components, but I have no idea which ones or by how much. I at least have a couple bits of evidence that this might not be a terrible idea:

  1. I asked EdgeStar support about sealing the bottom gap:

[Me]

I recently purchased a couple EdgeStar AP14001HS dual-hose air conditioners, and noticed that the intake hose moves quite a bit less air than the exhaust hose. It seems that the extra air is "leaking" into the condenser compartment where the bottom meets the front of the unit. See the attached photo, where I temporarily covered the gap with masking tape. Are you able to tell me whether this gap serves a necessary function? Otherwise, I would rather leave it covered, because I chose a dual-hose model to keep the inside/outside air isolated from each other.

[EdgeStar Guy]

Hello Paul,

Thank you for contacting EdgeStar support.

The area that you've taped up is considered an overflow release. You are perfectly welcome to keep that area taped up though as it shouldn't cause an issue. My engineers have informed me that it's OK to do this.

[Me]

Thank you. I had suspected that the gap was to prevent the unit from filling with water, though it seems bigger than necessary.

The AP14001HS specs say:

  • Cooling Capacity (ASHRAE) 14000 BTU
  • Cooling Capacity (SACC) 8600 BTU (38% lower)

According to this article, "infiltration air" is a major factor in the SACC measurement: https://support.edgestar.com/hc/en-us/articles/115005480926-What-is-SACC-Seasonally-Adjusted-Cooling-Capacity-

Have your engineers evaluated what effect sealing this gap (and other intake leaks) has on cooling efficiency?

[EdgeStar Guy]

Hello Paul,

Thank you for getting back to me.

I wasn't able to get an answer for this from my engineers about the effect on sealing the gap will have on efficiency. They did say that when the units are tested, they are tested with this gap to produce that SACC rating. There's no modifications to the units done while testing. The efficiency of the units includes the air gap.

It doesn't look like there has been factory level testing with the gap sealed, but the engineers who work on these units have performed their own tests and found covering this gap to not be an issue. They weren't able to give me additional information on the SACC though as it's not something we can test at this location.


  1. Someone on a plant-growing forum reported sealing a Whynter ARC-143MX tightly enough to maintain a high-CO2 atmosphere. It's not clear for what duration it actually ran, but the thread spans 4 years and the author doesn't mention a failure.

So I wouldn't say that there's no risk of damage, but at least it's been tried before.

After sealing these gaps, I could feel more air moving through the intake port, and less air coming from the exhaust when I briefly obstruct the intake.

Stand back, I'm going to try science

In order to test these modifications, I installed the air conditioner in a somewhat-sealed closet with a 1.5m² volume. I initialized the temperature to roughly 72°F, set the A/C to 61°F (the minimum value), and let it run for about 3 minutes until the blower shut off.

This was repeated 3 times in the factory configuration (red lines), 3 times with the gaps sealed (blue lines), and finally 2 times in "single hose mode" (black lines) with the intake sucking directly from the closet space. I logged the temperature using a phone pointed at a thermometer, running Open Camera on 10-second repeat:

open/sealed graph

I don't think my setup is rigorous enough to calculate any absolute efficiency numbers, but clearly the sealed configuration does a better job of cooling, and single-hose mode is abysmal.

Rant

I find it disgraceful that the portable A/C companies are so clueless about efficiency that improvements can be made using basic household supplies. This reminds me of the computer PSU industry before 80 Plus, where everything is garbage and nobody knows what to buy. Why is all the innovation focused on single-hose designs?

Places like the Bay Area are full of apartments and condos that are gradually becoming unlivable as temperatures rise, so it would be nice if people could just throw money at a decent product.

It's possible that http://www.climax-air.com/ knows what they're doing, since they make (as far as I know in 2020) the only dual-hose portable with a variable-speed compressor. But I've only looked at the website, since their supply is very limited. Maybe I'll check again when the EdgeStars wear out.

Photos of the closet setup

(The second AP14001HS visible in the mirror was used to set the room temperature.)

closet experiment 1 closet experiment 2

Building-related Notes

Each unit consumes about 10.5 amps, so it's important to map out which circuit breakers feed which outlets, and avoid sharing a circuit with a high-drain appliance like a microwave or electric kettle. Ideally, they should also sit on opposite legs of the main breaker. So far, I've had no issues sharing a 15 amp circuit with a refrigerator or computer.

On a day that peaks around 95°F, two A/Cs running continuously can keep 850 sqft in the mid-70s. My IR thermometer says the ceiling is considerably warmer than the walls, so it would probably be useful to improve the attic insulation.

I plan to run these in "heat" mode during the winter, which should consume less energy than the resistive baseboard heaters, but time will tell how well that works.

One caveat to this installation is that my windows are locked/taped into position, so I can't open them at night when the air is cooler outside. It would be nice to have an automatic "ventilate" mode for this purpose. However, an A/C cooled with cool air produces even colder air, so it doesn't need to spend much time running in this state.

Simpler Hacks

This unit blows indoor air mostly upwards. I opened the case to remove the built-in deflector, and put a Frost King HD9 in its place. This creates a roughly-horizontal air stream, and also seems slightly quieter without those extra fins in the way.

deflector

The hoses may be insulated using a 6 inch "tubular cotton stockinette bandage". After 5 minutes of runtime with 2 layers of cotton, I measured 122°F at the hose and 102°F at the cotton surface. This isn't the greatest insulating material, but it's cheap, easy, and looks reasonable enough.

stockinette

You can rip open a standard furnace air filter, and cut the zig-zag part to fit the air intake's plastic frame. Note that this will restrict airflow, so it probably makes sense to run the blower on high. I increased the density a bit after taking this photo:

air filter

Soundproofing

I was thinking about sticking some neoprene foam to the outside of the case, but decided that accumulating mass that way is too expensive, and that just wrapping the A/C in a blanket works quite well. The hoses prevent anything from obstructing the room air intake.

Here is my "A/C burrito" prototype:

burrito prototype

With the unit running for hours when it's 90°F outside, the hottest point under the blanket is around 94°F, so it seems to do a reasonable job of keeping itself cool.

My eventual plan is to make a burrito from 1 pound/sqft mass loaded vinyl (MLV), wrapped in a cotton blanket. The cotton's purpose is to absorb some sound (because MLV is primarily reflective), and to look nicer than raw MLV.

To hold everything together, I want to hammer staples through the layers of cotton + MLV + cotton. The staples will also hold strips of velcro along the top of the burrito, with opposing velcro hot glued to the A/C's case. The soundproofing needs to be detachable for maintenance.

Network Control

I would eventually like to control these wirelessly from a Nest thermostat, using ESP32 microcontrollers. This should reduce short cycling, power down the 60-70W fans that would otherwise run continuously, and switch automatically between heating and cooling mode. Perhaps I could also reduce noise by setting the fan speed based on duty cycle.

This will require:

I managed to capture the remote codes using LIRC's mode2, and play them back from a Raspberry Pi, so porting to the ESP32 should be straighforward.

Reverse engineered IR protocol: all marks are the same length, with data encoded in the spaces. There appear to be 32 bits per packet, organized as [id, ~id, code, ~code]. I sent all 256 codes, hoping to find undocumented features like "set power to X" or "set mode to X", but they were all just duplicates of the standard 6 buttons, so understanding the protocol is pretty useless.

Here are the simplified IR codes in irrp.py JSON format.

I expect that a downward-facing analog photocell should provide enough information to synchronize the "mode/on/off" state. If I want to synchronize the fan speed, switching to Dehumidfy mode will force this to Low. I don't know if I'll automate temperature control, but sending 29 "up" commands will clamp to the maximum value.