Through-wall AC unit shopping, help!

Hello all,
I live in SC and for some reason the through-wall A/C’s we buy keep developing mildew and nasty smells from the profound amount of humidity in the air through Summer. First I tried with a through-wall unit and then w/ a smaller through-window unit. I thought maybe the drain hole to expedite the water out of the unit was plugged so I had some folks come over and clean the unit out but 2 weeks later it just smelled again and I stopped using the unit. So I’ve decided to scrap it and just buy a new unit. Only this time I’d like to over see the whole process from the choice of the unit to the installation and angle that the unit sits at in the space. I’m hoping to be the difference between a smelly unit and a non-smelly unit.

I would be looking for something that can be maintained. I know it’s a tall order, but that’s why I’m here asking questions. The unit that currently resides in the hole is
25 1/4" x 16 1/4". I would need a a minimum 10, 500 BTU A/C preferably a bit more with heat or a heat pump unit. If anyone would be so kind as to recommend a unit or brand I would be most grateful as time is against me to when spring brings the heat. (I don’t use this unit in winter, just a space heater and fresh air from the window if needed). I’m quite picky about filters as well because I have allergies and the louvers that control airflow should be as easily changeable as possible not the angled ovals that you you rotate to change the air direction. The better I am able to maintain this unit, the better the chance I will have to not have the same problem the way I see things. Anyone have any good experiences with brands that I should know about? Please do chime in, thanks.

I have absolutly no background, so FWIW:

If your current models don’t work, why repeat the process? I"m guessing the through/wall are of the same basic design as a window unit.
Why not look into what are called “mini-split” systems - they act like a central unit, but, instead of having a coil in the plenum, they just run the copper tubes to a small cooler and blower unit, typically mounted above a larger window.

Do not ask a pro about these unless you want to risk a pissed-off pro… They are marketed towards the DIY market, and pros hate them. Their way of dealing with them is to charge as much to install a split system as they would a central unit (so I’ve heard).

Some units will support 2 heads - i.e. will allow 2 cooler units too be run by a single compressor.

Here’s the first thing I found with pics of the system

Google Split Air conditioner and “mini split air” for the DIY models

There are products you can use: here is one I googled:

Split packs are better for many reasons: efficiency, energy conservation, much less noise, no danger of water accumulating in the unit, and usually easier to clean the evaporator fins than on a window shaker. Also, you don’t need to use up a window and can place the air handling unit anywhere you want, either near the floor or up near the ceiling. It does involve punching a hole through a wall for the coolant piping, however.

Oh, and they’re much cheaper than a heat pump.

maybe, but the costs are generally higher to both install and purchase, but the bigger question if we have to change the conversation to this is: Are split pack A/Cs considered part of a house’s square footage?

The biggest advantage to my purchasing a heat pump is that it is considered part of the house and therefore can translate into a better house sales profit should the house ever be sold. I am also not a rich man, I’m hoping there is a option between replacing A/C units every summer and punching a new hole in the house for an uber pricey unit.

Aren’t there any A/Cs that offer a way to maintain them?

Splits and mini-splits are permanent installs, so they would be considered part o the house (not its square footage; I know of no HVAC which adds to sq footage - they don’t make the place bigger).

As I mentioned, some of these are DIY - the big draw for “using a pro” is that they have the EPA card which allows them to buy refrigerant (“freon”). They also have the very expensive tools to inject it and measure it.
The split systems defeat this by having the buyer measure the distance from where they are going to put the compressor to where they will put the interior part. The copper lines (called a “lineset”) are cut at the distributor and the unit is pre-charged with the refrigerant - the owner simply places the compressor here, hangs the cooler there, connects the lineset and opens the valves - it’s done.
They even sell a high-density plastic pad to replace the concrete pad the on which the compressor is typically set.

It also is a much more secure system - with a wall or window unit, the bad guy needs to simply cut the supports, and the unit falls out of the wall, leaving a huge hole for entry.
The split system uses a hole about 3" in diameter for the lineset.
Run the lineset through a PVC pipe for appearance sake.

Ok message received on split systems but let’s assume I’m not going that direction and possibly explore the other side of things.
Especially as I’m not the one that gets final decision on this upgrade and everything is a bottom line. I need a more economical solution than this. As for square footage that is indeed the truth; at least in SC it is. Fact: Heat pumps add square footage to a house as they are considered part of a home.

I have no doubt that split systems are nice, but I’m almost certain this option will not be the one WE go with. I was hoping for through-wall solutions or ideas even. Cleaners that you spray into such units do not work so great because once you’ve installed the unit you aren’t able to have access to the deepest portions inside the chassis. Not to mention in many cases the components need to be physically wiped down to be the most effective. I was hoping for something with a access door possibly.

The thing is, one unit I had for for 5 or more years with no problem, then all of a sudden it started smelling, the other window unit was a smaller cheaper unit from Wal-mart and it only took about 4-6 months and I had a very similar issue. I’d rather focus on prevention; to find the root cause. It’s apparent to me that the kind of unit purchased makes a difference in regards to the onset of the problem.

Can you get a garden sprayer wand into these units? If so, perhaps put a 45 degree bend at the very tip, and rotate to spray in all directions.
Standard 1 part bleach to 2 water to control most mold/mildew/slime.
If it is a very sturdy unit, perhaps a pressure washer in place of the garden sprayer
Obviously, you need a removable drip tray - and make is a resin one, not cheap UV-rot-R-Us plastic.

Also obviously, be prepared to repeat.

No magic words to make a window A/C NOT a window A/C.