Daikon is way worse than Mitsubishi from what my hvac guy tells me

Mitsubishi Electric or Mitsubishi Heavy Industries?

I sourced opinions far and wide and in the end it seemed to be a coin toss between Mitsubishi Electric and Daikin. A lot of it comes done to parts availability, and both seem very strong in Australia.

I live in a cold climate

Mitsubishi is gold standard in cold climates. It’ll pull heat from -30F air.

There's no reason that's unique to Misubishi. My parents Fujitsu has done so.

Both brands trade off as best cold weather heat pumps in ratings/evaluations (quick Google search should confirm), they’re both fairly high quality versus competitor brands.

Dealer salespeople are loyal to their brands and shit talk the other brands, so I'd take that with a grain of salt. I own both brands, they are basically the same.

>And mistakes by installers will cost even more.

I once looked at a house with a new GSHP horizontal loop installed in the desert southwest US. I talked to the installer and they said the loop was only 12” deep. There’s no way the ground maintains steady temp at that depth, meaning you’re losing efficiency in the hot months when you need it most. Not to mention thermal pollution which will exacerbate the problem and the risk of hitting the loop with even minor ground work. They were adamant it was a good design.

Unfortunately, many installers jump on the bandwagon without the necessary expertise.

Twelve inches? If that's true it seems like it would get ruined quickly by roots, animals, vehicles, lawn mowers, and basically everything else.

Yeah, I know it seems more likely that was a typo, but that's what they told me :) Tbf, roots, animals, and mowers probably aren't that big of an issue because it was mostly xeriscaped desert.

I take your point, but installation faults in central gas heating are also very common, but perhaps less obvious. The main one I’m thinking about is poor sealing or placement of the return duct, causing entrainment of air from the wall cavity. Source: local experts, and then I inspected my friend’s houses (hah).

I love our Daikin mini-splits (came with the house), but as you allude to I've had to become an mini expert on deep cleaning them. They've can get GROSS with mold when used for cooling, and the cursory filter only does so much. That being said, now they stay clean for a few years after a deep cleaning -- though my first few attempt before I refined the process did not stay clean nearly as long. (Proper water pressure and disinfect is key.)

Cleaning basically involves a dedicated cover + drain that diverts water to a bucket, and blasting it with what's effectively a "low power pressure washer" I can use indoors (carefully), and "Lemocide" to properly disinfect... And coil cleaner for the fins. Takes me a good 4+ hours per unit, largely spent preparing the area in case there is any rogue spray. (Though TBH I may be a bit obsessive about getting it right.)

I also had a drain leak as you mentioned -- blasting the drain line with aforementioned "low pressure washer" helped with that. Still a bit gross to deal with. (And learning how to properly disassemble and clean the drip tray is the final thing I've put off leaning for a completely-thorough deep clean... I'm a bit horrified anticipating what I'll find...)

The no 1 reason I bought the Daikin model referenced over the comparable Mitsubishi Electric is that it has the ‘MOULD PROOF’ function. It runs the fan automatically after you have had it in cooling mode, to evaporate the moisture build up from the interior condenser coil, thereby removing the moisture required for the growth of bacteria and mould.

So far, it seems to be working! Better than relying on everyone to manually do it (literally this is the instruction in the Mitsubishi Electric user manual).

If you live in any kind of area with high humidity you just shifted the mold from the AC unit to the rest of your house. Hell even here in the desert I'm not sure I'd want to use that "feature".

I live in the desert. Any humidity we can get in the summer is good.

We are talking about the tiny amount of water vapour left on the interior condenser. The idea is to bring that back up to room temperature so that it doesn’t stay there near the dew point. The total amount of water inside the house does not change!

It only becomes mold by sitting and growing. If the A/C dries it after use, it doesn't have any time to grow.

Yes, over time - any amount of moisture will produce some mold. But it will be negligible.

Where does mold even get the energy to grow, it really seems to spring up from nothing but water.

The surface of our planet is so rich in bio material that some tiny amount of mold can be found in almost all unfiltered air. Instead of trying to eliminate all of it, home builders focus on preventing it from growing. Indoors, mold often has everything it needs to grow except standing moisture, so it's important for everything to either dry out or circulate water.

The fins in the heat exchanger will get covered in dust and dandruff over time. This provides a reasonable media for the mold to grow on.

That definitely helps and I used to do that in my car where the A/C got smelly pretty quickly. Just run the "fan" for a few minutes after you turn off the A/C and it doesn't get gross.

But one problem is the dust in the house. It will collect on the unit and hold moisture and give a great substrate for mold to grow. But regular cleaning usually takes care of that.

We also had a drainage problem after ours were installed. We were very fortunate that another, more experienced tech from the same company came by to follow up on a different issue and took it on themselves to inspect the drain line. It would have leaked into our wall for a long time before it became apparent something was wrong. These units (ours are also Daikin) are a dream to operate but you definitely need to triple-check the drainage on first run.

I'd love to see a youtube video of your cleaning methodology.

Most of the videos from HVAC people are... sketchy to the say the least.

I've seen videos where they dismantle the whole indoor unit and leave the coil just hanging from the line set or zip tied to the backplate while they take the fan and drain pan outside to clean.

One easy thing we've found that helps with drain clogs is to use a shop vacuum from outside to suck it out (using a towel/rag to get a good pressure seal). Takes around 5 minutes per drain per cooling season.

This is a video for the Mr. Cool brand of mini splits. Starting about the 45s mark you'll see how they do it without removing the unit. https://iwae.com/resources/videos/mrcool-care-kit-ductless-m...

I'll try recording something next time I clean one of the units (one needs a deep clean this spring); no promises though. In the meantime, here are some quick notes/resources.

This video shows a similar process using water pressure to clean the unit: https://www.youtube.com/watch?v=xcIVAv8YbPQ

Some more tips and modifications:

- I cover the electronics in a garage bag held with tape. No need to unscrew the black cover over the power wires to disassemble (I unnecessarily removed this a few times heh).

- I ended up really liking this cleaning shrowd after trying a few; the hard pieces on the sides are key for making it easy to secure nicely, which many others lack: https://www.amazon.com/gp/aw/d/B083S85X97

- I spend more time (like 30min+) spraying the blower wheel so it spins. I alternate spraying with fresh water with spraying diluted "Lemocide" (@10% dilution) from a spray bottle a bunch of times depending how dirty it is. I use this <https://snowjoe.com/products/sun-joe-wa24c-lte-24v-150-psi-m...> which at 100 PSI is 10x stronger than a hand pump sprayer, but 10x weaker than a real pressure washer. I.e. the sweet spot IMO.

- I use foaming coil clean from a can to clean the fins if they're particularly dirty. (WARNING: I have not used in the same cleaning as the Lemocide since I haven't confirmed if they're compatible, so be careful of any reactions if you use both in the same cleaning.)

- I take the outer casings outside for a quick rinse with the hose and dish soap if they're really dusty.

- I tape cheap plastic mirrors at 45 degree angle above the unit so I can see it from above and carefully vacuum the back coil (there are 3 folded over in a U, and you can only see 2 from the front). Otherwise this just accumulates junk and is hard to see. This also really helps with finding the 3x clips at the top of the case that secure it to the back housing.

I may have a few more notes worth sharing at some point; feel free to ping me if you have any specific questions.

Edit: See also this quick video on unclogging the drain line on a Daikin (though I used the sprayer against the tube instead of my mouth...): https://m.youtube.com/watch?v=GDrHe-rli98