I added a non-wi-fi Mitsubishi AC to Home Assistant

199 pointsposted 6 days ago
by ichacas
(medium.com)

111 Comments

akifbayram

3 days ago

I’ve been working on a similar setup using the M5Stack NanoC6 and AtomS3 Lite, and put together a parts list and wiring guide on my site: https://serin-labs.com/parts.html.

I also built a web flasher with firmware configured for those boards, so you can install directly from your browser without any fiddling or configuring. The ESPHome option uses the same echavet/MitsubishiCN105ESPHome project mentioned in the article. I also included a YAML generator for that project so you can more simply customize the config. There are also separate firmware options for HomeKit and Matter. https://serin-labs.com/flash.html https://serin-labs.com/esphome/generate-yaml.html

I run Serin Labs and sell assembled kits and the cable separately.

For anyone with City Multi, P series, or M series systems with a branch box, you may also be interested in a multi zone controller I’m developing: https://serin-labs.com/multi-zone-controller.html. It connects to the system’s communication bus, allowing one device to control all zones without needing a CN105 adapter at each indoor unit. It also exposes operating data such as refrigerant pressures, temperatures, power, compressor frequency, and fault codes, with everything running locally. Software is still in development.

hanrelan

3 days ago

HN is awesome sometimes, I actually just installed 3 of your devices in my ACs to get them all wifi enabled. Worked perfectly, thank you!

Is it possible to flash them from Google home firmware to esphome without USB? I might move away from Google home soon but I'd hate to have to reopen up my ACs again.

akifbayram

3 days ago

Awesome. I'm glad to hear that.

It's not possible to cross-flash a different firmware track over the air but since you're already using the Matter-compatible firmware, you can pair it directly with Home Assistant, fully local. It won't be as configurable as the ESPHome firmware, but it'll get you the controls you need.

robbiep

2 days ago

That’s incredible.

I have an airtouch which I love but my parents have a Mitsubishi system that I’m fairly sure would be compatible, and a large floor space to manage.

Apologies for the question, but for multi zone, you mention that the controller can pick up temperature. My understanding was that temperature is only captured at the intake, not in zones? (I’m familiar with airtouch where I have ?BTLE temperature sensors in the rooms/zones that are paired to my system). But how does this work with a Mitsubishi zoned system? Or am k over-reading the capabilities. (Or is it a similar deal, I just haven’t seen where to acquire these zone temp sensors from)

akifbayram

a day ago

Thanks! I just took a look at AirTouch. It seems they have a nice ecosystem. Their Mitsubishi Electric offerings [1] use the CN105 port (like the OP's device).

I use the word zones on the Serin Multi Zone product page but it's interchangeable with indoor units. One indoor unit equals one zone.

You can override the room (intake) temperature per indoor unit/zone using a controller plugged into the CN105 port (like the OP wrote about). Depending on the controller, it can pair with a Bluetooth sensor or listen to any other type of sensor from Home Assistant. By going the ESP32 path, you can use simple, off the shelf $10 BLE sensors.

The Serin multi zone controller uses the centralized communication bus which isn't capable of overriding the indoor unit's room (intake) temperature. But if that is a must (which it is for ducted units), you can have both the multi-zone controller and a controller at every indoor unit without issue. So if you have an MHK2 thermostat on the wall and don't want to use their Kumo app anymore, the Serin multi zone controller will give you local control and you'll be able to retain the remote temperature sensor from the MHK2 thermostat.

[1] https://theairstore.com.au/product/airtouch-gateway-mitsubis...

robbiep

13 hours ago

I appreciate you taking the time to reply - that helps a lot. So essentially I get this and plug it into the CN105 port, and then everything will be in home assistant and I can get room/zone temperature control via BLE as well.

akifbayram

12 hours ago

Spot on. If you're using Home Assistant, you can push any temperature sensor available. Zigbee, Zwave, BLE, 433mhz rtl sdr, etc. At one point, I was using the proprietary temperature sensors that were paired with my ecobee thermostat (for my ancient natural gas fired hydronic boiler). For the BLE sensors, your HA server must have bluetooth capabilities. I use a bluetooth dongle attached to a short USB extension cord.

DANmode

2 days ago

> I also built a web flasher with firmware configured for those boards, so you can install directly from your browser without any fiddling or configuring

Awesome

cgrin

3 days ago

The Nano is fine to connect directly because it has diodes on the data pins but the S3 Lite needs a level shifter or it'll eventually stop communicating with the air handler.

micromacrofoot

2 days ago

yeah came here to say this, I have my mini splits set up on the S3 light with level shifters, not worth skipping because they'll end up failing on you - requires a little soldering but nothing complicated

wiring:

1. Mini split black (GND) → ATOM G

2. ATOM spare G → shifter GND (either row)

3. Mini split red (5V) → ATOM 5V

4. ATOM spare 5V → shifter HV ref

5. ATOM 3V3 → shifter LV ref

6. Mini split yellow → shifter HV1

7. Shifter LV1 → ATOM (G2 / GPIO2)

8. Mini split white → shifter HV2

9. Shifter LV2 → ATOM (G1 / GPIO1)

if the gpio ends up being reversed you can handle it in software

doug_life

3 days ago

Thanks. I’ve been looking for a clean ots solution and somehow managed to not come across your company yet. Just purchased pre-assembled module!

OxfordCommand

2 days ago

i've installed 4 of your devices last week. they work flawlessly.

hatsix

2 days ago

I've got four units already hooked up with esphome, but the branch box diagnostics is what I need... the unpredictable nature of multi zone units is infuriating. Why is one room 10 degrees above it's set point and still pumping out heat?

I've got my own devices and can make my own cables, if you're looking for someone to test things out

akifbayram

2 days ago

From what I've read and experienced over the years, the indoor units of a Mitsubishi multi zone system never fully close their valves, so refrigerant flows through them even when they aren't actively heating or cooling. This becomes a problem when the indoor unit also runs the fan non-stop to get an accurate reading of the room temperature, since a thermostat with a remote temperature reading typically isn't available.

I got around this by disabling the fan from blowing when the indoor unit isn't actively calling for refrigerant. The refrigerant still flows through the indoor unit but since the fan isn't running, it isn't dumping conditioned air into the room. Every unit has a different way to disable the fan when it's not heating or cooling. My mini splits needed a jumper cut on the indoor control board but my air handler was configurable via a thermostat.

This raises the issue of getting a proper temperature reading of the room. Without the air flowing over the thermistor in the indoor unit, the reported indoor temperature becomes wildly inaccurate. To get around this, a thermostat with a temperature sensor is needed. Mitsubishi has a few off the shelf options. I went with the popular route of adding a Bluetooth sensor to my ESPHome builds and I sell a bundle including the controller and remote temperature sensor. More information here: https://serin-labs.com/controller/room-sensors.html

usagisushi

3 days ago

Mitsubishi AC units that support M-NET have a CN105 port. IIRC, my specific model uses a JST PA 5-pin connector rather than a JST PH 5-pin.

As a small hack, I used the Python scripting interface in Home Assistant to replicate this [1] feature from Panasonic HVAC that gradually raises the cooling set point towards the morning. It is quite comfortable during the summer.

[1]: http://getnavi.jp/appliances/681340/ (ja)

acyou

2 days ago

These mini split inverter units seem to be good for +/- 1 C, but the 2 C swing can feel quite substantial.

PID control seems to be lacking overall, the control laws seem to be more basic. In particular, my unit waits until temperature deviation from setpoint exceeds 1C before cycling on. If I want finer control, there are a few options I can think of: 1. Spoof the temperature, add a TEC , heater, cooler or something to the sensor on the remote 2. Manipulate the controller buttons, change the setpoint down or up by 0.5 degrees so the unit kicks on after a 0.5 degree change instead of a 1 degree change 3. Spoof the temperature sensor itself, hack into the wiring with some transistor based circuit 4. Hack into the actual unit, fully take over the compressor and fan control 5. Buy a better unit or off the shelf controller 6. Spoof the remote control, reverse engineer the IR communication temperature signal

This last option seems the least intrusive and cleanest, I see other people have done it, it's definitely a lot of work even with AI.

briHass

2 days ago

Is your unit one of the ubiquitous Midea rebadges? Or at least one where the remote does 'follow me' type periodic, remote temp reporting?

If so, you're right, the easiest way is to build/buy an IR blaster module for a microcontroller (ESP32 if you want wifi) and connect a temperature sensor. HA/EspHome is overkill for this, but can be useful for the large catalog of pre built integrations. Most of them are built using/on IR libraries for 'Arduino' anyway, so you can easily roll your own with a half dozen lines of C++.

Mapping out your own PID correction algorithm (esp says the room is 72 F when it's really 70 F to get it to cool sooner), but usually just having the remote room temp sensor near where you'd be sitting instead of near the ceiling or in the return air stream gets you close enough.

acyou

2 days ago

Thanks for this. Yeah, it has the follow me mode that sends temperature from the remote control every 3 minutes. I think it's a Senville from Home Depot. The remote control sensor only seems to read at 1 C resolution, so it seems like using the follow me mode with the stock remote is right out of the question.

My biggest worry is the heat from the microcontroller affecting the temperature on the temperature sensor. I want to use a Sensirion SHT45, it has 0.01 degree temperature resolution and is supposed to be accurate to 0.1 C. But I need to locate the temp sensor far enough away from the microcontroller to make the overall remote controller form factor awkward. I have a Raspberry Pi 4 that does the temperature data logging and web server, but that runs pretty hot.

no_time

2 days ago

>Mapping out your own PID correction algorithm

I want to do this but I'm worried about stressing the compressor with extra start/stop cycles would shorten its lifespan. Maybe they are programmed to overshoot/undershoot the set temp to prolong lifespan?

Disclaimer: I know next to nothing about how ACs work beyond the very basics.

acyou

20 hours ago

Yeah, you can cause it to short cycle for sure. But you can also get better control without excessive short cycling. If you're worried about short cycling, just include that in the control algorithm.

Short cycling would be bad in the sense that the motor frequently turns on. The maximum current is during motor start and the maximum motor coil cooling is when the fan is running at high speed steadily. So if it starts a lot and doesn't run much at high speed you might tend to overheat, sure. That would definitely drastically reduce the motor lifespan.

If you are still starting periodically and running for awhile, you can see where this goes.

I think it's not overshoot/undershoot that is happening so much as delayed kick on.

briHass

14 hours ago

One of the biggest benefits of modern minisplits over conventional split systems (like are still common in America) is that their compressors are variable speed inverter types. This allows them to slowly ramp up to speed without the massive inrush of current.

That said, it's still a mechanical device that can experience stresses caused by cycles. Refrigerant systems also deal with gas/liquid phase changes and high pressures, so most units I've worked with do have a compressor lockout timer that allows a few minutes for temps/pressures to stabilize before kicking the compressor back on.

xmddmx

2 days ago

Would running the unit in Fahrenheit improve the sensitivity?

acyou

2 days ago

I don't think so? But I would have to do some testing to tell. The unit thermometer precision appears to be 0.2 C. I think the remote thermostat precision is worse than the thermostat on the unit itself.

nemosaltat

3 days ago

I did a similar thing, heavily aided by Claude, after seeing the protart modules posted here on HN last year. https://github.com/samstevenm/minisplit-local-public

Apologies for the Claudish, especially if anyone wades through the blog posts. I cringe when I reread them, but having some documentation on a working system is better than the ~none I was publishing before.

hattmall

2 days ago

If anyone is looking for something similar it's worth looking into A somewhat less complex solution that preserves all functionality. Use the IR receiver plus a broadlink IR Hub. You can meet all the goals here, run it all locally the only downside is no 2 way communication. So if you do change the thermostat via the wall it won't be reflected in your app.

seniorsassycat

2 days ago

This project isn't very complicated, doesn't require extra power source, and doesn't beep every time you change the settings.

BrandoElFollito

2 days ago

You can add a camera pointing to the display and analyze the image. You would have a perfect galvanic separation for reasons.

sippingabonedry

3 days ago

For anyone wondering why he would ever do this, it seems to be a type of hidden mini-split system used in euro-style shoebox flats, with a super-proprietary thermostat. Wi-Fi capability is an option at additional cost, but was not purchased.

In the USA, wired thermostats tend to use standardized 24V wiring schemes, or 208V/240V for mains voltage heaters (electric heat, common on the west coast, especially in shitty apartments, central hot water/steam heating with 24V controls is more common on the east coast).

murderfs

3 days ago

Most new construction with heat pumps are going to use similar thermostats, both because of improved efficiency since the outside unit wants to know how much heating/cooling load is being requested, and more importantly, because builders are lazy and would rather use a battery-powered wireless option than run thermostat wires.

Off the top of my head, Mitsubishi, Rheem, Lennox, and Carrier all have similar default options, with converter boxes for retrofits to 24V controls.

numpad0

3 days ago

Is this "mini" split? This type of panels are pretty standard for office buildings in Japan. Usually networked into building management system somewhere. Most household mini splits come with an IR remote, and don't support these panels. Standalone third-party thermostats are rare.

sethhochberg

2 days ago

People tend to mix the terms around a lot, but generally you'll see the manufacturers use "ducted split system" or "mini split", where mini splits are the self-contained wall or ceiling mounted units.

I live in an NYC apartment with a similar Mitsubishi ducted split system - very short run ductwork just because the apartment itself is small, but takes up way less space than traditional American-style air handlers, even the apartment sized ones. The entire air handler is suspended above my bathroom ceiling, in between the drywall and the slab above.

My system was originally installed with the 2-wire serial wall thermostat but I converted it to one of Mitsubishi's Redlink wireless units because I needed to relocate the thermostat. But since Redlink isn't wifi, and the Mitsubishi networked thermostats and cloud platform get pretty poor reviews... this project is super interesting to me.

zb

2 days ago

Even for ducted systems, these proprietary controllers are the only thing you can get in Japan, and by extension places like Australia/NZ where the systems are all imported from Japan. (Europe is still largely yet to discover heat pumps, judging by reports from this past summer.)

Gigachad

3 days ago

I had this same control panel in Australia. The actual AC unit was part of the strata common property and I think somehow shared between multiple units on the floor.

HeavenFox

3 days ago

FYI this kind of thermostat is actually better. American style thermostat put your HVAC system in either on or off state (basically PWM), whereas this kind of communicating thermostat can tell the system what the temperature is, so they adjust power accordingly. I do wish they have standardized protocol though.

bob1029

3 days ago

Single stage hvac systems tend to have better performance in the max capacity cooling cases (Texas) and last significantly longer than units that rely on non-linear electronic devices.

The difference can be as extreme as 10+ years of service life. There are residential systems that were installed in the 80s and 90s that are still running fine today. The hermetically sealed scroll compressor is an engineering marvel. The electronics will generally fail before any meaningful mechanical wear is incurred.

thatfrenchguy

2 days ago

Single stage forced air / air handlers AC systems are basically only found in North America because they are so grossly inefficient and because most people in the rest of the world realize they can save money by not having all of their rooms ran off the same system. The rest of the world runs on mini splits for that reason.

ufmace

2 days ago

I don't understand why it's so common for Europeans to act like they speak for the entire rest of the world outside of North America.

gruez

3 days ago

>Single stage hvac systems tend to have better performance in the max capacity cooling cases (Texas) and last significantly longer than units that rely on non-linear electronic devices.

Why?

bob1029

3 days ago

Inverter systems have more conversion losses than single stage. Most of the time, I definitely intend to run my system as hard as it can. There are only 4-5 weeks out of the year where variable speed would make a meaningful difference.

Semiconductors wear faster than copper wires and contactors and are much harder to replace. I can take a part from my neighbor's condensing unit and it would almost certainly work in mine. The make/model is largely irrelevant. I can go on Amazon, search "Start+Run Capacitor" and buy the first thing I find.

ssl-3

2 days ago

> Most of the time, I definitely intend to run my system as hard as it can. There are only 4-5 weeks out of the year where variable speed would make a meaningful difference.

The system never catches up, even at night?

bluGill

3 days ago

Because all too often the electronics are what fail and replacement parts are not available so the whole thing is scrap even though the compressor is still good.

deelayman

3 days ago

The thermostat is better only because it takes advantage of the inverter modulation capabilities in the heat pump. I don't have the sense that inverter modulation is the norm for most home ducted systems, even new builds in North America.

I've only observed ductless systems like this in retrofitted, older homes in Canada. And at that point they're usually not integrated with the home's existing heating system / thermostat.

bluGill

3 days ago

It is starting to happen in the US as well.

sippingabonedry

3 days ago

Depends on your definition of better.

It's a tradeoff I'm willing to make for simple, open I/O. It's not PWM but rather a "call" for heat, cooling, or fan. If I'm refinishing the wall I can (and have) put in a $3 thermostat in its place so I don't destroy the $300 one with paint and dust.

It's also very easy to debug and repair, as I experienced on a day when the temperatures exceeded 100F and was able to execute an emergency repair myself.

If companies like Nest and Ecobee were not allowed to exist, we would all be stuck with the overwhelmingly universally overpriced, proprietary garbage the OEMs put out.

madaxe_again

3 days ago

I did similar with our coffee machine a year ago - I was bored of getting home from the school run to a cold pot of coffee because the machine automatically turns off the hot plate after 30 minutes, and it seems there is no such thing as a WiFi connected drip coffee machine. Kettles, yes, coffee machines, no.

Dead simple. Cracked it open, chucked an ESP32 in there connected to the soft power button, and to the “machine is on” indicator on the display, which was conveniently on its own pin. No need for any thermal protection cleverness as the machine does that itself.

Now I just turn it back on when I’m heading home, and no longer have to wait for the pot to warm up again.

I then decided to stop using the “make coffee at time” functionality baked into the machine, as the kid gets up when the kid gets up, and the machine would either start early and wake her, or she’d get up before it and I’d have to go start it. Now, she opens her bedroom door, I get “kid is awake” alert on my phone, and the machine brews the coffee.

dwedge

3 days ago

> Now, she opens her bedroom door, I get “kid is awake” alert on my phone, and the machine brews the coffee.

Out of all of the smart home threads and articles I've read over the years this is the only sentence that made me wish I had it. It's genius

bluGill

3 days ago

Until the kid uses the bathroom in the middle of the night and goes back to bed. Though the GP seems to not mind stale coffee so perhaps he won't care.

Exceptions like the above make automations hard.

kotaKat

3 days ago

DR stands for "didn't realize"; the first time it happens you just run back to the drawing board and add some safety boundaries on it.

So... just make sure the automation only becomes available from ~6 AM to 8 AM. ;)

bluGill

3 days ago

Sure, but in home automation there was a whole lot of those didn't realize situations that you won't get right. In the one end I often go for the question, 'is it really worth the bother of trying to set this all up'?

In most cases, there's nothing wrong with the switch on the wall. I don't need a complex home automation. I do have Home Assistant. It isn't very useful. It's kind of nice to have a couple of lights on from dark until 9 p.m. but with the efficiency of modern LEDs, it's probably cheaper to just leave those lights on 24-7 than to leave my home assistant machine on 24-7.

madaxe_again

2 days ago

I gate it exactly as the parent says - automation only runs between 0530 and 0800, and when we’re home.

I literally couldn’t do without HA - I live off-grid, and it manages everything from monitoring water tank levels & running pumps to a power grid distributed over three independent and geographically distributed battery banks. Monitors for anomalies and tells me what is acting up - for instance today I got sent on a mission to find out why an array of PV was underproducing by 33%. Wouldn’t have noticed until it started having energy budget impacts otherwise. Makes decisions on whether today is a passive cooling/heating day or whether we have the energy budget to run climate control, when windows should be opened/closed to maximise efficiency, which blinds to close when depending on where the sun is to prevent or encourage passive solar gain, when to run the partially pumped storage hydro and in which direction, when to pull the pin on the deluge system and where if it’s set to wildfire mode. It has literally saved the house - not our lives, as we’d already evac’d and left it in charge of firefighting.

Stuff like the coffee machine and opening the blinds in the morning are just easy quality of life improvements, something less to have to manage manually, as my days are full enough that removing any point of friction is useful.

And yeah, I’ll take slightly stale coffee now over fresh coffee in ten minutes.

dwedge

2 days ago

It seems pretty easy to throw in an earliest time to trigger it

globular-toast

3 days ago

I'm hoping to get a mini-split system installed soon and thought I might as well look for something with HA integration. It's not easy. Some manufacturers like Samsung actually want to charge you monthly for cloud integration! Completely out of the question obviously. I came across this, and Mitsubishi is supposed to be good anyway. I would prefer something that's actually supported but I can't seem to find any other options.

I could also very easily wire my units in so no need for WiFi. Maybe I can find a wired ethernet module.

nemosaltat

3 days ago

I used this guys thing https://clima.protoart.net/ after someone mentioned it in an HN comment last summer, then used claude to extend it this summer. A year in, I’m very pleased. Matter or thread would be nice, but these are super straightforward out of the box and totally local.

The manufacturer documentation [0] for everything is great and it was perfect for my goal of getting them to show up in Savant as native thermostats [1] (likely beyond typical scope for split units).

[0] https://protoart.net/knowledgebase/me_cn105_ata_wifi_http_ap... [1] https://github.com/samstevenm/minisplit-local-public

damascus_kei

3 days ago

I have a Daikin system. I use Faikout(ESP32 that controls the heads via the debug port) to control my units from home assistant. Works great!

Their official service needs an app and cloud access to control it. And I absolutely refuse to do that.

https://codeberg.org/RevK/ESP32-Faikout

Gigachad

3 days ago

My ideal system would be something that does matter over thread with zero external internet access. Matter over thread devices are all standardized so no proprietary app required, and the newer iphones have a thread radio built in so you can control them without even a hub.

XorNot

3 days ago

Wifi with a firewalled network is a lot easier to debug, which is how I do it in my house.

There's no Internet from the IoT SSID.

dobremeno

2 days ago

I have my AC connected using Matter (over WiFi, not Thread) using esphome-matter, a relatively new extension to ESPHome + a small open PR [1]

Since it's running ESPHome you can easily verify everything it's doing.

Thread would be even better but this is good enough for me. 100x better than the original cloud app it came with. Still no proprietary app required, works on every platform.

[1] https://github.com/DavidvtWout/esphome-matter/pull/53

koyote

2 days ago

The non-ducted systems will usually have an IR remote. You can buy devices to blast IR at it and HA has good support for that. This is what I use.

Cakez0r

3 days ago

Fwiw I have a Samsung AC system and Claude was able to one-shot a custom web dashboard to control it.

scosman

2 days ago

I've done this exact mode on my Mitsubishi ACs. Despite being old units that came with the house, they are instantly responsive and report back current temperature flawlessly.

ESPHome device are consistently faster and more reliable than any smart home tech I buy at 10x the price (not hard with $3 boards).

userbinator

3 days ago

My idea of HVAC is that it should be "set and forget", so "smart" is the polar opposite of what I want. The round Honeywell on the wall has been doing its job for the past few decades, and will likely last many more with only an occasional cleaning.

skolos

3 days ago

If you have same schedule every week, don't go on vacation, your kids don't have breaks, don't have seasons, then 'set and forget' dumb thermostat will work for you without any problems. For the rest of us we need some 'smartness' in our thermostats.

user

3 days ago

[deleted]

userbinator

3 days ago

You shouldn't need to change the temperature regardless of those things. My house remains at 68-72F basically all the time. Thermal cycling accelerates aging of materials.

spicypixel

3 days ago

Sounds expensive at the equivalent rate of 38 cents a kilowatt hour that I pay during the day.

userbinator

3 days ago

Power is cheaper than things failing earlier than they could have due to thermal cycling.

rcxdude

3 days ago

Do you have any citation for thermal cycling through the range of an AC inside a house affecting the failure rate of any household goods? Based on my experience this does not seem likely to be the case: thermal effects tend to be exponential or high powers of temperature, and most thermal cycling that people worry about is on the order of 100C or more. 10/20C of variation seems unlikely to be relevant.

(There is a case where if your house is well insulated enough, then it can be worth avoiding cycling your AC during the day, because it is both less efficient and will wear more while pulling the temperature down and this can be worse than just leaving it running in a sufficiently insulated house. It still is probably worth turning it off if you're away for a week, though)

ssl-3

2 days ago

> because it is both less efficient and will wear more while pulling the temperature down

That's just not true. Aircon is a heat pump. It pumps heat more efficiently when more heat is available to be pumped.

Warmer indoor air increases evaporator temperature. A higher evaporator temperature means that the system operates with less temperature lift. This means that the system does less work (per BTU pumped) to cool a house that is hot inside, than one that is already conditioned inside.

Equipment longevity also tends to be increased with less-frequent, longer runtimes than with more-frequent, shorter runtimes. There's less temperature cycling, fewer in-rush current events, and the lubricating oil in a running compressor is actively circulated to the parts that need lubricated. Reducing the number of compressor start-ups is a good thing; these machines like to run.

So even if same number of BTUs enter the home and need pumped out whether the aircon is running or not, then: Letting things warm up inside when there's nobody home to care about that constitutes an improvement in a broad number of ways.

Reality is even better: On a hot day, a house that is hot inside takes in fewer BTUs than one that is cool inside, due to the reduced temperature delta between indoors and out. When we have fewer BTUs coming in, then we have fewer BTUs that we must ultimately pay to pump back out.

dgacmu

2 days ago

But with most houses, the AC will cycle on and off throughout the day anyway - raising the temp while you're gone will often result in less cycling. Especially if you also increase the hysteresis range while out. So you get a triple efficiency win, from better AC efficiency, less AC motor wear, and less heat loss to the outside.

duckmysick

3 days ago

Isn't the thermal cycling greater outdoor than indoor because of the differences in the outdoor temperature between day and night? So most ordinary materials indoors should be fine with a delta of even 10 Kelvins/10 Celsius/18 F.

All of the material thermal failures I can think of come from localized and more extreme sources: electronics, lightbulbs, washing/drying clothes, washing dishes in a dishwasher. Water below freezing point too, but that's because the temperature fell below a threshold. None of these are from heating or cooling rooms directly with HVAC.

userbinator

2 days ago

Yes, it's MUCH worse outdoors, but indoor temperature (and humidity) swings are not good either. I guess most people here just haven't paid enough attention to it as it's a very long-term effect, but definitely noticeable.

duckmysick

a day ago

So did you have two rooms with the same objects in them but different temperature swings, over a long period of time, and then compared?

What's the baseline and what's the safe delta?

userbinator

2 days ago

Everyone I know offline keeps their house at a constant temperature year-round, yet apparently it's controversial enough to be a downvoted opinion here? WTF?

dzhiurgis

3 days ago

How about sleep? Ideal temperature is 18C.

fhdkweig

2 days ago

That is 64F. Not everyone considers that an ideal temperature.

dalyons

2 days ago

As in scientifically proven to be biologically ideal, proven to have the best sleep outcomes. You can have different preferences of course, doesn’t change what’s ideal.

jonathanlydall

3 days ago

For some people they may only opportunistically (perhaps they have excess PV production at that moment) run their AC or temporarily turn it off when they temporarily have other power demands at that moment (eg running dishwasher, washing machine, microwave, kettle, etc) and don’t want to pay for grid energy while doing so.

“HVAC” is essentially not a thing in houses in South Africa likely due to having a mild climate, this also makes insulation in houses optional and mostly not done.

So most people with AC here are probably using it as a luxury and will happily have it be off a little if it meaningfully reduces energy usage while still making their house noticeably more comfortable.

wjnc

3 days ago

This is exactly the case in my household. Excess solar is pretty much worthless here, so with a smart AC you can dump the excess solar into your house as either heat or cold. This (currently) has a lot better ROI than installing a household battery. (Battery tech and availability might change this.)

I am enamoured by making dumb AC's smart by this method, since you probably have a lot less IT risks than by using the suppliers app. I think the trade off is between IT risk and mechanical / technical risk, since adding your own parts have an effect on warranty (or at least: willingness to repair by the supplier).

porknubbins

3 days ago

Isn’t this is only true with central air though? Most other types of ac are not full climate solutions to leave running all the time and need some manual control.

At least that’s how I use the mini split in my garage. I have to remember to give it 15-20 minutes headstart before I use the garage or will be really hot.

sippingabonedry

3 days ago

Check out Uncle Pennybags over here with AC in his garage...

All "smart" t-stats can be used in "dumb" mode but the remote control and monitoring is really the killer feature. Scheduling and presence is meh, if you're obsessed with energy savings I guess.

I'd rather know if the system has failed when I'm 500 miles away before the pipes freeze.

llsf

3 days ago

Does anyone know if this could be used to "cap" the AC settings ? It could be useful in an airbnb place, where I want to limit the lowest (e.g. 18 degres Celsius) or hottest (e.g. 22 degres Celsius) the guest can set the AC.

burner420042

3 days ago

To answer your question, yes you could certainly do that and override what ever the physical thermostat was set to. You could also set max hours per day (kWh)for usage or adjust for variable rate plans. As with anything you'd need to test.

Edit: Looking through the repo and the article I see nothing blocking you. You certainly won't break anything!

llsf

3 days ago

Thanks! I don't think I would need to do max hour per day.

sippingabonedry

3 days ago

If you controlled the AC temperature remotely it's a great red flag to never rent that Airbnb. Some people like it cold when they sleep.

jonathanlydall

3 days ago

I don’t think they’re proposing remotely controlling it, just so that the guest would experience being unable to change the temperature to outside the allowed range.

Of course any guest is free to write in their review “can’t make temperature lower than 18°!” but the number of people choosing not to book for that reason in any given year is likely 0 or very close to it.

There are a lot of people who don’t “get” thermostats and their intuitive model of ACs is like that of getting a bath to a particular temperature by turning a faucet to full hot or cold to get what they want.

And if these people are out of the room when it reaches the actual temperature they want (and would change it), then the AC is left possibly for hours working full time, burning maximum energy and related wear and tear by trying to hopelessly achieve an unattainable temperature.

llsf

3 days ago

I understand, and I could make it clear in the description that AC is capped at 18 degres C minimum (65F), so people who like it very cold could skip my airbnb.

Some AC can go ridiculously low (http://news.bbc.co.uk/2/hi/uk_news/england/3144803.stm). I do not want to change the temperature remotely, I just want to not have the AC used to extremely cold temperature. I am fine to advertise it to weed of people who like it very cold.

sippingabonedry

3 days ago

I should have bothered to do the conversion... when I read your post I was immediately reminded of the recent laws in Italy that capped AC in public spaces to a minimum of 25C... 18C is awfully cold for a residence!

Most programmable thermostats in the US do have built-in limits for device protection.

I've never met anyone who sets AC in a home to lower than 68F and that is an absolute extreme. Most central AC systems are designed for ~20 degree temperature differential so on really hot days you'd have trouble getting it that low anyway unless the system is oversized.

userbinator

2 days ago

Room temperature varies by country and region: https://en.wikipedia.org/wiki/Room_temperature

18C is not uncommon in the UK. They seem to like it colder. Italy is down south so 25C may already be getting cold for them. Then there's the Indians who like it closer to 30C...

nottorp

3 days ago

> 18C is awfully cold for a residence

Yeah, why set the upper limit to 22 and not like 24-25? It will save you even more power for those that don't sit in your airbnb in a 3 piece business suit...

DrammBA

2 days ago

> Some AC can go ridiculously low (http://news.bbc.co.uk/2/hi/uk_news/england/3144803.stm).

Did you just post a link to a 23 year old news article with no sources on an http-only site as supporting evidence that your airbnb unit's AC unit can go dangerously low?

You really think your guests will get frostbite if you don't do them the favor of limiting the AC temperature (with the unintended side-effect of saving you some money)?

ssl-3

2 days ago

Lots of digital thermostats (both relatively dumb and very smart) allow for temperature adjustments to be locked within pre-set limits. If your customer disdain drives you to want that kind of thing, then just find one and install it.

spicypixel

3 days ago

Anyone tried this on the Bosch units? Their WiFi module comes as an addon too.

pampas

3 days ago

Research it with an LLM. I've ordered all the stuff for Panasonic and Daikin after a deep planning session. It told me what connectors I need that Panasonic needs a level shifter. Both brands have open source libraries for the internal protocols and wiring. I wanted Zigbee so the ESP32 C6 was the way to go. The Panasonic units I have already have Wifi but most companies suck at this kind of thing. I couldn't get the Panasonic Wifi to pair with my router. Daikin also sell Wifi modules and people don't to like them.

noja

2 days ago

This seems to be better featured than ir blasters like Tado Smart AC Control (which is not bidirectional)

a012

3 days ago

This is kinda unrelated but I learned while researching for my new AC that there are two Mitsubishi brands/companies, one is Mitsubishi Electric and the other is Mitsubishi Heavy Industrial. And their ACs are not the same, so just saying Mitsubishi AC probably could lead to problem. The one OP has is Mitsubishi Electric by the first photo.

mrexroad

2 days ago

Technically, they’re both part of the Mitsubishi Group, the former zaibatsu; there are number of other Mitsubishi companies in this conglomerate as well.

However, the Mitsubishi Pencil company is entirely unrelated to the Mitsubishi Group. Ironically, they share a very similar three diamond logo, which they registered and used years before Mitsubishi Group.

nicman23

3 days ago

my solution is to capture the irs with flipper and replay them with tasmota