New air-con, part 4

As you know, I got air-con last year, and it had to be taken out. That was a Mitsubishi system. It did not manage to heat or cool even the smallest room sensibly, and had a show stoppers in terms of temperature control of the rooms. So yes, removed. We did keep the lossnay for fresh air though.

I have now got 4 Seasons Solutions to put in new air-con. It works. A lot of this blog is comparing the Mitsubishi with my new Daikin system.

Outside unit

The Mitsubishi system was set up with two outside units on the back wall. Each drove an inside unit. The Daikin is done with one outside unit. It is ironic that the old system seemed to really lack power to actually heat or cool even with more units of a similar size.

A single unit is better, not just for appearance but if there are any issues with planning permission. A heating only single outside unit is actually a permitted development. Yes this unit cools, but you then get in to interesting debates about what happens if you change a heating only (permitted development) to a heating and cooling (non permitted development) and how such a change "does not change the external appliance of the property" so is outside the scope of planning permission. One hopes we don't get in to that debate. In our case I have pictures of the place from just before we moved in with two large outside air-con units that had been there for years, so at best this is about the fact that the air-con location is slightly different. I doubt there will be issues, and retrospective planning permission is not usually an issue. If it was two units, it would be a different matter. It was quite handy as the second power cable and RCBO can be used for the solar install now.

Inside units

The Mitsubishi system had two inside units, each covering two rooms. I should have decided against this, in hindsight. The plan was that we would have motorised vents to allow each to work one room, the other room, or both. That actually worked. We also had relays to switch the controller from one room to the other (it oddly only handles one controller!). That too worked. What did not work is using the controller for temperature, so we could never control temperature in the second room on each unit (assuming the air-con worked properly in the first place, which it did not). So that was a show stopper.

The new system has 4 separate inside units. Even so, it is cheaper. It is cheaper than the rest of the original bill after paying for the lossnay to stay, even.

Like the Mitsubishi, these inside units are ducted. This is nice as it means no big wall mount unit - which frankly would have been difficult to find space to mount in some rooms.

However, one of the rooms has no loft. With the Mitsubishi system, we managed to run the air flow duct behind plaster board (there was a surprising gap) and behind wardrobes in a room above. It was a lot of work (which we did, not the installers). We decided that trying to run two more ducts, at 4 times the size each, would really not be practical. So we went with one of the 4 rooms having a wall mount unit. The pipework for this was somewhat easier.

We kept the original duct for the lossnay, so we still have fresh air.


The ducts were different. The new system had ducts that are 4 times the size of the Mitsubishi system. This is where we changed one to the new ducts.

The vent/covers are nicer too.

What is more fun is the original Mitsubishi installation had ducts that were half the size of this, i.e. 1/8th of the size we now have, and they were adamant they should have been enough!

Wired controls

The Mitsubishi system had a separate control for the lossnay and air-con, which was annoying in itself for an integrated system. It allowed one air-con control for each inside unit. It could not use the controller as temperature reference - crazy.

The new system has wired wall mount remotes. They are not bad. (yes, some holes to fill).

The system can use the controller for temperature - yay, and all 4 rooms have separate control (the wall mount uses an IR control though). The system, as a whole, is only heat or cool at once, but each room is separately controlled at separate temperatures at the same time. As we have central heating (also controlled by Shelly modules) if we ever need mixed heat and cool we can do that easily enough.

The new controllers also have bluetooth and an app. This means the controller itself is pretty simple, and all the admin or installer menu stuff is on the app. Not a bad compromise.

Computer integration

This is where the Mitsubishi was really limited. There was no WiFi or bluetooth. The unit did have some connections that allowed for external control, so as fan speed, but not something simple like heat/cool mode. I was expecting to connect to this, and maybe even reverse engineer the wired remote. I stopped doing that when it seemed clear that the whole thing was not going to work well.

The Daikin system, however, has bluetooth on the wired controllers, and wifi modules. OK, yes, I have reverse engineered and replaced the WiF modules, but even so, that was not too hard. What they provided did actually work (if you are happy with a cloud based system).

The fact I now have fine control using my own WiFi modules is a real win. At present it is heating my room over night (see image on right).

Some limitations of ducted systems

Having now tried two ducted systems, they are a little different than the wall mount I have been used to, and some things still hold true for that.

Both systems had few fan settings. The Mitsubishi had 4 levels, but only the top two actually ran the compressor, the first two just blow air, so very limited. The Daikin has 3 levels. The wall mount Daikin has 5 levels and "auto" and a "night" mode. I'd love a "night" mode on the ducted systems to be honest, but looking in to noise attenuators possible, or just getting used to it.

Another caveat is that a ducted system, having vents in the ceiling, it can take a while to heat as the heat fills from the top of the room - this creates a noticeable lag in heating at bed level. The wall mounted unit is much better at this as it able to direct the airflow down and create more circulation.

The proof of the system

The real proof will be in the summer, and we will see. Tests so far suggests it just works, and works really well.


Almost forgot, as people will ask: It cost around £10k and took a week to install.

Part 5


  1. Thanks very much for your detailed descriptions. I'm very interested in getting air con fitted in our new house after we move, and I am looking at a simple Daikin unit.
    Do you plan to share your circuit diagram and code?

  2. Hi RevK

    I basically got almost the same system installed as you this week. I have a 6 wall units (FTXM20 and FTXM35) and 3 duct units (FNA35). The indoor units are driven by two outdoor units (4MXM and 5MXM).

    My main purpose will be to heat the house in winter. But cooling in summer is also nice to have :-)

    My wall units also unfortunately have the Cloud Only Wifi module (brp069c4x) built in with permanent SSID broadcasting. With my channel devices the Wifi module is still missing but should be delivered soon. Currently I have only like you the wall control terminal with Bluetooth....

    First of all I would like to thank you for your great work! I am thrilled to see a solution based on an ESP32 chip that is addressable via MQTT :-).

    If I understood you correctly, I can remove the original Wifi module inside my wall devices (Perfera) and replace it with your ESP32 PCB?
    If I also understood you correctly this is also possible with the channel devices (FNA)?

    If so, I would be very happy if I could order 10 pieces of your PCB from you. If possible completely equipped.

    In your blog post Part 4 you write about your channel devices. I assume that you also use FNA (https://www.daikin.de/de_de/produkte/fna-a9.html) here.
    With me, the FNA devices are installed in recesses in the floor. The air flows directly out of a ventilation grille.
    Unfortunately, I am very dissatisfied with the volume even at the lowest level. I am also of the opinion that here is a significantly too high volume flow.

    Noise insulation is due to my installation situation unfortunately not so easy possible. I have thought about whether it is possible to run the fan at a lower speed. That there is on the part of Daikin a software update or another possibility I doubt.
    Ultimately, I thought of an electronic hack. do you have an idea here?

    Many greetings from Germany

    1. Mine have ducting to vents in the ceiling, and the noise is not too bad - getting used to the one the bedroom. The airflow seems OK. I am currently facing a slight issue with it going in to some economy type mode that is only 50% duty cycle and not cooling, but that is being looked in to. I'm not making the module commercially yet, but they should work. I'll blog if/when we make some to sell.

  3. If I understood you correctly, I can remove the original Wifi module inside the wall devices (Perfera) and replace it with your ESP32 PCB?
    If I also understood you correctly this is also possible with the channel devices (FNA)?

  4. Hi, thank you very much for your answer.
    I have ordered your PCB from JLCPCB. Until the board is here and I have it assembled I could in the meantime with an esp32 NodeMcu with your code already try everything, right?

    1. The PCB has a FET on the receive side to avoid 5V going in to a 3.3V GPIO, but it does actually work directly on the 3.3V pins anyway. The code can be configured to use any GPIO as Tx or Rx, so yes, any general ESP32 board should work fine.

    2. I could perhaps send you one...

  5. Hi RevK,

    next thursday a Daikin technical support person will come because of my loudness issue. In advance I was told that it is possible to throttle the airflow. Whether this is now done by software or with a hardware modification remains to be seen. If you are interested in this I will keep you informed.

    I will also make my displeasure known regarding the topic "Cloud only".


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