Faikin Oyu — installation and setup

Faikin Australia

Fitting the Faikin Oyu to the P1/P2 user interface terminals on a Daikin Altherma 2 or Altherma 3, split, monobloc or hybrid, and putting the whole system into Home Assistant over MQTT.

Runs entirely on your local network · needs no Daikin account, ONECTA app or cloud relay · MQTT on every module, with Apple Home, Google Home and Alexa reached through Home Assistant.

Last updated 13 October 2026.

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Safety firstThis is work inside a live appliance.Isolate power to the whole system, indoor and outdoor, before you open anything. If you are not comfortable opening the unit and working on a terminal strip, get your installer to do this part. It takes them five minutes.
No flashing neededYour module arrives ready.Altherma 2 and Altherma 3 run the same firmware, and every module is commissioned and tested before it ships. There is nothing for you to flash, and you should not attempt to reflash it. Firmware updates then arrive over the air.

1. Before you start

Which systems this fits. Altherma 2 and Altherma 3 run the same firmware, so one module covers both. Altherma 4 is still being decoded and is sold separately as a test unit.

  • Altherma 3, split or monobloc, including the Altherma 3 H HT, the H MT and R MT ranges, the GEO ground-source models, and the E-generation ECH2O models that carry a BRC1HHDA wall controller. This is the one most people need.
  • Altherma 2, the 2012 to 2018 generation (version letters CA and CB in the model number), split or integrated tank. The Altherma 2 monoblocs are monitor only, no control, see below. This also covers the Altherma hybrid, the EHYHBH and EHYHBX hydrobox with the EHYKOMB gas boiler. The hybrid points, gas boiler active and boiler running hours, come through on it. The older AA-generation hybrids have had less field testing than the Altherma 3, so on those the developer may need to look at your system remotely after it is installed.
  • Altherma 4 is in testing and not yet supported. A small number of test units are offered at cost to owners who are happy to help with decoding. See the product page.
Monitor only, no controlEarly R410A Altherma units can be read over P1/P2 but not controlled.The Oyu supports them for monitoring only. Readings come through to Home Assistant, but you cannot change setpoints, modes or hot water from it, and these units report fewer values than an Altherma 3. This covers:
  • EKHBH and EKHBX hydroboxes, AA, AB, BA and BB versions (first-generation Altherma LT, roughly 2006 to 2012), including EKHBHE and EKHBXE
  • EBHQ, EBLQ, EDHQ and EDLQ, the Altherma 2 low temperature monoblocs
  • EKHBRD, the original Altherma HT (R134a cascade, roughly 2008 to 2015). This is not the Altherma 3 H HT, which is fully supported.
  • EKHVMRD and EKHVMYD, the Flex Type HT hydrobox

Systems this does not fit.

  • ECH2O models with the RoCon controller. The Altherma 2 ECH2O and the D-generation Altherma 3 ECH2O (EHSH, EHSX, ETSH, ETSX with a D in the version) run on a CAN bus and have no P1/P2 user interface. The later E-generation ECH2O with a BRC1HHDA controller does, and is supported.
  • Any Altherma that does not have a pair marked P1P2 USER INTERFACE on the X5M strip.
  • Splits and ducted systems. The Oyu is for your Altherma and nothing else, and nothing else we make fits an Altherma.

How to check in thirty seconds. Find the terminal strip marked X5M. On a split or hybrid it is inside the indoor hydrobox. On a monobloc there is no indoor unit, so it is inside the outdoor unit's switchbox. Look for the pair labelled P1P2 USER INTERFACE, which is the pair your wall controller already runs on. If that pair is there, the Oyu fits. On the monitor-only models above it reads but does not control.

Go by the label, not the numberOn most Altherma 3 hydroboxes the pair sits at positions 11 and 12. On the hybrid hydroboxes it has been found at positions 1 and 2. The numbering moves around between generations, so use the P1P2 USER INTERFACE marking, not the position. This is also not the same place as on a Daikin split or ducted system, where P1/P2 is on the REMOTE CNTRL block next to F1/F2 and T1/T2.

Not sure which Altherma you have? The model number is on the data plate, on the indoor hydrobox for a split or hybrid and on the outdoor unit for a monobloc. Send us a photo of the plate and of the X5M terminal strip and we will confirm it fits. The compatibility finder on this site also covers Altherma: type the indoor unit model number and it shows the generation, or Monitor only, no control for the early units above.

How the bus is shared. The Altherma P1/P2 bus carries one Main and up to two Sub devices. Your wall controller is the Main and stays exactly as it is, with full function. The Oyu joins as a Sub. On an Altherma 3 a Daikin LAN adapter for the ONECTA app (BRP069A61 or BRP069A62) can take the other Sub slot, so it can stay fitted and ONECTA keeps working. The ONECTA WLAN cartridge that plugs into the user interface itself (BRP069A78) is not on the bus at all and is unaffected. If both Sub slots are already in use, for example by a second wall controller and a LAN adapter, one of them has to come off before the Oyu goes on. On an Altherma 2 or a hybrid, if anything other than your wall controller is wired to the P1P2 USER INTERFACE terminals, send us a photo and we will confirm before you order.

2. Wire it in

  1. Isolate power to the whole system, indoor and outdoor.
  2. Open whichever unit holds the X5M strip. On a split or hybrid that is the indoor hydrobox. On a monobloc it is the switchbox inside the outdoor unit.
  3. Find the pair on X5M marked P1P2 USER INTERFACE. These are the terminals your wall controller is already wired to.
  4. Connect the two module wires alongside the existing pair. The connection is non-polar, so either wire can go to either terminal. Wire is 24 to 12 AWG, 0.6 to 2.4 mm. The supplied lead has ferrule ends sized for the X5M screw terminals.
  5. Restore power. There is no separate power supply to run. The module is powered from the bus.
Monobloc ownersThe switchbox is outdoors and the Oyu is not weather rated, so it needs somewhere dry and within Wi-Fi range. The same P1/P2 pair also lands at your wall controller indoors. That is the same two wires and the same bus, and it is often the easier and drier place to connect. Ask us if you are not sure which suits your install.
A U2 error after a restart is normalEach time the Oyu restarts, for example after a power cut or a firmware update, the Altherma user interface may show a U2 error while the module drops off the bus and comes back. That is expected and is not a fault. Clear it on the user interface and it will not come back until the next restart.

3. Get it onto your network

No app, and nothing to install. The setup is a web page served by the module itself, so any phone or laptop with a browser will do.

  1. Power it up. The module brings up its own Wi-Fi network, named FaikinAC- and four characters.
  2. Scan the QR code on the label with your phone camera and it joins that network for you. You can pick it out of your Wi-Fi list by hand instead if you would rather.
  3. The setup page opens by itself. Choose your home Wi-Fi from the list and enter the password. The module is 2.4 GHz only, so pick a 2.4 GHz network or a combined one.
  4. Enter your MQTT broker address, the port (1883 unless you have changed it), and the username and password if your broker uses them. You can do this now, or leave it and come back to it later once the module is on your network. It is the same page either way. The Activation Code field can be left blank.
  5. Press Save and Reboot. It tells you the IP address it has been given, then restarts, which takes about twenty seconds.
  6. Browse to that address whenever you want status, settings or a firmware update.
Telling a wiring problem from a network oneThe Status page shows HVAC Status and MQTT separately. MQTT connected but HVAC disconnected means the module is on your network but not talking to the heat pump: check the two wires are on the P1P2 USER INTERFACE pair and that the system has power. HVAC connected but MQTT disconnected means the wiring is fine and the broker address, port or credentials need another look. If both are connected and nothing appears in Home Assistant, check that MQTT discovery is enabled on your MQTT integration.

4. What you get in Home Assistant

Your Altherma already knows its flow temperature, its return temperature, how much energy it has used and how much heat it has produced. It just will not tell you without a cloud account. Here is what the Oyu publishes. Values are polled from the P1/P2 bus rather than pushed, and in our bench testing they come through in under five seconds. On the monitor-only models in section 1, the readings below that the unit reports come through, but none of the controls work.

Control

  • Leaving water temperature setpoint
  • Space heating on and off, and mode
  • Domestic hot water setpoint, 30 to 65 °C
  • Domestic hot water on and off, and hot water boost
Room temperature setpointA room setpoint is only available when your system has a room temperature source: a Daikin room thermostat on the P1/P2 bus, such as a BRC1HHDA or the EKRUCBL, or a Bluetooth temperature sensor paired to the Oyu (ask us which sensors are supported). It is also not used while the Altherma runs on weather-dependent control, because the leaving water temperature then follows the outdoor temperature curve rather than the room. Without a room thermostat or a paired sensor, the room temperature the Oyu reports is an estimate rather than a measurement. In that case the usual route is a Home Assistant automation that reads a room sensor of your own and nudges the leaving water setpoint to hold the room where you want it. Room setpoint support has not yet been confirmed on the older AA-generation hybrids.

Water and air temperatures

  • Leaving water temperature (LWT)
  • Return water temperature (RWT)
  • Mixed water temperature (MWT)
  • Domestic hot water tank temperature
  • Room temperature (measured when a room thermostat or paired sensor is present, otherwise estimated)
  • Outside temperature

Energy, split out properly

  • Energy consumed by the compressor, the backup heater and in total
  • Energy produced for heating, for cooling, for domestic hot water and in total
  • Which means you can calculate your real COP in Home Assistant, per mode, without a separate energy meter

System state

  • Heat pump mode, heating mode and main zone status
  • Domestic hot water active, and tank power
  • Defrost active
  • Water flow rate in litres per minute
  • Pump running hours
  • Error flag

Hybrid systems

  • Gas boiler active, gas mode, and boiler running hours split between heating and hot water
Worth knowingEntities you do not have will not appear, or will read as unavailable. A system with no domestic hot water tank will not report tank temperature. A temperature that reads -128 °C means that sensor is not fitted on your system. It is a placeholder, not a fault and not a real reading. Some newer hybrids do not measure water flow, so the energy-produced counters will not populate on those.

5. Home Assistant, Apple Home and the rest

MQTT is the point. It is the most widely supported protocol in home automation, and it means the Oyu is not locked to any one platform.

  • Home Assistant picks it up automatically over MQTT discovery. No YAML, no template sensors. Everything above appears as proper entities with the right device classes and units.
  • The Home Assistant Companion app gives you full control on iOS and Android, with widgets, notifications and location triggers. For most people this is a better daily experience than the vendor app it replaces.
  • Apple Home works through the HomeKit Bridge built into Home Assistant. That runs entirely on your own network, no cloud and no subscription.
  • Google Home and Alexa both have well-trodden paths out of Home Assistant, either through Home Assistant Cloud or your own setup.
  • Anything else that speaks MQTT can consume it directly, including openHAB, Node-RED, ioBroker, Domoticz and Homebridge. You are not obliged to use Home Assistant at all, though it is the path we support and the one that needs no configuration.

This is exactly the arrangement that makes the Faikin Faikout so flexible, applied to your heat pump.

6. Status, firmware and updates

Browse to the module's IP address for status, settings and firmware updates. The pages are Setup, Status, Firmware Upgrade and Reboot. Updates arrive over the air, so a fix reaches you without you doing anything.

The module needs the internet only to fetch firmware updates. Control is entirely local. Pull the internet and it keeps working.

It ships commissioned and tested, and you cannot and should not flash it yourself. Altherma 2 and 3 run the same firmware, so there is no wrong version to order between them. If something on your system does not read correctly, email us. The developer can look at it remotely once the module is on your network.

When you email us about a problem, include your heat pump model number from the data plate and the Build Version and Protocol version lines from the Status page. That is usually enough for us to see what is going on.

7. What it does not do

  • No control of early Altherma units. The monitor-only models in section 1 are read but not controlled.
  • No direct Matter pairing. An Altherma exposes roughly sixty entities and that does not map onto a Matter thermostat, so there is no code to scan straight into Apple Home the way there is on the Faikin Ninja. You reach Apple Home, Google Home and Alexa through Home Assistant instead, which is how the Faikin Faikout has always worked.
  • No vendor app of our own, by design. The built-in web page is for setup and diagnostics. Day to day you use the Home Assistant Companion app or whatever dashboard you already have, which is a better app than we would ever write.
  • No field settings. Installer-level configuration stays on the wall controller. The Oyu does not change or store your Altherma's own configuration.
  • No room temperature setpoint without a room sensor. A room setpoint needs a room thermostat on the bus or a paired Bluetooth sensor, and is not used under weather-dependent control. See section 4 for the details and the Home Assistant route.
  • Not a replacement wall controller. It runs alongside yours, not instead of it, and it is not part of the heat pump's control loop. If the Oyu, your Wi-Fi or your MQTT broker goes offline, the Altherma and its wall controller carry on exactly as before.
  • Entities you do not have will not appear, or will read as unavailable. A system with no domestic hot water tank will not report tank temperature.

8. Questions we get asked

Can I set the room temperature setpoint?

Only if your system has a room temperature source, either a Daikin room thermostat on the P1/P2 bus such as a BRC1HHDA or the EKRUCBL, or a Bluetooth temperature sensor paired to the Oyu, and only while the Altherma is not on weather-dependent control. Otherwise the writable controls are the leaving water setpoint, space heating on and off, the hot water setpoint, hot water on and off, and hot water boost. In Home Assistant an automation can hold a room temperature by adjusting the leaving water setpoint from a room sensor of your own, which gives you a room setpoint to adjust either way.

Why does my Altherma show U2 after the Oyu restarts?

While the module restarts it briefly drops off the bus, and the Altherma reports that as a U2 communication error. It is normal. Clear it on the user interface and it will not return until the next restart.

Is a hot water setpoint really useful?

More than it looks. The most common automation on an Oyu is raising the hot water setpoint when solar export is high and dropping it back in the evening, so the tank soaks up power you would otherwise sell for a few cents.

Does it work on a hybrid?

Yes. The Altherma hybrid, the EHYHBH or EHYHBX hydrobox paired with an EHYKOMB gas boiler and an EVLQ outdoor unit, runs on the same firmware as the Altherma 2 and 3. The gas boiler points come through alongside the heat pump ones. On the hybrid the P1P2 USER INTERFACE pair is often at positions 1 and 2 on X5M rather than 11 and 12, so go by the label. The older AA-generation hybrids have had less field testing, so the developer may need to look at yours remotely after install.

My Altherma is monitor only. Can I still use the Oyu?

Yes, for monitoring. The readings your unit reports come through to Home Assistant, so you can log and chart them and build alerts on them. You cannot change setpoints, modes or hot water from the Oyu, and the early units report fewer values than an Altherma 3. Order the Altherma 2 and 3 option.

What happens if mine has a fault?

Tell us. Most things we expect to fix in firmware, which reaches you over the air. If it turns out to be the hardware, or if the product simply does not do what you needed, our no-risk returns cover you. The Altherma 4 test units are the exception: they are sold at cost on a best-effort basis.

What happens if the Oyu, my Wi-Fi or Home Assistant goes down?

Nothing, as far as the heat pump is concerned. The Oyu is a local add-on on the bus, not part of the control loop. Your Altherma and its wall controller carry on exactly as before, and the Oyu picks up again when the network comes back.

Do I need Home Assistant?

It is what we recommend and support, and it needs no configuration because the module is picked up automatically over MQTT discovery. But this is a plain MQTT device, so openHAB, Node-RED, ioBroker, Domoticz and Homebridge can all read it directly if that is your setup.

Is there an app?

The Home Assistant Companion app, on iOS and Android, with widgets, notifications and location triggers. We do not ship an app of our own and we are not going to, because the Companion app is better than anything we would build and it puts your heat pump on the same dashboard as everything else in the house. Setup itself needs no app at all, just a browser.

Does it work with Apple Home?

Yes, through the HomeKit Bridge built into Home Assistant. That runs locally on your own network, with no cloud and no subscription. What it does not have is the scan-a-code Matter pairing on the Faikin Ninja, because sixty-odd heat pump entities do not fit a Matter thermostat.

Google Home, Alexa, SmartThings?

All reachable out of Home Assistant. Google Home and Alexa are the most direct, either through Home Assistant Cloud or your own setup.

Will it fight with my wall controller?

No. The module joins the bus as a Sub device. Your wall controller, Madoka included, remains the Main and keeps full function. The bus has room for two Sub devices, so only if both are already taken, for example by a second controller and a LAN adapter, does something have to come off first.

Can I keep the Daikin ONECTA app?

Yes. If you use the ONECTA WLAN cartridge that plugs into the user interface (BRP069A78), it is not on the bus at all and carries on as before. If you have a Daikin LAN adapter wired to P1/P2 (BRP069A61 or BRP069A62), it takes one Sub slot and the Oyu takes the other, so on an Altherma 3 the two run side by side. The Oyu does not need ONECTA and does not talk to it.

I have a monobloc. Does that change anything?

Only where you connect it. A monobloc runs the same P1/P2 user interface bus as a split, so the module works the same way. The difference is that there is no indoor hydrobox, so the X5M strip is in the outdoor unit's switchbox, and the module itself needs to sit somewhere dry. Connecting at the wall controller end indoors is usually simpler. An Altherma 3 monobloc (EBLA, EDLA) is fully supported. The older Altherma 2 monoblocs (EBHQ, EBLQ, EDHQ, EDLQ) are monitor only, no control.

Does it need internet?

Only to fetch firmware updates. Control is entirely local. Pull the internet and it keeps working.

Can I flash it myself?

No. It ships commissioned and tested, and updates over the air. Do not attempt to reflash it.

I want the Matter pairing. Can I have the Ninja instead?

Not on an Altherma. The Faikin Ninja is for ducted, Sky Air and VRV air conditioning, and it will not control a heat pump. If you have both, buy both. The Ninja handles the aircon with Matter, the Oyu handles the heat pump through Home Assistant, and they meet on the same dashboard.

Which Altherma do I have?

The model number is on the data plate, on the indoor hydrobox for a split or hybrid and on the outdoor unit for a monobloc. A rough guide: model numbers with D or E as the version letter after the capacity (EHVH08S18DA6V, ETBH16E9W) are Altherma 3; CA or CB (EHBH08CB3V, EHVX11S26CB9W) and the EHYHB hybrids are Altherma 2; EP at the start (EPBX, EPVX, EPSX) is Altherma 4. EKHB, EKHBRD, EKHVM, EBHQ, EBLQ, EDHQ and EDLQ are the early units: monitor only, no control. Send us a photo of the plate and of the X5M terminal strip and we will confirm it fits.

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