Tado and Daikin Altherma 3H HT Air Source Heat Pump

I am going to be replacing a traditional gas boiler and hot water tank operating in 'call for heat' mode. I had initially considered a modern gas boiler such as Worcester Bosch operating in modulating heat control mode along with matching solar thermal panels.

However I am now considering instead getting an air source heat pump system connected to radiators. I originally discounted this approach both because the early systems had a single massive floormounted internal unit that would typically be fitted in the kitchen and because originally they were very expensive.

There are now air source heating systems which combine a smaller wall mounted unit roughly the same size as a standard gas boiler with a separate hot water tank which I am hoping to fit in the location of the current standard hot water tank. On top of this improvement, with an air source system I will not need to buy and pay for the solar thermal tiles I had originally intended and the cost of air source heating systems has come down although still expensive.

Tado tell me that their system will work with the Daikin Altherma 3H HT I am considering getting. I was wondering however if anyone here has experience of using Tado with air source heating systems and even better any experience of this Daikin system.

See - https://www.daikin.co.uk/en_gb/product-group/air-to-water-heat-pump-high-temperature/daikin-altherma-3h-ht.html

Do such systems operate in a modulating manner?

This system and some other air source systems can also operate in a 'reverse' mode whereby they cool the house. Can Tado handle this? Would this involve also using their Air Con product?

Can one room be cooling whilst another is heating?


  • I have been thinking about just this setup for later this year myself actually so, although I can't offer any experience, if you do go for it I'd love to hear how you get on!
    Have you already got solar PV? Or planning to add it at the same time? I'm hoping I'll be able to get 4kw of solar PV at the same time as replacing the gas boiler.
    And which water tank are you thinking of? I'm considering the Mixergy tank, but not sure I can justify it
  • @stevenumber11

    I am planning to get Tesla Solar roof files when/if they eventually start selling them in the UK. I am only able to consider this because I would do it at the same time as replacing my roof.

    It is my understanding that the way this and other air source heat pumps work is that they have an outside unit (big) which captures the heat from outside air, it sends it to - in this case a small wall mounted unit which is the main controller, internal pump, etc. this then sends it to their own matching water tank for storing the heat. I therefore do not believe it is also necessary to have a traditional hot water tank as well since the entire air source heat pump system does this task.

    Older and still current larger systems combine the internal controller/pump with the tank in to a large floor standing unit the size of many fridge/freezers which in my case would take up too much space in the kitchen.

    They show their tank on page 11 of their brochure which is available via the following link.

    I am hoping this tank can be located in the same place as my current traditional tank.

  • @jelockwood
    Although I expect Daikin would love everyone to buy their water tank as well, I'm pretty certain there is no need to. My reading of the way they advertise the heat pump is that it's designed to be compatible with existing plumbing. So you should be able to connect it to any water tank you like as far as I can tell. If they've somehow engineered the wall mounted unit to only be compatible with their own water tanks, I have to admit that might put me off
  • @stevenumber11

    I will have to wait and see what they say when I eventually reach out to them or a reseller.

    The tank in this case would be used to store both hot water for taps etc. and I am presuming hot water for the heating i.e. radiators. Again I have yet to speak to them and have never previously had an air source heat pump but I feel it is more like a combi boiler system.

    Since it cannot heat up on demand or instantly from gas it has to extract heat from the air and store it somewhere so it is available for use.

    I need a new tank anyway.

  • The hot water tank does not need to supplied by the Heat Pump manufacturer. Mine is by World Heat Cylinders and preplummed with all the LG (in my case) stuff added. It also combines the main hotwater and a buffer tank for the Central Heating.

    You can also have the cyclinders custom made, no idea on the costing but they can be made to fit whatever space you have available. Then there is the pressurised and vented options. I've added pictures to show you the before and after main tanks.

    I also have two 25l expansion vessals for the hot water and heating systems so there is potentially more than that one tank.

    Don't forget the green homes grant, you maybe able to get a decent contribution from the government. For us it was £5k which made the project viable.

  • Wow, that's some water tank, @armsinit!

    So, do you have a tado thermostat controlling your heating with the LG Heat Pump? How's it working for you?

  • That tank is a beast! Any ideas how much that weighs when full?
  • @gary333 333 Ha, no idea on the weight, there is a double joist there so it should all be good.

    @stevenumber11 They are working really well together. The water is left to the LG, Tado has nothing to do with that. It just heats up when the temperature in the tank drops.

    Only problem I had was in one room the radiator is not large enough to warm it to the desired temperature. It's in the kitchen and not enough space to increase it's size. I took that off the bridge so it can't call for heat which saved me a bit of money. It's on there is because of people opening windows and the door to the garden.

    Before the heatpump we had an old dumb boiler control. Some rooms would not get warm while others would overheat. After the switch everything is at a good temperature and stays that way.

    There is a big difference between having smart thermostats in isolation mode and connecting to the bridge and deciding when the boiler fires up. I would recommend that to anyone in terms of comfort in your house, I don't think the brand matters at all.

  • @armsinit

    For the room with the radiator that is too small and there is not enough space to fit a bigger one.

    I am guessing you mean there is not room for a wider or taller radiator, however it might be possible to get a 'thicker' one. The most common type of radiator is a steel one with fins on the back, these can be either single layer or two layers facing back to back. If you already have this type and it is already a double one then you have the biggest that will fit. However if instead you are using a radiator styled like older cast iron radiators then these are shaped differently and can be effectively two layer, three layer or even four layer. Obviously the thicker ones stick out more from the wall.

    Above is a single panel radiator

    Above is a double panel radiator

    Above is a four column 'cast iron' style radiator, as mentioned 2 and 3 column versions are also available - look at the end view and you can see the columns.

    The important thing is to get a figure for home many BTUs you need for the room and get a radiator listed as being sufficient for that. (BTU stands for British Thermal Units and at least in the UK is the type of measurement used.)

  • @armsinit

    I am guessing you mean there is not enough room width or height wise to fit a bigger radiator.

    It maybe however a 'thicker' radiator might be possible. Standard typical radiators can be either a single panel with fins on the back or two facing back to back. However it is also possible to get a radiator designed like old style cast iron radiators and these can have 2, 3 or even four columns with it being thicker the more columns it has. See the following pictures.

    Above is a standard single panel radiator.

    Above is a standard double panel radiator.

    Above is a four column 'cast iron' style radiator. As mentioned these are available with 2, 3 or as the picture above four columns. (Look at the end view.)

    You should get a figure for how powerful a radiator you need in this room, here in the UK radiators are measured in BTUs - British Thermal Units.)

  • @jelockwood A thicker radiator wouldn't work in the space either, it's already a Type 22 (K2) . As we are normally in that area after the food has been cooked that does make it comfortable enough.

    Our bedroom which is in the loft does have a type 33 (K3), that took 4 guys to get up there as it was over 100kg and 2m long.

  • Hello jelockwood

    I have just had the same Daikin system installed with a Tado. It is currently wired in a volt/potential free fashion in a similar way to a combi boiler(into the Tado Wireless Receiver). My indoor Daikin unit is an ETBX single phase, if you go to the linked page, in the installation manuals section, there is a link to an 'Addendum book for optional equipment'. Within that look at the wiring instructions for a 'Wireless Room Thermostat'. There is no support on my Tado Wireless Receiver for AC, so it is not wired in for cooling(terminal 34). You can attach another thermostat for two zones, but it would need to be a wired one. On the software side(see Installer Reference Guide - Section 9.5.3), the internal unit needs the settings changed for the 'Main Zone', with 'Control' set to 'External Room Thermostat' and 'Thermostat Type' set to '2 contact'(even though I have not wired in cooling/terminal 34). This is so switching terminal 35 on/off indicates heating on/off(not cool/heat when set to 1 contact).

    The Tado is not currently managing hot water, as there is no documented way of doing this on the Daikin side. However, the Daikin system does support water heating with a schedule and a reheat function. The latter is triggered on a drop in temperature of the hot water tank sensor, I wonder if I can wire the Tado Hot Water circuit in between to trigger the reheat signal... I have oversized my hot water tank deliberately as I schedule it to heat up at night when the electricity is 5p a kWh(Octopus Go Tariff).

    The "external wireless thermostat" interface does not support a modulation signal, it is simply on/off. Although I would assume that you need a high temp as your radiators are not up to par for use with a low temp HP. Therefore the leaving water temperature will always need to be high to heat your home effectively, which is set statically. The modulation signal is only supported over Daikin's proprietary connection for their own room thermostat/internal display/LAN controller, this is a power and data connection in one(I suspect it is similar to HomePlug power line comms). There is no support for OpenTherm, so no modulation with third party thermostats :-(

    Some features you are probably not aware of are in the Smart Grid Lan Adapter(BRP069A61). This can track excess solar/wind generation(using an external smart meter with pulse output) and modulate the heat pump on the power consumption side to produce hot water(to store in a buffer or hot water cylinder or both). It has a variety of switching modes for smart grid functionality for signalling from your electricity provider(or a MyEnergi Eddi with comms board). It also had/has IFTTT software support(which I have not tested), so it could work with the Agile Octopus tariff, for example - to only run when electricity is less than 5p kWh.

    The Tado AC system piggybacks an IR signal/receiver, which this Daikin system does not have, so no cooling control possible at the moment. We may be able to wire the Tado wireless receiver in for cooling using the CH NC terminal in the future, but I don't think this is currently supported. The Daikin heat pump can't heat and cool at the same time, as it is the external unit that expels or collects heat and this can only be in one of these modes thermally.

    Daikin either need to support OpenTherm, or Tado reverse engineer Daikin's proprietary power/data connection protocol for modulation support. You never know, Daikin could start making Smart TRV's that connect back via WiFi to the LAN adapter to support modulation...

    hope this helps


  • Thanks @CrazyAdeMar1ne a very detailed and helpful answer.

    Please keep us updated on the progress of your Daikin and Tado setup.

    I have not yet implemented this yet myself but I am still leaning towards the Daikin Altherma system to replace my gas boiler, I get the impression the Daikin Altherma can generate hotter or at least warmer 😀 temperatures than most Air Source systems, it's outdoor unit also looks a bit more attractive. I would be getting the matching Daikin water cylinder. I am also considering a separate Daikin AC unit for a bedroom which would be straightforward to use with the Tado Smart AC controller. I will be replacing my radiators so will fit bigger ones and I am also at least partially looking at fitting internal 'spacetherm' insulation to some of my solid brick walls. (So no option to do cavity insulation.)

    In view of the relatively poor integration between the Daikin Altherma and Tado are there any options to use the Daikin controller and standalone smart TRVs? It would be nice if Daikin had some solution themselves but so far they have stubbornly chosen to be a very anti-smart home company particular in Europe. (They have a fancy thermostat the Daikin One+ which they only offer in the US - https://www.daikinone.com/)

    One hopes that 'Matter' will result in many brands becoming more open as this - hopefully will be a very popular well supported standard that all manufacturers will eventually support.

  • The Daikin Altherma 3 H High Temp is a fab piece of kit. No brainer. They can also be joined in a cascading fashion based on demand for larger properties.

    Daikin do have showrooms you can visit to see their kit in the flesh, the are called "Sustainable Home Centres", the outdoor unit is quite large, you might want to see one in the flesh. As the Renewable Heating Incentive is ending next year you may want to get things sorted!

    I was thinking about installing some of Daikin convection wall mounted units on the second zone for cooling, sometime in the future. If you're replacing radiators anyway, you may want to look at the floor standing convectors for the rooms where you want heating and cooling. The heating circuit is filled with glycol antifreeze so it can be reversed for cooling in the summer.

    From a noise point of view, Daikin make a Monobloc version, if you would have a bedroom above where the internal unit would be. The circulation pump can be a little noisy running the central heating, this is not an issue with the monobloc, as all hydraulics are in the outside unit.

    They are also releasing a slightly smaller Mid Temp split model to target smaller properties for the £5k heat pump grant that's appearing next year to replace the RHI...

    I may try and use the Daikin Madoka room thermostat for modulation sometime in the future, after I have sorted out all the radiators and insulation. This may allow me to run at lower output temps, in this case the Tado Smart TRV's would no longer be able to turn the heat pump on/off...

    As to the Daikin modulation protocol and Tado compatibility with it, after a little research it is commonly referred to as the P1P2 interface. And people have already reversed engineered it! And built ad-hoc devices to program through it! See this Github Project. Hopefully Tado can take this as inspiration and support it as a digital interface in a similar fashion to OpenTherm!



  • Wow, Adrian: deeply grateful to you for delving so deep, and then typing it out!

    I'm also a)persuaded that tado gives me good temporal and spatial control; and

    b) thinking of replacing my old (v old) gas boiler with a Daikin Altherm 3 HT.

    It seems that getting the two to talk together smoothly is at the very edge of what'll be practical (and probably the very edge of warranties).

    So here's a fundamental question which might help: suppose I take the easy option, and have tado simply run in an old school "call for heat"- yes/no- fashion... Would that matter? Is there a substantial efficiency gain to modulation in heat pumps? (I understand that the fan noise is more trying if it's going on and off, rather than slowing and then accelerating).

    All thoughts very gratefully received