Hack my Heat Pump and publish data onto emoncms

(Emiliano Maina) #1


I am joining a DYI project in order to leverage on software (instead of physical external sensor) to collect data from a popular Heat Pump here in Itay, Rotex HPSU Compact.

The machine has an undocumented CAN bus available where data flows (both read and write).

First sniff testing are successfully on-going using ELM327 cheap box.

Thinking of a more engineered solution with the goals of:

  • publish data on the cloud ( is the preferred one)
  • changing heat pumo configuration

I am proposing existing multiple options based on Arduino or Raspberry Pi:

Any comments ? Any reccomendation ? Anyone interested in joining the stuff (I am not actually doing the job !) ?

Thanks !


(bart.ellast) #2

Don’t go telling Daikin (rotex) you are about to hack in their heatpump. :wink:
They are NOT happy at all with people doing that (not that i care :slight_smile: )
I have done the same with a daikin altherma using their own proprietary communication interface(don’t know the hardware type, but i have a converter to rs232). Had to figure out the protocoll though.

I have other heatpump of the stiebel eltron brand. They use Kromschoeder controllers. These also use CAN bus.
I read those using a USBtin interface ( connected to an emonpi so it works fine on a raspberry with no config.

I use node-red to get the data of the altherma (serial rs232), for the stiebel CAN i found software available.
But node-red also has CAN node (
Maybe try that one!

(Emiliano Maina) #3

Consider that I asked Rotex support for documentaion but that kindly tell me: no! You are not the first one asking for !

Thanks for the link you shared !

At the end I ordered a PiCAN2. To me sounds more open. I bought also a new Raspberry3 that I could use to upgrade my existing OEM installation to have one system only.

Is there any already available libraries to push data to emoncms ? I don’t want to reinvent the wheel if possible.

(bart.ellast) #4

Easiest solution would be node-red or the input API using http requests to post your data.

(Emiliano Maina) #5

Can you explain me better ? Maybe with reference to same example ? I don’t know Node-Red at all.

My goal is, at leat at start, to implement the easiest solution (including learning curve from zero). Easiest but clean !

(bart.ellast) #6

Node-red is software designed to connect all sorts of devices together.
It works with seperate nodes that you can easily connect together. Emoncms has a node, so sending to an receiving from it is peace of cake.

It also has serial nodes (which I use for my Daikin) and ,as I said, a can node is available to Install.
In between nodes you can add functions with code you write yourself (JavaScript).

Node-red makes is easy(ier) to create code and connect devices.
I have no background in coding, but Google and the node-red group community are a big help.

Check out node-red, it’s really worth it!
You can always write your own code and send through the input API with http requests, but getting the can data like that I can not help you.
I have a python script that sends data out to emoncms though.(Stiebel heatpump).

When I’m at home and you are interested I can send you my node-red flow interfacing the Daikin heatpump through serial. But contact me pm for that if you’re interested.

(Jon Murphy) #7

here is the Node-Red website -->

User contributed nodes and flows -->

and here is the Node-Red google group -->!forum/node-red

(Emiliano Maina) #8

Thanks !

Too many things to learn !!!

How does this fit with MQTT ?

(Jon Murphy) #9

depends on what you want mqtt to do…

You can grab data from the candump node via nodes mentioned by @bart.ellast. Then calculate & manipulate the data as needed, and then send it via MQTT to the local emon device.

(Emiliano Maina) #10

Conceptually it sounds very easy.

Everything to be learnt !

Thanks for now !

(Emiliano Maina) #11

Just to let know everybody it’s done !

Still refining and documenting (in Italian).

(bart.ellast) #12

Did you end up using node-red and the can nodes? Or something else?
Great to see a hpsu unit monitored. Should be very similar results to our altherma unit.

(Emiliano Maina) #13

At the end Python Can based scripts:

I Hope Altherma performs better than my HPSU Compact.

Defrosts are awful and I’ve escalated with Daikin providing my data.

My dashboard is here:

Can you share your ?

Thanks. Ciao.

(Emiliano Maina) #14

Please joint zanac project !

(bart.ellast) #15

What do you mean With defrosts are afwul? With outdoor temps around 0-1degr they are very frequent yes. When temps drop below 0 this improves because there is less humidity in the air.

What is your indoor heating system ? Underfloor?
With a complete underfloor heating system and low eaving water temperature you can expect a seasonal cop of around 4. (In Belgium that is).

The Daikin altherma version has a controller that’s more intelligent then the rotex, but I don’t know if it would perform any better.

(Emiliano Maina) #16

Underfloor. The point is that defrosts are always with a frequency very
high, and never with a medium/low frequency.

Please be aware that Daikin defrost algorith doesn’t consider at all any
actual frost.

Defrost algorithm is fully managed by external unit that is anyway Daikin.
And now it should be exactly the same in Altherma and HPSU Compact.

Please read here …

2017-02-10 12:21 GMT+01:00 bart.ellast <
[email protected]>:

(bart.ellast) #17

I know how defrost cycles work on the Daikin units. (Been placing them since 2008, you don’t want to know how the early models faired with defrost).
The controller difference will only be at indoor unit level.

Interesting article, will read that more in depth when I’m home.

Defrost management is something I find to be an area of improvement on nearly every brand.
We also install a very well and highly regarded German brand that is waaaay more expensive than daikin.
One of their selling points is defrost times. When monitored they are even worse than the daikins
Normally when an altherma does defrosts you can visually see frost.
That other brand does defrosts when you can see nothing at all. Seems based purely on outdoor temperature and time.

(Emiliano Maina) #18

My issue is that some Daikin HPSU Compact are working fine (1 defrost every 2 hours more or less always) and some (MINE + other monitored systems) really behaving different (very often 25 mins, never longer than 1 hour 15 mins).

So HPSU Compact can work as documented. Daikin has to make working as expected also mine.

(SubOrbit) #19

Can you share some info of how you connected to your Daikin altherma unit? I have a Daikin HT unit at home and would very much like to connect to it as well.
Which communication interface are you using? Can you share some info about the protocol?

(Emiliano Maina) #20

Here you can find documentation (unfortunately in italian):