DHW flag for Daikin Altherma 3

Hey Everyone,

I have the basic “Level 3 (COP) EmonPi with MBUS Reader” setup with one heat meter on the primary flow \ return and an electric meter for the ASHP.

I am looking to get some more in depth monitoring and wanted some guidance on how would be best to achieve this (accuracy favored over setup cost).

I would like to have the DHW separated out as I have seen with others (Using the DHW Flag) and ideally monitor the backup and immersion heaters.

For the Backup and immersion I am assuaging that it would be obtain two more electric meters same as the current and add them to the RS485 daisy chain and then add this to the combined electricity feed.

How have others configured the DHW flag to be set, would it need a separate heat meter on the cylinder feed or is there a way I can pull the setting directly from either the Daikin controller or elsewhere online?.

is there anything else in the system I could interrogate to feed in information on the DHW status?

Thanks for any advise.


Looks like my 3 way valve (ESBE) may have an answer.

There is an add on sensor for the valve consisting of a microswitch with NO/NC/C contacts - ESBE Valves Auxiliary Switch Adaptor Kits | Plumbing Superstore®

Is anyone aware of a USB dongle or other way to get the signal from one pair of the wires into the EmonHP (possibly a digital to rs485 USB adaptor)?.

I have been looking around but without much success (unless i go via china or pay £80+).

Another approach is to read the data you need from the Daikin directly. The p1p2 bus which connects with two wires to the madoka and control panel carries all the daikin info and includes the flow /heat meter and tank temp and just about everything else.

Details are here.

GitHub - Arnold-n/P1P2Serial: Monitor and control Daikin/Rotex (hybrid/Altherma) heat pumps via the 2-wire P1/P2 thermostat interface with an ATmega328P, ESP8266, and electronics. The P1P2Serial library and P1P2Monitor program perform low-level bus operation, the P1P2-bridge-esp8266 program interprets data from/to MQTT supporting Home Assistant MQTT discovery. P1P2Serial may also be used for other Japanese Home Bus System based standards: DIII-NET (F1/F2) bus, Mitsubishi M-Net bus, Toshiba TCC-Link, Hitachi H-link, Panasonic/Sanyo SIII-Net, Haier, York, and others.

Not sure if Arnold is still suppplying the small box of electronics but you can try contacting him.

I cannot help with the setting up as it was done for me by a helpful expert but i can say that it works well. It connects to your wifi and so can transfer the data to the emonpi for subsequent processing and storage.


Do you wire the P1P2 sensor at the Madoka? If so, that’s a bit of a no-go for me as having a random plastic box in the hallway isn’t going to get approval :laughing:

I think my alternative to be able to get DHW signal in emonHP is to use ESPAltherma.

I wired mine into the back of the main MMI screen as this is in the airing cupboard out of the way. Needed a few wago connectors to allow for all of the cables to be connected but otherwise all working well.