Thank you OpenEnergyMonitor: Octopus Daikin ASHP monitoring

Yes agree with @HydroSam, I have the same auto bypass valve fitted by Octopus. Try closing it fully ( noting current position to be able to put it back)

I promptly closed that down fully after they left! No issues…

This is an interesting point:

The data I am publishing is basically from the same heat pump as yours, and is derived from:

ESPAltherma (M5StickC-Plus connected to X10, then posts over WiFi to Home Assistant, which in turn posts the data to Emoncms cloud service, and then input processes the heat delivered feed there)

And myenergi CT clamp (feeding data to home assistant and then again onto Emoncms cloud.)

It will be interesting to see if there is anything useful in comparison over the winter period with regards to accuracy etc.

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Hi Stephen,

I have everything needed to make ESPAltherma work too except the knowledge and patience to get Home Assistant working!

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Honestly, that was the easy bit! :joy:

If the auto by pass is fitted then I wouldn’t close it completely but set it so that it only opens when all the TRVs are closed (and any non TRVd rads) . There is a set up procedure for this on the Daikin. You will find that the pump trips below about 7 lpm as far as I can remember, so you want to set the bypass just above this trip point by trial and error. Although it is not ideal to be close to the pump I would imagine that the above procedure should take care of that as the Daikin will be running the pump at maximum in the test and so the pressure across the bypass will be at the highest it will ever see (the bypass is really a relief valve).

Just before anyone else says how bad their installation is - I found that my installers had a) duplicated my 22mm pipes to my HW tank with 28mm (really? the pressure drop across 10 m of 22mm is hardly an issue) and b) connected the flow and return of the original 22mm with a ball valve which they left fully open. A brilliant set up! So I bought and fitted a bypass and set it up as above.


I’ve added an option to show instantaneous COP in the MyHeatpump app which may be useful for this discussion, see: MyHeatpump App Instantaneous COP


Hi Matt @matt-drummer

The ESPAltherma doesn’t need HA. It uses JSON over MQTT so would probably integrate directly with EmonCMS, or any other MQTT-subscribing collator e.g. NodeRed, Python script turning it into CSV etc. I was actually an IT guy, and although I’m using HA at the moment, I have an extreme dislike of it.

If you were to run it at the same time as the OEM stuff, you would be doing the world at large a huge favour with your comparative stats!

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Hi Stephen

I’m very interested in the ESPAltherma setup, but I’ve looked at the installation manual for my EDLA09D3V3 and I can’t see any connections marked X10 on the circuit/PCB diagrams.

What model pump do you have?

Cheers thanks

I looked at fan-assisted rads when I was considering an ASHP. This could be a great solution to the “defrosts too much at 50/20/-2” problem, just slap them on the downstairs K2/3s and drop the flow temp to something sensible. Turn them off when it’s not so cold - or maybe not!

I seem to have another minor issue today.

I have little gaps of electricity consumption in the data. They seem to last 20 seconds each time.

Heat produced and no electricity consumed.

One of 40 seconds at 10:59:30

Good spot!

If that really is an auto bypass then out tentacled friends have really screwed up this installation.

Perhaps revisiting the basics of “is it plumbed in correctly as an open loop system; is the heat meter actually measuring the heat delivery” by drawing out a schematic of all the pipes and valves is where we need to start.

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I strongly disagree here.

The installation is a screwup if the emitter circuit cannot flow at least the minimum output of the heat pump at all times. You need to redesign the emitter circuit to suit the heat pump if this is the case. An appropriately designed emitter circuit / appropriately sized heat pump will NEVER need an auto-bypass.

Remove the TRVs (or set all to “6”) and balance the rads. Short-circuiting the supply back into the return to deal with a totally inappropriate emitter circuit is NEVER the right thing to be doing.

Yes it’ll avoid tripping the low flow alarm but it’s about as wise a thing to be doing as covering the smoke detector so that you can light the house on fire without tripping the alarm.

The ONLY place where intentional “bypassing” is legitimate is where the emitters operate at a higher dT than the heat pump (e.g. you have microbore and need a 10 degC dT to get the heat through the pipework; but the heat pump can only work at up to say 7 degC dT; so you “bypass” the heat pump flow vie a 4-pipe buffer or in the case of something like a Viessmann a carefully controlled bypass valve within the indoor unit to facilitate different detlaTs on the circuits)

Utterly ridiculous bodgery in other scenarios.


Hi @John

It’s basically the same as yours: EDLA11DA3V3 (a derated 16kW unit which we know as for example: physical dimensions, refrigerant charge, water pump (a 180watt beast shown below!), and the compressor is the same across all model designations)

My data is starting to show here now:

Bottom of page 46 onwards relates to our units:

e-b-d-la09-16d-3-v3-w1-eeden20-data-books-english.pdf (3.3 MB)

The X10 is easily accessible and located in the middle towards the right of the board.

Make sure you turn off the power before opening and/or connecting anything

Attached some photos to assist.

Possibly worth a new thread on Daikin ESPAltherma integration as it seems to work quite well!

@marko - what is ironic here is that they fitted the ABV to mine as well, yet did a positive thing that I thought I was going to need to do afterwards:

Removed UFH:

  1. Pump
  2. Mixing valve
  3. Honeywell 2-port valve
  4. All actuators
  5. All controls

They kept the entire UFH open loop…great!

(But they then failed to balance any of the 5 x ~100m 100mm c/c loops, nor any radiators🤦🏻‍♂️)

[quote=“Stephen_Crown, post:309, topic:24589”]
what is ironic here is that they fitted the ABV to mine as well[/quote]


[quote=“Stephen_Crown, post:309, topic:24589”]
yet did a positive thing that I thought I was going to need to do afterwards:

Removed UFH:

  1. Pump
  2. Mixing valve
  3. Honeywell 2-port valve
  4. All actuators
  5. All controls

They kept the entire UFH open loop…great![/quote]


FFS again!

Sounds like you got a keen Octopus apprentice that knew you should run the UFH open loop but didn’t know anything about how to setup a heating system such that it actually worked / didn’t know that an auto bypass valve shouldn’t be used OR instead has been instructed by their boss to install the bodge-valve-to-reduce-lowflow-alarm-callbacks.

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I only see it as a safety bypass if a future user was ever daft enough to close all the TRVs and towel rails. Not much point I agree if the HP can sense the low flow and trip itself. I just wanted to get the silly ball valve out and the bypass fitted onto the same nuts in 10 mins.

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Hi Colin,

The ABV is having no effect on my system.

My flow temperature is fixed at 42c and has been since yesterday evening, I haven’t changed anything.

Obviously the outside temperature and the inside temperature are affecting the COP.

But, do you know why my flow isn’t at 42c as set?

My room is set at 22c but it is 23c in here, I would assume this is holding back the flow temperature to control the room temperature?

My fixed flow temperature is not a fixed flow temperature, it is just a maximum?

I love this new feature, it really shows up what is going on in terms of performance. It’s all over the place!

To me it isnow really clear how the radiators, the minimum electrical input of the heat pump and the heat loss of the house are really holding back the heat pump. I can really see the limitations of the heat pump and the house fighting each other and destroying the efficiency. Really interesting!

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The bypass valve should never come into play in normal operation it should be closed now.

Your system is doing much the same today as yesterday but it’s hard to understand why the decent period from 5 to 09:30 just does not repeat in the later cycles. I would have hoped that it would rush up to the set flow temp stabilise and then switch off when the room thermostat hit it’s hysteresis limit. As a check - is your room temp hysteresis set at 1c? More about this later.

What you system is doing is dawdling up to temperature and I think, being switched off by the room stat before it gets anywhere near the flow set point of 42. As a result your rads are nowhere near the minimum HP output. You’ll see that the COP is just getting to its ideal COP near to 4.0 just before it shuts off. The main puzzle for me is why your room temp is not really showing any movement when it switches on and off it should be snaking up and down given that your system is oversized.

Trystan and I have been doing some tests on his Mitsubishi and my Daikin in the last 24 hours. The Mitsubishi is able to fast cycle without really losing any efficiency and it does not seem to matter if the radiators are able to match the output as he gets that COP even with a sawtooth profile.

My Daikin - since 11:30 today has dropped COP from 4.5 to 3.5 when I put up the flow temp by just 2.5c and switched off the modulation - just to make it cycle. But with mine you can see a pronounced wiggle in the room temp curve caused and it is behaving differently to yours when cycling. I cannot say I really understand what is happening but my best theory is that Daikin firmware is set to optimise the continuous running performance and has good tools to do so with modulation and dt control. Other units seems to be wired to be efficient at cycling quickly. If anyone here understands this better please enlighten us.

One major difference is the room temp hysteresis - in my unit it is set at the minimum of 1c .

; During the day I have it set at 19 and it does goes up to 19.5 and down to 18.5 when modulation is off. Trystan can set his in 0.1 or 0.2 increments
We’ll keep working on it…


Thanks Colin,

I don’t fully understand what is going on, all I do know is that it is not a particularly happy marriage between the heat pump and the house as it is.