Anyone monitoring a new R32 Ecodan?

You’re clearly doing something very right @greentangerine

You got your 14kW Ecodan down to drawing just 1kW this evening:

I’ve only ever seen mine go down to 1.6kW and that’s very rare.

Do you attribute your low draw to switching to the auto-adapt Mitsubishi controllers?

I’ve absolutely no idea tbh.

I went to auto adaptation because the Nest thermostats controlling the WC curve setting (I e. on or off) wasn’t working well at all and with a lot of solar gain, I couldn’t persuade myself then (and still can’t) that the system not knowing the internal temperature and relying on the temperature outside was in any way a sensible control method that can run without inveterate frobnication.

Unfortunately Mitsubishi don’t publish much at all about auto adaptation but for me it’s working fine, TRVs and all.

The three pipe buffer tank probably helps greatly as well by adding some volume.


Have a read


I found the trouble with both fixed flow and weather compensation modes is a) FTC tries to get up to target temperature as fast as possible, and b) doesn’t wait long enough between cycles to let the system cool down again. I personally prefer auto adapt because it’s in less of a hurry to get hot, and it pauses between cycles for the flow to drop by 10 C.

There are settings on the FTC that affect room mode but not the other modes.:

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Yes I find it strange that can set the lower and upper limits for AA but with WC there is no way to set the hysteresis.
I suppose if I had a perfectly designed system that wouldn’t be an issue as the emitters would be correctly sized to get rid of the heat and the heat pump able to modulate down its output to give nice long runs.

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I’ve only just now figured out that the minimum flow temp for my system is 35 C if I want nice long runs, as that’s how hot my radiators need to be in order to emit 4 kW from the heat pump on it’s lowest power. Unfortunately, the house only needs that amount of heat at 0C or below…

[see this post in another topic for numbers]


I thought your occupants were helping by leaving the windows open :slight_smile:

Can any of you just confirm my interpretation of what the auto-adapt is doing? I believe it’s doing something like this where I gently walk the desired flow temperature (blue line in space heating) up to stop it racing up to the number you would have for weather compensation.

For example here the weather comp flow temp is about 32 but I hold the desired flow temp down and gently walk it up from 25 to 32 so my oversized Ecodan doesn’t get carried away.

Given the outdoor temp of about 5 °C the CoP Mitsubishi predict is about 3 so you can see it helps in my case bring it up to about 3.8.

Yes, that’s a defrost at 08:00 which sadly seems to have heated the outside up to a balmy 12 °C.


Yep, it’s doing the flow temp stuff and a bunch of other things.

It’s similar to what I have to manage the flow temp and to decide if things should be on using hysteresis. As @Timbones has said a number of times, it’s better for the family if it’s based on a vendor-supplied and supported bit of tech than hand-rolled sketchy scripts.

The next trick is to get auto-adapt to use the effective outdoor temp by taking account of the humidity and wind-speed which I’ve been using to nudge up the weather comp curve when it’s stormy because our 200 year old house gets more of a chill with the wind and rain lashing against it :slight_smile:

Sometimes it eases up slowly (first cycle below, COP 4.2) but othertimes it will still up race up to WC temp quickly (2nd cycle, 3.7), perhaps because it was colder out?

The only nudging I do is to periodically check the room temperature, and if it’s 0.5 C above the set point I’ll knock the thermostat down by 0.5 C - i.e. “the house is warm enough now, thanks”. Otherwise auto-adapt will keep warming the house up to +1 C. Though maybe I should leave it alone to do all the “intelligent learning” the marketing says it does…

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Auto Adapt: I’ve noticed that the first cycle in a set (i.e. while thermostat calls for heat) ramps up quicker than subsequent cycles. See this period from this morning:

Here’s an example of two runs, without much change in outdoor or indoor temperature, the first one is pretty good but the second one is dismal with quite a few drops in output and what looks like unnecessarily high ramping up during the run.

Yesterday there was a mixture of both sorts of run.


Yes, seen this sort of thing before. What size is this model? Nicely configured graphs. All going nicely for 1st period. Then it goes into oscillation/hunting where it is slow to respond, then overreacts. My guess is that it’s the discharge sensor and EEV control that needs tweaking. I have failed to get a dialogue with Mitsubishi about it. Hard to believe they have not noticed it

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It’s a 8.5kW.

Is this happening any many other systems of just a couple of Ecodans?

One of my reasons for using HomeAssistant for my thermostats, was the ability to set a step of 0.1°C on my UFH. I simply found steps of 0.5° (effectively a 1°C tolerance) too great for my comfort level. Using HA I have steps of 0.1°C which is much better.

I was disappointed to find that Mitsubishi’s controls will only allow 0.5 C increments and readings, as my previous homemade integration was controlling the temperature within ±0.05 C. However, it seems to be [mostly] okay for comfort.


Mostly seen it on the 6, which is almost identical to the 8.5 Only seen it on the Ecodan. When running well, COP is excellent. maybe its a bit like a performance car… great when going well, but coughts and splutters when out of its comfort zone… thing is, you should be in the comfort zone

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Will be interesting to see if it changes over time as the AA adapts and as outdoor conditions change.

Also I have a large radiator still to install and might get some primary pipework consolidated and made larger so will see if it still does it after or if I just happen to be in some set of conditions that makes it happen.

I have had a bit of a look on the HPM graphs. I could not see anything like it, and certainly not as dramatic as that. Not seen on older Ecodans

I have a 8.5KW Ecodan but have taken control of the circulation pump via PWM to be able to dictate the DeltaT. Work well at the moment for example


My run from last night as I have cheap overnight electricity and means the house is warm when I get up.

The other major advantage is noise reduction so I softstart the pump, ramping to the higher speed as this softens out the startup sounds


Do you mind sharing the logic you use to set the pump speed?