That’s really useful, thanks Sam.
I have suspected it, but never seen it confirmed against OEM. I knew it gave figures on whole kWh which makes it useless over short periods but that rounding error should be small over a month. Clearly there’s something else amiss. Whenever I look at instantaneous via MMI (LWT-RWT) * Flow and electricity via a CT clamp its usually in the 4-5 COP range.
No, only one - Googled the unit, and it is a pressure vessel, by the looks of it. It’s a CIMM AFC/CAR 18L.
have you tried increasing the maximum run time for the hot water cycle
The schedule was for up to 3 hours.
It got to 40C and went back to heating the house after about 1.5hrs.
Plenty of time I would have thought left not to scare it off.
As a compromise for now, I set the Comfort temp down to 45C.
It pulled that up no problem in short time and went back to heating house.
Will see how we get on with 45C for now.
Would like to get COP friendly ECO setting working though.
You may need to check the below setting
Space heating priority, Maximum running timer, Additional timer and Anti-recycle timer.
I had a issue where sometimes my DHW would stop heating before it got to temp at radium times and temp. this was down to max run time
Thanks very much.
I’ll check the consumption / CoP of the Comfort mode on 45°C first.
Then dig into this…
It definitely sounds like this is problem / feature.
Another one I’m gearing up for is LWT control only…
I understand you can schedule the LWT and thus meld it to cheaper tariffs that way rather than through Off / On through the Madoka.
I have my Daikin 9kW set on LWT but leave mine running all the time. I understand this is the best way to run HP when using LWT. I have been adjusting the WC to see the best setting and it seems to about 39°c for my requirements. Not sure if you can set a schedule when using LWT but would be interested if possible.
Forgive the question, but how have you got it set to LWT? I believe mine was originally setup this way (the Madoka only showed a 0-10c option which I believe is the LWT offset) but after an Octopus visit due to the house not getting above 14c, the system is now set to a schedule - like a boiler, and I can’t work out how to set it back to LWT-control. Is it a reset & recommission job?
Thanks!
Yes, you can on the MMI, though not on the app. Schedule is in the form of a delta to the LWT - up to +/- 10.
That is interesting news!
I wasn’t sure where I’d read it, or if it was a Google AI answer pulling in material from various sources and getting it’s wires crossed between usual room temp schedules and LWT settings🙂
This is enough to get me to give it a go…
I’ll miss the Onecta easy control though…
You have to go into the Installer’s menu. In there you should see an option ‘Control’, this has 3 options:
LWT, Internal Thermostat ( this is usually Madoka ) and External Thermostat ( a third manufacturer thermostat) [ may not have exact wording for thermostats]. Select LWT and exit, press the Home button and it will say do you want to reset - select ok.
Go back to User’s menu and adjust the WC as necessary. The Madoka just becomes a simple thermostat.
Thanks for that. Come to think about it I did set something to -2 must check if this is the DT.
Hi, I think I have gotten confused about the ratings on radiators. So I have a total of 9.3kw with my radiators at delta t 45c, per my design spec. I have a heat loss of 8kw, well 7.9 kw if we want to be precise. Now I thought this delta t was referring to flow rate but looking at it again it appears to refer to the difference between the temp of the radiator and the room temp. So this would imply a flow temp of 65c! When the planned flow rate is 45c. Or is it that in my design spec when they refer to 45c, they are referring to actual max flow rate , which is the specced flow rate of 45c at -2 c outside? Clearly something if off somewhere, I’m getting at the moment a flow rate of 33c and my rads are at 27c ( well as pointed out by someone else at the top of the rad) which is consistent interestingly with the return water temp. What am I misunderstanding.
I wonder how solar gain is handled (or not) by LWT management?
Our property receives gain when it’s sunny as it faces south and is not that deep
Hi @HeatStig
I think you’ll find that it generally isn’t.
In most heat pump controllers, weather compensation is a pretty blunt instrument, just resetting the target LWT based on a single temperature sensor located in the Outdoor Unit.
It doesn’t usually take any account of wind speed or direction or air humidity, or if it’s raining (all of which can affect house heat loss), and may be subject to some cold air recirculation from the evaporator if the heat pump has been located poorly.
For sure, solar gain can have a big effect on room temperature, which is why it may be a good idea to have an element of roomstat control of heat pump output also.
Don’t know about LWT, but on weather comp it’s ignored, the only impact will be if the rooms get so warm the radiators can’t get rid of their heat. For me, solar gain is a bonus. But last little while haven’t seen any sun.
In LWT mode, the Madoka becomes just a user interface to manually adjust the offset. It will not operate in response to room temperature or even turn off heating at all* (subject to [4-02] which governs the outdoor temperature at which the heat pump will operate below).
*although you can still manually turn the heating on and off.
You’d need a third party tool interacting with the Onecta API to make adjustments based on the room temperature. Home Assistant is often used this way (I use Switchbot thermostats to average several rooms and input infrequent offset adjustments via the API to compensate for solar gain, cooking etc.).
So what governs the target room temperature of the system? It must be aiming at something.
Thanks for the info.
Yes, if going LWT only disabled the override (switch off) of the Madoka at high solar gain, then it could be wasteful / overheating even, esp if one was away or couldn’t intervene.
There’s always the tradeoff of total shutdown/cool down saving verses the spin up energy use once the heat need is resumed.
The hysterisis of the thermostat and as you say the bluntness of the control systems hamper the ideal.
It feels like the manufacturers are still at babystep stages with all this.
Better than boiler yes, not at Starship Enterprise environment control level yet 
Getting the weather curve right so you have just enough heat to maintain the temperature of the house at both ends of the curve.
Interestingly, to me at least, once you have the curve right, indoor temps tend to sit where you want them, even if it stops heating to do hot water, for example. It’ll gradually come back. But you do really need external modulation to keep it in check, at least that’s my experience so far. Whether that modulation is using the Madoka (if you can deal with the 2c hysteresis) or Home Assistant for finer grained control in LWT mode is up to you.
