More learnings…
The Madoka can modulate in both directions. At modulation 10, what I observe is:
- at 0.5c over setpoint, the first modulation kicks in. Flow target drops by 3c.
- at 1c over setpoint, the second modulation fires. Flow target drops by another 3c.
- if the room temp then drops below 1c over setpoint, flow target raises by 3c.
- interestingly, the first modulation is only cancelled when the room drops below the setpoint.
- at 1.5c over setpoint, heat pump switches off completely.
It also modulates in reverse…
- at 0.5c under setpoint, the flow target increases by 3c.
- I’d imagine the same is true at 1c.
- If you adjust the setpoint up, say from 19c to 20c and the current indoor ambient temperature is 19c, the flow target is immediately increased.
- the same is true in reverse, but if you reduce the setpoint to, say 19c but the room is 19c or above, the heat pump will shut off until ambient drops to 0.5c below setpoint again.
I’ve been running in RT mode for the last week and I think using the Madoka is useful, if you want to avoid third party tweaking using Home Assistant and the Daikin API.
I think my issue with it in mild conditions is the oversized heat pump can’t modulate its output low enough so we overheat the house. I’m still not decided whether to use the LWT/HA method or RT. Perhaps it’ll become clearer if I have the right size heat pump.
After having further radiator troubles, I decided to try reopening all the lockshields fully, to see if we still had the problem of the attic radiator not warming after Daikin set the ABV correctly. I left the landing radiator at 1/4 since it is the first in the loop. All rads have worked since, although the attic rad is cooler than the other first floor rads when the circ pump drops to it’s minimum 11lpm but it is at least producing heat. If anything, upstairs is maybe 1c warmer than ideal, so I might yet throttle them all down to maybe 1 turn open or something, maybe.
[edit: I ended up throttling down the landing to 1/2 turn, bed 3 also 1/2 turn - it seemed to heat quite easily, downstairs loo and bathroom both 1 full turn open. Everything else fully open. Now we have heat everywhere, including the attic and good flow. I’ve also had to reduce the flow target a couple of degrees because the house was overall on a warming trend again - which suggests further that the flow was too restrictive across the whole system.
So it seems the original issue with the attic rad was the failure of someone to set the ABV correctly. Yay. So much time and effort wasted on that.
Also, one of my first posts was how noisy the circulation pump was at full chat. That also went away after the ABV was set correctly. I’ve kept it at 100% and it seems to be running much more stably now. Defrosts are still a mess and reducing the pump speed to 60 or 70% hasn’t changed that. I think the real issue was, despite the flow sensor reporting x lpm, the flow around the system was too restricted. DT during the cold snap peaked at 10-11c after defrosts, then eventually settled at 5c. After opening all the lockshields, this peak reduced to 8c but it settled at 5c much more quickly. Will need to wait for the next cold snap to know if the backup heaters would kick in again.
Annoyingly, I’d probably never have touched the lockshields if that attic rad was working, if the installer had set the ABV at commissioning it would have been. So many hours lost. Why didn’t I ask Octopus for help? I did. They promised to send someone but that someone didn’t turn up.
Oh yes, and the thing nobody tells you about heat pumps…
There is a lot of care taken to keep the heat pump at least 1m from the boundary and there are so many videos on youtube showing how quiet they are. But when its frosted up, it’s so very loud with high speed fan noise. It’s like a constant roar. Then, when it enters a defrost, you get a loud sound like a truck releasing it’s air brakes. If I had known, I’d never have agreed to site it on the patio below our bedroom window. And they are triple glazed. Maybe it’s something you get used to, I don’t know yet but for sure we can’t ever open the window again if we want a good nights sleep. Even the trickle vents have to be shut to keep the noise out.
An Octopus installer is coming out tomorrow.