Yup set that this morning once I realised what happened. Does that also apply when you ‘boost’ it? As I’m still testing the best time to do it and the best offsets etc, I’ve just been doing it via a boost. Seeing how many days/showers I can get from the tank before it has to be recharged. Was a bit chilly yesterday morning after 3 showers in 3 days (live on my own), think the tank was down to about 15C at the pocket 
I think I will be landing on running it every other day, 3 days is too much a stretch.
Aha, the beauty of the Mixergy is that even when it’s nigh on empty, it’s still got usable water in.
My lad took it down to less than 3% left last night and there was still 43C usable water in there.
Which make for a cracking recharge starting point last night and good COP for 11C outside.
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I didn’t think the stratification worked with Mixergy and ASHP combo, in that it just does a complete recharge of the cylinder whenever you heat it, rather than being able to keep it at a certain level?
Looking back it was 20C at the pocket at the start of the shower, 15C at the end. But still gave a decent shower. I have a digital mixer which will flash when it can’t get to requested temp and it didn’t complain. But at the end of my shower, I tested it to see how much hot I had left (whacking it up to max), it didn’t get much hotter than I already had it so I don’t think it would have done another shower. But it wasn’t completely out or cold, I was being a bit harsh in my previous comment. My old ex would have definitely complained if she went in after me mind, it wouldn’t have been hot enough for her! Think it did quite well to keep the water bearable for 3 days. It is a rainfall shower too, so god knows how high the flow rate is, its not economical for sure 
Last proper run (not cut short!) of the DHW heating with 5kW and Vaillant cylinder, think it did pretty well.
Does anyone know any settings to tighten up the dead band on the SensoComfort when using Room Mod as Expanded? I’m trying to heat the house mostly in the IOG off peak, so currently have it set to 21C overnight, and falling back to 20.5C during the day. However, at the moment, its at 20.6C and still heating. It’s been 20.5C for 3 hrs and 20.6C for over half an hour.
I think the temp below target for heating to cut in is 0.2-0.3C from what I’ve seen, will it do the same above the target temp? As the UFH is slow to respond, the other rooms are now overshooting.
Correct, but there is still stratification during the usage of the tank once fully charged. What you can’t do is partially charge the tank and have/maintain stratification when heating with ASHP. In theory the Mixergy tank has an improved inlet difusor making it stratify better than a standard UVC (which is what @Zarch is showing), but to be fair all UVC stratify to a certain extend https://community.openenergymonitor.org/t/vaillant-arotherm-owners-thread/21891/525anyone.
I think I read on this forum that the design of the cylinders changed a few years ago and the more recent ones do allow a variation of partial charging with the Heat Pump kit.
My Mixergy when left on the Agile tariff automatic setting does run partial charges that don’t affect the temperature at the top of the cylinder.
You can see how it heats the bottom of the tank first and only starts to pump that water to the top when the bottom temperature starts to match the top temperature.
I do find the Agile algorithm a bit flaky with the Heat Pump though.
There’s probably more guesswork involved as to how long it will take to heat. Understandably, the balanced DHW setting seems to confuse it more.
The heating run in the screenshot should really have started 30 mins earlier for example.
Mine does exactly the same, this isn’t what Mixergy refer to when they talk about “partial charging” though. Partial charging means you can heat/use/heat use just 30% of the tank if you want to. This is not supported with ASHP. Your graph doesn’t show partial charging as charge ends at 100%, does it sometimes heat and not end at 100%?
It does. Not that often. It did happen today though.
The first block was the Mixergy with nothing else scheduled for the next 90 minutes.
I boosted manually which is the second block.
I see what you mean about the partial heating. You just end up with hot at the top and bottom with a cold section in the middle.
I wonder if thats deliberate though, or actually Mixergy thinks you have are using top coil and not ASHP?
I’ll send them an email to see what the expected behavior should be.
On another note, I had to ask them to increase a delay setting from 15 mins to 45 mins.
If the charge didn’t increase over a 15 min period the cylinder was switching to the immersion as it assumed the Heat Pump couldn’t provide enough heat for some reason.
The problem was that this was being triggered if someone was having a shower during a heating phase.
They increased this setting to 45 mins and a new entry appeared in the settings.
They increased mine to 1hr. I had issue during defrosts last winter, it was switching to immersion too quickly rather than waiting.
4 posts were split to a new topic: DIY Controller for radiator fans
Has anyone played around with this heat curve tool: https://heatcurve.psimonkey.org.uk
I wonder whether it’s based on the Vaillant heat curve formula linked to by @Andre_K above.
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I pasted the site source code to ChatGPT and asked what the equation was that’s being plotted:
var y = 2.55 * (hc * (targetTemperature - x))**0.78 + targetTemperature;
That’s exactly my fitted curve. 
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Excellent!
I wonder who developed the tool, and where they gleaned the values from…
I would guess they got it from this forum. This is the only place I posted the equation and there is another, slightly different one somewhere on the internet. That someone else got the exact same values as me sounds a bit far fetched given that I digitized a plot to get them. Unless of course I accidentally rounded my results to the true values 
. How did you find the tool?
I found it in my inbox, from someone called ‘S. Nakamoto’…
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How accurate are people finding their outdoor temperature sensors to be (mines wireless if that makes a difference)?
When running with the room temperature mod set as Inactive I was finding the house temperatures were exceeding the setpoint. I dialed the heat curve back a bit (and reduced the set point) and found a happy medium for a time. I’ve now set it to Expanded (and am having a play with varying the setpoint to run higher during the cheaper Octopus Cosy windows).
I’ve already applied an offset on one of my two sensocomfort units (as it was out vs the other and the emonTH). I seem to remember that the (potential) inaccuracy in the internal calculation of the COP on the Vaillant units was mainly pinned on the measurement of the flow and return temps (rather than energy usage).
Just wondering what others experiences are / whether the school of thought is (to wait for colder weather) and just continue to tinker with the heat curve until achieved room temps match set/desired temperature?
(In the meantime I’ve setup HA to send to Emoncms the Vaillant recorded outside temperature for ease of comparison)
My wired outdoor sensor is typically within 1°C compared to other outdoor sensors around the house.
Yes. However, while an error of 1°C is catastrophic for heat measurements, it is not problematic on the outdoor sensor.
I personally also have not found the perfect heat curve setting. In warmer weather I’m increasing the setpoint by 0.5-1°C. I did the math and figured out I could not achieve the desired behavior just by modifying the heat curve.