There is something terribly wrong with the control of LWT. Where do the peaks come from?
I presume you mean the big >50 degree peaks: almost certainly DHW heating. Note the set LWT hasn't increased, those peaks happened outside the main space heating control logic. They may be timed, or manually started.
Midea 14kW (for now...) ASHP heating both building and DHW
@jamespa yes that's exactly what I assumed it was rather than anything being wrong. As per previous graphs I've posted the actual LWT fluctuates around the set LWT. I can get whole house electricity consumption from my tesla app. This doesn't seem to show me that much of interest though to be honest. Just steady peaks and troughs throughout the night, and reasonable consumption overall.
There is something terribly wrong with the control of LWT. Where do the peaks come from?
I presume you mean the big >50 degree peaks: almost certainly DHW heating. Note the set LWT hasn't increased, those peaks happened outside the main space heating control logic. They may be timed, or manually started.
Oh right...didn't realise Tasos might have meant the large peaks. Those are for my DHW as Cathoderay says.
@jamespa yes that's exactly what I assumed it was rather than anything being wrong. As per previous graphs I've posted the actual LWT fluctuates around the set LWT. I can get whole house electricity consumption from my tesla app. This doesn't seem to show me that much of interest though to be honest. Just steady peaks and troughs throughout the night, and reasonable consumption overall.
Seems obvious to me unless Im missing something, and the big peaks are presumably DHW.
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
I don’t have UFH. It’s been running at 25C even when the outside temp is 4 or 5 C at night the last few days when there’s been no cloud cover.
I think statements of this kind should be considered in the right context, because it may mislead people into thinking that there is something terribly wrong with their system. Warming a big house (at what IAT ?) with 25C leaving temperature at 4C OAT, seems to me a miracle unless the house is very well insulated and has a large radiator capacitance. Therefore, I would like to see this information along perhaps with a 24-hour graph of all relevant parameters, if possible.
If something is physically unrealizable, there is no algorithm in the world to realize it.
Agree it would definitely be of use/interest to see the homely dashboard.
@papahuhu ...regarding homely, it might well suit a lot of people. Incidentally I did get a call from them during our summer holiday randomly, enquiring as to why I had disconnected it! Again, I don't particularly mind activity tracking and algorithms, but I don't really like the principle of some random people in Manchester having such a degree of control over my central heating, knowing if I am using it or not and calling me out of the blue asking me why I have disconnected it, and if I want to change max and min flow temps having to do it through them. I just find them a slightly odd and frustrating set up, personally speaking.
Incidentally I've noticed havenwise have started advertising £400pa savings as well but you look at the small print and that's savings versus a gas boiler. Just find it all a bit smoke and mirrors with these sorts of product, but perhaps that's just me. Maybe however they do realise decent savings and that is what I want to establish.
To clarify as well, our install wasn't ECO 4. We had agreed payment terms, our installers breached their contract, and that's it really. We didn't pay the final instalment (thousands) and they haven't even bothered asking for it. I ended up redoing some of their plumbing as even that they couldn't get right. I still have some outstanding electrical work to do but generally I'm happy enough just fixing the last remaining bits myself and optimising the controls. I think the options for midea are generally very limited.
This post was modified 1 hour ago 2 times by benson
Think I may be getting somewhere. The lowest permissable outlet flow temp on the Clivet unit is 25, so I have dialled this down to 26 at 15 OAT.
Close up of IAT, so I changed the parameters at around 2000hrs, and it's been much more steady with less peaks and troughs.
Wonder what the perceived benefits were of setting the min flow temp on homely to 35 degrees C....?
I think you need to be careful with axis scales. The lower chart is what some might call a gee-whizz chart of part of the upper chart. Both show the same IAT data, but tell a different story, until you look at the Y axis scale, when it becomes clear the lower one has been 'tweaked' such that the apparent variation is much magnified. In reality, the IAT was in a narrow range, between 19.6 and 21.3 degrees, and spent about half the time at or very close to 20.7 degrees.
Going back to the upper chart (which is a semi-gee whizz chart, Y axis doesn't start at zero) , I don't see anything too strange there. OAT goes up then down and stabilises at around 10 degrees. For some reason (I have picked up on this before on my charts) the controller seems to increase the set LWT during this period of stable OAT, or maybe the OAT change is just enough to trigger the set LWT changes.
What I am less clear on is how the automations (quasi room stats) ate interacting with the WC. The right half of the chart looks like classic WC in mild conditions, the heat pump is slow cycling to reduce output, with the mean actual LWT at about 30-31 degrees, perhaps a bit lower than it should be at 10 degrees OAT, but what matters is the IAT is stable at around 21 degrees. What's happening on the left hand side is less clear. Had the automations turned off the heating?
Is there any way you can add the automation activity to the chart? Presumably at any point in time it has a state, say 0 for off, 1 for on, can you add that to the chart? I do think running both WC and tight room temp control at the same time might be over-egging the pudding. Really the best option is just WC (plus or minus several hour deliberate setbacks if wnated, but they are best left out of the equation until the WC is properly set up), with gradual tweaking of the WC settings to get it just so. Even then there will be variations, eg from solar gain and wind chill, but they are best dealt with by using some form of 'load' or 'demand' control or compensation ie auto-adapt depending on IAT (which is not the same as crude thermostat control).
I think I am right in saying your primary concern was getting the set (and actual) LWT right at warmer OATs. If so, the best primary way to do this is through the WCC settings.
Midea 14kW (for now...) ASHP heating both building and DHW
As per previous graphs I've posted the actual LWT fluctuates around the set LWT.
For the umpteenth time, this is normal Midea and Midea clone behaviour in mild to moderate conditions. It is slow cycling, and no one has ever demonstrated that this causes any problems. If the IAT is steady and where you want it, the heat pump is working exactly as it should do.
Remember, the IAT is the only thing that really matters. If it is OK (and nothing truly bizarre is happening), then all is well.
@cathoderay yes I can have a look at doing that. In summary though it is around 2000/2100 last night that I just put the heating on, disabled the automations, and changed the set LWT lower on the WC curve. It is still on, but taking into account that it is a sunny day today with forecast of 17 I might switch it off for daytime.
As per previous graphs I've posted the actual LWT fluctuates around the set LWT.
For the umpteenth time, this is normal Midea and Midea clone behaviour in mild to moderate conditions. It is slow cycling, and no one has ever demonstrated that this causes any problems. If the IAT is steady and where you want it, the heat pump is working exactly as it should do.
Remember, the IAT is the only thing that really matters. If it is OK (and nothing truly bizarre is happening), then all is well.
Edited to correct typo
Yes I know that, and have been paying attention! I was trying to clarify as I thought that is what Tasos was questioning.
Again, I don't particularly mind activity tracking and algorithms, but I don't really like the principle of some random people in Manchester having such a degree of control over my central heating, knowing if I am using it or not and calling me out of the blue asking me why I have disconnected it, and if I want to change max and min flow temps having to do it through them.
I am of the same mind. Just wait until Big brother starts playing this game as well, through the 'newspeak' of demand side response. It is currently supposed to be opt in, ie opt in to random people in God knows where turning remotely off your heat pump to 'balance' grid load, but i can very easily see how this could be socially engineered into something more compulsory. We should always be very careful what we wish for.
Incidentally I've noticed havenwise have started advertising £400pa savings as well but you look at the small print and that's savings versus a gas boiler. Just find it all a bit smoke and mirrors with these sorts of product, but perhaps that's just me. Maybe however they do realise decent savings and that is what I want to establish.
Of course these people (Homely, Havenwise and similar) market their products on the back of claimed savings, which turn out to be dodgy at best. Most of the time, the owner of the heat pump can achieve any genuinely realisable savings themselves, by setting their system up the right way. Furthermore, as you have found, Homely is not a 'fit and forget' solution, it is a 'fit and get nuisance calls' solution, with the added 'benefit' that you lose direct control of your own system.
Midea 14kW (for now...) ASHP heating both building and DHW
That would be useful, to see how the automations and WCC interact, by comparing charts with and without the automations being on.. My hunch is you don't need the automations, as long as you have the WC settings where they should be. If any fine tuning is needed, 'auto-adaption' (of the set and so actual LWT according to the IAT, rather than on/off control by a thermostat/automation) is the way to go.
Midea 14kW (for now...) ASHP heating both building and DHW
We did insulate very well before installation, heavy loft insulation and 2 roof in roof refits on top of the existing between rafter rockwool. It took us from EPC F up to a high B as all the installers told us that we needed a 3 phase system if we didn’t and there was no way I was digging up the driveway to do that. We also changed from 3 zones to a single open loop, 25 out of 27 rads were upsized and we changed from gravity fed to a 300L pressurised DHW, 10s of metres of new primary copper was installed. I haven’t touched the controller since installation, with the one exception of disabling the DHW sanitisation as that was Yes, the efficiency has shocked me. I don’t know if the reason is the insulation or a good install, as both were done concurrently. If anything I’m finding the house overly warm at night. We only have a cheap heat pump, everyone told me they were poor and the control system was amongst the worst on the market, I’m finding it to be brilliant and love the simplicity and economy I get from the homely. I can only get the headline power consumption and heat generation figures from the controller, but the control system consumption figures are accurate as they accurately correlate with the data from my powerwall 3 and my smart meter data. One thing I’ve noticed which I find perplexing is that whether the OAT is 4 C or 13C, I’ve never seen the outlet flow temp deviate from 25C for space heating, I can only guess that is because the heat pump is a bit oversized and has never had to run above its minimum output. Maybe that’s because the emitters are correctly sized and we are also retaining most of the heat. It is running once every 120 minutes, for about 40 mins, I guess this cycling also indicates it’s at its minimum output. I run a homely node set point of 17C during the day and 15C at night, but it seems to ignore the 15C and run at 17.4 +/- 0.2 C day and night. That’s annoying as it is too warm to sleep for me and I look forward to mean OAT dropping further. The installer is performing a quality audit in October, so I will ask them then, to be honest I’m only running the space heating at the moment to check the install before the audit. In the past I’ve never turned the heating on before November as I was too mean.
