Modulation is disabled when you set control to LWT. It also isn’t possible when using a 3rd party thermostat.
If the system is set to Room Thermostat control, then modulation changes the target flow temperatures based on how far away the indoor temperature, as measured by the Madoka thermostat, is from the required temperature set on the thermostat.
The Home Assistant automation used to adjust the LWT based on the ambient temperature discussed in the other thread is essentially recreating the modulation feature but for LWT control.
right that’ll be why it’s not modulating then. but I was referring to cycling as in on and off of the pump in rapid succession , oscillation…
I’m still confused whatever I’ve seen lots of posts and lots of forums regarding the LWT demand being below 30 causing these pumps to cycle… is that a different modulation or the same thing … I might even contact Daikin tech for an definitive answer on this one.
The modulation config options in the Altherma control software is pretty much unrelated to short cycling of the units. What I’d say, from observations of my own system, is that modulation is just another thing that too often “moves the goalposts” for the Daikins, which reduces their efficiency as they hunt around trying to hit a target LWT that is almost permanently moving.
I’d say the number 1 cause of short-cycling (as well as reduced efficiency) in the Althermas is the default 1C overshoot value coupled with the Daikin’s method of attempting to reach the target LWT as quickly as possible at start-up which invariably leads to flow temperatures above the overshoot value.
mmm interesting. so should I remove the 1C overshoot in the installer settings… think it might be the field codes actually I can’t remember
remember I’m running on the weather curve LWT not the room thermostat not a fix set point … those those are the only three control modes.
?
Yes I’d 100% recommend increasing overshoot to 3C or 4C. In Leaving Water control there is still a target flow temperature (as set by your WD curve) and this value can be overshoot by the Altherma.
The unit will only overshoot for a short time after start-up whilst it settles back down to the target flow temperature. It just needs that overshoot headroom to be able to get to the steady state.
Overshoot is only available in Installer profile, in the “Space Heating” menu [9-04]
Blimey , yikes …I thought you meant remove it put it to zero.
The overshoot tends to raise the LWT and heat the house to like 23° which is too uncomfortable as you say that’s only when the system starts though
To increase it by 3° …likely to take the room to about 26C
just to repeat the question subtly again I think just to tease out of you … is setting Y2 to 25 c going to be a problem as I said lots of people recommend not going below 30
I don’t believe the overshoot can be disabled, the minimum value is 1C.
Setting Y2 to 25C and keeping overshoot at 1C will cause your system to cycle. At worst that’ll be short cycling, the problematic kind of cycling where the compressor is stopping and starting multiple times per hour, causing excessive wear on the system components and probably reducing its lifespan. At best with those settings you’ll just be reducing the efficiency, using more electricity to produce the same amount of heat if you just had a higher LWT for Y2.
Thank you … ok, so setting Y2 to 30 means that LWT is too high, house gets too hot so I need to turn the heating off on the Onecta app (or get older sister to do it through the climate entity) which will cause it to cool down and then I turn the heating back on again later…and tgen off, and so on… 1 This can’t be good… I don’t know how else to do
or would setting the overshoot to 4C and keep your way to at 25 be ok? as that would only affect startup -. you mentioned.
Your system isn’t going to run at 25C flow temperature unless you have an unreasonable amount of emitter capacity (and even then maybe not).
Either approach is going to lead to the same thing, the overshoot value is just going to let the system run at a 25+4C flow. So if your system can maintain 29C (which the majority of Althermas reporting to heatpumpmonitor.org cannot), then you’ll be basically in the same position as running at 30C flow and being too hot.
If your system cannot maintain 29C, it’ll cycle but a bit less than if you had Y2 at 25C and overshoot at only 1C and run a bit longer between cycles.
You’re going to need to use Onecta/HA automation to turn off the heating when you get too warm.
I’ve just checked on the installer settings overshoot it was already 4C, I assumed it was the default 1 as in in the manual.
according to the MMI sensors, right now LWT is 28 and the house is sticking around 18.9 C which is ok for sleeping It’s been like that for about the last 2 hours. absolutely no idea if the pump is cycling though have no way of measuring or monitoring that
So basically if I understand you correctly then I should just dial Y2 to 30, leave the overshoot at 4 and then use home assistant to modulate the system on and off if it gets too hot/cold … correct?
Yeah that’s what I would suggest is going to give you most efficiency and comfort from how you describe the system is working currently.
It certainly makes it more difficult to know exactly what the right Y2 setting is for your system without monitoring data. I’ve seen very few Althermas that run at a steady 28C LWT (maybe 1 on the whole of this site - and that’ll most likely be because they have a lot of underfloor heating).
You’d get a better understanding of how your system is working if you have something like a Shelly CT monitoring the Heat Pump electricity feed, or if you don’t want to interfer with the heat pump install, just on the main incoming grid connection. You could then see real-time electricity power usage in Home Assistant (heat pump cycling would be pretty easy to identify even on the whole home feed).
ok I’m going zzz now so I’ll do this tomorrow set it all up
yes I think I’ll get a Shelly CT there’s a separate supply to the pump on its own circuit so I can clamp around that and integrate that into home assistant
I don’t want to tamper with the monoblock because it’s under warranty with octopus 5 years so I don’t want to get in there and start messing about with electrics.
I think the most important thing is to get that heat curve to 30C at lowest, and used home assistant for modulation in concert with my array of switchbot temperature sensors throughout the rooms we seem to react and be more responsive and the crappy madoka.
thank you very much for your help on this I can’t wait to monitor it and come back with some results for you to cast of you on thanks a lot Cheers
edit:
one final thought what if I use smart TRVs to control down radiators if they get too hot I guess that would mean the return temperature the return flow, would be the same as they leaving water temperature and no delta T … I guess that’s a bad thing also though
As conrad mentions change to pure weather compensation the modoka seems to interfere a lot and not convinced its instance , you can turn the modulation to 1 but the modoka still has effects
This will improve your comfort, because it will prevent the room temperature from rising excessively. However it could make the cycling problem worse.
The heat pump cycling is triggered because the radiators can no longer dissipate the minimum level of heat that the heat pump can produce. If some radiators are shut off then their ability to dissipate heat is removed, so you now have even less capacity to dissipate the heat.
Having said all that, this is the configuration that I run with smart TRVs on some radiators. Once the heat requirement for the house drops below the minimum output of the heat pump there has to be some cycling, or you have to allow the house to overheat, those are the only two options. Its then a balancing act as to how you manage the cycling (including ignoring it) vs comfort.
It depends, for example limiting bedroom temperature may allow you to let the rest of the home get warmer overnight, so premitting longer cycles. Then in the daytime you can let the bedrooms overheat if they are not in use.
I made this spreadsheet a few years for a friend who was interested in getting his gas fired boiler to condense as much as possible and also with the view of installing a Heat Pump at a later stage, he had upgraded the house insulation and reckoned that his rad outputs are now sufficient if they emit 45/50% output at a OAT of -10C, I based the calcs on a 47% output, interestingly, he also says that he hasn’t a hope of running with WC only, especially in his south facing rooms, but I suppose that’s a problem/challenge for everyone. WC John.xlsx (16.8 KB)
