Homely, currently only available for Samsung and Midea heat pumps, claims to be a 'smart' control system for these heat pumps, smart insofar as it can tune the weather compensation to suit varying conditions, thus solving the basic weather compensation curve's Achilles' heel of being a 'dumb' curve. Apparently it uses modbus and RS485 to interact with the heat pump, which makes sense, the Midea unit has these. No doubt Homely have plans to make it applicable to other brands in due course.
Has anyone had any real world experience with Homely? If so (a) does it work as in achieve more effective (rooms more reliably at desired temps) and efficient (lowest possible COP at all times) control and (b) what if any monitoring does it do (and if it does monitor, can the data be downloaded, or is it a pencil and paper job, as it is with that blasted Midea app)?
Lastly, how does it compare to the various open source home automation projects like Home Assistant and domoticz? Clearly it is proprietary, and it only manages an ASHP, but does it do that better or worse than the open source projects. The latter, so far as I can tell are still at the 'enthusiasts' stage, fiendishly complicated to set up, and more often than not definitely do not work 'out of the box'.
Midea 14kW (for now...) ASHP heating both building and DHW
I have a feeling @grahamh has some experience here. He suggested them to me some time ago, but I have been working on fixing the hardware issues in my system first, before I even consider the software side.
12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE
I have been working on fixing the hardware issues in my system first, before I even consider the software side.
Point taken, but my hardware, as in the plumbing etc, is pretty much where it is, with the only possible variation being removal of the PHE, which I am not yet ready to do. I don't see any harm in tackling the software/control side of things in parallel with hardware, as long as its one change at a time, and records are kept, so you know what changed what.
What I don't get is why the Midea unit in effect ignores what is happening in the house, which at the end of the day is what really matters. It only cares about the outside temp, and then makes assumptions about how much heat the house needs. Sometimes this works, other times it does not. For example, it can't handle a overnight setback even by just a few degrees. The house cools down, and needs a small boost in the morning to get it back to daytime temps, but the Midea unit can't do that, because it only knows what the outside temp is, and ignores the fact the house is actually colder than it should be. Nor can it handle weather effects like solar gain and gale loss, more occupants in the house, firing up a wood burner etc.
In an ideal world, the main control of flow temp (and rate) would be broadly set by the weather comp curve, and then this would be tweaked by a strategically placed indoor sensor that measures the difference between actual and desired indoor temp. If the house was cooler than it should be, up the heat output a bit, if it is warmer than it should be, then lower it a bit, by modulating output, rather than using blunt on/off control. This should also remove some if not all cycling, leaving the compressor running in Steady Eddy mode for as much of the time as possible.
I get the impression from other discussions the Ecodan units can do something along these lines. The question is, can Homely achieve much the same thing with Midea and Samsung units?
I've emailed Homely asking relevant questions, but no reply yet. I just wonder how many people have actually installed Homely and used it for a while - perhaps very few. If not many, it is definitely all a bit of an unknown.
Midea 14kW (for now...) ASHP heating both building and DHW
@batalto - I've also made some possible progress on the modbus/RS-485 monitoring (which I gather is also what Homely uses, hence looking into it as a possible out of the box solution). The DIY route may also not be that complicated: hard wire a cheap ~£10 RS-485 to USB converter into the Midea wired controller, simple two wire A to A / B to B connection (I'm guessing this may be Headroom Heat Pumps 'incredibly simple bit of hardware') and then plug the USB end into a computer and the modbus data should be available on a com port, and readable using open source modbus monitoring software. For a more permanent, always on permanent record solution, something like a raspberry pi might be the answer, don't know, haven't ever used one. The modbus register has addresses for the various parameters eg 104 (PLC:40105) is the RWT, 105 (PLC:40106) is the LWT and 138 (PLC:40139) is the flow rate, and with those three, you can calculate the actual heat output.
Midea 14kW (for now...) ASHP heating both building and DHW
@cathoderay I'm fairly sure you can get an indoor sensor for the Midea unit - but it doesn't have auto-adaption like the mitsubishi units. I could see it via a software update, but I also assume that it's not a priority for Midea given how many products they have in that space. I'm expecting AC units are the bulk of the sales Vs heat pumps for them.
12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE
Agreed on compensation curves being a weird way to run a heatpump - especially given the outside temperature is (much) lower at night and heatpumps work (much) less efficiently in lower temps. Am following others' replies on Homely...
I have been working on fixing the hardware issues in my system first, before I even consider the software side.
Point taken, but my hardware, as in the plumbing etc, is pretty much where it is, with the only possible variation being removal of the PHE, which I am not yet ready to do. I don't see any harm in tackling the software/control side of things in parallel with hardware, as long as its one change at a time, and records are kept, so you know what changed what.
What I don't get is why the Midea unit in effect ignores what is happening in the house, which at the end of the day is what really matters. It only cares about the outside temp, and then makes assumptions about how much heat the house needs. Sometimes this works, other times it does not. For example, it can't handle a overnight setback even by just a few degrees. The house cools down, and needs a small boost in the morning to get it back to daytime temps, but the Midea unit can't do that, because it only knows what the outside temp is, and ignores the fact the house is actually colder than it should be. Nor can it handle weather effects like solar gain and gale loss, more occupants in the house, firing up a wood burner etc.
In an ideal world, the main control of flow temp (and rate) would be broadly set by the weather comp curve, and then this would be tweaked by a strategically placed indoor sensor that measures the difference between actual and desired indoor temp. If the house was cooler than it should be, up the heat output a bit, if it is warmer than it should be, then lower it a bit, by modulating output, rather than using blunt on/off control. This should also remove some if not all cycling, leaving the compressor running in Steady Eddy mode for as much of the time as possible.
I get the impression from other discussions the Ecodan units can do something along these lines. The question is, can Homely achieve much the same thing with Midea and Samsung units?
I've emailed Homely asking relevant questions, but no reply yet. I just wonder how many people have actually installed Homely and used it for a while - perhaps very few. If not many, it is definitely all a bit of an unknown.
One possible, and very simple, way to achieve a reasonably accurate control of indoor temperature, would be to install a suitable thermistor in the living area, and connect this thermistor in series with the outdoor temperature thermistor.
If both thermistors have a negative temperature co-efficient (NTC), their resistance will reduce with increasing temperature.
The system should therefore operate in the following manner.
If the outside air temperature increases, the resistance of the outdoor thermistor will reduce, and in doing so will cause the controller to lower the LWT. If the indoor air temperature increases the resistance of the indoor thermistor will reduce, which will have the same affect. By suitable selection of thermistors and adjustment of the weather compensation curve, it should be possible to achieve reasonably constant indoor temperature under varying conditions.
The only drawback that I can foresee is that the ambient temperature indication on the controller would not be accurate.
I can provide further details if anyone is interested.
The only drawback that I can foresee is that the ambient temperature indication on the controller would not be accurate.
@derek - this is a very interesting idea, but I fear there may be other drawbacks as well, given the addition of an indoor thermistor in serial with the outside one might involve a soldering iron and/or crocodile clips, another 'what could possibly go wrong' scenario. At this stage, I am trying to find out if anyone has actually used Homely, and if so whether it 'does what it says on the tin'.
I'm fairly sure you can get an indoor sensor for the Midea unit - but it doesn't have auto-adaption like the mitsubishi units. I could see it via a software update, but I also assume that it's not a priority for Midea given how many products they have in that space. I'm expecting AC units are the bulk of the sales Vs heat pumps for them.
Yes, I have also seen it, in the manuals, but I think it is a simple on/off room stat, and is used instead of weather comp, not with it.
Homely may be able to do much the same as the Mitsubishi units, because as I understand it, modbus RTU/RS-485 should be two way, it can both read data and control the unit (set settings). For example, 2 (PLC:40003) may be able to set T1S ie the LWT (T1 is the actual LWT, T1S is the set LWT). But at this stage we have no evidence either way of what it can/can't do.
Midea 14kW (for now...) ASHP heating both building and DHW
Homely, currently only available for Samsung and Midea heat pumps, claims to be a 'smart' control system for these heat pumps, smart insofar as it can tune the weather compensation to suit varying conditions, thus solving the basic weather compensation curve's Achilles' heel of being a 'dumb' curve. Apparently it uses modbus and RS485 to interact with the heat pump, which makes sense, the Midea unit has these. No doubt Homely have plans to make it applicable to other brands in due course.
Has anyone had any real world experience with Homely? If so (a) does it work as in achieve more effective (rooms more reliably at desired temps) and efficient (lowest possible COP at all times) control and (b) what if any monitoring does it do (and if it does monitor, can the data be downloaded, or is it a pencil and paper job, as it is with that blasted Midea app)?
Lastly, how does it compare to the various open source home automation projects like Home Assistant and domoticz? Clearly it is proprietary, and it only manages an ASHP, but does it do that better or worse than the open source projects. The latter, so far as I can tell are still at the 'enthusiasts' stage, fiendishly complicated to set up, and more often than not definitely do not work 'out of the box'.
I have honeywell evohome. You can consume the RF bus's data of that honeywell system into a home-assistant PC via a USB-RF module. The protocols are fully reverse engineered by people far cleverer than me and there's a guy sells the RF modules pre-built. To get it working I wrote no code, just installed other peoples code according to the docs...but yes you do need to be some kind of geek...
That gets you this:
which is an "aggregated heat demand for the house" out of 100. Evohome can natively send this as an opentherm percentage demand signal to a suitable boiler, (rather than the simple basic on/off) . I'm trying to figure out if there'll be a way that I can use this to get better control of a heat pump (there ought to be). I don't have a heat pump yet...
Homely, currently only available for Samsung and Midea heat pumps, claims to be a 'smart' control system for these heat pumps, smart insofar as it can tune the weather compensation to suit varying conditions, thus solving the basic weather compensation curve's Achilles' heel of being a 'dumb' curve. Apparently it uses modbus and RS485 to interact with the heat pump, which makes sense, the Midea unit has these. No doubt Homely have plans to make it applicable to other brands in due course.
Has anyone had any real world experience with Homely? If so (a) does it work as in achieve more effective (rooms more reliably at desired temps) and efficient (lowest possible COP at all times) control and (b) what if any monitoring does it do (and if it does monitor, can the data be downloaded, or is it a pencil and paper job, as it is with that blasted Midea app)?
Lastly, how does it compare to the various open source home automation projects like Home Assistant and domoticz? Clearly it is proprietary, and it only manages an ASHP, but does it do that better or worse than the open source projects. The latter, so far as I can tell are still at the 'enthusiasts' stage, fiendishly complicated to set up, and more often than not definitely do not work 'out of the box'.
I have honeywell evohome. You can consume the RF bus's data of that honeywell system into a home-assistant PC via a USB-RF module. The protocols are fully reverse engineered by people far cleverer than me and there's a guy sells the RF modules pre-built. To get it working I wrote no code, just installed other peoples code according to the docs...but yes you do need to be some kind of geek...
That gets you this:
which is an "aggregated heat demand for the house" out of 100. Evohome can natively send this as an opentherm percentage demand signal to a suitable boiler, (rather than the simple basic on/off) . I'm trying to figure out if there'll be a way that I can use this to get better control of a heat pump (there ought to be). I don't have a heat pump yet...
Ian
I very much doubt that this is showing heat demand, since it is allegedly going from 100% to 0% over a period of a few hours.
@derek-m yes it is. the zero's are heating off (timed programming turns all off). So on the scale, zero is definitely no heat demand, 100 is definitely "as much as possible please", and the numbers in between are calculated in some honeywell proprietary way which may or may not be opentherm compliant.
I haven't had enough experience with Homely to be sure but I wasn't impressed. One reason was that it came with a little button that was the sensor but could not keep in wifi contact with the router that came with it.
I thought it was very basic so after a few days I spoke with the member of staff who was monitoring the installation and his words were that it does not give control it takes control. It took a fair slice of electricity too.
It was the last hope for getting a sensible system and I couldn't afford to let it carry on picking my pocket.
However, claims that my heat pump is good for the environment have proved to be true because I switched the whole thing off last April and lived in a cold house since (small oil fill radiator to stay alive) the glaciers are reforming as we speak.
