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Mitsubishi Ecodan & Raspberry Pi automations

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(@steevjo)
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@walkers-heatpump setting 19.5C as target temperature would keep it closer to 20 on average. Yes could go over half a degree but shouldn’t go under by much more than half a degree either.

i’m almost convinced that since having a heat pump I have become more sensitive to changes in the input heat to a room - even to the extent of sensing when the heat pump is doing its defrost cycle and wishing it would get back to heating!

bigger picture - maintaining our living room to +/- 0.5C of set temp is a miracle 😀

Our experiences with solar pv, ASHP, battery, and EV: ourhomeelectric.co.uk


   
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(@derek-m)
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Posted by: @walkers-heatpump

I've not tampered with it for a few days and I feel like it's learning better without my interference, better at dropping flow temps and sticking to it so I'll give it a break for a while! It still seems a bit too alike my old boiler tho! On the auto setting, my old boiler would crank up to the max and then modulate down from there - that's what it feels like on auto-adapt at the mo, it spends best part of an hour getting up to 45°, before cycling and modulating to the flow temp it should be (or closer anyway)

I also get it going a degree over target temp - which again feels a bit too much like boiler boom and bust. It's tricky setting a temp because 20° is about right for us but 21° feels too warm - so we set to 19° knowing it will get up to 20° however we then have to wait for it to get down to 19° before it kicks in again

It would appear that your heat pump controller is operating in the manner that I would expect a controller to operate, though it should be remembered that the controller is designed to keep the indoor temperature constant, rather than keep varying it.

Let me explain how a controller is designed to operate.

A basic controller has two inputs, the desired value or setpoint (SP) and the measured value or process variable (PV), along with one output (O/P). When PV = SP, O/P does not change.

The PV for your heat pump controller is the indoor temperature measured by a sensor, the SP is the value that you set on the controller display, and the O/P is the required LWT, calculated in conjunction with the weather compensation.

When the overnight setback is initiated, SP is reduced from 20C to 17C, if PV is still at 20C, the controller will now be measuring an error of 3C. For the controller this is a large error, so it will lower its output quite dramatically and reduce the required LWT. A further control system within the heat pump controller will see this much lower required LWT, and will reduce the speed of the compressor to try to get the actual LWT to match the required LWT. I suspect the compressor will be pulled back to minimum speed and will eventually stop.

Of course the indoor temperature does not immediately fall from 20C to 17C, in fact I doubt that PV will get down to 17C during the setback period. The indoor temperature will gradually fall at a rate dependent upon the thermal mass of the building, and the temperature difference between indoor and outside.

Say that the indoor temperature falls to 18C by the end of the setback period. If the SP is now changed from 17C to 20C, the control system will now be measuring an error of 2C, but in the opposite direction, which means instead of reducing the required LWT, it now needs to be increased. A large error equates to a large change in output, so it is quite possible that the compressor will be ramped up to full speed.

Once more the indoor temperature will not immediately change from 18C to 20C, but will gradually start to increase at a rate dependent upon the difference between the heat energy output of the heat pump, and the heat loss of the property. The heat energy output must exceed the heat loss for the indoor temperature to be increased.

As the indoor temperature starts to increase, the error between SP and PV will start to reduce, until it reaches a point where the compressor starts to pull back from full speed. The required LWT will gradual be reduced, which in turn will lower the heat energy output of the heat pump, to the point at which the heat energy output matches the heat loss, with PV equal to SP.

In the real world control systems will often experience an overshoot, where PV increases above SP, and then gradually pulls back. This is perfectly normal.

To minimise energy consumption during reheat after a setback period I would suggest the following, though what works best may vary under different operating conditions.

1) Limit the maximum LWT setting, to prevent the compressor from running at full speed. This will probably reduce the rate at which the indoor temperature can be increased, so it may be necessary to restart the heat pump earlier.

2) Make smaller SP changes in a controlled manner, so instead of going directly from 17C to 20C, go from 17C to 17.5C to 18C and so on and so forth over a period of time.

3) Try varying the time interval setting within the controller to match the time delays inherent in your home, though these time delays will vary with changing weather conditions.

 


   
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(@walkers-heatpump)
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Thanks Derek, that's really helpful. It does seem to be modulating down better now, it's just that initial steep climb. A few days ago after reading through the thread I changed our return from setback to half a degree increases every hour to try to get it to ease off a bit, not sure how much impact it's had, might need to tweak to 45 mins instead, will see how it goes. 

On the time interval we have that set to 40 minutes at the mo. I was looking at the flow temps this morning, e.g. in the attached it's keeping them pretty well to around 36° then suddenly around 45mins it shoots off higher before cycling from the looks of it. I'd wondered whether that was linked to the time interval - it reassesses, increases flow temp sharply but then finds its beyond the WC target temp +3° (thermo temp adjust) and so turns off...but then I checked the weather comp curve we have set and it should be down at about 29° at 6/7° outside so it's way off that already!

I'm prob just overanalyzing it all anyway, just interesting intriguing stuff! Got decent COPs above 3.5 over the past week when temps have been 1-8° for the heating periods so can't really complain. Loving the magic of heatpumps!

 

Screenshot 20230426 201540

 

This post was modified 1 year ago by Walkers Heatpump

   
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(@sunandair)
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Posts: 345
 

I missed this thread because at the time I was dealing with far more basic problems with our inefficient installation. Also the headline “Raspberry Pi automations” wasn’t on my radar.

im hoping I might get some help from contributors to understanding these gaps in my knowledge...

So where are we with latest understanding of Ecodan and AUTO Adaptation? 

Are there any new refinements which appear to work? Eg half degree increments etc.

does weather compensation settings have nothing to do with AA?

 

Posted by: @derek-m

Original message:-

Thank you for the reply.

Yes, several of the forum members did use the wireless controller, but found that when they initiated Auto Adaptation, the response from the controller was much too aggressive. Instead of gradually changing the temperature of the water produced by the heat pump from say 35C to 36C, it would bump the temperature up to approaching 50C, which is far from efficient. This would cause too high a temperature so the controller would then lower the water temperature to below 35C.

This caused the heat pump operation to cycle in an inefficient manner. This is not how I would expect Auto Adaptation to operate.

The description of Auto Adaptation in the manuals is rather vague, could you please clarify how it is designed to operate. When operating in Auto Adaptation mode, should the controller 'adapt' the system response, over time, to match the heat loss characteristics of the home in question?

My understanding of how Auto Adaptation should operate is that, the water temperature produced by the heat pump should follow the weather compensation curve, but if the indoor air temperature is below the desired temperature, the Auto Adaptation would add slightly to the weather compensation to gradual increase the water temperature, and hence increase the indoor air temperature. The reverse should occur if the indoor air temperature is too high.

Could you please clarify if my assessment of the control philosophy is correct?

Reply:-

Good Afternoon Derek,

Yes your description of the Auto adaption mode is quite accurate.

The controller will constantly monitor room temperature and vary the flow temperature depending on the outside ambient temperature and how far away the target temperature is from the actual room temperature.

It also has a self-learning function which will follow similar patterns it adapted to in the past. For example, if 3 days previously the outdoor ambient was 5 degrees and the room stat was set to 22 degrees and the room was at 20 degrees, it will look at the flow temperature it used that day to get the room up to 22 degrees and adapt the flow temperature accordingly. If the room temperature does not increase over a 1 hour period it will increase flow temperature by 1 degree every hour until it reaches room target temperature.

I hope this helps

 

I believe @derek-m described this “ambient temp/target temp/LW temp” as a recognised heating control system in a recent post which I cannot find right now.

 

Ive not been able to find the info field shown in this pic from @mjr so could mjr  point me in the location On MELCloud where I might find it?

34636C89 9BDC 417D 91A7 D3C6BD88FC0A

And moving on to the title name

Does Raspberry Pi work with Ecodan? What specific Raspberry Pi system works? Does it give accurate energy usage data or does it use Ecodan estimated data? 

I am operating in auto adaptation mode with settings which appear to be effective but I want to be sure it’s not just happening by luck.

lastly... @kev-m I think you have a different energy monitoring system I would be interested to know what you are using.... and how easy it has been to implement.

Any help is gratefully appreciated...

 

 


   
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(@derek-m)
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@sunandair

I do believe that there are a number of forum members who have managed to get reasonable to good results from Auto Adaptation (AA), but there are others who have struggled, either because the characteristics of their home were not suitable, the internal settings in the controller were not correct, or their expectations of how it should function were not even possible.

As far as I am aware AA was developed to help maintain a constant indoor temperature under varying conditions, it was not developed to provide a controlled, energy reduced, startup after an overnight setback, which defies the laws of Physics. If a heat pump is stopped for several hours, the heat loss does not also stop, so when the heat pump is restarted, it not only needs to supply the present heat loss, but much of the heat lost during the setback period. The controller can only do so in a reasonable timescale by ramping up the LWT to a high value and increasing the heat energy output. AA mode is just following normal control philosophy in this situation.

Unfortunately heat pump controllers don't appear to possess a 'ramp' function, which would allow the desired temperature setpoint to be raised gradually, in a controlled manner, over a lengthy period of time.


   
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(@kev-m)
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Posted by: @sunandair

IAnd moving on to the title name

Does Raspberry Pi work with Ecodan? What specific Raspberry Pi system works? Does it give accurate energy usage data or does it use Ecodan estimated data? 

I am operating in auto adaptation mode with settings which appear to be effective but I want to be sure it’s not just happening by luck.

lastly... @kev-m I think you have a different energy monitoring system I would be interested to know what you are using.... and how easy it has been to implement.

Any help is gratefully appreciated...

 

@sunandair

I use the standard Ecodan MMSP package like this.

https://library.mitsubishielectric.co.uk/pdf/book/Ecodan_MMSP_Application_Guide#page-1

I then grab the csv file Melcloud produces into Python as and when I like to produce these graphs and numbers. 

It was very easy to implement for me; I told my son what I wanted and he did it!  I was going to try and do it myself but took the easy way out.  If you or anyone else wants the code let me know. You do need the pulse output heat and electricity meters and the Ecodan wireless module to make it all work though. 

Screenshot 2023 04 28 15.52.49

 

 

Screenshot 2023 04 28 15.54.12

   
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(@sunandair)
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Joined: 2 years ago
Posts: 345
 

 

Hi Derek thank you for your reply

Posted by: @derek-m

I do believe that there are a number of forum members who have managed to get reasonable to good results from Auto Adaptation (AA), but there are others who have struggled, either because the characteristics of their home were not suitable, the internal settings in the controller were not correct, or their expectations of how it should function were not even possible.

I’m hoping to clarify the subtle changes and current thoughts on Auto Adapt and how it functions. You had a very interesting letter from a Mitsubishi engineer which I posted above however from his reply I can’t be clear if he actually confirmed if AA actually makes any reference to Weather Compensation.

can you confirm your understanding of what he said about Weather Compensation.

I’ll post it here again

 

 

Posted by: @derek-m
 

A basic controller has two inputs, the desired value or setpoint (SP) and the measured value or process variable (PV), along with one output (O/P). When PV = SP, O/P does not change.

The PV for your heat pump controller is the indoor temperature measured by a sensor, the SP is the value that you set on the controller display, and the O/P is the required LWT, calculated in conjunction with the weather compensation.

When the overnight setback is initiated, SP is reduced from 20C to 17C, if PV is still at 20C, the controller will now be measuring an error of 3C. For the controller this is a large error, so it will lower its output quite dramatically and reduce the required LWT. A further control system within the heat pump controller will see this much lower required LWT, and will reduce the speed of the compressor to try to get the actual LWT to match the required LWT. I suspect the compressor will be pulled back to minimum speed and will eventually stop.

Of course the indoor temperature does not immediately fall from 20C to 17C, in fact I doubt that PV will get down to 17C during the setback period. The indoor temperature will gradually fall at a rate dependent upon the thermal mass of the building, and the temperature difference between indoor and outside.

Say that the indoor temperature falls to 18C by the end of the setback period. If the SP is now changed from 17C to 20C, the control system will now be measuring an error of 2C, but in the opposite direction, which means instead of reducing the required LWT, it now needs to be increased. A large error equates to a large change in output, so it is quite possible that the compressor will be ramped up to full speed.

Once more the indoor temperature will not immediately change from 18C to 20C, but will gradually start to increase at a rate dependent upon the difference between the heat energy output of the heat pump, and the heat loss of the property. The heat energy output must exceed the heat loss for the indoor temperature to be increased.

As the indoor temperature starts to increase, the error between SP and PV will start to reduce, until it reaches a point where the compressor starts to pull back from full speed. The required LWT will gradual be reduced, which in turn will lower the heat energy output of the heat pump, to the point at which the heat energy output matches the heat loss, with PV equal to SP.

In the real world control systems will often experience an overshoot, where PV increases above SP, and then gradually pulls back. This is perfectly normal.

To minimise energy consumption during reheat after a setback period I would suggest the following, though what works best may vary under different operating conditions.

1) Limit the maximum LWT setting, to prevent the compressor from running at full speed. This will probably reduce the rate at which the indoor temperature can be increased, so it may be necessary to restart the heat pump earlier.

2) Make smaller SP changes in a controlled manner, so instead of going directly from 17C to 20C, go from 17C to 17.5C to 18C and so on and so forth over a period of time.

3) Try varying the time interval setting within the controller to match the time delays inherent in your home, though these time delays will vary with changing weather conditions.

 

I’m asking this question because it seems you describe a very complete system which may not need to refer to Weather Compensation…..

second part of your reply

 

Posted by: @derek-m

The controller can only do so in a reasonable timescale by ramping up the LWT to a high value and increasing the heat energy output. AA mode is just following normal control philosophy in this situation.

Unfortunately heat pump controllers don't appear to possess a 'ramp' function, which would allow the desired temperature setpoint to be raised gradually, in a controlled manner, over a lengthy period of time.

Yes this was a question raised back in February on the KEYSTONE COP thread. So it would be good to know if you think this is a viable way to suppress the aggressive temperature rise of AA. The attached post was my first reference to a graduated “Soft Start” to early morning ramp up after a setback.

My earlier post on creating a slow ramp was on Keystone COP on 2nd February 2023. We are still using it to reduce the aggressive start of AA after a night time setback. 

Also I’ve noticed reference in this thread to a ‘Boost’ in the morning whereas we have been doing a rise in 1 degree increments from 5am in an attempt to emulate what that Homely app does- a gentler take-off like a high aspect glider.

And in your example I t’s becoming clear that the setback probably needs to tie in with the speed at which heat migrates away from the building to avoid a long recovery.

To be honest our bedroom is too hot with a downstairs thermostat setback of 17c. So with a well insulated house nestling at 16 degrees in the early morning perhaps using something similar to auto adapt won’t surge on the power if it’s only got to raise the temperature by 1c to get to 17 degrees, then 18. Etc.  

the difficulty might be setting a schedule with that many incremental changes?

It’s interesting to read others on this thread have been trying this.

 


   
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(@sunandair)
Prominent Member Member
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Hi Derek,

here was the original correspondence you had with the Mitsubishi engineer back on 22 December 2022.

what I can’t see from his reply is any reference to Weather Compensation and it’s influence on AA. However you do mention WC in your letter to him. 

Posted by: @derek-m

Original message:-

Thank you for the reply.

Yes, several of the forum members did use the wireless controller, but found that when they initiated Auto Adaptation, the response from the controller was much too aggressive. Instead of gradually changing the temperature of the water produced by the heat pump from say 35C to 36C, it would bump the temperature up to approaching 50C, which is far from efficient. This would cause too high a temperature so the controller would then lower the water temperature to below 35C.

This caused the heat pump operation to cycle in an inefficient manner. This is not how I would expect Auto Adaptation to operate.

The description of Auto Adaptation in the manuals is rather vague, could you please clarify how it is designed to operate. When operating in Auto Adaptation mode, should the controller 'adapt' the system response, over time, to match the heat loss characteristics of the home in question?

My understanding of how Auto Adaptation should operate is that, the water temperature produced by the heat pump should follow the weather compensation curve, but if the indoor air temperature is below the desired temperature, the Auto Adaptation would add slightly to the weather compensation to gradual increase the water temperature, and hence increase the indoor air temperature. The reverse should occur if the indoor air temperature is too high.

Could you please clarify if my assessment of the control philosophy is correct?

Reply:-

Good Afternoon Derek,

Yes your description of the Auto adaption mode is quite accurate.

The controller will constantly monitor room temperature and vary the flow temperature depending on the outside ambient temperature and how far away the target temperature is from the actual room temperature.

It also has a self-learning function which will follow similar patterns it adapted to in the past. For example, if 3 days previously the outdoor ambient was 5 degrees and the room stat was set to 22 degrees and the room was at 20 degrees, it will look at the flow temperature it used that day to get the room up to 22 degrees and adapt the flow temperature accordingly. If the room temperature does not increase over a 1 hour period it will increase flow temperature by 1 degree every hour until it reaches room target temperature.

I hope this helps

Apologies: my previous post timed out so I couldn’t add this letter to it. Hope it’s complete enough to make sense….!


   
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(@sunandair)
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@kev-m Thanks Kev for all that information I’ll have to see if my son will be as obliging as your son has been😂😂😂

But seriously, your information will be really useful for us to look at this in the coming weeks. Thanks


   
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(@derek-m)
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@sunandair

This is the way that I interpret the reply from the Mitsubishi Engineer.

The controller measures both the outside temperature and the indoor temperature, which it compares against the desired indoor temperature setting.

The fact that he mentions the outside temperature indicates that the controller will be using WC. If your controller is operating in WC mode only, even when correctly adjusted to the heat loss characteristics of your home, it will not keep the indoor temperature constant at the desired value. This is because the controller is only measuring, and responding to, the outside temperature, and does not know what is happening to the indoor temperature.

When operating in AA mode, your controller is measuring the indoor temperature and comparing it against the desired setting, but is also using the WC functionality to do the initial heavy lifting so to speak. So WC sets the LWT at a value dependent upon the outside temperature, if there is solar gain which causes the indoor temperature to start to increase, the controller will see that the indoor temperature is rising above the desired setting, and will use the AA functionality to lower the LWT slightly, to bring the indoor temperature down to the desired setting. So in AA mode, the required LWT is calculated using the WC value +/- the AA value. For reasonably accurate indoor temperature control, it is therefore necessary for the WC settings to match the heat loss characteristics of your home, and the AA responds to limit temperature swings away from the desired setting.

To try to answer your query about overnight setback, let's try to assess what may be happening within your system.

I don't know the settings within the control algorithms used inside the controller, but let's assume that a 0.1C increase or decrease in indoor temperature causes a 1C change in required LWT. So if an overnight setback takes the desired temperature setting from 21C to 18C, the controller will now measure a 3C difference between desired and actual temperature, and will reduce the required LWT by 30C. If WC has calculated a LWT of 35C, then the combined LWT will now be 5C, which I believe will cause the compressor to slow down and stop.

If the WC curve settings require a 1C change in outside temperature to cause a 1C change in required LWT, and the outside temperature falls by 5C overnight, then the WC calculated LWT will now be 40C, which together with the AA calculated adjustment would produce a combined required LWT of 10C. As the indoor temperature reduces, so will the AA calculated adjustment, so if the indoor temperature falls to 19.5C, the combined required LWT will now be 40C - 15C = 25C. The compressor will still probably be stopped.

At the end of the overnight setback, the desired temperature is increased from 18C to 21C, and now exceeds the actual indoor temperature by 1.5C. The combined required LWT will now be 40C + 15C = 55C, which will cause the compressor to be ramped up to full speed. As the indoor temperature and the outside temperature start to increase, the combined required LWT will start to reduce, and the compressor speed will be lowered.

To try to prevent the compressor from operating at high speed, the desired indoor temperature could be raised gradually, say at a rate of 0.5C per hour. Unfortunately this poses a further problem, in that if the setback temperature is 18C, then the first temperature increase would be to 18.5C, which is still below the actual indoor temperature, so the compressor may not actually start. Even when the compressor starts, it could take up to 6 hours for the indoor temperature to reach 21C.

You could try reducing the setback to 19C, 19.5C or even 20C, which may cause the heat pump to restart earlier than desired on colder nights, but would allow gradually ramping the temperature back up to be more effective.

At the end of the day it will probably be a matter of trying different options until you find the ones that work best for you, though what works well under certain weather conditions, may not perform too well the following day.


   
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(@sunandair)
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Posted by: @walkers-heatpump

Have smaller temperature changes from setbacks (?) I've just changed mine to half degree changes now every hour from 3:30am

Hi @walkers-heatpump, interested in the way you have set up your temperature changes especially after a setback. How are you applying your half-degree adjustment to your target temperature I noticed the Ecodan own adjustment has limited schedule numbers of changes. So you may have found a way of building a scheduled increase in room set temperature. 

do you have a separate third party schedule?


   
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(@walkers-heatpump)
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@sunandair No we just use the Mitsy controls. Have a setback to 17.5° at 6pm, then to 18° at 3:30am, 18.5° at 4:30am and 19° at 5:30am. Not certain I've seen it much different yet to the simpler schedule but it may learn and settle

Its interesting what the Mits engineer said, from my experience so far the flow temps do drop but they dont get to where my curve is set. I wonder if they do consider the curve or whether it just effectively makes its own curve - ramps up at first to get temps moving as per Derek and the once temps are up it makes a calculation considering temps outside and adjusts accordingly 


   
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