What you want to do is to edit the curve to set a new baseline. For example if it's currently set at 40C at -3C ambient and 24C at 15C ambient and +4 works for you then moving to 44 at -3 and 28 at 15 and setting the -4 to 0 will have the same effect. You can then offset the new baseline to make it even warmer if you need to. That's moving the whole curve up; you can actually move one or both ends up, down, left or right if you want. There are three little graph icons to do all of this, the upper and lower flow temps as I've described and also one where you can slide the curve L to R. You might have to experiment a bit ...
It's quite hards to visualise what's happening though and if you're handy with excel you can plot/compare the curves and work out the flow temp at each ambient temp.
This youtube has the basics of how to get to the editing
This post was modified 3 years ago 2 times by Kev M
Thanks Kev. I’ll have a play with adjusting the curve as you describe. As for excel……….. forget that. It’s all Greek to me and is way beyond my comprehension.
Retrofitted 11.2kw Mitsubishi Ecodan to new radiators commissioned November 2021.
14 x 500w Monocrystalline solar panels.
To recap, I switched from 2 x zone thermostats with weather compensation to weather compensation only. This means that I have set the thermostats to 30C and let the flow temperature control the house temperature. I made this switch on 8/11/21.
In terms of comfort, it's good. The house is a contant temperature. It's been a little difficult to get that right and have overshot a couple of times, making it too warm. In terms of usage/cost it's been OK. There were some cold days and usage wasn't horrendous. In terms of efficiency, I don't know for sure because my system isn't working out COP propertly at the moment. However, I think my COP is better because flow temperatures are lower and the science says it should be.
This is my usage for heating only over the month. Total is 668kWh. Average 22.3. High 44.4. Low 10.4. The house was 21-22C throughout.
This shows how usage varies with average ambient temperature.
If I add HW, my total ASHP usage in November 2021 was 719kWh. In November 2020 I was using storage heaters and an immersion heater and these used 1913 kWh E7 units. I was also using a couple of electric towel rails and had the log and coal burners going most nights. The towel rails have gone and I've lit the log burner 3 times this November. The cost of the electricity this year isn't much less than last (my E7 rate was 7.6p/kWh 😯) but it's a big reduction in C02 emissions for us, which is nice. For information, my peak E7 usage was Jan 2021 at 2748 kWh. I'm glad I'm not paying for that now.
Overall I'm reasonably pleased. I still have some fine tuning to do and I want to get the COP calculations/MMSP working (I must get onto the supplier. Again). I'm experimenting with turning the heating off at night; the jury is still out on that. There are also some changes to the settings @derek-m has suggested I want to look into.
In the slightly longer term I want to try the Ecodan auto adaptation function but that will need wiring changes and/or additional hardware.
Verdict? So far, so good.
This post was modified 3 years ago 2 times by Kev M
Once more you have provided excellent data, that shows what can be achieved when your system is better optimised. For you, switching from storage heaters to an ASHP was indeed a total 'no brainer', not only have you greatly reduced your carbon footprint, but I shudder to think how much it would have costs to run the storage heaters this coming Winter.
Whilst weather compensation seems quite good at keeping the indoor temperature reasonably constant, for more accurate control the use of auto adaptation will be necessary. I estimate that the energy savings that it may be possible make, with better controlled and slightly reduce indoor air temperature, would pay for the cost of even the wireless version to be added.
I have been doing some calculations, and I suspect that switching your ASHP off overnight for a number of hours, may in fact use more energy and turn out to be more expensive. Being the Engineer, I don't wish to dissuade you from carrying out the test, since I would be interested in seeing whether my theory and calculations are indeed correct.
The offer to help try to resolve your problems with the MMSP system still stands.
If you are interested in carbon intensity and how it varies by region over a day this app is quite interesting. Quite huge differences by region at the moment from zero in north Scotland to 323 in east Midlands. Some of the domestic energy providers have something similar on an app or their website. Ovo have their Greenlight tool.
thanks for all your help. I think I know where you're coming from regarding switching off as I've read a couple of case studies that supports what you're saying. In any case, I'm not sure I like waking up to a cold house having got used to the opposite.
To recap, I switched from 2 x zone thermostats with weather compensation to weather compensation only. This means that I have set the thermostats to 30C and let the flow temperature control the house temperature. I made this switch on 8/11/21.
In terms of comfort, it's good. The house is a contant temperature. It's been a little difficult to get that right and have overshot a couple of times, making it too warm. In terms of usage/cost it's been OK. There were some cold days and usage wasn't horrendous. In terms of efficiency, I don't know for sure because my system isn't working out COP propertly at the moment. However, I think my COP is better because flow temperatures are lower and the science says it should be.
This is my usage for heating only over the month. Total is 668kWh. Average 22.3. High 44.4. Low 10.4. The house was 21-22C throughout.
This shows how usage varies with average ambient temperature.
If I add HW, my total ASHP usage in November 2021 was 719kWh. In November 2020 I was using storage heaters and an immersion heater and these used 1913 kWh E7 units. I was also using a couple of electric towel rails and had the log and coal burners going most nights. The towel rails have gone and I've lit the log burner 3 times this November. The cost of the electricity this year isn't much less than last (my E7 rate was 7.6p/kWh 😯) but it's a big reduction in C02 emissions for us, which is nice. For information, my peak E7 usage was Jan 2021 at 2748 kWh. I'm glad I'm not paying for that now.
Overall I'm reasonably pleased. I still have some fine tuning to do and I want to get the COP calculations/MMSP working (I must get onto the supplier. Again). I'm experimenting with turning the heating off at night; the jury is still out on that. There are also some changes to the settings @derek-m has suggested I want to look into.
In the slightly longer term I want to try the Ecodan auto adaptation function but that will need wiring changes and/or additional hardware.
Verdict? So far, so good.
I have similar although slightly reduced usage (593kWh) and I've been running 21º - 22º room temp 24/7. So you can assume to be running a similar COP.
This chart for 29/11 shows the difference in COP in relation to ambient temp. from 0º in the morning to 10º in the evening.
This is last night, switched off (no thermostats, just off). The ups and downs before midnight are a bit of cycling and hot water. From what I can see, it probably saves money. The heating is off for 6 hours. 20 on the vertical axis is 1.2kW so 7.2kWh saved. The peak at 6am is about 1kWh to get the flow temp up so say 6kWh. After that, I don't think consumption was much more than it would have been. So in exchange for 5-6kWh saved we had a colder night (that we slept through) and a cooler morning, that we definitely noticed; the house took 3 hours or so to warm up again (it was down 2-3C). I could have upped the flow temp to warm it up quicker but that would definitely have used more energy.
Is it worth it? I don't know. It would add up, especially if it were colder. But maybe I'd rather be warmer and slightly poorer.
This post was modified 3 years ago 2 times by Kev M
Thanks Mark, excellent data, which clearly shows the direct correlation between ambient air temperature, energy consumption and efficiency.
For those of you who are not using weather compensation, this is what can be achieved, without having to manually keep changing the water flow temperature.
This is last night, switched off (no thermostats, just off). The ups and downs before midnight are a bit of cycling and hot water. From what I can see, it probably saves money. The heating is off for 6 hours. 20 on the vertical axis is 1.2kW so 7.2kWh saved. The peak at 6am is about 1kWh to get the flow temp up so say 6kWh. After that, I don't think consumption was much more than it would have been. So in exchange for 5-6kWh saved we had a colder night (that we slept through) and a cooler morning, that we definitely noticed; the house took 3 hours or so to warm up again (it was down 2-3C). I could have upped the flow temp to warm it up quicker but that would definitely have used more energy.
Is it worth it? I don't know. It would add up, especially if it were colder. But maybe I'd rather be warmer and slightly poorer.
I did wonder if leaving it to 6am to turn the pump back on was optimistic. Even with the high temperature heat pumps in the current trials I have seen them turn their pumps on earlier. Their might be a sweet spot that works in your setup and lifestyle requirements to save a few KW, somewhat depends on if it is worth it as you say.
It may better to turn the pump on an hour earlier and see what that feels like and does for the consumption.
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