Nice talking to you yesterday. How is your system performing today?
Morning, after setting up the curve with you and turning all thermostats up to 30ºC I saw the internal temp beginning to rise so I notched it down to -4.
Since then the heating has been a constant 22ºC.
Only a snapshot I know but compared to a pretty constant COP of 2.7 with the settings the installers left me with, this is looking remarkable.
Nice talking to you yesterday. How is your system performing today?
Morning, after setting up the curve with you and turning all thermostats up to 30ºC I saw the internal temp beginning to rise so I notched it down to -4.
Since then the heating has been a constant 22ºC.
Only a snapshot I know but compared to a pretty constant COP of 2.7 with the settings the installers left me with, this is looking remarkable.
That is excellent news Mark, thank you for having faith.
I would suggest that you set your thermostats to 25C rather than 30C.
The fact that you had to offset the control to -4 would indicate that the weather compensation still requires further optimisation. If you would care to monitor your system for a little while, and collect as much data as possible, it should then be possible to calculate more appropriate settings for the curve.
(For information, the monitoring software stores by the minute data and the energy used is measured in Wh. So where the yellow line is at 40 on the graph, the ASHP is consuming energy at a rate of 40Wh per minute, which would be 2.4kWh per hour. Or you could just say it's drawing 2.4kW of power during that minute.)
These are for 08/11/21. It was 4C all night and flow temp is mid-high 30s. I made the changes to ditch the thermostats and use weather compensation at 6pm on the the day before. The ASHP is running fairly constantly all night, warming the house up to about 23.5C. The small peak about 7am is the hot water, the bigger one after is the heating kicking back in. The outside temp starts rising and the flow temp drops. The ASHP starts cycling about 3 times an hour. Until 6pm, the curve I was using was heating the house to 23.5C. I moved it down 2 at 6pm and you can see the flow temp drop slightly and the cycling period increase. The house is now about 21.5, which feels fine.
How do the numbers stack up? The energy used is more than on my example of Nov 5, where it was 30.6 on what was actually colder day. Am I disappointed? Not really, because the house was heating up for a lot of Nov 8 (which will use more energy) and it ended up far too hot at 23.5C. On Nov 5, the house was 17-18C at night and during the day and max 21C in the morning and evening.
What's encouraging is that at about 11C outside, between 6pm and midnight yesterday the ASHP kept my whole house at over 21C using an average power of about 520W. I know it's not cold at the moment but that's quite impressive. I'm a bit concerned about the cycling but I'm told 3 times an hour is OK. I wouldn't have noticed it without the monitoring and my fridge and freezer do it too now I think about it.
More data and numbers as they come in. I also need to get the monitoring recording COP (I'm onto it)
@kev-m Excellent data Kev, many thanks. It is very similar to the data I am getting from my control system, where the controller keeps switching the central heating pump and boiler on for a short period of time to top up the radiators. Varying the frequency dependent upon the heat demand.
It would be interesting to know what your central heating pump is doing, does it switch on and off with your ASHP, or does it run continuously or otherwise?
Hi Kev, Justin, Mark and anyone else who may be interested,
I have thinking of ways in which it may be possible to speed up the weather compensation optimisation process.
In my neck of the woods, the ambient air temperature reached a blistering 16C today, and overnight it is predicted to fall to 9C.
Taking the alleged 7C change it temperature, your weather compensation should request an appropriate change in the water flow temperature from your ASHP, dependent upon your compensation curve settings. This should be reasonably easy to check.
The change in water flow temperature should correspond fairly closely with the change in ambient air temperature, but any change in indoor air temperature may lag by several hours.
If there is no appreciable change in the indoor air temperature overnight, then the slope of the weather compensation may be close to that required.
If the indoor air temperature falls by 1C overnight, then the slope of the weather compensation curve needs to be increased. If the indoor air temperature is reducing by 1C for a 7C change in ambient air temperature, then the slope needs to be increased by approximately 0.14C per degree change in ambient temperature.
If your weather compensation is set to 55C WFT @ -5C Amb., then it would need to be increased to 59C WFT @ -5C Amb.
If your weather compensation is set to 50C WFT @ 0C Amb., then it would need to be increased to 53C WFT @ 0C Amb.
Obviously, if the indoor air temperature is increasing overnight, then the reverse should be carried out.
thanks, I'll keep an eye on the room temps. If moving the curve isn't right I'll try tweaking the slope as you suggest.
One of the changes I've go my eye on is letting the Ecodan controller control the system via room temp. That's the way the manual recommends for best efficiency. This old brochure I found explains it but I assume it's similar now
I can either buy a Mitsibishi wireless remote, a thermistor or move the main control panel (not going to do this).
I think this will do the same as you're suggesting above, i.e. as well as normal weather compensation, it will constantly adjust the curve according to desired and actual room temps.
thanks, I'll keep an eye on the room temps. If moving the curve isn't right I'll try tweaking the slope as you suggest.
One of the changes I've go my eye on is letting the Ecodan controller control the system via room temp. That's the way the manual recommends for best efficiency. This old brochure I found explains it but I assume it's similar now
I can either buy a Mitsibishi wireless remote, a thermistor or move the main control panel (not going to do this).
I think this will do the same as you're suggesting above, i.e. as well as normal weather compensation, it will constantly adjust the curve according to desired and actual room temps.
Yes Kev, that is my understanding of 'Room' control, but since everyone 'insisted' on having their controllers in the airing cupboard, I have not suggested it yet.
Joking apart, personally I would go for the wireless remote controller, which although probably more expensive would be easier to install and more versatile. I do enjoy spending other people's money.
I did suggest to Justin that he give weather compensation a try before going down the route of a wireless remote controller. Maybe you could see if you can find someone who already has the full system to get their views on how it performs.
@kev-m The controller has just 2 wires, you can and I have many times used the thermostat wires to connect the controller allowing you to move it. It is polaritary sensitive but data 5V DC so will not shock you. They say you cannot do it and need shieded cable, I have never had a problem. It is the best way to control the system if on radiators, it does not work very well if you have under floor, weather comp wors best. Just swtch the heat pump off and move it.
Yup, I'm happy to let someone else try it out. I agree about the wireless remote. The thermistor is cheap (£20) but has to be hard wired into the main control box (in the attic) and mounted on a wall somewhere. That involves wires and holes in the ceiling, which I'd rather avoid. As you say the wireless one is more flexible.
Your question about the pumps - do they run when the compressor isn't? I don't know, I'll have a look.
Brendan, do you mean move the main Ecodan control panel? I'd actually only have to move it a couple of feet from the airing cupboard into the hall and the existing cable is long enough.
As Brendon suggest, if it is your thermostat that is in the hallway, you may be able to use the present cable. Twisted pair screened cables are recommended to help avoid electrical interference and crosstalk between adjacent cabling, but it may work okay.
Brendon would be better able to advise you should you decide to go down this route.
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