@kev-m That may be Ok, Do you have the return temperature?
Sort of. Melcloud seems to be a bit s^!t at getting data out. This is one of the traces you can get. The red line (unhelpfully) is, I think, return and the blue flow. It's smoothed somehow so might not be a lot of help. Return seems 3-4C less than flow.
Below is the same period for the more detailed graph. The close up a couple of posts up is from about 1/3 of the way along where you see the plateau. The two peaks near the end are HW. The cycles are average every 40 minutes or so.
I wonder if the sensitivity can be changed so it comes on and off less. Don't know if that would be a good thing.
I think I might have better data when my MMSP is sorted out. I know what's wrong now and have told the supplier.
Update, ticking along at about 11-12 kWh per 24 hours. House is still consistently 21.5-22C so I've turned the compensation curve down another 1. Let's see if the thermometers (or Mrs M) notice.
Interesting graph from today. The usual cycling when it was 12C. You can see ambient going down and flow going up; weather compensation in action. It then seems to settle down running steadily when outside temp 6-7C. I assume that's as low as it (the ASHP) can go. The wiggly trace at the end represents about 1.2kW of power if my calcs are correct.
Interestingly, the house is a little warmer now that when it was warmer outside.; temp has crept up to 22.5C. That suggests my compensation curve isn't quite the right shape. It'll do for now though, more observations needed before I change anything.
Interesting graph from today. The usual cycling when it was 12C. You can see ambient going down and flow going up; weather compensation in action. It then seems to settle down running steadily when outside temp 6-7C. I assume that's as low as it (the ASHP) can go. The wiggly trace at the end represents about 1.2kW of power if my calcs are correct.
Interestingly, the house is a little warmer now that when it was warmer outside.; temp has crept up to 22.5C. That suggests my compensation curve isn't quite the right shape. It'll do for now though, more observations needed before I change anything.
Thanks Kev, excellent data once again.
Although I don't have an A2W ASHP, I operate my system in very much the same manner as an ASHP with auto adaptation. I am carrying out some trials at the moment with simulated weather compensation, but last week when the ambient air temperature was fairly constant throughout the whole day, I noticed that the water temperature was reduced by several degrees during the daylight hours. It was only several hours after dark that the water temperature started to increase again. Since the indoor temperature was being controlled at 21C +/- 0.1C, then the change in water temperature would appear to have been due to solar gain, even on a cloudy day.
Your increase in indoor temperature may have been due to not fully optimised weather compensation, along with solar gain effect. If true, this could pose a slight problem to fully optimising the weather compensation. I suppose more data over a larger temperature range will be needed to prove this one way or another.
@derek-m This effect is normal at this time of year if you are running full weather compensation without suffucient thermal mass in your property, (most newer properties on radiators).
This is the weather compensation curve I'm using. Baseline is the blue, I've moved it down -3 on the Ecodan screen. It's doing a reasonable job of keeping the house at 21-22C between 6 and 12C ambient so far.
As a couple of posts above, at 7C ambient the ASHP stops cycling and holds the flow at a very steady 30C. My fag-packet calculations from the MMSP data say that it's then taking about 1.2kW to keep my whole house heated. At 12C it's about 25C flow and averages about 600W. I'll be very interested to see how is does at 0C and below.
I'm still not convinced keeping my house at 22C or so 24/7 is the cheapest way to do it. I don't think we'll go back to letting it cool during the day for comfort reasons, but dialling down at night only is something I want to look at. Yes, the ASHP will have to work a bit harder to raise the temp in the morning but if it's not running at all between say 10pm and 6am that's got to be a factor. Watch this space.
What you could try as a test, is switching your ASHP off for one or two hours and monitoring how quickly the temperatures fall.
If you turn the temperature down a degree or two overnight, I think that your ASHP will still need to operate to maintain the lower temperature, but then will have to work harder to get the temperature back up.
It will be interesting to see what the differences are between the two methods.
This is energy consumed over the first week of the new regime. I've also plotted average outside temperature; that can be a bit misleading because it hides the highs and lows.
Overall I'm happy. I've no data to compare but I'm quite encouraged. Some cold weather needed to test further but so far so good. House has been close to 22C mostly; still a bit warm. Today I'll change my compensation curve so that what is now -3 on the Mitsubishi controller becomes 0
What has surprised me most is how lukewarm radiators still work. Flow has not been more than low 30s and outside temp has been as low as 6C. I never would have believed that was possible.
This post was modified 3 years ago 2 times by Kev M
@kev-m how does that look if you plot temperature on the X axis? Is the power use fairly linear?
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 too found energy consumption was higher on the 15th November, about 15% higher.
Did you get your MMSP system giving more reasonable data?
I'm in the process of developing an Excel spreadsheet, to model system performance based on the Ecodan data that you supplied. When it is completed it may be possible to compare actual system performance against the ideal, which will hopefully highlight any design weaknesses.
Do you have details of the calculated heat loss for your home and at what ambient temperature the assessment was made? Also, do you have details of the heat output rating of your heat emitters at a delta T of 50C?
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