I've had my LG Therma V running for a week now. We have underfloor heating throughout. DHW is set to 50 degrees and water flow temp is set to 40 degrees.
We've used between 35 and 65 kWh per day for heating and hot water (unfortunately I don't think I can get data that splits it out).
Each room has a thermostat in. I've noticed that a couple of rooms are calling for heat all the time (the bigger rooms and the ones with largest heat loss), but most rooms call for heat occasionally when it drops by a degree and then it warms up in a few hours and goes back off again.
From the therma data log, it appears that the outside unit is switching on and off every 12 minutes or so, which doesn't seem right!?
After reading this thread (or trying to keep up with it!) am I right in thinking that it would be cheaper to run / more efficient to:
* Change from 40 degree flow temp to weather compensation curve
* Set all room thermostats to 30 degrees so they are effectively always calling for heat all the time
If so, can anyone help me to configure the weather compensation curve please?
I've looked at the manual and have found these pages:
I just had this from my ASHP installer when I asked them about weather compensation mode - I have a LG Therma V, with UFH downstairs and radiators upstairs. Would welcome feedback on their reply from this audience.
"Hi Dan,
All good here thanks. Glad to hear you’re both on the mend, it’s a tough gig being ill with a little one isn’t it!
When we have rads and UFH working together we tend to find using the weather compensation curve is not particularly effective. It can mean that there’s low temperature water in a convective radiator panel which doesn’t provide sufficient output. Our customers with similar set ups are far happier to hit a set flow temp of 50/55 which ensures the panels convect warm air into the rooms.
You can experiment with using the weather compensation mode to see if it suits, but we would recommend just to keep the set flow temperature. Ultimately the thermostat will turn off once it’s hit the set temp so the heat pump will be operating for a shorter period of time at a slightly higher flow temperature and you’ll find little difference in the ultimate efficiency. You could try adjusting the set back temperature by a few degrees which would mean the temperature in the house is maintained.
Hope that makes sense and do come back to me if there are any further issues re. upstairs heating."
It is fairly straightforward making the adjustments, but first you need to decide what settings to use. It would appear that the default settings are a water flow temperature (LW1) of 35C at an ambient air temperature (Out1) of -10C, and a water flow temperature (LW2) of 28C at an ambient air temperature (Out2) of 16C.
35C at -10C seems rather low and 28C at 16C seems rather high. Possibly more appropriate initial settings would be 50C (LW1) at -10C (Out1) and 20C (LW2) at 16C (Out2). That way you should only need to change the values of LW1 and LW2. With these settings the predicted water flow temperature at 0C, would be approximately 38.5C.
If you have data showing the previous water flow temperatures, at various ambient air temperatures, you would be able to check if those values fall on the proposed curve.
If you find that the indoor temperature is not correct, then you will need to change the value of either LW1 and/or LW2 to change the slope of the weather compensation curve.
I've heard talk of a special tariff for ASHPs. If they removed the green levy, that would be a good start. But then that might be considered double-dipping for those already getting RHI.
I think a special tariff for ASHPs that kicked in for the winter months would be a good option if they intend to keep gas prices much lower than electricity. It could encourage more to make the switch.
It seems to fluctuate on the pressure gauge across the day between 0.7 bar and say 2 bar. Depends on what the ASHP is doing but often after heating water or first thing in the morning the pressure is low, but then throughout the day it increases to say 1.5-2bar
I had air in the system before and vents were closed after I had a leaking pipe.
However, that was fixed, air was purged, but have been told it can take a long time for air to release from the system and to keep topping up the pressure?
@hr_3 Mine does fluctuate too. Perhaps not by as much as yours though. That said, when it is operating, it seems to be at target pressure. Its only when it's not operating that it drops.
Here is our data from 2021. Surprisingly we managed to save a little compared to 2020 given that the last two months our electricity tariff is nearly double what is was for the rest of the year. Next years spreadsheet will make for brutal reading. The ASHP does impress me in regards to how efficiently it heats a large house like ours but it doesn't handle our hot water consumption well at all. We have a 500l tank which takes quite a bit of energy to heat up and with 6-10 showers being run a day and the occasional bath there is very little we can do. With hindsight it might have been worth keeping our old oil boiler with a small tank just to heat the water as I'm sure it would be much cheaper although I don't think the RHI would have allowed this.
Here is our data from 2021. Surprisingly we managed to save a little compared to 2020 given that the last two months our electricity tariff is nearly double what is was for the rest of the year. Next years spreadsheet will make for brutal reading. The ASHP does impress me in regards to how efficiently it heats a large house like ours but it doesn't handle our hot water consumption well at all. We have a 500l tank which takes quite a bit of energy to heat up and with 6-10 showers being run a day and the occasional bath there is very little we can do. With hindsight it might have been worth keeping our old oil boiler with a small tank just to heat the water as I'm sure it would be much cheaper although I don't think the RHI would have allowed this.
Yes, 20p/kWh is going to hurt. Not sure what you could do about the HW; that's a lot of showers.
@george do you have a mixer shower? If so, maybe consider installing a valve so you can close off the cold 100% and turning down the water temperature to exactly what people like. You would still need some kind of bacteria cycle, but you wouldn't need such a high tank temperature. And you could schedule the hot water cycle for overnight or the middle of the day giving lots of time for the tank to cool through day use.
Most mixers add cold as a matter of course, no matter how high they are turned up
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
