Air Source Heat Pumps (ASHP) - How have your energy usage and costs changed since getting one installed?

My understanding when i looked into them some time ago, of course i may be mistaken....

The charge and discharge temperatures are different. The devices aren't flowing out water at 65%, it flows out around 40 degrees i seem to remember. Although there are quite a few different models so it may well depend on the setup

There was some info in the manuals on temperatures but i admit i only skim read. 

I checked with Sunamp, as the first battery is unusual in having such a low temperature. They confirmed the output temperatures.

Had a scary £7.50 electricity day on Sunday (according to my smart meter - still transitioning to a new supplier so I don't have online access yet). However, that seems to be down to the pump running unnecessarily long when the temperature is at its coldest.

I have my thermostat set to 20.5° from 6am to 10:30pm and 18° overnight. What I have been finding is that the heating comes on at 19° and keeps going until it gets to 22° (so a tolerance of 1.5° each side.

With some of the cold outside temps we’ve had recently, it seemed like the pump was struggling to get up to the desired radiator leaving water temperature (LWT) of 50°. I would check around 9am and the LWT would still only be 41° after 3 hours of operation. It would then limp along until midday with the rads warm at best. When added to a second round of heating later in the day, and reheating the hot water after a bath, the result was the £7.50 day 

What I did on Mon and Tue instead (still cold outside), was stop the heating around 8am when it had got up to 20-20.5°. This meant that the second round of heating happened earlier in the day - mid afternoon - and with higher daytime temps it raised the house up to 22° pretty quickly. This has resulted in 2 consecutive days with pretty similar use both at less than £5 rather than £7.50.

I’m wondering if the system scales back the LWT after the target temp has been reached, and then operates at lower temps to do the tolerance above the target (i.e. between 20.5° and 22° in my case)? If so, doing that seems to have caused my system to run for an unnecessarily long time and increased rather than decreased costs.

I’m noting those comments @mrmojorisin04 

If that strategy reduces the overall electricity consumption for you, then it’s something we need to be fed back to Kaluza.

If they built in support for that within the Flex Platform and Time Of Use tariff, it would be very attractive to the growing number of consumers with Heat pumps.

The part that needs careful thought is how Flex might be able to ‘stop the heating around 8am’ without manual intervention. There needs to be remote-operated switch installed somewhere.

Flex incorporates weather-input and AI machine-learning algorithms. So it has the potential to do the calculations as to when it’s optimal to turn off and then restart your system.

Hi @Transparent 

That would certainly be attractive. In the meantime, as a workaround I’m thinking I could extend my daily schedule to three temp changes rather than two. So I might set it to 20° between 6am and 8am, then 20.5° between 8am and 10;30pm and then down to 18° overnight.

If I change the thermostat manually when it’s running then that normally stops the pump, so hopefully a schedule change will do the same. For example, if it’s running and the temp is currently 20.5.°, it doesn't matter if I move it up to 21° or down to 20° in both cases, it stops running (presumably until the temp fall to >1.5° below target).

Let us know if that temp-change idea at 8am does the trick.

If not, then I have a number of other ideas how to go about it. It’s obviously important to ensure that the mechanism

• can operate under control from Flex
• doesn’t lock out the heating system if Flex fails one day(!)
• can be retro-fitted to existing installations
• automatically ties into whatever Time Of Use tariff you may have
• will continue to function whether or not your supplier is OVO

Are you aware that we have a video-chat with Robin Abraham of Kaluza next Tuesday (7th)? Have a look at the Invitation and the questions/points already suggested.

Really good to see all this learning. 

Could you explain what a leaving water temperature of 50 degrees means and why it is important in your setup?

Do you know if your heat pump is setup with any sort of weather compensation, ie lower flow temperature at higher outside temperature and higher flow temperature at lower outside temperature? Or is the heat pump setup for a fixed flow temperature for the heating irrespective of outside temperature? 

@mrmojorisin04 my LWT is 42 deg as set by the installers. I have a night temp set at 19 and day at 21. 50 deg seems quite high. Could you put your house and heat pump details in your sign-off tag line please, so we can see how things compare… Thanks !

Sure, signature updated 

50° LWT is what the Daikin engineer who did an audit set it to (the installers had it at 55°!). As I’m quite happy with the heat levels in the house, I might try dropping it a degree or two.

42° does seem quite low for radiators though. When mine were not getting above 41° they were warm at best and it took forever to heat the house.

Ah ha! Maybe mine’s too low !!