Well if its a 12kW model and if Im reading your graph correctly its only using 2kW intermittently, I would guess that its struggling to generate a low enough power output. I had a similar issue with my 5kW model and discovered that raising the flow temperature to 38C at 17C outside on the weather compensation setting got rid of the cycling. It seems counter-intuitive but a higher flow temperature gives a bigger temperature difference between the emitters and the internal room temperature and so the heat pump can push more energy into the house. Try it, it might work and you have lost nothing if it doesnt 🙂

@bontwoody thank you I’ll give it a go. Just trying to find that balance between heating and economy. 
today it seems to be spiking at 2.3-3.5kw so being a little hungry so need to nip in bud 😊

@lfranklin You may find that as the weather gets colder, it will stop on its own because the demand is higher, but it does look like it is cycling a lot which might not be good for the compressor long term.

Posted by: @bontwoody

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Well if its a 12kW model and if Im reading your graph correctly its only using 2kW intermittently, I would guess that its struggling to generate a low enough power output. I had a similar issue with my 5kW model and discovered that raising the flow temperature to 38C at 17C outside on the weather compensation setting got rid of the cycling. It seems counter-intuitive but a higher flow temperature gives a bigger temperature difference between the emitters and the internal room temperature and so the heat pump can push more energy into the house. Try it, it might work and you have lost nothing if it doesnt 🙂

What happened to the IAT when you raised the WC curve?

@derek-m it went up marginally Derek, but to be honest I was happier with it slightly hotter. My appendages seem to get cold at anything under 22C 🙂

@derek-m my apologies for probably silly question but what does IAT stand for please?

Internal Air Temperature. We really shouldnt use these acronyms but we do 🙂

BTW, please let us know what happens after you try the changes out 🙂

Posted by: @bontwoody

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@derek-m it went up marginally Derek, but to be honest I was happier with it slightly hotter. My appendages seem to get cold at anything under 22C 🙂

Yes, many of us prefer the IAT slightly warmer. One of the pleasures of growing older. 🙄 

Of course increasing the IAT, increases the heat loss, which in turn increases the demand on the heat pump, and could possibly increase the electrical energy consumption.

This is one of the areas I have been investigating to see what may be the most efficient and cost effective method of operation.

When you raised the WC curve, did your heat pump run continuously, or did it run for a longer period and then stop for a longer period? Did the electrical energy consumption increase or decrease?

Whilst all heat pumps are likely to cycle at some point during milder weather conditions, I suppose it is a matter of finding the settings which work best for your particular circumstances.

Is it just a matter of finding the OAT at which your heat pump pulls back to the minimum LWT, and runs continuously, without cycling. Then set these parameters at the mild weather end of the WC curve. It is still important to get the slope of the WC curve correct for colder weather operation.

An alternative method I have suggested in the past, is to raise whole WC curve using the offset by 1C or 2C, and then use a room thermostat to start and stop the heat pump at a temperature 1C higher than desired. The heat pump is therefore likely to run longer at slightly higher loading to raise the IAT, then stop for a lengthy period of time while the IAT falls back to the thermostat setting.

Posted by: @lfranklin

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@derek-m my apologies for probably silly question but what does IAT stand for please?

Sorry I should have made it clear. Most forum members now use the abbreviation IAT to denote Indoor Air Temperature. Bet you can't guess what OAT means. 😎 

@derek-m yes, I managed to get it to run continuously. You can see the difference if you look at my graphs for the last couple of weeks here:

EMONCMS.ORG "https://emoncms.org/app/view?name=RoseCottageHeatpump&readkey=1a60decebfd925c412d19c85fb1adacc"

Emoncms - user login

I also raised the temperature of the high end of my WC from 15C to 17C which should have had the effect of raising my flow temperature slightly again say at 12C OT.

It all seems to work nicely at the moment, so roll on the cold weather and Ill see how the low end of the WC works 🙂