Compensation curve settings when using an Ecodan Air Source Heat Pump with under floor heating

You know heat pumps are becoming popular when your neighbour has the same one as you! 😁

I would have thought that underfloor heating would help with the CoP.

Have you compared flow rates? This may impact on efficiency.

Maybe theirs is cycling on/off more than yours?

James your neighbour should be running their UFH at 30-35° and getting SCOP nearer 4.

Are they trying to run the ASHP like a boiler, E.g. on/off with a thermostat or running 24/7 only using weather comp? The latter is what they should be using, regardless of system emitter type.

On the Daikin system you do set an emitter type, quick for radiators, slow for underfloor heating. This alters the way the heat pump behaves. 
 

As Jason said, I’d also expect the leaving water temperature and weather dependant curve to be much lower than in your system. The max. leaving water temperature on an underfloor system my father-in-law has is 35C at -2C outside, whereas on mine it’s 42C (reduced from the 50C set by the installers). 

Thanks for the replies. they are running it as you would expect, on all the time and on a thermostat. I think they need to get the installer back in!

On all the time good, thermostat bad. 
Thermostat needs to be set high (say to a “just too warm” to be comfortable setting) and experiment with weather curve to give the actual desired temp. Can only really do that experimentation in the winter.

That should reduce cycling which is the enemy of the heat pump. It is worth asking how many cycles per hour are showing on the controller as that gives a good idea on the cause of poor efficiency.

Hi 

we have recently installed a Mitsubishi Ecodan 8.5kw. I have it set to 20c downstairs and 18c upstairs. I have it running 24/7 for heat and hot water. Hot water is set at 45c.

Does this seem Ok? House is 1850sq foot, 4 bed, two story.

I have no clue how the compensation curve and what this should be set at? Any recommendations ?

thanking you in advance.

Maurice

Hey @Maurice Kelly ,

This sounds like a good one for some of our heat pump experts. I’ll see if @hydrosam is around. :)

Hi @Maurice Kelly and yes great question. 

Some of us heard from @jason.lewis earlier this week as he showed us the stats and best practice with their heat pump. We recorded it and hope to share that recording on the forum soon. I’ll add a link here when it’s live. 

In the meantime perhaps Jason or other Ecodan heat pumpers are around to advise: @Mimi @M.isterW @Nicllb @TonyShep @lycandroid @James_N @Hillsides @Urban7 @Scottychops @Brennie66 @Jenp to name a few...

Thank you. 

Great stuff thank you!

I have had my Ecodan for 2 years now. I only have one ‘zone’, the house is set to 20C during the day and sets back to 19C at night. My understanding is that for heatpumps the set back is smaller than for a boiler. I found that if I set it back more it took too long to get the temp back up in the day.

My hotwater is set to 49C and is on eco mode (which I think is more efficient but heats more slowly). I switched of the ‘hysteresis’ setting and have the HW on a timer to heat up twice a day, at night and at midday (as I have solar)

The weather compensation curve is the most important thing. There are youtube vids showing how to program it and switch it on. The point is that the temperature of your CH hot water varies depending on how cold it is outside. For example mine is set at roughly 45 when its -5c outside, through to 32C when its 18C outside. The curve will be different for everyone depending on you house size, heatloss etc etc. You need to experiment, trying to get it as low as possible such that it still maintains the desired indoor temp

@Maurice Kelly  sorry I have a Daikin so cannot help with control settings. 

But, in general our ASHP is set to deliver 40 degrees at -2 outside temp, down to 30 degrees at +15. Our Nest thermostat is set to 22 degrees which is only needed when solar gain is high. I have also opened our TRVs wide open to get the flow rate up, leaving weather comp to do its thing, that way we get best COP out of the system.

At that curve setting we get about 19/20 degrees over 16 hours, all very comfortable and decent performance. 

I suspect you will already have a weather comp curve set within your controller, and it is just a case of changing the setting to switch it on. 

I just moved into a new property. 5 bedrooms upstairs and 4 big size rooms downstairs.  Big house but newly build. Pretty well insulated.  

Downstairs we have a zone with underfloor heating. Upstairs zone with radiators.  Ecodan Mitsibushi heat pump.  

My Electricity bill for January was over £600.  I am trying hard to figure out how to save costs.  Have changed the underfloor heating thermostat to 19.5 and upstairs radiators to 19.5.  

Both upstairs and downstairs swithces off for 2 hours when I go to bed as the sound of the pump makes it hard to fall asleep as it is by our window.  The rest of the time I keep the downstairs running with upstairs only switching on at 3am as I struggle to sleep if the bedroom is to warm at night.  Downstairs runs all the time except for the 2 hours around bedtime.  

The HW goes on 2 times a day to get to desired temp and the rest of it I try to keep fairly simple.  I tried experimenting a bit this week by lowering the air flow temp but then the house does not get warm enough and logic tells me the machine works harder.  So back to square one trying to find a solution that will keep the house comfortable but also cut cost. 

any advice or help with cutting usage would be much appreciated.