Are you running the heating on a schedule @Maurice Kelly ? It’s should be on all the time for best efficiency (with poss a setback of a degree or two overnight).

Can you describe a bit more about the components of the system ? 

Can you see the flow rate ? My system has a better cop on dhw than heating which seems to be because the flow rate was higher doing the dhw. (My problem has been diagnosed as low refrigerant - to be checked by my installer soon)

What does your installer have to say about the low cop ?

nb don’t despair !! Heat pumps are great !!

Do you have something controlling the internal temperatures? A thermostat or TRVs?

Good morning , 

two thermostats one on each floor . See attached re flow rates from the system info .  Running constantly not on timer . Weather comp mode , 39/-3c  25/12c

Your thermostats could be fighting with the main controller and causing problems with flow temperature. Are your thermostats Mitsubishi wireless units. Like this? 

https://les.mitsubishielectric.co.uk/products/residential-heating/control/wireless-controller-and-receiver

Yes both like that . What would the issue be? Or how could I check ?  

What cop were you getting in feb ? Do you have a buffer tank ?

What have the outdoor temps been like, where do you live ?

There are three ways to run an Ecodan heat pump 

1 - Fixed flow temperature. The system always produces water at the same temperature and you generally use a thermostat in the house to tell it when to turn on and off.

2 - Weather compensation. The system heats water to different temperatures depending on the outside temperature. It requires no internal thermostat because you set the compensation curve so it heats the house just enough and no more.

3 - Auto adaptation. This uses the wireless mitsubishi thermostat and manages the flow temperature to keep the house at your ideal temperature while trying to maximise efficiency.

I wonder if yours is set to weather compensation but the internal thermostat is stopping it performing correctly. Lots of people find that auto adaptation gives better, and more efficient, results so can I suggest you try that?

If you don't mind me asking, who specified and installed it? This information is something your installer should have talked about with you.

Hi , 

Ok I followed the process to set up with weather compensation mode and then pressed the auto adapt (as per video instruction) , would this be where I’ve gone wrong ? Re the internal thermostats are they not just telling me water temp each floor is set to and currently reading ? How do they interfere with efficiency ?

Should I put it on weather compensation mode and see if that improves the COP ? 
 

installed by plumber during retrofit , didn’t spend a huge length of time with me on the settings . 

Thanks

Maurice 

Similar Cop for both months 

Hi , 

Ok I followed the process to set up with weather compensation mode and then pressed the auto adapt (as per video instruction) , would this be where I’ve gone wrong ? Re the internal thermostats are they not just telling me water temp each floor is set to and currently reading ? How do they interfere with efficiency ?

Should I put it on weather compensation mode and see if that improves the COP ? 
 

installed by plumber during retrofit , didn’t spend a huge length of time with me on the settings . 

Thanks

Maurice 

The thermostat shows the target room temp and the actual room temp. It would affect efficiency if it keeps turning the heat pump on and off.
The water temp in the radiators will be whatever the weather dependent graph sets it at for a given outdoor temperature, eg mine is 31 deg at 12 outside. 

Ok my graphs is similar. How do I make sure the thermostat doesn’t affect the efficiency. We set them and left the alone . I think my system is on auto adjust mode . My pump does turn off when the water and temp at at the required temp , is that not a good sign? 

@M.isterW has the same system as you, so he’s better placed to answer exactly what to do. Mine’s a Daikin and doesn’t have auto adapt.

Thank you 

Unfortunately our system is a little odd so I've reached the limit of my knowledge. We use a fixed flow temperature which isn't the most efficient way to run the system but we have limitations that stop us using either weather compensation or auto adapt.

In your position I would investigate how to get the system set up properly in auto adapt mode. Once it's set up it might take a bit of time to adapt to your house but eventually you should see an improvement in COP.

This video explains how to set your system to auto adapt mode https://youtu.be/RX31v4NoQf4

I'm not sure what happens if you have two thermostats connected to the system. I would be tempted to switch one off and let the other do all the work for a few weeks.

Do you have TRVs on your radiators? If you do, they should be fully open.

Sorry, another question... was a heat loss calculation done to determine how big your radiators and heat pump should be?

BER assessment said all radiators downstairs changed to larger type , not TRV. And upstairs stayed the same . 

Ok thanks , sorry for all the questions , new to this . I thought the compensation mode would heat house in sync with outside temps until desired heat house reached as per thermostats temp setting . All a learning curve . 

Thank you must go though this 

Hi

thats a video I used before too . He says it runs the weather compensation mode in the background . I believe my system is already on this mode. They don’t what to do with the thermostats . My system seems to come on for awhile then shuts off for a good period of time . Water and floor stats seem to be at or slightly above their setting all the time. 

You could try lowering the curve values a bit to see if the pump stops switching off. Bit of a stab in the dark. 
 @OrphM62 has an ecodan so may be able to suggest something ?

Ok , so really the pump /fan should be going all the time ? I turned the auto adapt off so it’s just on compensation mode now .