Interesting stuff. Increasing your flow rate to 37C from 27C will definitely help. I've set ours manually to 40C and the house is feeling cosy. More than acceptable. Your battery strategy is sound and you will save a packet doing that given the crazy tariffs.

We've never found cold windy weather to have an impact on the performance of the pump. It probably contributes to greater heat losses from the house. The worst weather for us is the -2 to 4C mark when it's really humid outside because the unit frosts over very regularly leading to an increased amount of defrost cycles which makes the pump work harder.

But please keep sharing your experiences. Very interesting.

@editor the question is, how will that affect the COP. But given we dont want to live in an ice cold house, its something of a null point

@batalto Hi Batalto,

Increasing the water flow temperature minimum setting from 27C to 37C will limit the operating range of the weather compensation.

Your Midea ASHP is better than many others, in that you can create your own weather compensation curve to match your home, rather than select one of the available curves from a list. The reason that installers prefer to provide 'fit and forget' thermostats, rather than controllers that utilise the weather compensation capability, is that it can take days or even weeks to correctly optimise the system or correct operation with weather compensation.

Rather than increasing the minimum water flow temperature setting, you should probably have increased the temperature offset by one or two degrees.

Did you record the operating parameters as I suggested?

@derek-m I've not been collecting those, I just haven't had the time at home - we were out all yesterday until 7pm. I will try to find a day or two to collect them.

I have a range of options I can play with. What I chose to change was the minimum flow temperature. At the moment I have it set at 37 degrees when its 17+ outside down to 55 degrees at -2. Are you suggesting lowering the max outside temperature before compensation occurs?

As a note, the heating has only just come on over the last few days. Frankly the biggest factor in our house is solar gain in the day. On a sunny day we can easily get to 23 or 24 even at this time of year. I think the biggest factor in the heating will be the "wife factor". When she is happy its not cold, those are the right settings!!

Posted by: @batalto

@derek-m I've not been collecting those, I just haven't had the time at home - we were out all yesterday until 7pm. I will try to find a day or two to collect them.

I have a range of options I can play with. What I chose to change was the minimum flow temperature. At the moment I have it set at 37 degrees when its 17+ outside down to 55 degrees at -2. Are you suggesting lowering the max outside temperature before compensation occurs?

As a note, the heating has only just come on over the last few days. Frankly the biggest factor in our house is solar gain in the day. On a sunny day we can easily get to 23 or 24 even at this time of year. I think the biggest factor in the heating will be the "wife factor". When she is happy its not cold, those are the right settings!!

Hi Batalto,

There are various problems in optimising an ASHP based heating system, the primary one being the slow reaction time compared to an oil or gas fired heating system.

Another problem is matching the weather compensation curve to the heat demand, which can take some time to achieve. Increasing the minimum water flow temperature from 27C to 37C, means that the water flow temperature cannot go bellow 37C even when it should do so.

It could be that to meet the heat demand at an ambient air temperature of 17C requires a water flow temperature of 30C or 33C, this is what you need to discover by monitoring your system. At the other end of the scale it could be that at -2C outside air temperature, you require a water flow temperature of 50C rather than 55C.

The offset value is designed to move the weather compensation up or down by a number of degrees. If your initial curve is set at 27C to 55C, then increasing the offset by 2C would change the curve to 29C to 57C.

Changes in heat demand due to chill caused by wind and rain should be accommodated by the control system, though it may take a little time to respond.

@derek-m I can actually move both the top and bottom

it has a max ambient, max flow temp and min ambient, min flow temp. At the moment these are;

Max Ambient: 17

Flow Temp: 37

Min Ambient: -2

Flow temp: 55

I can edit any of those up or down as I see fit

Posted by: @batalto

@derek-m I can actually move both the top and bottom

it has a max ambient, max flow temp and min ambient, min flow temp. At the moment these are;

Max Ambient: 17

Flow Temp: 37

Min Ambient: -2

Flow temp: 55

 

I can edit any of those up or down as I see fit

Hi Btatlto,

The objective, for optimum operation, is to match the water flow temperature to the heat demand. To do so you would need to monitor the actual indoor temperature in relation to the desired temperature, along with the outdoor air temperature and the actual water flow temperature.

Based on your present settings, a 1C fall in outdoor air temperature, should produce an approximately 1C increase in the water flow temperature.

If the required water flow temperature to meet the present heat demand is below 37C, then of course there will be no change in the water flow temperature, and you should find that your heat pump switches on and off. Because I cannot see your system and how it is responding I am having to make assumptions.

What I suggest, if you have the time, is that you monitor your system with the above settings and see how it responds, remembering that changes in actual indoor temperatures will be very slow, unless they are caused by solar gain.

If, over a range of outdoor air temperatures, you find that the actual indoor temperature is deviating from the desired temperature, then you need to adjust the slope of the weather compensation curve. If the indoor temperature increases above the desired value with falling outdoor air temperature then reduce the maximum water flow temperature setting.

One thing of which I am not certain about, is if the minimum and maximum water flow temperature values are actually limits, in that the produced water flow temperature cannot go below or above these values.