Daiken ASHP hot water

Exiled_Tyke

I find my hot water tank heats quicker than I need it to and is averaging a COP of just less than two (although admittedly this will include the weekly legionella cycle which after much research I decided to keep).   This suggests to me that that the ASHP is running hotter than I need it to for  hot water. Is there a way to alter the difference between the ASHP flow temperature for the given target tank temperature? 

Strummer22

What's the target temp? The first step to higher efficiency is to set it as low as you are happy with. For me it's 46°C.

For my GSHP (Ecoforest ecoGEO) I've limited the compressor to 50%. This slows the heating rate for both hot water and central heating, improving efficiency, but is not suitable if your unit doesn't have an inverter or you need 100% compressor power to meet heating demand.

Exiled_Tyke

I'm reducing the target temp gradually to see what I can get away with. Currently it's 43 degrees. I may manage one or two below this but that's pretty much the limit. 

I read somewhere about 'differentials' or some similar term but can't see anything directly relating the Daikin.  I'm also experimenting with the space heating which is almost how I want it so can't really do anything which will affect that.   

Strummer22

Exiled_Tyke said:

I read somewhere about 'differentials' or some similar term but can't see anything directly relating the Daikin.  I'm also experimenting with the space heating which is almost how I want it so can't really do anything which will affect that.   

In this case probably referring to the difference in temperature between the water entering and leaving the heat pump. Usually set to a target of around 5°C. Unless it's wildly different to that, you're not likely to gain much efficiency by trying to adjust. I'm afraid I don't know anything about Daikin's displays or controls as to how you could access or edit this.

NedS

Strummer22 said:

What's the target temp? The first step to higher efficiency is to set it as low as you are happy with. For me it's 46°C.

For my GSHP (Ecoforest ecoGEO) I've limited the compressor to 50%. This slows the heating rate for both hot water and central heating, improving efficiency, but is not suitable if your unit doesn't have an inverter or you need 100% compressor power to meet heating demand.

I achieve a similar effect by turning on Quiet Mode (Samsung heat pump) during my DHW runs, which effectively limits the compressor to running somewhere around 70% max. This effectively feeds the heat in slower, giving more time to transfer the heat from the coil into the tank, and ultimately limits the maximum flow temp needed to achieve the DHW tank set point temperature.

Depending on heat pump, a quite mode or setting to limit output/compressor speed can achieve this, so some method to limit dT to something like 5C will have the same effect.

I ran some tests back in the summer, and found I consistently used less energy and achieved a higher COP by heating the DHW longer and slower using this method. Also helps in the summer that more of it can be covered by solar on a sunny day by extending the run and keeping power consumption within that generated by the solar array.

Exiled_Tyke

NedS said:

Strummer22 said:

What's the target temp? The first step to higher efficiency is to set it as low as you are happy with. For me it's 46°C.

For my GSHP (Ecoforest ecoGEO) I've limited the compressor to 50%. This slows the heating rate for both hot water and central heating, improving efficiency, but is not suitable if your unit doesn't have an inverter or you need 100% compressor power to meet heating demand.

I achieve a similar effect by turning on Quiet Mode (Samsung heat pump) during my DHW runs, which effectively limits the compressor to running somewhere around 70% max. This effectively feeds the heat in slower, giving more time to transfer the heat from the coil into the tank, and ultimately limits the maximum flow temp needed to achieve the DHW tank set point temperature.

Depending on heat pump, a quite mode or setting to limit output/compressor speed can achieve this, so some method to limit dT to something like 5C will have the same effect.

I ran some tests back in the summer, and found I consistently used less energy and achieved a higher COP by heating the DHW longer and slower using this method. Also helps in the summer that more of it can be covered by solar on a sunny day by extending the run and keeping power consumption within that generated by the solar array.

This looks like great advice - thank you.   I'll give it a go.  I see I've for three levels of quiet to try so I'll work through them until I find a sweet-spot.   (Why on earth is this stuff is restricted to the installers menu?)  

And I love the idea of running it this way in the summer too. - Just a pain that I will have to set up the quiet mode schedules and then the DHW schedule not only separately but on two different devices!   Working out when to do the switch over will be additional challenge!