Octopus Heat Pumps

oliver1951

Hi, have now had my Ashp for 2 weeks. In the height of summer testing is tricky. Mainly using it for hot water, and that infrequently. I don’t have any monitoring devices apart from the Daikin MMI. I have the altherma 8kw. I find the ONECTA app practically useless. I have a mixergy cylinder,( water pressure too low for the Daikin cylinder). So trying to assess my COP. The MMI does provide figures for energy produced and energy consumed. But I have found the reporting is internally inconsistent. Total is different from sum of parts. Also I know exactly when I am using it and I know the load during the use period, so I know what it’s consuming. Those aren’t the figures the MMI is giving. So I’m looking to see if anyone has any experience to share in using the MMI and how they have found the accuracy of the reporting. Thanks  

Spies

It's annoying they don't really have a tariff for people with a heatpump and ev, it would be nice to have intelligent go but with the cosy dips during the day. 

MP1995

Spies said:

It's annoying they don't really have a tariff for people with a heatpump and ev, it would be nice to have intelligent go but with the cosy dips during the day. 

That's called a massive loss leader that's why lol

Spies

Is there a spec sheet for the Cosy, as some people already have them according to my chat with Octopus today... 

stripling

oliver1951 said:

Hi, have now had my Ashp for 2 weeks. In the height of summer testing is tricky. Mainly using it for hot water, and that infrequently. I don’t have any monitoring devices apart from the Daikin MMI. I have the altherma 8kw. I find the ONECTA app practically useless. I have a mixergy cylinder,( water pressure too low for the Daikin cylinder). So trying to assess my COP. The MMI does provide figures for energy produced and energy consumed. But I have found the reporting is internally inconsistent. Total is different from sum of parts. Also I know exactly when I am using it and I know the load during the use period, so I know what it’s consuming. Those aren’t the figures the MMI is giving. So I’m looking to see if anyone has any experience to share in using the MMI and how they have found the accuracy of the reporting. Thanks  

Have you seen Heatpump Monitor Org?

It's beyond my level of geek, technically-speaking, but it's a great resource to see data-driven heat pump monitoring and discussions. I think everyone agrees that all the basic monitoring kit supplied with the heat pump, whatever the manufacturer, is pretty basic and either not accurate or sufficiently detailed. 

michaels

stripling said:

oliver1951 said:

Hi, have now had my Ashp for 2 weeks. In the height of summer testing is tricky. Mainly using it for hot water, and that infrequently. I don’t have any monitoring devices apart from the Daikin MMI. I have the altherma 8kw. I find the ONECTA app practically useless. I have a mixergy cylinder,( water pressure too low for the Daikin cylinder). So trying to assess my COP. The MMI does provide figures for energy produced and energy consumed. But I have found the reporting is internally inconsistent. Total is different from sum of parts. Also I know exactly when I am using it and I know the load during the use period, so I know what it’s consuming. Those aren’t the figures the MMI is giving. So I’m looking to see if anyone has any experience to share in using the MMI and how they have found the accuracy of the reporting. Thanks  

Have you seen Heatpump Monitor Org?

It's beyond my level of geek, technically-speaking, but it's a great resource to see data-driven heat pump monitoring and discussions. I think everyone agrees that all the basic monitoring kit supplied with the heat pump, whatever the manufacturer, is pretty basic and either not accurate or sufficiently detailed. 

Amazing variation in SCOPS but hard to know why and not nearly enough data on each to get a good idea.  I am struggling to choose a suitable heat pump, looking for weather comp and max modulation but the only one I have found that have documentation showing the range of output at different air temps are the Viessmann ones which unfortunately cost 7k compared to 3-4k for all the others of the same size.

I think I may need to do some modelling based on my daily gas consumption to work out whether cycling and lower efficiency at higher air temps is more costly than inefficiency at low air temps - low temps are less common but obviously will use more energy on the cold days.

NedS

michaels said:

stripling said:

oliver1951 said:

Hi, have now had my Ashp for 2 weeks. In the height of summer testing is tricky. Mainly using it for hot water, and that infrequently. I don’t have any monitoring devices apart from the Daikin MMI. I have the altherma 8kw. I find the ONECTA app practically useless. I have a mixergy cylinder,( water pressure too low for the Daikin cylinder). So trying to assess my COP. The MMI does provide figures for energy produced and energy consumed. But I have found the reporting is internally inconsistent. Total is different from sum of parts. Also I know exactly when I am using it and I know the load during the use period, so I know what it’s consuming. Those aren’t the figures the MMI is giving. So I’m looking to see if anyone has any experience to share in using the MMI and how they have found the accuracy of the reporting. Thanks  

Have you seen Heatpump Monitor Org?

It's beyond my level of geek, technically-speaking, but it's a great resource to see data-driven heat pump monitoring and discussions. I think everyone agrees that all the basic monitoring kit supplied with the heat pump, whatever the manufacturer, is pretty basic and either not accurate or sufficiently detailed. 

Amazing variation in SCOPS but hard to know why and not nearly enough data on each to get a good idea.  I am struggling to choose a suitable heat pump, looking for weather comp and max modulation but the only one I have found that have documentation showing the range of output at different air temps are the Viessmann ones which unfortunately cost 7k compared to 3-4k for all the others of the same size.

I think I may need to do some modelling based on my daily gas consumption to work out whether cycling and lower efficiency at higher air temps is more costly than inefficiency at low air temps - low temps are less common but obviously will use more energy on the cold days.

@michaels Midea publish tabulated data for minimum power input (PI) and output capacity, together with COP values at common ambient temps:

https://mideauk.co.uk/products/m-thermal-r32-monobloc-air-to-water-heat-pump/

For example, their 8kW model at 15C ambient, and a flow temp of 35C will modulate down to 3552W output for an input of 528W.

DougMLancs

@michaels yes many manufacturers do seem to be reticent about publishing their modulation data. People’s observations/heatpumpmonitor.org data seem the best way. An 8kW Daikin appears to modulate down to 280W (https://community.openenergymonitor.org/t/performance-of-9kw-daikin/25243/23). My 9kW Panasonic I’ve seen as low as 200W on a heating cycle.

smallblueplanet

DougMLancs said:

@michaels yes many manufacturers do seem to be reticent about publishing their modulation data. People’s observations/heatpumpmonitor.org data seem the best way. An 8kW Daikin appears to modulate down to 280W (https://community.openenergymonitor.org/t/performance-of-9kw-daikin/25243/23). My 9kW Panasonic I’ve seen as low as 200W on a heating cycle.

But sorry, what does that actually mean?

NedS

Have a look at this video from John Cantor, particularly the bit at the end of the video at around 20:10:

https://www.youtube.com/watch?v=0oszaqP0TI4

The graph shows how COP efficiency varies with compressor speed, and explains why manufacturers limit how low the compressor speed can modulate so efficiency doesn't fall off a cliff. Ideally you'd like your ASHP to be operating in the 30-60% range for maximum efficiency. Most manufacturers seem to limit the low end to around 25% from what I've seen. The performance of different compressors may vary.

Manufacturers want COP to be as high as possible as this is the headline marketing figure that will sell their ASHP.