Thank you OpenEnergyMonitor: Octopus Daikin ASHP monitoring

[matt-drummer (Matthew Gregory)]

So I find myself in a position I never thought was possible.

My Daikin Altherma 3 operates more efficiently banging in heat as required by the Madoka controller at higher temperatures than it does running low flow temperatures on pure weather compensation.

Whilst it had no problem heating the house to 22c for 24 hours at these flow flow temperatures the COP is worse than it is running hotter.

It goes against everything you ever hear about heat pumps.

Whether it is a system design issue, a heat pump design issue or a fault I don’t know.

Hopefully Octopus will come to review the setup soon but I am really expecting to have to go to Daikin for an explanation.

[Vinny]

@matt-drummer

The circulation pump was using even more until I turned it down to it’s minimum of 60%.

There are 2 settings for the max pump speed, one only for sampling, the other for heating/sampling.
Which one did you change? If you changed just the sampling setting, then in heating it starts at 24lpm then settles down at 11lpm. I would like to know if you can change the heating setting to 14-17lpm at all time. Try that and let’s see the result.

Can you find a few hours when from a minimum steady state, you open the windows for a few hours such that you mimic a higher output from the radiators, but not much so it doesn’t increase the consumption over 1kWh.

We need to understand why there was a higher output on the second longer cycle, from the beginning.
From the same ish power input.

We need to understand what makes such a difference in COP at the same outdoor temp, was the house colder in the day with the better COP? The indoor temp on the graph doesn’t necessarily tell the whole house picture.

[Vinny]

@Vinny

We need to understand why there was a higher output on the second longer cycle, from the beginning.
From the same ish power input.

ugh, might be the defrost in between

[John (John Gouk)]

Hi Matt

This is indeed a bit of a shock. As I said, I don’t have the flow temp/volume monitoring, but I do have a monitor for the HP’s view of the LWT, and a reasonable idea of the power consumed. I also see similar cycling, rather than a constant output at these low flow temps. House temp is great… I also worked out the nominal flow temp required by the WD curve for the current ambient (12-13deg), and it’s about 29 deg. The LWT is fluctuating 32-27deg or so, which is about right, on average. I guess it’s not able, in the current configuration, to deliver a steady flow at the required temp.

I’ll read the manual and see of there’s any more useful settings - interestingly, there is a pump control variable which can be set to

• 0 => constant (!), not recommended!
• 1 Sample: The pump is ON when there is heating or cooling demand as the leaving water temperature has not yet reached the desired temperature yet. When thermo OFF condition occurs, the pump runs every 3 minutes to check the water temperature and demand heating or cooling if necessary.
• 2 Request: Pump operation based on request. Example: Using a room thermostat and thermostat creates thermo ON/OFF condition. Remark: NOT available in leaving water temperature control.

If you hear anything more from Octopus/Daikin, or get more answers, ping me on this thread :-).

Cheers thanks

[John (John Gouk)]

Haha looks like Vinny is on the case!

[matt-drummer (Matthew Gregory)]

Hi John,

I think I have the pump control set as best I can, I will explain in a reply to Vinny’s post before yours.

I will be updating this as I go, maybe it’s boring for some reading about the exploits of a novice with heat pumps but i think it will help other Octopus customers in the future. It’s also useful for me to track my progress.

Performance is better today as it has always been running with Madoka influence. The COP for heating is at about 3.70, not 5.0 but better nevertheless.

[matt-drummer (Matthew Gregory)]

Hi Vinny,

Thanks for your help.

Sampling pump mode is only available in pure weather compensation and I had that running from Sunday afternoon to Monday afternoon. I set that at 60% as it already knew about this from earlier experiments. 60% is as low as it goes and it reduces the consumption from around 150w which I believe is 90% down to 100w.

I am also running the pump in request mode at 60% with Madoka influence, I made sure each time I have changed the mode of operation. It was originally set as continuous.

I cannot see any way to get any more control of the pump speed.

My heating performance is better as I am currently running it.

The house has always been at around 22c since the heating came on on 14 October, I have never let it get cold in here so heating demand has been in direct relation to the outside temperature. I have always run it on the WD curve. The internal temperature being reported is not the one the heat pump is operating from, that data is coming from an OEM thermostat/humidity sensor. The thermostats are not quite in the same place right now as I had a communication issue (a loss of connection) so had to move it. I should move it back really.

I am confused by some things, the other Octopus Daikin in Hampshire produces 50% more heat at 1kW of electricity than mine does.

I am also confused by the erratic nature of the heat production, it’s not as smooth as others as noticed by Marko.

I have done some calculations regarding my radiator sizing and I am going to replace five radiators with bigger versions, I bought them today. I always thought they were too small but the heat loss survey said otherwise. They’re OK but bigger won’t hurt.

The house is heated to 22c inside at 30c flow temperatures with 7c outside, which is good. The problem seems to be the heat required by the house is less than the heat pump can deliver at it’s minimum power and maybe the minimum power of the heat pump at those flows temperatures is more than my radiators can deliver.

My radiators are calculated at delivering 9kW at 50c flow and 21c or so inside, a bit vague but that is what the radiator schedule says. They seem to cope with more than 11.5kW @ 35c flow looking at my data.

I can also increase my heating load by adding another room that is currently not heated by the heat pump.

I have an office building attached to the back of my house. I planned to heat it with my gas boiler but never really thought it was up to it.

So I think I have a heat pump that is a bit too big and the best way to deal with that is to increase the house heat loss!

If the heat pump couldn’t heat the office and the house on the worst of days than I can just stop heating the office and use all the heat available for the house.

That is my plan and any comments are welcome as usual!

[Vinny]

Something doesn’t add up, your DHW COP it’s very low as well.
Are you able to compare the flow rate and temperatures from the heat pump vs heat meter?

[matt-drummer (Matthew Gregory)]

Hi Vinny.

Yes, I noticed this too, or should I say it is not what I expected, I don’t really know whether it is poor or not.

One big disappointment with the Daikin, as it probably is with others, is the lack of information available and what there is is pretty vague, not very granular.

The Daikin MMI controller reports that it consumed 1kWh of electricity to produce 2kWh of heat.

It does separate DHW from heating.

The only way I can find out more is to watch the flow temperature and flow rate `live’ on the MMI I think.

I think it may be useful if I photograph my heat meter location.

[Vinny]

@matt-drummer

I think it may be useful if I photograph my heat meter location.

I think we will get to the point of asking for some schematics of everything involved and whatever photos you are able to share.
Would be helpful for you to open the menu and compare them.
How much time have you spend looking to see if you have air trapped?

[matt-drummer (Matthew Gregory)]

[Robert.Wall]

Drag & Drop into your post is the easy way.
Alternatively, use the upload button (the bar with the up-arrow growing out of it at the top of the box you type in) and navigate to the file.

[matt-drummer (Matthew Gregory)]

I don’t have a bar with an up arrow coming out of it, just a hyperlink button, but I just dragged them in as you suggested, thank you

[Robert.Wall]

You don’t see this?

[matt-drummer (Matthew Gregory)]

Oops, sorry, yes I do.

Other things on my mind and not looking carefully enough!

[TrystanLea]

@matt-drummer

So I find myself in a position I never thought was possible.

My Daikin Altherma 3 operates more efficiently banging in heat as required by the Madoka controller at higher temperatures than it does running low flow temperatures on pure weather compensation.

Interesting thread! this result does not seem to be as unusual as one might think. There’s a seems to be a sweet spot between trying to run as low temperature as possible and low end part load compressor efficiency. @glyn.hudson has his WC curve with a minimum temp around 35C below which he couldn’t measure an improvement in efficiency - that temperature is of course dependent on the combination of the heat pump and radiators as a system rather than the heatpump alone.

I was puzzling over the Daikin Monoblock datasheet with my farther in law (owner of the Hamshire Daikin on HeatpumpMonitor.org) it seems that the same compressor is used for a wide range of model capacities. Compressor model 2Y350BPAY1P#C is used for EBLA09DW1 (9kW) through to EBLA16DW1 (16kW). There is also very little difference in the evaporator heat exchanger dimensions across these models 1136 / 1166 / 1195 mm. The only aspect that appears to change significantly between the 9kW and 16 kW model is the fan speed 48 m3/min vs 85 m3/min?? Refrigerant charge is also the same across the models…

If we compare that with the Mitsi Ecodan R32 range as an example:

• 5kW PUZ-WM50VHA has the SVB130FBBMC-L3 0.9 kW compressor
• 6kW PUZ-WM60VAA has the SVB220FEGMC-L1 1.5 kW compressor
• 8.5kW PUZ-WM85VAA has the SVB220FEGMC-L1 1.5 kW compressor (note same as 6kW model)
• 11 kW PUZ-WM112VAA has the DVB28FBAMT 2.2 kW compressor
• 14 kW PUZ-HWM140VHA has the AVB36FJDMT 3.67 kW compressor

The external dimensions of the 5kW ecodan is 950x943x330, vs 14kW 1020x1350x330, refrigerant charge 2.0kg vs 3.3kg.

I guess the first observation is that there’s a lot of variation in what you get from different manufacturers!
The second is that the compressor efficiency curve on the Daikin units may not be as well matched to individual model sizes given that the same compressor is used across the range?

I want to be careful not to make too many sweeping statements or reach conclusions to early on what the above means exactly… my farther in law is planning quite a few more detailed tests for this winter to understand the performance of his unit and system

[John (John Gouk)]

At least Daikin got the relative fan capacities in proportion to their nominal output!

So what is your f-in-law doing that is different? Or perhaps his system is a better “system” in respect of the Daikin’s operational characteristics?

[TrystanLea]

Good question, I haven’t studied the difference in the Daikin systems enough to really say, can we unpick anything clear from the data?

Here’s the monthly comparison between ‘Baisingstoke’ and ‘Weston super mare’. I will call these A and B respectively.

Monthly SCOPS’s routinely slightly higher on A:

Flow temperature when running higher on B than A:

Significant drop off in carnot efficiency on B in summer? outside sensor error or heat meter air issue?

More standby consumption on B?

[TrystanLea]

Comparing ‘Baisingstoke’ A and ‘Farnborough’ C. Gives quite different results:

Monthly COP:

Monthly COP when running, why the more recent drop off in performance for C?

Not really a significant difference in recent flow temperatures:

Standby very similar:

[TrystanLea]

Comparing the heatpump dashboard for A vs C in the last month:

A: Emoncms - app view dashboard

C: Emoncms - app view

A lot more heat delivered and electric consumption over the total monitoring period for A vs C. Standby a significantly greater proportion of consumption for C vs A perhaps?