Performance of 9kW Daikin

Hi Matthew,

Welcome to the forum.

I just called Daikin customer support.

The first time they suggested I use quiet mode to reduce electricity consumption, it doesn’t work.

The second time I requested a visit as I wanted the heat pump checked.

They didn’t check anything but went through the problems I was having and we went through my data.

I was promised a report but never heard anything more.

After a while I went back to Octopus and accepted their offer to swap the heat pump after I initially declined.

I declined initially because the offer didn’t come in a nice way.

But once I had conclusive data showing my heat loss they were more supportive of the swap.

I think at first you need to talk to your installer, have you done that?

It may help if you give some details of the installation such as house size, calculated heat loss, what you think the heat loss is and your emitter spec.

I’m sure I can guess, but maybe explain what issues you are facing.

Do you have any monitoring?

As much information as possible will help us to help you.

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Many thanks for your reply. I suspect I might waffle a bit here as I share my experience to date and answer the question raised, so apologies.

As yet I haven’t approached my installer about poor performance / over rated unit. I had a few issues with the install which have been dealt with now, but before I go back with something else I want to collate evidence and present it in a way that ensures they either take action or I can approach MCS with it to mediate if they say no.

The heat pump was installed in July last year, I wanted to use a heat geek installer but none were available in my area at the time, so I approached Daikin directly and they sent me the details of my nearest ‘Certified installer’, which wasn’t actually that near at all. I live in Swindon and they are based out of Poole!

They came and completed a heat loss ‘survey’, he was here less than half an hour which I have later discovered probably indicates its not been completed that well. The survey itself I didn’t get until post installation, it estimates my heat loss around 5300w. I guess even with it I probably wasn’t that clued in at the time that a much larger unit would cause efficiency issues.

I recently used HeatPunk website to complete a survey myself and its suggests 5200w, so I suspect it’s probably in the right ball park. The house is detached, four double beds and is around 170sqm / 1800sq ft in size, built in 2016 with very good insulation and glazing etc.

The major issue with the installation which has now been fixed was in the 0c and below weather the RCBO for the heat pump kept tripping. The issue: they had installed a 16amp rated cable and 16amp fuse for a 32amp unit…… the back up heater circuit was fine…. For a certified installer I found this error surprising.

Anyway monitoring wise I used the amazing guide which I believe you put together (thank you) to connect a M5stack to the serial port and send data to my Home Assistant. This was suggesting as was the Daikin MMI display that my COP was around 3.0, much lower than the survey said it would be. The other thing it showed me was cycling, lots of cycling. The only outside temperature it appears not to cycle at is below 0c.

Recently I bought some power usage monitoring (EmonPi2) kit from Open Energy Monitoring to monitor the electric consumption. As we have solar and batteries with usage monitoring I suspected that the Daikin energy data was incorrect. I am now seeing the data varies quite a bit, for example the base watt draw reported by Daikin unit is 780w vs 940w monitoring the cable direct, which is more inline with what is suggested is the minimum watt draw of the unit by others in the forum. I monitor the BUH separately and this has not been used at all. I do wonder what the point of it is.

The COP now with the cable monitored sits around 2.6. The COP for heating is worse than the COP I get for heating the water which is around 2.8.

I suspect the heat produced is also reported incorrectly via the Daikin unit, so I have recently purchase and waiting for installation of the heat meter which I am getting installed by a local plumber who is training with heat geeks at the moment. I am going to work with him on a few tweaks to see if anything can be done to improve performance.

For instance the system has a buffer unit within a Daikin Preplumbed R32 tank. It has its own circulation pump, which is oddly triggered by some temperature monitoring on the tank itself. (This was the other issue I experienced as the installer couldn’t understand how to set it up correctly…. Again a surprise seeing they are meant to be Daikin certified.) The buffer was installed because I was told that our modern microbore piping wouldn’t be compatible.

It turns out that the microbore itself connects to a 22mm main artery which runs through the property from the tank location, and the microbore connection is limited. The ‘heat geek in training’ plumber I am using suggested that I dont need the buffer, and he can replumb the tank to be a volumiser instead, removing the additional pump as the heat pump circulation pump is more than capable, which may improve efficiency of heat delivery, but still wouldn’t deal with a unit being too big.

So I see my journey as being in stages as we make some tweaks and finally have enough evidence to prove what is at fault… It may be the tweaks get me to a place / compromise I am happy to live with, if not I suspect I will end up where you are and need the unit swapping for the 8kw unit which can modulate down.

My EmonPI is only collecting data locally at the moment, once I have the heat monitor installed I plan to push this to the shareable site, which I can then share with this forum.

As I said I see this as a journey and will be happy to share so others can learn as well.

Kind Regards

Matthew

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If your heat loss survey shows 5.3kW then you have already proved that the installer has not acted competently in the installation as they should have given you either the old 7kW or the new 8kW heatpump.

My heat loss at -2 (Farnborough, Hampshire)is around 5.4kW and when octopus re calculated this (from the original calculation of 7.3kW) I was instantly offered a swap.

The current 4,6&8kW unit are the same just software derated so may as well get the 8 (minimum power of around 270w, not 900w)

If the installer complains you can push for it to be changed as if that was your heat loss survey then a 9kW would not be compliant with building regulations as it is not able to heat the property efficiently (a condition of the underlying law).

Hopefully you get it sorted soon as the smaller unit is soo much better.

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Hello, Old topic I can see, but just wanted to double check before I go into battle with the our installers. I have an issue with our heat pump cycling over 30/45mins or so when the outside temp is 7 degrees plus with a too warm house temp of 22.5 degrees. I see the cold days or/and cold night I get longer run of two hours plus.
A little info on the house etc.
Built 1999 4 bed house (120 sqm) Detached. 5 year old replaced windows, good insulation (EPC B1).
All new heat admitters upstairs, Ground floor single zone UFH unrestricted and pumped direct from the ASHP.
• Setting – pump speed 60% Flow range 10 l/min to 17 l/min
• Modulation – on (0)
• Weather comp on and curve set with a 24h always on setting

  • What I was trying to achieve is setting the Madoka at 22 degrees and have the weather curve set so it water temperature would warm the house to 21 degrees to try and get long run times.

As I type the outside temperature is 7 degree, leaving water 33.5 degrees, Return 31.4 degrees with a Shelly EM telling me we are using 596.9watts. From my reading here this shouldn’t be possible as if I understand correct as 900w in the min? Since installation at the start of October I have a COP of 3.43.
Am I missing something or do I have an oversized 9Kw (9-16 model) ASHP and should looking to push for 6-8Kw model?
Many thanks in advance.
Stefan

I had been doing similar, with madoka set to 20, but WD aiming to keep it around 19.5. That’s the point at which modulation kicks in, so the theory was that there was a little feedback to keep it stable. But since you don’t have any modulation, not sure the thermostat is doing much? (I’ve now given up on Madoka and just use LWT mode.)

Do you have any overshoot configured? That allows the LWT to rise above the configured value which can extend the run time.

Hi, thanks for the reply, I do have an overshoot of 1 degree. I have someone coming out tomorrow to review and discuss.

As I type the outside temperature is 7 degree, leaving water 33.5 degrees, Return 31.4 degrees with a Shelly EM telling me we are using 596.9watts. From my reading here this shouldn’t be possible as if I understand correct as 900w in the min?

Was that steady-state? I think you can get the Daikin 9kW power consumption down towards 800W at low enough flow temps and rates (@John might know more), but I think 600W sustained would be behaviour we’ve not seen before?

Have you asked for a delta-T of 3C?

I’ve never seen a figure that low! I’ve had average power figures with the pump cycling of 500W, but not when actually running. I don’t believe @matt-drummer did with his 9kW either. I don’t think you can set the dT directly on the 9kW, it’s via the UFH/rads/fancoil setting, unless I’ve missed that. So I’m very interested to hear more about this.

What settings do you have? Emitters UFH/rads/fancoil? WDC x&y? Do you have a EmonCMS.org entry?

Same here. My 11kW Daikin might average 500W as it cycles on and off. I think the lowest I’ve seen when it’s running is about 800W.

Emoncms can produce a power histogram and mine looks like this starting 3 nov

Hey, So here is my shelly output for last night.

So the engineer has been round and said i’ve covered 99% of what he would have done. He did flatten the curve a little bit, but he agrees it does look like the heat loss calcs could be wrong as heat pump is struggling when outside temps are above 6 degrees. He said our heat loss calcs on paper is -3.2 is 8.4kw. This AM the outside temp was 1 degree and the heat generated was 3.14avg with a flow temp of 38.8 degrees with a house temp of 22+ degrees.

Hey, the delta-t target is 5c

Here is my shelly from last night. Note it’s connected just to the heat pump feed, rather than HP+ Booster(immersion)+Backup heater.

You can see it repeatedly dumping a load of heat into the house only to then trigger a defrost due to the low temps It never gets to steady state.

Yours is looking suspiciously neat and tidy.

Hello, So below i’ve attached more info like rads sizes etc. we are running ground floor UFH and I can confirm you can change the dT on the 9kw

Mine too is connect to the heat pump feed like yours. I do have around 480watts of untracked power usage, but some of that’s going to be ghost power usage like, Audio kit, fridge, alarm, Garage, CCTV etc.
It really does look like pulling under the 900w while running to me.

My 9 kW Daikin when running never goes below 900w which I believe it is rated at.