Thank you OpenEnergyMonitor: Octopus Daikin ASHP monitoring

marko · 30 October 2023 11:02

You will not be able to use the pressure independent presettable danfoss TRVs. Those are intended for large heating systems that experience a wide range of differential pressure and operate at large (20-30C) deltaT between supply and return.

If your rads really are pretty much equal in deltaT then your existing setup may not be terribly out of balance…

We could do the math if it got to a steady state at a decently high flow temperature. The room also needs you be at a known temperature and without drafts though. (you can’t open windows too reduce it to 20C because that introduces extra air movement which will increase radiator output)

You can also try the heat meter balancing version.

pump on all rads open. Note flow rate.
switch off one rad, not flowrate, switch on again

Repeat until you see the effect of turning off each rad by the difference in flowrate between everything and one less. Compare against what it should be by math.

That isn’t perfect (shutting off flow to one will reduce pipework pressure drops and increase flow to others; especially on branched systems with marginal pipe sizing; less so on manifold type systems) but will pickup gross imbalance.

matt-drummer · 30 October 2023 11:08

Hi Marko,

Thank you again.

Yes, I dismissed those trvs straight away as unsuitable.

I cannot see any major issues with the balance as it is now and I intend to change most of the radiators in the next couple of weeks so I am not going to spend too much time on this now.

matt-drummer · 30 October 2023 14:11

No preheat or warming up the compressor for the first run of the day here. It was warmer outside on Saturday afternoon than it was this morning and the heat pump had already bee running. Maybe it is something it does to prepare for a DHW cycle., who knows!

HydroSam · 30 October 2023 17:56

I think it is a pre-heat thing when the pump goes from standby to full loading. On my display I get a small icon depicting when this happens. Daikin refer to it in the manual as Hot Start Mode active. That’s all the details they provide in my manual.

matt-drummer · 30 October 2023 18:13

Thanks Sam,

It did something during/before my DHW on Saturday.

It did not do it this morning even though it was colder and the load this morning was much higher than Saturday, 3 and a bit kW on Saturday, 11kW this morning.

It doesn’t make sense to me.

matt-drummer · 30 October 2023 19:42

Time to display my ignorance and stupidity again!

I have been looking at some other heat pumps for a few minutes.

So my house might be good or bad in terms of heat loss and my radiators may be good or bad too.

But the heat going into my house is the heat it needs at the room temperature I have set.

My heat pump is achieving that room temperature.

So if my house needs 3.3kW of heat at this moment that is the same as any other house taking 3.3kW of heat.

Is that correct?

If so, my heat pump is is consuming 1kw of electricity to produce 3.3kW of heat why are some other similar sized heat pumps only consuming 500w to do the same job and why are some other similar sized heat pumps producing 6+kW of heat whilst using the same amount of electricity as mine?

Logically I come to the conclusion that my heat pump is either defective or badly designed?

I know this is stating the obvious but my heat pump is either consuming too much electricity for the heat produced or it is not producing enough heat for the electricity consumed, I can’t see any other explanation.

I have also taken account of my flow temperature, increasing it or lowering it makes no appreciable difference, if anything lower flow temperatures make it worse.

Is there any other plausible explanation?

I have tried it for a couple of days at higher flow temperature so I am going to give it another go at lower flow temperatures and see what happens.

Maybe these heat pumps are designed for different climates and perform better with more sustained lower outside temperatures. They cannot have designed it to work like this when data from the competition is so readily available?

matt-drummer · 30 October 2023 20:47

Low flow temperature

High flow temperature

Really high flow temperature

Really not much in it, room temperatures the same in each case except the really high flow where I let it get as high as it could. It made barely any difference to the COP, it should have destroyed it compared to the other examples.

Heating is barely any better than DHW heated to 50c.

And this is a Daikin 10.6kW Altherma 3 in Basingstoke.

Why would it be producing so much more heat than mine for less electricity, it’s essentially the same heat pump? Flow rate is the same, outside here is 3c warmer, my room temperature is 1c higher and my flow temperature is about 2c higher.

matt-drummer · 30 October 2023 23:02

Is there any clue to monitoring issue here?

COP for 30 minutes is 4.73 which is more like where it should be but COP in window is only 3.68 for 27 minutes.
I see discrepencies between these two figures all the time now. I don’t recall seeing this for the first week of heating but for the last week I have been noticing this.

It may be something or maybe not?

matt-drummer · 31 October 2023 17:30

DHW today

DHW yesterday

I don’t see how it can be so different, starting temperature was the same and everything else is similar. Just the amount of electricity used today is significantly more

ColinS · 1 November 2023 19:32

Matt,

I’ve been monitoring the energy use for DHW in my daikinhants11kw installation and thought it might be useful for you to compare with. IF your COP readings are wrong due to metering issues this will get round this to get to the absolute heat pump performance. I have a 250Litre tank and, although the probe only measures tank temp at one point the delta T vs electricity usage on the tank for yours should be proportional.

How big is your tank and how do i identify you on openenergymonitor.org? I might then be able to do the comparison for you.

You can see there is a wide scatter of results- the points at the top right are for the legionella cycle.

Colin

ColinS · 1 November 2023 20:10

Just realised I can only do it for you with the tank temp … are you measuring that?

HydroSam · 1 November 2023 20:55

Matt
It might be nothing but the response of your flow and return temperature data doesn’t look quite right to me. It’s more ‘steppy’ than others, and seems to often have a lower resolution jumping around a degree. If you compare to my hot water trace from today, temp data is much smoother. I wonder if the temperature probes aren’t seated correctly?

FYI - Also an 11kw Daikin but the older generation, and they seem to have changed the heating characteristics. Mine goes full bore from the start, whilst yours and the DaikinHants 11kw of @ColinS
are more gradual in temperature rise.

matt-drummer · 1 November 2023 21:12

Hi Colin,

I changed to a scheduled DHW heat @ 14.00 every day to 50c on Thursday 28 October.

I have disabled the disinfection cycle for the time being as well as the reheat. Scheduled + reheat at 45c used more electricity than heating to 50c once a day. It would also reheat and then heat again a couple of hours later on the schedule at a COP of less than 1. That’s just stupid!

The starting point probably varies but I know today was 35c as I checked and I am pretty sur every day has been 35c except for Saturday which was 37c.

My tank is 205 litres and I am an Octopus customer in Ipswich. The only one so far on there.

matt-drummer · 1 November 2023 21:23

Hi Sam,

Yes, the heat production seems erratic to me and it has some peaks and troughs in it that I would not expect to see.

The temperature sensor in the heat meter is pre installed and sealed.

The other temperature probe is in a pocket of a tee piece. It seat on a rubber o ring and it is either seated or leaking, there is no scope to get it wrong without leaks as far as I am aware and can see.

I am puzzled by it.

DHW was fine today, about a COP of 3.

It does seem to vary and there is sometimes this lump of electric use with no heat output that Marko and Vinny have commented on.

I seem to be unable to affect the heating COP much. Nothing I do with flow temperatures makes any difference.

It was looking better this morning but deteriorated after the DHW cycle.

COP was about 3.6 for heating this morning and later was only about 3.3.

The heat pump seems to be more efficient when pushed a bit harder, ticking over does not appear to be its thing.

,I now have a thermal imaging camera.

All of my radiators are at roughly the same flow and return temperature and the difference between the flow and return is 4 to 5c on each radiator.

I can clearly see the hot water entering each radiator, flowing across it and leaving cooler with the camera.

I think I can confidently say that my radiators are well balanced.

I am stuck in a bit of a rut with it now. I am out of ideas and waiting for Octopus to contact me regarding the remedial works and the set up. The installation audit was on 23 October and so far not a word from them.

At least it is working and we are not cold.

ColinS · 2 November 2023 09:10

I’ll have a look at the DHW comparison later today.

It’s interesting to see that your 9kw unit seems to have the same minimum compressor power as my 10.6kw - about 920-950w.

You can adjust the flow temp overshoot number between 1 and 4 degrees - if it is now on 1 then increasing to 4 will decrease the cycling frequency and might increase the COP a bit.

It does look as though the radiator system is too small for the heat pump BUT that means you should be OK at sub zero temps when mine is struggling. Incidentally they did try to sell me a 16kW unit to start with - maybe they knew about the low temp performance drop off.

When I have a moment I’ll see if I can replicate your system on mine by shutting off a portion of my radiators.

ColinS · 2 November 2023 09:13

Field Code 9-04 for the flow temp overshoot

matt-drummer · 2 November 2023 09:44

Hi Colin,

Yes, I don’t think there is an awful lot of difference in any of the heat pumps in the range.
My minimum output is very similar to yours in terms of power consumed and heat produced.

The performance is better in the morning when the house is a little cooler.

It all points to radiator issues and I am sure it is the sizes. It’s in hand though as I have most of my new radiators. I am just about to order some K3s for the the rest.

I knew that they were not big enough as I had already done my own assessment before the Octopus heat loss survey.

I am not sure how much better it will make it but it will eliminate any doubt of the radiators holding the heat pump back.

It’s not that the radiators are too small for the house, at 6c outside they can heat the house at 30c flow with no problem.

The heat pump is too big for the heat loss of our house and cannot operate at a low enough output for the heat required.

We’ll see.

Thank you for the overshoot advice. I have seen that and I wasn’t sure if it related to room temperature or flow temperature. I can’t remember what I have it set at, it’s either 1 or 2 but I will check when at home later.

I don’t recall seeing much in the manual about it, or anything actually?

One thing that is mentioned is concerning modulation. This is mentioned when setting the emitter type.
It talks about enabling modulation when radiators are selected to compensate for something but I don’t really understand what it is talking about.

I have enabled modulation and it is set at 10, I think it can be varies between 1 and 10.

Do you know anything about this setting?

ColinS · 2 November 2023 09:48

Your system first hour on this morning, outside temp 11.5c

My system, first hour this morning, outside temp 9.5c. Similar room temps for both.

Compressors behaving identically the only puzzle is why yours switched off after 50 mins. The flow temp you are recording might not be the same as what the Daikin is reading? I say this only because the flow temp was not continuously going up when it switched off…
Here is the same data for my unit but taken locally and I have added the Daikin Flow and return temps which match closely with the probes I installed (double lines). It also shows the pump speed green lines which yours is probably mirroring.

ColinS · 2 November 2023 09:52

My house is 230m2 vs 120 m2 so this rings true for 10.6kw vs 9kw heat pumps

matt-drummer · 2 November 2023 09:53

Hi Colin,

How did you retrieve the information from the heat pump?

I actually have all that I require to install Espaltherma, except the skills and knowledge to get Home Assistant installed and working.