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My Heatpump App Setting Up - Level 2

Hi All,

Wonder if someone can cast there eye over my graph feeds and see if this is correct?

I have a 6KW Daikin Monoblock ASHP connected to a low temperature raditor systema and a 200l hot water tank. These are the details on the side of my outdoor unit.

image

Recently ive clagged in 3 sensors. 1 under the bottom of the heat pump for the ambient and the flow and return temperatures. (I lagged the sensors after photo was taken :slight_smile: )

As i do not have a heat meter I am going be the level 2 system guide on the open energy monitor. See below for reference.
image

Because I want the data in HA aswell I have done all the calculations in HA and MQTT them across to emoncms. I followed the guide below for the relevent caluations.

https://learn.openenergymonitor.org/sustainable-energy/building-energy-model/heatpumpmodel

So Ill copy my HA sensor.yaml code incase anyone else is interested or sees an issue with it.

“T_condensing”
"{{ (states(‘sensor.heatpump_flow_temperature’) | float) | round(1) + 277 }}

“T_evaptorating”
“{{ (states(‘sensor.heatpump_ambient_temperature’) | float) | round(1) + 267 }}”

“Carnot Practical COP”
{{ 0.5 * ((float(states(‘sensor.t_condensing’))) / ((float(states(‘sensor.t_condensing’))) - (float(states(‘sensor.t_refrigerant’))))) | float | round(1) }}

“Heatpump Heat Output Value”
{{ (float(states(‘sensor.emon_heatpump_power’))) * (float(states(‘sensor.carnot_practical_cop’))) | round }}

Ive set the My Heatpump App up and im now logging data.

Last night the heatpump ran to heat the hot water. Do these figures look correct? The heat output was indicating nearly 12KW? The electrical input was nearly 3KW.

Going back to the info on the side of the outdoor unit it states 6kw @ 4.26COP and calulation of the website.

Heatpump_output= Power_input * Practical_COP

6000= Power_input * 4.26

Rearranging the formula we get :slight_smile:

Power_ input = 6000 / 4.26 = 1408 watts (not sure what temp that is at???)

With that being calculated is 12KW and 3KW about right? Or have is just answered my own question. :grinning_face_with_smiling_eyes:

Maybe this a question for heatpump guru @TrystanLea?

Any help comments would be much aprreciated .

Cheers

Gareth

Hello Gareth, something definitely amiss there, is there any way that you are measuring 2x the power input to the heat pump?

Hi Trystan,

I checked today and the power input for the heatpump is pretty accurate.

It ran again yestoday and has similar readings to what is stated on the side of the heatpump. Around 1400 watts was equated around 5800W.

Is it possible that my heatpump can output more than 6kw in heat? I was looking at the technical data and its only stating nominal values. Maybe there are are min/max values that it run at? It does state max load is 18amps @ 230V which would be around 4Kw electrical input.

I suppose the only way I am going to solve the mystery with out calulation is to know the flow or install a heat meter?

cheers

Gareth

Hi Gareth. Interesting… I’m not exactly sure how many ASHPs are speed-controlled but a fixed-speed type would follow a heat-output curve where the heat output is considerably more when its mild out, and much less when its cold. Mitsubishi have a ‘flat’ output, but (I assume) slowing it down in mild weather (the speed value (Hz) can be accessed in the controller. Mitsi call this ‘normal’ output. Is it possible that yours actually goes to maximum revs? Your 6kW rating given at Air +7 and water at 30/35. This is a bit surprising because you really need to know the output when its sub zero… when you most need the heat. Anyhow, I wonder if your sensors are strapped on accurately enough… I mean for a heat meter they are immersed in the water. There could be an error if taped on. Did you use paste? have you lagged on top?

Morning @johncantor . Originally I strapped the sensors to the flow and return in the outdoor unit. I found that these sensor temperatures eventually dropped to pretty much the same as ambient when it hadnt ran for several hours. Meaning that when it fired back up again to heat the hot water the initial heat output values were incorrect. To remove this error I have strapped 2 more sensors to the flow and return where they come into the house by the hot water cyclinder. This way (and I hope you agree) the heatoutput ‘calculated’ value from these sesnsors will be more accurate. My understanding is the heat output calulcated value is only accurate during steady state conditions?
Inside the house I have recently strapped 2 of the DS18B20 to the flow and return using foil tape and lagged- so im hoping the error is minuscule. Graphs to follow for comparision :slight_smile:

Morning,

Over the weekend I did some more experiments. I have set up 2 heatpump apps to simulated the heat output.

First one I call “My Heatpump 1” uses temperature sensors strapped to the flow and return with in the outdoor heatpump unit(right next to the heat exchanger). You can see from the graph below that my temp delta between flow and return is around 4°C. And I get a heat output of up to 10Kw and steady state conditions doesnt start till around 00:40.

My Second one is called “My Heatpump 2” and this one uses the same calculation as above but the temperature measurements are taken from the flow and return pipes that enter my heating system(before any zone valves) inside my house. As you can see that the temperature delta between the flow and return is much greater. Up to 14°C at one point. 8Kw peak heat output. During heating the hot water I could physically feel by hand a large difference in temperature between the flow and return.

My conclusion is that taking the readings inside the heatpump unit are not accurate at 4°C delta. I feel that the because the return temperature measurement is so close to the heat exchanger there is some heat conduction through the pipework. Therefore taking the measurement inside my house factor’s out that issue and any losses in the heat pipework.

What do you guys think? @johncantor and @TrystanLea . As these calculated heat outputs are different. Which one do you think is more a true reflection on my installation?

I am able to borrow a ultrasonic Clamp on flow meter. I might see what the flow rate is and in l/s when my system is running and use the heat output formula to calculate it that way? Am I rightly think I can use that formula below?

Heatoutput = l/s * 4.19 * Temp delta

You opinion would be much appreciated :slight_smile:

Cheers

Gareth

Hi Gareth,

interesting to see your graphs. Question- does the circ pump start only when the heat pump starts? or is it on before and after? I note the flow and return are not together before the compressor starts… normally, looking for both readings being exactly the same is a check on the integrity of the sensors. What happens when the system stops? usually there is at least some pump-overrun. I have come across Ecodans before where the circ pump is on max speed, and flow is too high

The second graph implies the pump is circulating before the compressor starts because they are the same.
The return temperature is between 30 and 40. whilst on the first graph (what the heat pump ‘sees’) is more like 45°. It would be better if the return could go straight back to the HP at 30 to 40

What low-loss header arrangement do you have?

Anything in the way (buffer or low loss header) can be a hindrance to best efficiency. However, it is often fitted to stop problems happening when (for example) you have only 1 radiator on. Its a matter of driving your system efficiently. What make of ASHP do you have?

John

Hi John,

Thanks for your reply.

Answers to questions.
does the circ pump start only when the heat pump starts? or is it on before and after?
Im not 100% sure. I can see if I can pull this data. Im pretty sure the pump starts straight away then the compressor starts shortly after. Ive seen it when the pump runs for 2 mins after the HWT setpoint is reached.

What low-loss header arrangement do you have? I do not have aloss loss header

What make of ASHP do you have? Daikin Altherma ASHP

UPDATE: I have created another app ‘My Heatpump 3’. This uses the flow and retun temps inside the house (same as my heatpump 2 app). But this time I have borrowed an ultrasonic flow meter and strapped it to the flow from ASHP into my system (cant attached to return- no room). When my pump is running the flowrate is 0.46l/s or 1.66m3/h. Because I am new to this I downloaded the datasheet and looked at the pump curves on setting 3 for my system. Looking at the curves I assume my flow rate is good for just over 5m and does use around 120ws when running. Im happy that Im building a picture.

image

I have used the formla: Where 3.98 is the water density (because I have around 15% glycol in my system. l/s= litres per second and temp delta is calculated in realtime = flowtemp - returntemp.

Heatoutput = l/s * 3.98 * Temp delta

Heatoutput = 0.46 * 3.98 * Temp delta.

And here are the graphs.


Would you agree that these seem like more acceptable figures?

What other checks can I do to make sure my system is running at its best?

Cheers

Gareth

Hello Gareth, so replies below

[gjones84] gjones84 https://community.openenergymonitor.org/u/gjones84
9 November

Hi John,

Thanks for your reply.

Answers to questions.
does the circ pump start only when the heat pump starts? or is it on
before and after?
/Im not 100% sure. I can see if I can pull this data. Im pretty sure
the pump starts straight away then the compressor starts shortly
after. Ive seen it when the pump runs for 2 mins after the HWT
setpoint is reached. This is probably quite normal
/

What low-loss header arrangement do you have? /I do not have aloss
loss header.
Have you 1 pump of 2 on your system? A sketch of pipe connections
would help… Given that the return from heating was lower than the
return to ASHP makes me assume there is mixing going on. Mitsubishi
cyclinder has a low loss header in it. I try to avoid low loss
headers unless its unavoidable.

/

What make of ASHP do you have? /Daikin Altherma ASHP Is it 9kW?
/

UPDATE: I have created another app ‘My Heatpump 3’. This uses the flow
and retun temps inside the house (same as my heatpump 2 app). But this
time I have borrowed an ultrasonic flow meter and strapped it to the
flow from ASHP into my system (cant attached to return- no room). When
my pump is running the flowrate is 0.46l/s or 1.66m3/h. Because I am
new to this I downloaded the datasheet and looked at the pump curves
on setting 3 for my system. Looking at the curves I assume my flow
rate is good for just over 5m and does use around 120ws when running.
Im happy that Im building a picture. That flow rate looks what would
be expected on a 10kW heat pump

image

I have used the formla: Where 3.98 is the water density (because I
have around 15% glycol in my system. l/s= litres per second and temp
delta is calculated in realtime = flowtemp - returntemp.

Heatoutput = l/s * 3.98 * Temp delta

Heatoutput = 0.46 * 3.98 * Temp delta. _This all looks good. _

And here are the graphs.

Screenshot_20211109-123742_Chrome
https://community.openenergymonitor.org/uploads/default/original/3X/4/7/47d88ae3f833aa9d90a218086e2d38edd495ecfd.jpeg

Screenshot_20211109-124043_Chrome
https://community.openenergymonitor.org/uploads/default/original/3X/4/1/41d05badf570bdf20cc0a0488d6a37fb9ae5911a.jpeg

Would you agree that these seem like more acceptable figures?

Screenshot_20211109-133938_Chrome2
https://community.openenergymonitor.org/uploads/default/original/3X/6/b/6bf6d4e734c3454a296ed4431c6d35d12d701cb6.jpeg

What other checks can I do to make sure my system is running at its best?

I’m not quite sure of your pipe config, but I tend to want to see
that ASHP flow temp = same as flow to radiators (is it rads). And
also that return from heating is the same as return temp to rads, BUT
this may not be achievable if several rads are off.

Your flow and return are quite high, but I’m guessing you dont have
enough radiator area to be able to keep the temperature lower? I’m not
sure. It seems to rise up to 45°C quite quickly

Hi John,

Ultimately this is what I’m trying to figure out is mine is a 6Kw heatpump. But does that mean that’s its max output? or is that 6Kw at its max COP of 4.26? If you scroll up I’ve posted a photo of my heatpump details.

My system is pretty simple. I have a outdoor unit with a single circulator in it. That goes to a 3 way valve that either heats the hot water or diverts the water to either 2 of the zone valves. Upstairs or downstairs heating.

The heating cycles I have shown so far are just hot water heat up cycles.

I’ve got my hotwater Setpoint set at 42… What do you recommend as setpounts for hot water and radiator Temp?

Cheers Gareth.

Hi Gareth, that looks nice and simple. I like systems with just one pump. The thing to look out for is that bypass valve. Ideally if would remain closed, BUT if you have few rads on, then the valve will have to open. I have found them tricky things to set up. Re your output… for Mitsubishi’s the ‘standard’ output is capped to the rating . i.e. a 5kW unit gives 5kW. this however drops when well below zero. The output could be higher in warm weather but I guess Mitsi reckon that you don’t want more heat when its mild. I don’t actually know what other models do… WRT your radiator temperature., whilst the lower the better is preferable, you will run into trouble when only a few rads are on, and it might be better to run at a higher temperature. at such times. I guess its a matter of doing some experiments. Can you arrange some ‘collaboration’ with you rads and zones? i.e. for some of the time, keep a lot of rads on. This helps give some long low run periods. If you need to run a small zone only… so be it, but hopefully that would be a relatively small amount of the total