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My aroTHERM plus is misconfigured


Bruno

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Well, not so happy today 

This night was warmer than yesterday, by ~5 degrees. I didn't change anything in the configuration, but 

-the HP was working intermittent all the time (picture attached) 

- the room lost ~0,6°, unlike yesterday 

 

What can cause this? 

- curve is at 0,9, temperature modulation 

- circulating pump is at speed 2 (out of 3)

- rads are balanced (correctly, I think ?

 

Thanks 

IMG_20220121_091733.jpg

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It looks ok to me - there's literally one cycle per hour. 10 minutes is often cited as the 'rule of thumb' minimum. Likely the total radiator output at the set point was less than the minimum heat pump output, meaning the set point was exceeded and eventually (at 0° minutes) the system shut down. 

 

That the temperature was not maintained suggests that the curve is too low.

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6 hours ago, J1mbo said:

That the temperature was not maintained suggests that the curve is too low.

It's strange how with a lower outside temperature it worked so fine...

I still don't really understand how the curve has so much importance over the setpoint temperature. If it's below the setpoint for so long, shouldn't it bump the setpoint until it reaches it? 

 

I did notice that the temperature at the buffer tank was around 40° which fits the curve setpoint. What should I do to increase the radiator output? Different balancing? Higher pump speed? 

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Maybe bump the curve to 1.0. Yes it will increase the flow temp as the deviation gets further away, but 0.6° is not very much.

 

Increasing the radiator circuit pump speed will reduce the dT across them. If it's somewhere near 5° as it is then it's probably about right.

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The last few nights were very cold again (1º at 8h00), still very dry and sunny days.

 

This was this evening's consumption graph, much similar to previous nights. Something I noticed is that after defrost kicks in (if that's really defrost, I have no way to confirm it) the consumption stays high at ~~2kW and never decreases again. Before the first defrost cycle consumption was much lower.

I have absolutely no idea what is that peak at the end (did not happen in previous nights). I only noticed this because it becomes a bit noisy when working at full power, so I went to check the energy meter.

 

I did check the unit's reported energy output and it was at ~~24kWh for today (so after 00h00), which means a ~~1,5 COP. I guess that's what it takes when it's just above freezing outside ?

 

img.png

Edited by Bruno
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Oh, I had no idea. Thanks ;)

My meter says 21,1kWh up to now, vaillant says 20kWh. Environmental yeld is 33kWh. 

So COP is 2,57

 

I'm still totally confused with be heating behaviour, can't get my head around this... 

Last night was cold, so flow temperature was high according to the curve. Higher consumption but the room temperature was kept. 

Now it's sunny, 13° outside. I already fixed the temperature sensor's position so it reads fine now. I bump the setpoint temperature to 22° on the "day" program, room temperature is only 20,5°. But the heat pump is stopping, because as it gets warmer outside, it reduces the flow temperature. This makes really no sense to me... 

I'm planning on installing solar panels also as a way to reduce the cost of heating during the day, but it seems a waste as the heat pump is only effectively heating the house at night... 

IMG_20220125_134821.jpg

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1 hour ago, Bruno said:

Now it's sunny, 13° outside. I already fixed the temperature sensor's position so it reads fine now. I bump the setpoint temperature to 22° on the "day" program, room temperature is only 20,5°. But the heat pump is stopping, because as it gets warmer outside, it reduces the flow temperature. This makes really no sense to me... 

I'm planning on installing solar panels also as a way to reduce the cost of heating during the day, but it seems a waste as the heat pump is only effectively heating the house at night... 

COP calculations aside? any thoughts about this?

 

edit: just looked at it again, 14,5º outside (so warmer), 20,3º inside. The room is still loosing temperature.

Edited by Bruno
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The VRC700 only shows the temperature in 0,5º steps but I have a digital thermometer (xiaomi) next to and the readings are within that 0,5.

For the outside temperature it's not that easy to check. Before when it was getting direct sunlight, it was measuring totally exaggerated values during the day, but now it isn't anymore. So I would say that it is now accurate.

 

But anyway I'm reading both temperatures in VRC700's display so that's also what the equipment "sees".

What I see from the buffer tank (in Multimatic) is that it's temperature is more or less OK with the curve: outside temperature 14,5, curve 0,9, setpoint 22º --> temperature in the buffer tank 36,5º (not sure what's the real flow temperature but I'd say it should be more or less that). However the room temperature is 1,7º below setpoint (and still dropping) and the heat pump seems to not care.

 

Tomorrow I will boost the "day temperature" to 23º and check if a bigger difference makes the HP "notice it".

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1 hour ago, J1mbo said:

 

(20+33)/20 = 2.65. The energy used by the compressor is mostly stored in the gas.

Oh, so that's how it works.  "Environmental yield" isn't clearly defined in anything I saw.. so assumed it was output.

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@Bruno Could the "system diagram" values in the schematics be wrong?  The manual I have clearly says that "8" is ASHP system without a heat-exchanger and "10" is for a ASHP with a heat-exchanger (HEX).  It also says that buffer management is available with both "8" and "10" but that it depends on you using a FM3 or FM5 functional module.  From your first post it looks like you don't have a HEX, correct?

 

My setup (hyrdaulic station + 25L buffer with no HEX or glycol even) has been setup with, and is running perfectly, using "system diagram 8".

 

 

Edited by Dan F
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6 minutes ago, Dan F said:

Could the "system diagram" values in the schematics be wrong?  The manual I have clearly says that "8" is ASHP system without a heat-exchanger and "10" is for a ASHP with a heat-exchanger (HEX)

I've been using the manual I linked in the first post as the first page says "for aroTHERM plus" and mine is just that ? I will see if I kept the printed manuals which came with the equipment later today.

image.png.cd0f706259ef49e6fbc5e56c5527955a.png

This is my setup and the configuration in page 5 says that "basic system diagram" is 10. I do, however, have a 100l buffer tank instead of a smaller (40l) as the manual says...

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I don't have that manual as mine is the VRC700, not the 720. But that makes me even more confused, so it's the VRC which defines the schematic and not the heat pump itself? ?

Because the manual that I followed suggests parameters for both the 700 and 720.

 

I can set it back to 8 for testing, not a problem. All of this started because I thought that 8 was wrong ?

Edited by Bruno
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1 hour ago, J1mbo said:

Why not give Vaillant tech a call. They are really helpful.

Thought about that, but I'm honestly puzzled about this and I'm curious to figure it out ?

 

Well the manual I have is neither of those ?

I have a "basic diagram block" for VRC700f/4 (which is correct) but it's from 2016, so it's totally useless for me... ??‍♂️

 

In other news I just got home, it's night and getting colder, so now the heat pump is now working continuously as it should. It's been cycling all afternoon with the room temperature still below setpoint. 

 

Looking at the manual where the parameters are described, I guess it's probably working as it should, although "what it should" might be kinda wrong ?

 

Temp. mod.: The built-in temperature sensor measures the current room temperature in the reference room. This value is compared with the target room temperature and, if there is a difference, results in adjustment of the flow temperature by means of the so-called "Effective target room temperature". Effective room temp. target = set room temp. target + (set room temp. target - measured room temp. target). The effective target room temperature is then used for controlling instead of the set target room temperature.

So basically what is happening is that I have 1,5° error which is added to my setpoint, which shifts the curve a bit. Taking those 14° outside, that would make flow temperature go from ~30° to some ~33° according to my current curve. Which is still not even close to enough with rads. 

Because the behaviour at night is now fine with very cold nights I would like to keep the current curve. And looking at the curve, I honestly don't see any other (even 4) which produces decent flow temperature with average outside temperature... 

 

Apart from the dynamic heating curve, I'm not sure if there is any further compensation over time. Maybe I'll try that. 

@J1mbomentioned in other topic a degree/minute compensation, but I have not find anything about that in any documentation... 

First I'll just set a higher setpoint during the day. 

 

I'm also preparing an integration with home assistant which hopefully will allow me to log more data. 

Edited by Bruno
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4 minutes ago, Bruno said:

I'm also preparing an integration with home assistant which hopefully will allow me to log more data. 

Using an ebus coupler?  Let me know how you get on with this as I'm interested to do the same given i) no modbus interface available ii) EEBus works well but is limited.

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5 minutes ago, Bruno said:

Not really. It works with the Internet gateway and polls the data like the multimatic app (probably equally as slow ?

https://community.home-assistant.io/t/vaillant-multimatic-integration/87240

Will take a look.  EEBus is very easy, especially from Loxone, where ebus is really quite low-level.  I wonder if this is something in between.  It seems it works with VR921 (sensoNet) according to docs.

Edited by Dan F
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21 hours ago, Bruno said:

 

@J1mbomentioned in other topic a degree/minute compensation, but I have not find anything about that in any documentation... 

First I'll just set a higher setpoint during the day. 

 

Degree-minutes is used by the controller to regulate energy supply. It's not related to anything the VRC700 is doing.

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