Thanks for those data, I’ll try increasing the delay.
Let me know if it works. Fortunately the bolus doesn’t wake me up but it would be interesting to know nonetheless.
Will do. It doesn’t always wake me so it may be a while😊
Apologies if this is old hat to group members, but I did a search and couldn’t find any mention. This is an eamil I received from app support:
"Thank you for contacting the Vaillant Group UK connected support team.
The old server is due to be decommissioned by the end of March
The sensoAPP and 700 apps are in the process of being upgraded to the myVAILLANT app on a new server.
All migrations to the new app will be complete by the end of March 2024
The VRC 700 systems migrations are currently underway and the new system is currently being prepared for the AmbiSENSE systems
Process for migrating to the myVAILLANT app
There will be an email and App notification when your system is ready to be migrated
NOTE: The myVAILLANT APP is sited on a new server and uses the email address as the username (unlike the old app where the username was independent)
# Create a new Account in the myVAILLANT app
# Login to the myVAILLANT APP
# SET up Home (name the gateway and add the gateway serial number
# Input the USERNAME and PASSWORD from the OLD app (so the new server can access the old account to transfer the data)
After this the system will update for 5 to 20 minutes to make the account compatible for the new system
Kind regards,
Vaillant Group UK"
Hi all, hope someone can help with this :
I installed a 125/6 monoblock with a hydraulic module meh 97/6, vrc and gateway. However, efficiency much lower than expected, therefore I want to study what is happening. Myvaillant app I have and even myvaillantpro. I can see trends in watertemperature, return temperature, pressure, statuscodes, but no graphs wrt compressure temps, eev, cop, flow. Rps, modulation pct. Myvaillant app can connect via eebus it seems, since I can switch it on in the app. What is the best way to get graps on everything or as much as possible that I can read on the meh, installer level? Which hardware/software?
By the way, having read the thread, under current warm conditions, system seems to control 2 degrees delta between return and water outgoing temperature, until it achieves target temperature. Then switch off and wait for temperature time integral. There is some water pressure stepping up/down, probably some flow control, I dont know what drives it. I have the integral at 90 degr*minutes, startup every 1.5 hrs
Hi JGJ,
your setup is similar to mine, I have the 105/6. Can you provide details on your house/emitter setup, e.g. expected heat loss at design temperature, type of emitters (radiators, UFH,…), weather compensation mode, design flow temperatures, flow rate etc.?
How do you get to the conclusion that efficiency is lower than expected? COP data from the myVaillant app?
2 degrees seems very low. Vaillant does not target a specific delta but is purely driven by achieving a certain flow temperature. If the flow temperature is above the target flow for a specific time (i.e. the energy integral rises >0), the system will shut down the compressor and just pump the warm water around until it has sufficiently cooled (i.e. energy integral is below your set threshold of 90°min).
Vaillant has notoriously bad temperature sensors and the whole efficiency calculation hinges on an accurate flow-return temperature delta. Please check what flow and return temperatures are when the compressor is off, e.g. between cycles when the energy integral is decreasing. If they are working as expected, both temperatures should be equal. If you see the flow temperature is lower than the return when the compressor is off, efficiency will be underestimated. In my system, flow is always 1.2K above the return, hence my efficiency is vastly overestimated.
The easiest route is getting the data from myVaillant into a local emoncms instance, but this will only give a very limited view as important metrices (like return temperature) will be missing.
Integrating MyVaillant app with EmonCMS - Hardware / Heatpump - OpenEnergyMonitor Community
The next step up is to set up a Raspberry Pi with an emonsd image and an ebus USB adapter that you can attach to the ebus data lines of your heat pump. This will allow monitoring all the data coming out of the heat pump, store it and graph it.
SD card image: emonSD Download — OpenEnergyMonitor 0.0.1 documentation
ebus adapter (unsure when you can get one): Reserve-my-adapter – ebusd
alternative ebus adapter (immediate availability): eBus heating bus couplers and gateways (esera.de)
You can then perform a simple calibration of the temperatures by adjusting for the wrong offset between flow and return within emoncms.
Thank you André, for extensive reply. Will answer one by one. House was built in 1878 in the Netherlands. Groundfloor 100m2 with 2 living rooms, kitchen, hallway, all separate with different levels of insulation. Upstairs similar surface, but not heated so much apart from bathroom and laundry room. Basis internet rules, ground floor heating would require 25 kW at minus 10 outside. Installed radiators combined is 16kW basis 75/65/20 C. This seems sufficient. Same radiators would do 5kW 45/35/20 I calculate.groundfloor 4 radiators open, 7 with trv. Upstairs 1 open 2 trv, 3 trv but hardly used. Flows I have seen between 1000 and 2000 l/h. Domestic hot water from combi hr, can use it for heating if required.
Myvaillant app last week cop 3.7, outside temp maybe 10, water temp 30. Earlier cop was lower. March 3.4. Heat curve control only. at 0.9, just adjusted to 0.8. 18 C at night, house tends to stay at 20C.
If picture is visible: this seems delta T control to me
Lower graph is pressure before the pump. Lower pressure is more flow I think. Water temperature and return quite aligned. However temperature measured at meh seems easily 4-6 C lower, wheras i can measure radiator to be in line with heatpump water temp.
Will dive into hardware/ software alternatives
@MadScientist For what it’s worth, my solution to this is using the time period programming. I set the heating off for 10mins before the scheduled DHW run and then resume heating 30mins after. I realised during the summer that the “rifle shots” following the DHW runs did not happen when heating was set off, and the divertor permanently in DHW position. I have aluminium thermaskirt emitters, and when the DHW bolus hit them, they would bow up by 2cm per 5m due to the deltaT between the flow and return sections of the emitter! It also sounded like war had broken out. Using the timer completely removes this issue in my case.
As an aside, I also run the DHW at 2pm which is the peak average outside temperature over the year here. That maximises DHW COP. I’m not worried about electricity tarrif as I have excess solar capacity most of the year.
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Andy, thanks for the reply. I found that if I resume the heating 30 min after the HW cycle, I still get some rad noise occasionally. However, increasing the time further to 60 min (as Andre suggested) appears to allow sufficient cooling of the ‘bolus’ to eliminate the problem. The temperature drop in the house even after 4 hours of the heating being off seems to be minuscule so I’m going to stick to this plan.
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Looking at your temperature graphs from myVaillant pro (how did you get access by the way?) it looks like the flow temperature actually does dip a bit below the return during the off phase, so I recon your COP figures will be a bit underestimated (you can probably measure the delta there in myVaillant pro). It would be great to have a more exact COP vs outside temperature figure than your eyeballed estimates. If you really only get 3.7 at 10°C outside something might be amiss:
At 10°C and 35°C flow, we would expect something between 5 and 6, except when the compressor is at full power which shouldn’t be the case for those temperatures. At max power, we’re at slightly below 4. Since your flow temperatures are actually below 35°C we should actually expect slightly higher COP values even.
Can you get us some more accurate data, for example screenshots from the myVaillant app where it shows the COP for a day and the average temperature as well? Along with your known weather compensation curve of 0.8 this would help better analyze whether there’s something wrong.
Thanks Andrė, I have the graphs from an installer, with limited experience with heatpumps. I had assumed that flow temp gets below returntemp when compressor is off, due to heat loss at the condensor. But maybe it is a sensor inaccuracy indeed. In myvaillant pro, difference is zero or 0.5 C. Temperatures are rounded off to x.0 or x.5 C. Screenshots below. I have reserved ebusd adapter. Software not possible on my synology ds214 play, but this is a next step
At those outdoor temperatures you should be around 31°C flow temperature and have a COP in excess of 5 unless your compressor is really running at full power. However, a 0.5°C error in flow-return will translate to a 20% error in delivered heat and hence COP as your actual deltaT is around 2.5°C. I would reckon that’s the source of the problem. You can do two more things: On the MEH, go into the installer menu (code is 17). There you can see the compressor speed when it’s running and also see flow and return temperatures down to 0.1°C in real time. Check the compressor speed when it’s on (in the middle of a cycle when it’s past it’s ramp-up phase) and also the flow and return temperatures between cycles. Then we’ll have an even more accurate picture.
Thanks, will check during the weekend. Btw, should electricity + natural source kw be equal to output heat? Numbers don’t match
Electricity use includes pump + standby; they’re probably subtracting that. See my reply here:
One other note: When it’s so warm outside, the energy just running the pumps between the cycles has a significant impact on COP. Have a look at this segment from my system. The COP when the compressor is on at 10°C outside temperature is 6.1 (almost exactly on spec). However, the full window COP with the pumps running in between is 4.7 (quite far from spec). That’s because I’m using so little electrical energy when the compressor is on (1.7 kWh) that the energy use of pumps + electronics (0.5 kWh) is really significant in comparison. Coupled with the error in your flow-return measurement that we saw on the myVaillant pro screenshot when the compressor is off, I think your system is performing exactly according to spec.
Very good points André, one minor remark: electrical power pump would dissipate in the heaters/tubes somewhere, it would still be heat, but not measured as dT at heatpump I’d say.
as promissed, herewith two operating points:
pump 100%, fan1 55%, fan 2 53%, EEV 26%,Twater 34.6C,Treturn, 32.7C, P 1.7, flow 1738, Tair 6.1C, Tcomp out 40.1C, Tcomp in 3.5C, Teev out 5.4C, T cond out 32.1C, Phigh 12.3 bar, Plow 4.4 bar, Tvapour4.5C, Tcondensor 38.9, overheat target 0C, act overheat -1, nom undercooling 7C, act undercooling 6.8C, rps 29.9, T outside 8.1C, T system -99C, ME in:open, MA2 out close, T heater out 28.7C. Compressor start -90Cminutes, compressor hyst 7C, Ttarget 34.5C, energy integral -77, elmpower 1.1kW, mod 27.2%
Between runs:
pump 65%, fan1 0%, fan 2 0%, EEV 44%,Twater 30.5C,Treturn, 30.8C, P 1.9, flow 1138, Tair 5.8C, Tcomp out 25.6C, Tcomp in 19.7, Teev out 13.4C, T cond out 23.3, Phigh 5.6bar, Plow 5.7 bar, Tvapour12.1, Tcondensor 11.6, overheat target 0C, act overheat 7.6, nom undercooling 0C, act undercooling.-11.5, rps 0, T outside 6.7C, T system -99C, ME in:open, MA2 out close, T heater out 28.6C.
-Would think T eev should be lower, it should be the temperature belonging to the pressure.
-T heater out should be T water, or at least above T return.
-Not sure what T system means, I have no domestic hot water vessel connected.
- am not sure whether ME, MA2 settings are correct, manual not so clear.
Between runs, Twater is 0.3C below Treturn. Sometimes 0.2C. Say 10% of dT. I see el. Power figures of 55-60 W when compressor is off. 1.4kWh/day. If this is 65% mode, 100% may be 2kWh/day if pump runs 100% 100%. But I see 2.2kWh/day gap sometimes in power balance.
Not sure how to properly calculate COP during the run without graphs on flow, elec power. I guess in above datapoint; (34.6-32.7)17384.186 kJ/kgK =13.8MJ/h=3.8 kW. COP= 3.8/1.1=3.5. With sensor accuracy correction 3.8-3.9
Graphs of today
Of course, the energy can’t just vanish 
. But the pump is not positioned between the flow and return sensors and hence is an external source that cannot be captured by the sensors (similar to the backup heater in the MEH). Actually you make a great point, thinking about it this heat would be captured by my external sensors at the pipes just where they enter the house, but 60W is too low to stand out above the noise, also probably a fraction of that is lost to the environment. (On second though, of course losses by the friction of water in the piping is not measurable, only losses in the pump)
Max pump speed is around 100 W I think so 2.4 kWh would make sense over a day. Probably the measurement accuracy at those low powers is also not that high, especially with an inductive load like the pump motor (my shelly shows a power factor <0.9, ).
Your measurements during the active compressor time indicate minimum power (30 rps).
Without flow measurement and an accurate capture of the data over the whole cycle it will be difficult to estimate COP during one of those cycles.
Do you have the outside temperatures for your datapoints or the whole day? The heat pump seems to have run without cycling for quite some time during the night (until around 7am) maybe detailed energy & temperature data for that portion could be used for a more detailed look. Flow&return seem to have been quite stable so that would be a perfect sample to analyze. So if you can get energy use, heat output, outdoor temperature and the deltaT for that time (say 6 hours from 00:00-06:00) this might give a clue on how close you are to spec COP.
Thanks André, the pump turns electricity into heat and mechanical power equal to pressure difference*flow. Ratio would be the pump efficiency. This heat would mainly be in the water in the outside unit and increases the water temp on top of the temperature rise coming from the heatpump cycle. The pressure difference, i cannot measure. However pressure before the pump drops from 2 to 1.7 bar between standstill and 100%. Would assume then 2.3 after pump, dP=0.6 bar. 0.6 x100000N/m2 x 1738 L/h= 60000x1738 N/m2x 0.001m3/3600 s=29Nm/s=29W. This mechanical power becomes friction heat in pipes and radiator (valves)
We also have 50 W modulating fans I just realised. Not sure whether it is 50 W each.
In the stable period yesterday, first 4hrs, myvaillant app gives for elect,source heat,gen.heat,outside temp; 0.838/2.0/2.7/6.6; 1.1/2.6/3.6/6.3;
1.2/2.7/3.7/5.7;
1.2/2.63.6/5.4. I calculate COP 3.2/3.3/3.1/3.0
There is something not right. Few weeks back, just after installation, there was also the error: temperature after compressor too low. I don’t have that anymore but it may be same issue.
Just received raspberry Pi, but need to wait for ebusd adapter.