So what happens to EnergyIntegral in that case? Is it frozen at the value when the pumps turn off and continues from that point when the next cycle starts?
It freezes it. 07:30 to 11:30.
But strangely, when the heating restarted, it let it drop to -90, even though i’m on the default -60.
PS. I also HATE how Energy Integral is frozen when DHW runs kick in as you invariably end up with a very short first cycle coming out of the hot water run.
Oh god yes. My DHW run is already triggered by HA, so I’m thinking about timing the run with a sensible EnergyIntegral value so it properly runs after the cycle. The other idea would be to automatically inch the desired room temperature up a few notches after the DHW run to force a longer cycle. Any other ideas are welcome.
Edit: Remembered another idea I had the other day, which I guess is only applicable in conditions when the heatpump is cycling (i.e. always for me). After a cycle is just finished and you’re in the compressor shutdown phase shortly increase desired room temperature by a large amount to quickly accumulate a negative integral. As soon as it is close to the starting value (-60 or -100 for me) start the DHW run. This way you should get a full heating cycle at the end of the DHW run.
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I think if you turn heating circuit off and then on again, this will reset the energy integral. That might be an easier approach. You’d detect when DHW run is happening and turn heating off, then when DHW is done, turn it back on again. Should start at minumum then.
If you want to get slightly more complex, only turn heating on once flow temp has dropped to a certain threshold. As, at least in my install, flow temp right after DHW run is still hot abd causes integral to rise faster.
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A much better solution, thanks. I just tried it out, works nicely!
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I think that your HP is oversized… and you’re strangle it with a low flow rate… “the higher the flow rate, the lower the flow temp” says UrbanPlumber so yes, open your radiator valves, they have to let the heat go out to the rooms to lower return T and improve DT, try with pushing the pump to 75% or even higher and lowering the Heat Curve
maybe not big enough
But the 7 kW HP do more even at the minimum !
my 5 kW goes up to 1600l/h at 100%, auto is 860 l/h = 50%.
that’s more heatloss before to reach the house…
Hi I don’t understand what that should mean. The flow temperature is set by the heat curve and outdoor temperatures alone. I have the heat curve currently at 0.5 and the flow rate is currently around 1010l/h. Flow temperatures I think are rather low compared to other people’s, who still have better COP. That’s why it’s a mystery to me.
The heat pump being oversized is everyone’s first guess and it is obviously my best assumption, but I want to understand better how that manifests itself. I need a bit more knowledge and data to confront the installer.
Essentially, I understand it should mainly be the number of starts/short cycling. Unfortunately I don’t have proper monitoring, but I don’t think cycling is really any worse than fur others with great COP. The average runtime per start is 1.25h in total. On proper heating days, I have seen the unit run nicely at around 30% modulation. Perhaps I need to log it a bit more often and now down compressor starts day by day…
In what other way could an oversized heat pump explain bad efficiency, other than cycling?
The dT is very low at around 1-1.5K but with the high flow rate, that’s still a lot of energy. So for a better COP, the energy consumption would need to be lower. Could something be causing a higher consumption?
I thought I needed to increase dT somehow, but without lowering the flow T, this means the return will require more heat and compressor would work harder?
Is it just that the compressor runs to long around 25% which might not be the optimum? In that case, would I need to strive for shorter cycles with slightly higher compressor modulation?
Decreasing the flowrate will help. Actually for radiators a delta T of 3 is ok and for underfloor heating a delta T of 5… You need to give time to the water to cool. Otherwise you are just circulating the heat without letting it to utilize in the house. Lower return flow temperature is actually alot better for the heatpump and the compressor itself. This causes higher efficiency on all levels - heat pump COP, lower waterpump consumption, beter work for the EEV and evaporator…
The time shown on my (newly installed) sensocomfort appears to reset to GMT+1hr every night, whether Daylight Saving is set to ‘Manual’ or ‘Automatic’. I cant find a time zone setting anywhere on the system. Vaillant told me on the phone to uninstall and reinstall MyVaillant, which has made no difference.
Has anyone else encountered this bug and if so whats the fix, alternatively has anyone found a ‘time zone’ setting?
Many thanks for any help
With mine (5kW unit) running to heat rooms to 21 deg, it runs pretty much continuously delivering heat. I only run it from 09:00 to 23:00 each day.
However, we run the rooms to 19 deg for the morning until 14:00, and during that time, it stops and starts. So in my opinion, it is oversized for 19 deg but perfect for 21 deg.
If I lower the heat curve value (it’s at 0.65), then rooms will never get to 21 deg in the evening.
But I have to say, that seeing my data on heatpumpmonitor is essential to validating what you “think” might be happening. The graphs make things very visual.
The way I understood it is that Vaillant keeps flow rate constant and in Auto mode will always try for the maximum flow rate of 1205l/l in the case of our 7kWh. This requires 61% pump power in our case. Someone mentioned this could be pushed higher and higher would be better, but I don’t think this is how it works. Also, I think lowering the flow rate doesn’t necessarily help. It didn’t seem to have any effect in ,my tests so far anyway. Lowering the flow increased dT, but the amount of energy transferred might well have stayed the same. With a high flow rate you don’t need such a high dT for the same amount of energy than lower flow with higher dT. I made a table for different parameter combinations. Keeping flow constant, it depends on how much energy is consumed and how big dT is:
The COP there would be the instantaneous COP. For longer COP you would need to estimate what each cycle uses. For us it looks about right, at dT around 1K, during mid cycle around 0.5-06kW and including some extra for compressor starts, around 0.6- 1 kWh used per hour the COP from the table is between 2.4-3.3, which I think matches well what we see (currently daily COP around 3, for dT I only have records when manually checking).
Now I wonder, what I can improve if anything. Lowering the flow rate e.g. to 850l/h as mentioned has not improved the COP and this might make sense. dT increased, but not so much, and quite in line with the calculations (~1.8K), compare with the same calculations using 850l/h:
So, how do I get a larger dT WITHOUT reducing flow NOR increasing consumption? I would think larger radiators would do it, but according to this simulator, the dT is not at all affected by radiator size Heating Simulator ?
I guess I need to look closer at consumption. When running. however I get very sensible values for consumption, so number of compressor starts could be the culprit? Average is around 1.25hours compressor runtime per every start. last couple of weeks 1.99hours/starts. That doesn’t sound too bad I guess, but is the average misleading?
I often see the compressor around the 25% mark, but also at 30% for a longer period, so looks OK.
Or do I just need to the windows open to satisfy my oversized heat pump and finally get a good COP ? 
true, I have wasted so much time clicking through the menu on the controller and don’t have the time or mental capacity to really analyse my records properly.
I wonder if I should invest in having that installed, or if someone with experience can definitely tell me that the ASHP is simply oversized. So far, I am not 100% certain, and monitoring might help to optimize, but it might also just show me more depressing data of something I cannot change anyway.
To me it is still a bit of a mystery, because I just don’t see clearly how the oversizing would affect our COP/SCOP (low heat curve and flow T, warm house, no excessive cycling as far as I can tell at the moment).
Can you please specify what do you mean for low flow temperatures? Whar are your flow temperatures? Flow is important criteria for COP but not so much. Also how do you measure the COP ot the system? I guess you use the menu from Vaillant? Also by volumizer you mean a vessel of 40 litres with the flow pipe from heatpump in and a flow pipe for the house out? We will discuss your calculations later.
So I looked back to your initial post (#613). You have a 7kW unit feeding i cylinder and a volumizer.
So the 28mm pipe comes into the house and I assume hits a 3 port valve to EITHER heat the cylinder or heat the water via the volumizer in the attic. So you have the guts of a 10m run to the volumizer and 10m back again.
So with the Volumizer, are two of the four ports closed off and no longer in use ?
And I wonder can you run for a day with no hot water ? Could the Hot Water be pulling down your COP figures ?
My heatpump is also really oversized, it cycles down to -10°C. It does not negatively impact COP, I’m getting a performance as per the datasheet. Vaillant has solved this issue quite smartly I must say.
This is impossible. If your house is as warm as you’d like, it requires the heating power given by cflow_ratedT. If you have a larger dT, you give off more power and your house gets warmer. If you want a lower dT, you necessarily need a lower flow rate.
Heat curve 0.40 to 0.45 most of the time so far. Currently 0.5. Room T mode Inactive, so flow T relating only to heat curve and outside T. Regularly flow T around 26-28°C for example. Currently 32.5°C at 7.5°C outside.
I only get the values from the app and the heat pump control unit. So far all seems to match up quite well, comparing.
Yes volumiser is a 4-port buffer (Vaillant 40L) now with only one in and one out and the other ports closed, i.e. a volumiser. It is placed on the flow side, whereas all schematics show it in the return. I wonder if that means anything but in my understanding it shouldn’t really make a difference?
I am sure I made a mistake somewhere 
Thanks
The only difference with being on the flow or return is that the water could cool before going to the rads (or UFH is applicable) rather than it being the opposite.
So with the Volumizer seemingly all good, are all of the rads open (no TRV’s) ? If you had 22mm pipework all the way to the rads, then I cannot see any reason as to why you shouldn’t be able to run at the normal full flow (2 x 15mm = the capacity of 1 x 22mm) once at least two rads were open.
So it possibly points to lockshield valves being closed down or there being some 15mm pipe sections along the backbone pipes between rads.
What makes me wonder was when you said about noise when running. That implies running hard, which you maybe wouldn’t expect if it was oversized.
Since you have the App, then you could setup Home Assistant on a PC, and pull the data in from the Vaillant Cloud, and even then upload it to heatpumpmonitor
The last one is:
How do you calculate your COP?
This a picture from the beggining of this topic that explains how to calculate COP of Vaillant heatpump.
Are your calculations in order with Vaillant explanations?
Hi Ivailo, thanks for all this. It turns out that:
- My VWZ MEH hydraulic unit shows on the screen an EEV outlet and an evaporation temperature
- The evaporation temperature did not turn up in the EBUS communication, it was not asked for, I am now asking for it.
- The EEV outlet temperature on the screen and on my RPI are the same values
- A snapshot during stable operation can be found below. EEV does not seem to step that much
- The snapshot seems logical apart from The EEVoutlet temperature, I still don’t get that. It can’t be an EEVoutlet temperature, for which there is no sensor anyway
- As per setpoint, there is no overheating.
- Subcooling setpoint is not achieved
| Parameter | Value |
|---|---|
| RunDataCompressorSpeed | 40.053 |
| RunDataHighPressure | 11.022 |
| RunDataCompressorOutletTemp | 36.651 |
| WaterThroughput | 1948 |
| Hc1ActFlowTempDesired | 34.874 |
| JRunDataFlowTemp | 34.459 |
| CondensationTemp | 34.400 |
| CondensorOutletTemp | 33.800 |
| JRunDataReturnTemp3digits | 32.527 |
| JRunDataSubcoolingNominalValue | 6.469 |
| SubcoolingActualValue | 0.500 |
| RunDataEEVOutletTemp | 10.1 |
| RunDataEEVPositionAbs | 55 |
| LowPressure | 4.200 |
| JRunDataEvaporationTemp | 3.050 |
| OverheatingTargetValue | 0 |
| broadcast_OutsideTemp | 7.965 |
| RunDataAirIntakeTemp | 6.92 |
| RunDataCompressorInletTemp | 2.965 |
| JRunDataOverheatingActualValue | -0.085 |
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Actually no idea what EEVOutlet temperature is? It`s a R290 unit right?