MikethePump

More and more interesting. How did you arrive at basic system 08, did Vaillant or the installer set that for you or have you done your own research and configuration?

Dan F do you have buffer only or do you have the Hex module? Vaillant did suggest that in Europe they more often had Hex modules and that VF1 worked in those environments.

well yes I have but we are in the depths of Vaillant schematics here. I believe from the manual below we are section 1 Buffer only. This does state basic system diagram code 10. However section 3 Hex only also shows code 10. Confusing! https://www.vaillant.co.uk/downloads/aproducts/renewables-1/arotherm-plus/all-schematics-wiring-notes-1799366.pdf

That’s interesting. I contacted a senior guy at Vaillant yesterday who confirmed that in my configuration the VF1 sensor does need to be disconnected to avoid the problems I experienced. It may be that it only relates to my particular configuration?

Not entirely sure what you mean by that? Is that the decoupler where the glycol side is separated from the internal heating circuit? if so no we just have a simple buffer in one side out the other!

Hi J1mbo Thanks for your comment, very interesting. None of the things you mentioned were changed. The VF1 sensor was disconnected and the system restarted. I have data which show the flow temperature dropping from 65-70c down to about 45c as soon as the fix was applied. The heat pump went from running near flat out at 5kw consumption to about 2.5kw. Everything performed as expected with no other changes. I wonder if perhaps you have different firmware or something in the VWZ AI.interface unit. The issue for me was that the requested flow temperature from the VRC700 was always and still is correct. With VF! connected the interface unit/heat pump just seemed to do their own thing with the flow temp hitting up to 72c when say 47c requested. I have to say my experience with Vaillant has been very good once I got them to recognise the issue. I will follow this up.

Hi I spotted this post while searching for Vaillant schematics for the Arotherm Plus. (I was actually looking to see if new schematics had been released!) I have that heat pump with a basic radiator setup, cylinder and 40l buffer tank/volumizer. I had problems after installation with wildly varying and very high flow temperatures, heat curves not working and very poor performance. I had undershoots and overshoots of room temperatures, all very confusing. I am using basic system 10 It turned out that there is an issue in the controller logic (and the schematic) when using the VF1 sensor with a simple buffer/volumizer tank. Following investigation by Vaillant It needs to be disconnected!! The system then measures the flow temperature using the sensor in the heat pump. The system then performs correctly using the heat curves and correct flow temperatures. (I use heat curve of about 1.0-1.1) Performance is then hugely improved. I have an overall CoP of 3.47 since the fix was applied (includes DHW) and got 3.67 Dec, 3.17 Jan and 3.54 so far in Feb. Best heating Cop is 5.15 on 30th Dec, best DHW is 3.54 Overall very pleased with performance. I have an accurate, certified MMSP monitoring system to measure inputs and outputs giving a CoP, The Vaillant app and interface units seem to report an underperformance for me of about 18%, maybe rounding etc? I strongly suggest that you contact Vaillant technical support, they have been great once the symptoms were identified. The App does not show VF! temperature after the fix but it does show flow temperature as Heating Circuit 1 for me. Hope it may help

Hi all We have installed a Vaillant Arotherm Plus ASHP, we have solar pv and battery storage. An average house, reasonable insulation, double glazing and radiators throughout. Projects really to keep me active in retirement and to prove that heat pumps can perform in houses without underfloor heating and super insulation. All going well apart from energy prices!!