Glad you found it useful Tom.
Are you able to break out heating and DHW COP?
Obviously the integral issue only relates to space heating.
What curve are you on? What’s your design temp?
Have you tried playing with the curve?
My Arotherm 5kw unit (installed 9/23) has the firmware bug and I’ve obtained a new updated control board from Vaillant, ready to fit.
I’m contemplating doing this swap myself as I have a background and experience which gives me confidence to do it, providing the swap just means the physical removal / refit / re-plug connectors while observing electrostatic protection, etc.
To those who have done the swap (or had it done), are there any other issues / settings to be done, please? Does the warranty need to be updated with Vaillant?
Ultimately, I can wait till next service for a ‘qualified’ person to do it, or am happy to do it myself if it’s a simple 'switch-off / open-up / earth-down / swap / close-up / switch back-on sort of job. Comments welcome!
Finally thanks as always to @Zarch (Mick) for the excellent write-up for the firmware issue.
Andy
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Did they make you buy it?
No, I managed to get it free. I spoke to Vaillant’s UK Product Manager for heat pumps at last year’s Everything Electric show at Farnborough. Armed with @Zarch 's write-up, I asked about the firmware issue (which they knew about) and they offered to have the board replaced by Vaillant service. In trying to subsequently set up a service visit, Vaillant declined to do the visit because I couldn’t answer their questions about easy and unobstructed access to the unit - I was having some building work done. I think they were being unnecessarily ‘picky’ but accepted their offer to send me the board anyway.
Andy
Good. I also got it replaced FOC (it’s my before/after data in the blog). Others not been as lucky though.
I watched my installer do it. Looked pretty simple.
Switch unit off. top lid off, front cover off.
The board is in a waterproof box at the front.
unplug, plug new one in.
put back in reverse.
If you’re unsure though, i’d get an installer to do it for you.
I specifically asked Vaillant what they needed to know when we swapped the board and they said nothing.
You’ll lose compressor / COP history as that’s stored on the board.
Hey no worries. Glad it helped!! 
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Thanks, Mick - very helpful. I’ll wait for better weather and have a go at it.
Cheers, Andy
Yes it’s about 3.6 heating 3.0 hot water across the two years using 48C water temp although water will drop in future as I’m heating the tank hotter at night now as I’m on an EV tariff now and I can get away with one heat per day at 8p per kWh if I do a nightly legionella cycle which takes the tank up to about 65.
Heating curve is 0.8. I’ve played a lot with hesting curve and radiator balancing (opening as much as possible) and this is what seems to hit target temp most consistently. Design temp was 50C which I’ve set as a cap for heating and in practice it never goes above low to mid 40s (we have house at 20C). I don’t use adaptive heating curve or room temp moderation.
My set up is a bit odd - because I’m close to a neighbour planning permission required me to run on quiet mode between 10pm and 6am so in winter the heat pump has quite a hard start as house temp drops 2-2.5C over night. Also efficiency is impaired because planning required having the heat pump as far away as possible from neigjbou’s bedroom window which means it is in a bit of a three sided box down the side of my house. I’m fairly sure I’m getting cold air recirculating in cold whether as air inlet temperature can easily be 4c below ambient temperature on a very cold day. So given these factors I’m ok with the efficiency but would always like more!
I’ve decided to get my engineer to change the board at next service.
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Hi Mick
First time poster here so go easy on me. Really interesting read and only had my ASHP for two weeks or so, I’m still learning.
With regards to Energy Integral setting (I think it is Compr.start heat.from, please correct me if I’m wrong) but do you recommend setting this to -100 from the -60?
I think I’m have the latest firmware on mine but will check.
Hi Yogi,
welcome to the forum. This is mainly a comfort question in my opinion. I’m running at -100, but there is mote time between cycles and the rooms cool down a bit more between cycles. For me, that’s around 0.3 °C max, so totally acceptable. It might be different for your house, so you should try it out. Pick the lowest value you find OK in terms of comfort. The number of cycles probably won’t be critical with either -60 or -100, Vaillant has a pretty good algorithm there. How many cycles per day are you seeing?
Hey Andre
I’ll experiment with it and try -100 or somewhere in between. I’m generally getting longish runs when warmer temperatures outside but it’s generally around 2.5 degrees outside the unit starts cycling which is normal due to the added moisture in the air.
I’m wondering if -100 will give me longer runs and improve COP, will try and feedback on here.
I do need to check the other bits out that Mick outlined eg firmware etc. I’ll check my cycles out too and post here.
I experimented with the COP impact - it is hardly measurable. On one hand you spend less time in the ramp up-phases at -100, on the other hand you have higher flow temperatures towards the end of a cycle. My main reasoning is reduced cycling leading to reduced wear even if the cycles at -60 are still within specs. But my heatpump is always cycling due to massive oversizing, so this is an added precaution.
It may improve COP marginally but there isn’t that much in it. So I wouldn’t reduce to -100 unless it has no impact on comfort. By comfort I mean room temperature flucations when cycling…
If you have radiators you probably don’t want to reduce to -100. However if you have UFH in a high-mass concrete floor then you likely can. It depends on each house/install.
Check what firmware you have before changing this value, as if you have the old firmware, setting changes won’t make effect.
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I have it on -100 with radiators. Fluctuations are between 0.2-0.4 °C, that’s tolerable in my opinion.
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I’m also running -100 with radiators on the Vaillant I installed for my parents, it increased run times with not significant indoor temp fluctuations: https://heatpumpmonitor.org/system/view?id=75.
The living room where the indoor sensor is gets lots of solar gain, so this can affect the indoor temperature sensor readings.
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It’s also going to depend on design flow temperature too. If you have radiators with 50C design temp I would assume you are likely to get more flucations than if you have 35C design temp.
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I’ve just checked my firmware and luckily I have the latest version so hopefully won’t have the bug outlined in Mick’s post and blog.
I’ve changed it to -100 today and experiment with it and see how I get on.
It’s early days for me as I’ve only had my system installed about 2 weeks ago.
Data here
https://emoncms.org/app/view?name=MyHeatpump&readkey=8f21605274780a0df694c37d97b64bd1
Everything working really well and learning how to function and ASHP moving from a combi boiler.
Our system is designed to 35 at -3.5 degrees, full radiators, no underfloor heating
We had an initial issue where myself and my installer believed the ASHP was under gassed as it wasn’t able to get to the flow temps easily enough which is should have been. Vaillant engineer come out and since getting Vaillant out and regassing it the ASHP has been fine and working lovely.
I’ve checked the cycles what Mick mentioned and so far with limited data it’s at 0.03 cycles per hour so far (I think that’s right). Will post full stats on here tomorrow.
I think it would be the other way around. Heating depends on the temperature difference between radiator and room. A 3K over/undershoot is roughly 10% of the nominal difference at 20°C room/50°C flow. At 30°C flow, this translates to 30% deviation from the nominal value.
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I’m trying to get to the bottom of a cascade of Aerotherms not behaving as they should. Even with a single pump running behaviour is not as I’d expect. I’ve just spent a fun packed hour sat in a cupboard recording the Energy Integral, Target and Actual Flow values from the interface. For sure I see the double counting issues with the integral falling quicker than it should, but I’m also seeing the pump do some strange things. I run pure WC, so nothing else should cause the pump to cut off.
Issue 1 - Pump goes into standby before integral gets to 0, so in the hour I spent watching it went into standby when the integral was -7, -19 and -26.
Issue 2 - When in Standby the integral doesn’t update on the interface, e.g. stays at -7.
Issue 3 - The target flow when in standby goes from the WC calculated value of 29 to 45. I did wonder if this was the max flow temp from the Sensocomfort as that was also set to 45 but that might have been a coincidence.
Issue 4 - When in standby, the actual flow temp reported by the interface fell gradually as I’d expect, eg by fractions of a degree, but after 5 minutes of the interface showing an EI of -7 it suddenly appeared as -61 and the pump started again.
So for those who have witnessed the 351.06.07 firmware issue, did you witness the pump going into standby at 0 integral as it should or has anybody else seen this sort of behaviour.
Thanks,
Dave
Unfortunately I have no experience with cascade systems Dave.
Have you tried Vaillant technical support? or your installer?