Many thanks for the article and this helpful thread. My install is only 7 months old and no third party monitoring so I don’t have all the figures, but:
Arotherm Model: 7kW
Firmware Version: 351.09.02
Pre-Install Heat Loss: 5.684 kW estimated by installer. My estimate is a bit lower: 60m2 floor area, 1950s ex-council house in the Highlands with external wall insulation, 100mm loft insulation and double glazing so maybe 60m2 * 65 w/m2 ~ 4kW?
Measured Heat Loss post install: TBC
System Volume: Not much. 6 small radiators and a towel rail. All new rads and pipework at install.
Compressor Hours: 594
Compressor Starts: 1174
Average cycles per hour (Compressors Starts / Compressors Hours): 1.9
What outside temp your system goes from constant steady state running to cycling: not sure, maybe around 0 degrees??? I don’t have any monitoring so it relies on me watching the thing.
I have just reduced the energy integral to -100degree mins. I’m hoping the cycles per hour will reduce going forwards.
The sensocomfort estimates our combined cop so far at 4.3 so maybe not too bad considering. This October is up to 4.5 with some tweaks. Granted, these values will be inaccurate.
Any advice in getting the most out of an oversized heat pump is welcome.
Glad you found the article useful Alistair. At least you’re on the latest firmware.
Shame you ended up with a 7kW as it sounds like a 5kW would have been fine.
There doesn’t sound much you can do other than ensure you keep your rads as open as possible to ensure working system volume (use TRV as upper limiters only and tweak curve down instead if rads getting too hot).
COP of 4.5 is good. My combined COP in October was 4.65 (heating 5.2, water 4.1)
Thanks Mick. Yes, I was relieved when I checked the firmware version. Thanks for the tips. I’ve been keeping the TRVs fully open but our bedroom stays too warm at night, so I’ve been experimenting with turning that trv down which is probably bad for cop, but not sure what else to do. I can probably go a touch lower on the heat curve but waiting for cold weather to adjust this.
Fairly limited data but the change to -100deg mins on the temp integral seems to have boosted my combined cop for the first 5 days in November to 5.0 (valiant numbers). This is higher than anything I have seen since the install in April. Anecdotally, and looking at our smart meter usage it seems like the heat pump is doing longer cycles as expected and has made quite a step up in efficiency. I wonder if this effect is exaggerated in slightly oversized and low volume systems? I’m quite surprised and happy to be honest. Will keep an eye on cycles per hour and update as winter progresses.
I have looked at this as well and see very very little difference in efficiency. Be wary of Vaillant’s COP numbers, they include standby pump and electronics use. This means that when you are at the heating threshold you will see a lower COP which is dominated by standby electricity use over the little heat you need to keep the house warm. As it gets colder, COP in the app will rise at first only to drop again as it gets even colder. This is only the total COP looking at all the electricity used vs. heat generated. Looking at just the compressor efficiency you see a steady monotonous increase with temperature as you would expect, but Vaillant’s app doesn’t show you this.
Vaillant changed the board at my expense. The first three weeks of heating this year (from 4th Nov), compared with same period last year resulted in COP changing from 4 to 5.1. Outside temperatures pretty comparable but lower thermal gain in the house. Judging from this result, I suggest it is not just “some geeks making a fuss” and that there has been a notable impact on performance!
Not to discard your experience here, but thats more than 20%, which would be huge if true. The defective energy integral setting leads to roughly 2x the cycles, which according to my own experiments yields slightly lower COP but nothing quite as extreme as 20%. Do you have a link to two comparable sections on the MyHeatpump app pre- and post fix?
No data as I have never managed to get the ebus data into EmonCMS. Simply based on the Vaillant numbers from the controller, recorded weekly by hand. The HP is always running at lowest output at this time of year (<500w input, including pumps) and cycles are down from 6 in 4 hrs to 4 in 4hrs.
I just noticed that Vaillant has managed to restore the historical data from the old board (it disappeared from the app when board was replaced). The energy efficiency for Nov 24 is reported in the app as 5.1 and for Nov 23 is 4.5, so different to my manual figures. There was a cold patch in late Nov last year with some defrosts, so will be interesting to see how full month figures work out after the forecast cold spell this week coming.
They look exactly the same and even the sw-version is the same.
To me it looks, that you can use both.
Can somebody confirm?
Is it possible to keep the faulty sw-version in the inside unit and just to swap the pcb of the outside unit?
Some replaced both pcbs, some only on the inner or on the outer unit. I‘m a bit confused.
Vaillant swapped just the board in the external unit, yes. P/N 0010033771 on the box of the board they supplied. Everything seems fine since heating season started at beginning of this month.
@tom.delahaye fixed price service visit of £490 incl. Covers any issues they find during the visit. Vaillant did suggest a third party could do it cheaper, but that would have got them off the hook if things were not sorted by just the external board change.