Just joined today and I have the same issue on my 7kw . My heat loss is definitely over 7 at -3 so it’s the first winter. Don’t shoot me down but I did install the system myself and used a 2nd hand pump. Works well on HW with my mixergy cylinder. On heating was having issues do paid for valiant come out service and they replaced the diverter and charged from 700g to a full re gas . I think 900 ISH. Anyway pump is a late 2021 model. All good but it’s a bit of an angry fridge when doing hot water or it’s 0 Deg. My heat curve is 0.75 do it works hard and as I say heat loss is over 7kw @ -3. I obviously investigated as an engineer ( not fgas) so panels off . Definitely imbalance in compressor at certain rpms . I have no warranty so this is not a let’s get it fixed gripe, it’s what it is. I say noise is tolerable, but I know if it’s cold outside. My system is outside a kitchen with 35mm primary on Tesla flex. Hoses so minimum transfer of vibration, but I notice it. No ya gonna shoot me down but I feel this push efficiency is resulting in small pumps being used, I follow the urban plumber and like his thoughts, but and here it is yes you get cycling that kills efficiently but in say - temps to say 5 ISH then s bigger pump would be better. Ok warm it cycling but the warm temperatures mean low running cost so what’s the issue , a trade off of efficiency when cost is low ? . I wanted arotherm as it’s quiet for the noise levels. Also it sorted of over performs for 7kw. I think we should put not silly large pumps in but bigger, just a bit and hope the manufacturers give better options.
Hello @ukpaisley and welcome!
I think that’s where a lot of us have got to now with Vaillants and a large part of the reason for the initial misunderstanding about output capacity was believing that the max output tables in the Vaillant datasheet were correct and included defrosts. The 7 was said to be able to output 8.6 kW on the datasheet which should have been fine for a 7 kW real world heat loss but we’ve found based on the monitoring here it to be safer to not assume that more than 6.7 kW can be sustained for long periods during heavy defrost conditions.
If I assume I will install 30kwh of batteries, then on the days with low to medium electricity requirements I will be paying about 9p per kwh including charging/discharge loses, but my marginal cost of electricity on the coldest days will be about 27p per kwh.
(But impossible to model problem of losing 15p for each kwh from PV that I fail to export.)
So saving a kwh on a very cold days is worth the same as saving 3kwh on a normal winter day. Efficiency loses due to cycling on normal winter days may be a price worth paying for a higher complete heating efficiency on the coldest days.
But the 10kw Vaillant seem to cost a few £k more then 7kw, and that pays for significant 1cop additional heat on a few days a year.
It seems that y’all are talking exclusively about the AroTHERM Plus (*/6
), not the Split (*/5
)?
No such problem with the Split AFAICT, at least not in BE/NL. (There’s a lively Vaillant HP owners thread on gathering.tweakers.net.)
Splits are not practical in the UK due to f-gas regulations and unwillingness of UK domestic plumbers to pay for the f-gas cert. (Our f-gas people don’t know about radators/ufh)
Splits also cost significantly more the monoblocks in UK.
hi Trystan ,
I know the vaillant have been the main topic on this, but do you know of any similar issues with Mitsubishis ecodans?
Especially the 11.2?