Bruno

So I was on the phone with the seller who provided this quotation. Turns out the 3-way valve isn't required because the DHW cylinder is to be connected as if it was a radiator, always connected and can't be disconnected, neither the radiators. According to him: - as the DHW cylinder is small and has a small "serpentine" (? It's the heating water circuit on the tank) is too small, it won't dissipate the heat produced by the ASHP, thus resulting in errors in the unit as the returning water will be the same temperature as the output. Q: is this really an issue? Can't the heat pump keep a big outside temperature (no matter the returning water until the temperature of the DWH cylinder reaches its setpoint and then shut off or divert to the radiators? - it makes no sense to use the heat pump to heat DHW without heating the radiators (eg summer) as the unit's COP will be 1, so it would be better to use an electric resistor. Q: does this make any sense? If there are 30 degrees outside and I want to heat the DHW to 55deg, is the COP worse? It goes against everything I read... I'm now a bit lost. Help?

Sorry for getting back to this. One of my quotations (the one I like the most) has both hydraulic separator and buffer tank. In this case I don't need a 3 way valve, but I don't understand how does it choose where to send the water to. In this case, should I expect a big temperature drop because of losses in both systems?

Uh, I thought it was mainly to prevent short cycling of the ASHP. I have a situation with my neighbour (which I'll probably discuss in another topic) where he has a 14kW LG, connected directly to radiators (no buffer) which is constantly working in peaks from 0 to 6kW (electrical power). Having the DHW in my case will also probably help having the buffer tank, right? When the cylinder is being heated, the buffer tank can continue to supply the radiators (although I would expect a quick drop in temperature in this case). What about the very different power ratings which I received, what do you think? And about the different models, any recommendation? (I believe the Vaillant would be better as it's more efficient and has a higher output temperature).

I asked some local companies for quotations, and I have to say I'm confused. I got: - 9kW LG Therma V - 8,5kW Vaillant aroTHERM Plus (2 quotations) - 12,5kW Vaillant aroTHERM Plus - 15kW "White brand" According to what we calculated here, the smaller ones should be more than enough, but the suppliers who quoted the bigger ones say that these are needed as the smaller ones would struggle. I also got quotations with or without buffer tank, the ones without include an "hydraulic separator" which I never heard of before. Oppinions? Thanks

I suppose that the biggest problem would be to have the necessary number of heaters as well as balanced power ratings. I can get a 2kW heater in the living room and another in a bedroom, but in reality I suppose that the proper way to do it would be to have several smaller heaters throughout the house. Nevertheless it's a great idea and I honestly never thought of that. And the math behind it is quite simple and was brilliantly explained ?

@J1mbo Thanks. That, sir, was awesome ✌️

I did look into it before, but although I understand the relation between the temperature and power, I have no idea how the difference will feel. The thing is, with wood I can run the heating during 3-4h at 70° and then leave it off for 20h until I turn it on again (and rest assured, if it's really cold outside, then after 20h it'll be really cold inside...) But what it if I have it on at 40° 24/7? Worse? Better? Can't tell.

Sorry for missing the correct English words. Elements is what is called here to the parts which make a radiator. In the attached image, the radiator is made of 8 elements. I'm not sure. The installers said that, although it would be a good idea to replace the radiators, as they're aluminium and with good surface, they should work. To be honest, that scares me a bit.

I have 63 "elements" in 8 radiators (from 12 to 5 elements each, depending on the room) and 2 towel racks. I'm considering replacing one of the radiators, the one on the end of the circuit as this usually gets less hot than the rest. As far as I know, a buffer tank is just a mass of water (the recommendation I see more often is 10l per kWh) between the heat pump and the heating circuit. The difference in the temperature of both sources is something I've been thinking about. All installers said that that's not a problem, even if the temperature is lower with the heat pump, it will be constant so the house will get comfortable.

Hi all. I currently have the setup as attached. Because I'm really fed up with wood (as it produces a lot of dirt, it's not possible to preheat and I need to burn wood every day for DHW) I'd like to install an ASHP, so I asked for some quotations and all the calculations point to 9kW. The goal is to install both systems together, so that I'm able to use the wood burner sporadically if I wish. I'd like to consider buying the equipment myself, then get a certified installer to... install ? - should I add an additional buffer tank? I've seen several schematics where a buffer tank is not represented, but the quotations I got do mention it - is it a good idea to buy online or is it too risky? The risk seems to pay off, as I've seen deals online much, much cheaper than the quotations I got. - I'm getting quotations around 7000€ (heat pump, buffer tank, accessories and installation). What do you think about this value? Thanks.

Thank you for the welcome ? In my case it's more about convenience. I use the "back boiler" for both DHW and heating, which means that I have to burn wood pretty much every day of the year. Not good when it's 30º+ outside ? (I do have an electric backup heating resistor which we use when it's terribly hot). About heating, I use 6-8m³ of wood each winter. It's not terribly cold in Portugal of course, but it does get cold. The main problem with wood (apart from dirt...) is that you can't preheat. It's really bad to get home from work in a very cold day, tired, the house is really cold, we start the fire and only ~2h later we get some comfort. Apart from the heating system, we are also investing in improving insulation, especially replacing the windows and insulating the window blind mechanism and its straps (and that really, really sucks in our buildings, awful window blinds - windows in general).

Hi @all Thank you for allowing me to participate in this community. I am looking forward to discuss my goal for my heating system, currently using a wood burner with water circulation and radiators, which I'd like to replace with an ASHP. I will open a topic for that shortly. Please apologize if sometimes I'm not using the correct English words. Eg I don't know how to call the "wood burner with water circulation" thin, but it's something like this (not mine, got the image online)