ᐅ Air-to-Water Heat Pump: Current Consumption and Data

I just read a 42-day weather forecast. It looks like it will take a long time this year before daytime temperatures reach 15°C (59°F). They are talking about the end of March or mid-April. We have simply become too spoiled by the last four years.

Wow, I remember Easter when I was with my parents, grilling in a constant 25°C (77°F).

Alessandro schrieb:

I need your collective intelligence because I’m so confused that recently I adjusted the water level indicator of my houseplant, simply because it looks like a taco setter :p

As you know, I have connected the buffer tank in parallel to the heat pump and am using more or less ERR.
The key here is adjusting the flow rate and pressure. Everything is set at the secondary pump, which supplies the underfloor heating from the buffer tank.

When I set the flow and pressure according to the calculation, the temperature difference in the heating circuits is very low, only 2-3°C (4-5°F), although 5°C (9°F) was calculated.
The calculation assumes a flow rate of 1300 L/min (340 gal/min) with a pressure of 2 m (6.6 ft) at a 5°C (9°F) temperature difference.
Because of this, the heat pump reduces the flow to 800-900 L/min (210-240 gal/min) to maintain that 5°C (9°F) difference.

The system works best at the lowest setting and with constant pressure. Here, the underfloor heating has a temperature difference of 5°C (9°F), and the heat pump runs at about 1000-1200 L/min (260-320 gal/min).
However, the flow in the underfloor heating circuit is only 900 L/min (240 gal/min).
In this case, the secondary pump only consumes 12 W and delivers 900 L/min (240 gal/min) at a head of 1.8 m (5.9 ft). That seems quite low to me.

Is a 2-3°C (4-5°F) temperature difference in the underfloor heating desirable, or is it simply too low?
Do you have any ideas?
Does it make sense to increase the pressure at the secondary pump and throttle all heating circuits so that they achieve a flow corresponding to a 5°C (9°F) temperature difference?

What exactly is your problem? I’ve read your posts and don’t understand the intention behind your questions.

Alessandro schrieb:

Is a temperature difference of 2–3 K in the underfloor heating desirable or simply too low?

The smaller the temperature difference, the more efficient the heat pump operates. Many designs even plan for only 4 degrees Celsius (7°F). So where is the real problem?

@stepfel
I’m tired of hearing the argument “it grows back.”

Oil and gas were once trees as well. Oil and gas also continuously form anew.

A cubic meter of wood simply burns much faster than it grows. So the whole argument is invalid.

The point about fine dust is correct. I have never looked into the effectiveness of filters for pellet stoves.

Bookstar schrieb:

I expected a comment like that, it was a perfect setup 😀. But you can also just google it; even with a "perfectly" adjusted heat pump, a pellet system tends to run a bit cheaper/more efficiently during operation (without further investment).

My neighbor maintains district heating systems such as biogas, combined heat and power units, and also private pellet heating professionally. He wouldn’t install something like that in his own house for free. He has an air-to-water heat pump in his new build.

We had district heating over biogas plus pellet heating for the last 10 years. It really failed every year, and about 5-6 years ago it burned down partially (about 50%). At first, it’s pretty cool, but you end up with a lot of technology that just doesn’t get better over the years.

And whether burning wood is especially ecological or growing monoculture maize everywhere for biogas is better, everyone has to decide that for themselves.

Bookstar schrieb:

Why did I expect a comment like that? It was an easy target 😀. But you can also just Google it—it's the case even with a "perfectly" set heat pump that a pellet system tends to run a bit cheaper/more efficiently during operation (without the initial investment).

You do realize that not everything Google returns is fact, right? 😉

Even if that were true... you still have to consider the higher upfront investment (how many years of heating will that cover?), the greater space requirements, and several additional costs that are often forgotten (chimney, storage tank, maintenance, electricity costs, etc.).

@Alessandro

Why not just let it run? As I wrote... a lower temperature difference means better efficiency. Or where do you see the problem?

My heat pump controls the pump pressure automatically (direct heating circuit). Depending on the outside temperature and demand, I have a temperature split of sometimes 2.5°C (4.5°F) or sometimes 4°C (7.2°F) (although it’s a modulating heat pump). The technician from IDM will come again for a detailed introduction. Does he even know what he’s dealing with? 😀 I still need to drill him on which settings have which effects. I haven’t found the pump setting yet, as I said.

...currently it’s back to 3.5°C (6.3°F) temperature difference, but the weather is just arriving here... right now it’s -1.5°C (29°F).