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

Alessandro schrieb:

It is solely for heating water and has a capacity of 100L (26 gallons).

To be honest? Just get your plumber and 100€ and connect the heat pump directly to the underfloor heating. Everything else is nonsense.

nordanney schrieb:

Honestly? Grab your plumber and 100€ and connect the heat pump directly to the underfloor heating. Everything else is nonsense.

I've suggested that many times already, but he's attached to his buffer tank plus pump 😉

nordanney schrieb:

Honestly? Just grab your plumber and 100€ and connect the heat pump directly to the underfloor heating. Everything else is nonsense.

I keep in mind that with a high and desired heating curve (bathroom set to 23–24°C (73–75°F)) including a buffer, the consumption is still moderate.

You’re asking questions where everyone says the design is fine and you’re just nitpicking because the temperature spread isn’t 5 K but 2.5 K.

It’s the same debate as with humidity. You don’t have a mechanical ventilation system with heat recovery but want to achieve the values you would with one.

Feel free to correct me if I remember it wrong.

No, I just want to understand if I might have a flaw in my reasoning.

My reference value is the buffer temperature.
If I have a small temperature difference (delta T) of 2-3 K in the underfloor heating at -10°C (14°F) outdoor temperature, it will naturally be even smaller at higher outdoor temperatures, which in turn causes the heat pump to cycle frequently.
Wouldn’t it make sense in my hydraulic setup to increase the delta T in the underfloor heating and operate at higher pressure, so that 1) the heat pump has a higher flow rate and thus greater efficiency, and 2) the buffer tank heats up less quickly?
The underfloor heating doesn’t care whether the delta T is 2 or 8 K, since the circuit is independent from the heat pump.

By the way, my domestic hot water circuit has a delta T of 6 K, while my utility room has a delta T of 1.5 K and is almost a hydraulic short circuit.

My energy consumption is quite constant at 28-30 kWh, despite using a high heating curve (18/30, 0/35, -15/38).

Alessandro schrieb:

Wouldn’t it make sense in my hydraulics to increase the temperature difference in the underfloor heating and work with higher pressure,

Actually, it’s done the opposite way. A small temperature difference, but a high flow rate. How do you expect the heat to be delivered if you put more and more heat (= high flow) into the underfloor heating?

Alessandro schrieb:

The underfloor heating doesn’t care whether I have a 2K or 8K temperature difference, since the circuit is independent from the heat pump.

The underfloor heating might not care, but energy consumption does. If you have an 8K temperature difference in the underfloor heating, “cold” water arrives at the buffer and has to be reheated using more energy. If it arrives “warm,” only a small amount of energy is needed to reheat it to the correct temperature.

halmi schrieb:

I have suggested that many times, but he insists on his buffer + pump 😉

Then the heating engineer needs a kick in the rear, and a “good one” should be hired. It’s that simple.

nordanney schrieb:

Your drawing clearly shows why having a buffer tank in a underfloor heating system is completely pointless. First, you heat up the buffer tank, then feed lower temperatures into the underfloor heating. Any normal person would just supply the underfloor heating directly at 33°C (91°F) with a higher flow rate than your 900 liters/min (240 gallons/min).

I don’t understand that, because if the heat pump is set with a temperature difference of 5K but the underfloor heating only requires 3K, the heat pump automatically reduces the flow rate, right?