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

RotorMotor schrieb:

How long was your longest loop again?

The highest pressure loss calculated is 5043 Pa (50 mbar).

RotorMotor schrieb:

What flow rate do you need according to your calculations, and what is the pump currently delivering?

The calculated flow rate is 1065 liters per hour (l/h). However, the pump adjusts the flow rate dynamically based on parameters unknown to me. The pump display shows values between 800 and 1400 liters (l). I have not yet found a setting in the Vaillant menu to fix the pump to a constant flow rate.

Daniel-Sp schrieb:

The ERR valves should be disabled and the overpressure valve should be almost fully closed. This is the only way to ensure that all the heat produced by the heat pump goes exclusively into the underfloor heating.

Regarding legionella protection: this is a very controversial and widely discussed topic.
If you follow a few key points, legionella are not a concern in a single-family house. The most important point is to avoid dead legs with stagnant water. Therefore, if there is a circulation system installed, it should be flushed at least once a day for about 5 minutes.
Secondly, the hot water storage tank should be sized according to the household’s needs and be regularly replenished with fresh water. For example, a 600-liter (160-gallon) hot water tank for one person would be problematic. For a family, 200–300 liters (53–79 gallons) is usually no issue. Even better is a fresh water station.
A legionella control cycle only makes sense if not only the storage tank is heated above 60°C (140°F), but this temperature is also reached simultaneously at all points in the system—that means all hot water outlets must be opened at the same time. Otherwise, you selectively promote heat-resistant strains where there is an infestation; there are studies on this. In fact, a temperature above 60°C (140°F) is often necessary.
During my clinical work for over 10 years in a pulmonology department—which also managed the internal intensive care unit of the hospital—there was not a single case of legionella pneumonia in residents of single-family homes.

Do you mean I should only run the hot water circulation and can set the hot water temperature to 45°C (113°F)? Should I turn off the legionella protection, i.e., heating to 60°C (140°F) using the heating element?

Yes, if a circulation system is installed, it needs to operate. But not all day, only during peak times in the bathroom. If the circulation runs all day, you will have significant heat loss in the storage tank and waste money.
In my opinion, a legionella prevention program is not necessary in a single-family house.

Daniel-Sp schrieb:

In my opinion, a legionella prevention program is not necessary in a single-family house.

This was also confirmed by our Vaillant service technician, who seemed very experienced to me. He also deactivated the electric heating element during the briefing.

OWLer schrieb:

The highest pressure loss is calculated at 5043 Pa = 50 mbar (0.72 psi).

The calculated flow rate is 1065 l/h (4.7 gallons per hour). However, the pump adjusts the flow rate dynamically based on parameters unknown to me. The pump display shows values between 800 and 1400 l/h (3.5 to 6.2 gallons per hour). I have not found any menu option on the Vaillant system to set the pump to a constant flow rate.

This flow behavior is actually typical for Vaillant and some other heat pump models. In my Vaillant air-to-water heat pump, the pump cannot be set to a fixed flow rate either. The only setting available is the residual head pressure, and then during the heating mode the pump usually runs at about 60-70% of its maximum capacity. For my model, that means approximately 600-750 l/h (2.6 to 3.3 gallons per hour) during heating, and during domestic hot water production the device manages around 1200-1350 l/h (5.3 to 5.9 gallons per hour).

Modulating heat pumps adjust the flow rate to achieve the optimal temperature difference between supply and return at the required heating output. This is important and correct for efficiency.