ᐅ Settings for the Heat Pump

In May 2023, we switched from a gas heating system to a heat pump.

• Outdoor air source heat pump Alpha Innotec LWDV 91 (LWDV 91-1/3-HSDV 12M-3)
• Indoor hydraulic station HSDV with electric rod heater 9 kW
• PSD750 buffer tank with domestic hot water module type BWM F35 V2

For heating, we have underfloor heating on the ground floor and radiators on the upper floor.
Set temperature for domestic hot water: 50 degrees Celsius (122°F)

In summer, without heating, we turned off hot water production at night and experienced a heat loss of about 5 degrees Celsius (9°F) in the buffer tank’s hot water.

Now in winter, with heating running, I am testing some settings. I am surprised that with heating running 24 hours and hot water production only during the day, we have a heat loss of about 15 degrees Celsius (27°F) in the buffer tank’s hot water. Is this normal?
In the morning, it then takes a very long time for the hot water to be reheated to the set temperature of 50 degrees Celsius (122°F).

just2enjoy schrieb:

Now in winter, with the heating on, I am testing some settings. I am surprised that during heating operation (24 hours) and hot water generation only during the day, we have a heat loss of about 15 degrees in the hot water storage tank. Is that normal?

Without knowing the system in detail, I would boldly assume that the water from the storage tank is being circulated as heating water in the underfloor heating system. Naturally, as long as the heat pump is not running because the water in the storage tank is still warm enough, the water will gradually cool down. Since you did not heat in the summer, you did not notice this.

Whether this is necessary with your installed system and its hydraulics, or if it is a design or implementation error, cannot be determined without more detailed knowledge of the system including the hydraulics. There is someone in the green forum with a similar issue.

KarstenausNRW schrieb:

Without knowing the system in detail, I would boldly assume that the water from the buffer tank is circulated as heating water in the underfloor heating. This naturally means that—as long as the heat pump is not running because the water in the buffer tank is still warm enough—the water will gradually cool down. Since you didn’t use heating in summer, you wouldn’t have noticed this.

Whether this is necessary for the system and hydraulic setup installed in your case, or if it is a planning or implementation error, cannot be determined without a closer understanding of the system and its hydraulics. There is someone in the green forum with a similar problem.

Attached is the concept diagram. I hope this helps.

This confirms my statement. Without the heat pump running, water is drawn from the buffer tank to provide heating. I don’t know if it can be set differently. I am not familiar with the heat pump or the system.