ᐅ How to reduce or optimize the energy consumption of a heat pump water heater?

Hello,

Unfortunately, this question regarding heat pumps has not been answered yet. Hopefully, I have better luck here. Our old domestic hot water boiler from the oil heating system recently and suddenly broke down. Last week, we therefore installed a new domestic hot water heat pump (DHW heat pump) with a 270-liter (4-person) capacity (circulation air mode) and connected it to the existing hot water circulation system. The circulation is quite useful because otherwise hot water can take quite a long time to arrive. A mechanical timer switch was installed, so the circulation pump now does not run for 7 hours at night and is also turned off for 3 hours during the day.

I have some general questions related to this, and maybe you can offer some tips or advice:

1. How can electricity consumption be reduced as effectively as possible when the DHW heat pump is connected to the circulation line, which is rather poorly insulated in the house?

2. According to energy-saving regulations, the circulation pump must run at least 16 hours daily to keep the pipes free from bacteria. Is this really necessary in practice?

3. What is the recommended target temperature for the DHW heat pump itself? Legionella protection at 62°C (143.6°F) is done once a month according to the settings.

4. The utility room housing the DHW heat pump has a volume of only about 16 cubic meters (565 cubic feet). A minimum of 20 cubic meters (706 cubic feet) is recommended. Forced ventilation (a ventilation grille with noticeable fresh air) is present due to the oil heating system. However, the room temperature (usually about 20°C (68°F)) drops noticeably by up to 5-6°C (9-11°F) during prolonged circulation air operation of the heat pump (down to 14-15°C (57-59°F)) and then rises again afterwards. Is this acceptable, or should I direct the exhaust air outside to improve the heat pump’s efficiency?

Thank you very much for your feedback.

Gnadenpinsel schrieb:

1. How can electricity consumption be further reduced most effectively when the heat pump water heater (HPWH) is connected to the circulation line (which is poorly insulated in the house)?

Run it even less. But then you might as well turn it off completely...

Gnadenpinsel schrieb:

2. According to the energy saving regulations, the circulation pump must run for at least 16 hours daily to keep the pipes free of bacteria. Is this really that important in practice?

As long as you use water regularly, this is not really an issue.

Gnadenpinsel schrieb:

3. What target temperature is generally recommended for the HPWH itself? Legionella protection at 62°C (144°F) is performed once a month according to the settings.

48-50 degrees Celsius (118-122°F) is sufficient. I would either disable the legionella program or run it weekly. Once a month makes little sense.

Gnadenpinsel schrieb:

4. The boiler room housing the HPWH has only about 16 cubic meters (565 cubic feet) volume. The recommended volume is 20 cubic meters (706 cubic feet). Forced ventilation (vent grille with noticeable fresh air) is present due to the oil heating system. However, the room cools down noticeably by up to 5-6°C (9-11°F) during longer recirculation operation of the HPWH (from around 20°C (68°F) to 14-15°C (57-59°F)). Afterwards, the temperature rises again. Is this still okay or should I exhaust the air directly outside to improve the HPWH’s efficiency?

Exhaust air is always beneficial. Whether it will actually improve efficiency significantly is doubtful; you likely won’t be able to measure the difference because any improvement is minimal.