We have a 300L (79 gallons) buffer tank, and our heating is supplied by district heating. Currently, the heating boost is set to run from 5:30 a.m. to 10 p.m. I have read that it is better to start the heating boost from around midday to optimize the efficiency of the solar thermal system, since the water is colder and can absorb energy more effectively. That sounds reasonable to me.
My question is: How much can I reduce the district heating boost time for domestic hot water production? At the same time, I want to ensure that Legionella prevention is adequately addressed. Currently, my domestic hot water temperature is set to 65°C (149°F). Would it theoretically be sufficient to run the heating boost for about 1 hour per day to raise the tank temperature to 65°C (149°F) and thus prevent Legionella?
What would be the most efficient approach regarding the solar thermal system in this context?
My question is: How much can I reduce the district heating boost time for domestic hot water production? At the same time, I want to ensure that Legionella prevention is adequately addressed. Currently, my domestic hot water temperature is set to 65°C (149°F). Would it theoretically be sufficient to run the heating boost for about 1 hour per day to raise the tank temperature to 65°C (149°F) and thus prevent Legionella?
What would be the most efficient approach regarding the solar thermal system in this context?
Yes, of course, there is no absolute setting for the heating system for house type X and occupant Y. It is always very subjective and must be adjusted over time until it works as desired. Even two identical neighboring houses can have more or less significant differences in their settings.
This applies not only to the DHW (domestic hot water) system but to the entire HVAC system.
This applies not only to the DHW (domestic hot water) system but to the entire HVAC system.
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BenutzerPC12 Sep 2020 18:52All right. I mainly wanted to address the issue of legionella protection. In theory, is it sufficient to turn on the domestic hot water system once a day (for, e.g., 1 hour) to properly manage this? I don't think that the solar thermal system alone is enough to heat the entire 300l (79 gallons) storage tank above 60°C (140°F).
BenutzerPC schrieb:
I don’t think the solar thermal system alone is enough to heat the entire 300 l (79 gallons) storage tank to over 60°C (140°F).With sunlight, it definitely is, and quite quickly.Of course, it can do that, just not in winter. And the controller must, of course, be set so that it does not turn off prematurely. Otherwise, as mentioned, our gas boiler runs an anti-legionella program once a week, although this only applies to the upper part of the storage tank.
I have a 300-liter (79 gallons) buffer tank, which is enough for two baths or three to four showers. From March to October, I only need to reheat three to five times at most, and my collectors are not facing south. However, I heat the water up to 75°C (167°F).
There probably won't be any control system that can predict both behavior and weather accurately. The best results come from manual control, where you completely turn off the district heating and only switch it on yourself when needed. The heating system should be set up so that it only heats the upper part of the tank first, and only when that is warm does it heat the lower part. Legionella bacteria are usually not an issue in private households with up to 500 liters (132 gallons) of water, and it is sufficient to raise the temperature to 60°C (140°F) every few months.
There probably won't be any control system that can predict both behavior and weather accurately. The best results come from manual control, where you completely turn off the district heating and only switch it on yourself when needed. The heating system should be set up so that it only heats the upper part of the tank first, and only when that is warm does it heat the lower part. Legionella bacteria are usually not an issue in private households with up to 500 liters (132 gallons) of water, and it is sufficient to raise the temperature to 60°C (140°F) every few months.