ᐅ Operate fresh water systems with partially very high and low buffer temperatures
Created on: 18 Apr 2020 14:29
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fraubauer
Hello.
I have noticed that with really warm weather now, the solar system is delivering good performance to the buffer tank.
The buffer temperature in the afternoon currently rises to about 80°C (176°F) at the top of the tank, where the supply to the domestic hot water is located.
In the evening, however, the buffer temperature at the top drops to about 60°C (140°F).
(The pellet boiler only starts when the sensor reaches 55°C (131°F), so currently it turns on in the mornings).
Question:
The domestic hot water is currently set to a target temperature of 58°C (136°F) for production.
The circulation is set to 53°C (127°F).
The supply line from the buffer to the domestic hot water is limited to 65°C (149°F) using a simple mixing valve.
Does it matter for the domestic hot water if in the evening it is only fed with about 60°C (140°F) from the buffer?
Producing 58°C (136°F) with a 60°C (140°F) supply is actually quite tight. It should really be around 65°C (149°F).
However, I wouldn’t mind if the domestic hot water is produced around 55°C (131°F) instead of 58°C (136°F) during this time.
When the boiler delivers again (with 65°C (149°F) at the top of the buffer), there will be enough supply temperature for the domestic hot water again.
Thank you very much.
I have noticed that with really warm weather now, the solar system is delivering good performance to the buffer tank.
The buffer temperature in the afternoon currently rises to about 80°C (176°F) at the top of the tank, where the supply to the domestic hot water is located.
In the evening, however, the buffer temperature at the top drops to about 60°C (140°F).
(The pellet boiler only starts when the sensor reaches 55°C (131°F), so currently it turns on in the mornings).
Question:
The domestic hot water is currently set to a target temperature of 58°C (136°F) for production.
The circulation is set to 53°C (127°F).
The supply line from the buffer to the domestic hot water is limited to 65°C (149°F) using a simple mixing valve.
Does it matter for the domestic hot water if in the evening it is only fed with about 60°C (140°F) from the buffer?
Producing 58°C (136°F) with a 60°C (140°F) supply is actually quite tight. It should really be around 65°C (149°F).
However, I wouldn’t mind if the domestic hot water is produced around 55°C (131°F) instead of 58°C (136°F) during this time.
When the boiler delivers again (with 65°C (149°F) at the top of the buffer), there will be enough supply temperature for the domestic hot water again.
Thank you very much.
F
fraubauer18 Apr 2020 18:23Joedreck schrieb:
Exactly like that. A domestic hot water system is essentially just a heat exchanger. The warm water from the buffer tank heats the cold water from the supply line in a continuous flow process.
If the water from the buffer is no longer warm enough, the domestic hot water system simply heats it as much as needed.
Completely harmless.Hello.
Yes, that’s exactly how I had imagined it.
But the reason for my question is the following.
Since the underfloor heating is practically no longer in use, the buffer tank temperature should actually be lower in summer than in winter. In winter, the heating runs and many people take long baths. In summer, the heating is off and most tend to take showers.
In winter, the buffer was always kept at about 65°C (149°F). The domestic hot water then reached around 60°C (140°F).
In summer (which is now the current period), I think 55°C (131°F) in the buffer should be sufficient.
The domestic hot water system would then produce about 50°C (122°F), which is perfectly adequate for showering, bathing, etc. (it still needs to be mixed with cold water).
And the solar system delivers plenty of energy to the buffer during the day, heating it up to around 75°C (167°F) on sunny days.
Now I just let the buffer temperature drop until the boiler kicks in!
So instead of the boiler reheating at 60°C (140°F) buffer temperature as in winter, it only does so at 50°C (122°F).
That way, the boiler only needs to reheat briefly in the morning.
This should be the most economical approach for the summer months.
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fraubauer18 Apr 2020 18:30Joedreck schrieb:
I don’t see a question here?Is my way of thinking correct?
In summer, lowering the buffer tank temperature and allowing the boiler to reheat later, since less energy is needed in the buffer.
I also consider keeping high buffer tank temperatures in summer (during the day due to solar heating is understandable, but in the evening, night, and early morning) to be a waste of energy.
The heating system reheats the buffer tank according to the temperature sensor settings inside the tank. Maintaining around 60°C (140°F) buffer temperature in winter is fine, but I believe that is too high for summer. In the evening, night, and early morning, 50°C (122°F) should be sufficient.
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fraubauer19 Apr 2020 10:08Joedreck schrieb:
Yes, it makes sense and is definitely possible without any problems. Depending on the situation, you can switch off the heating including the domestic hot water system yourself, as long as the water temperature in the morning is still sufficient for your needs.Thank you very much for your help.
So I can safely keep the setpoint of the domestic hot water at 58°C (136°F) (circulation at 53°C (127°F)), even though sometimes early in the morning the flow temperature from the buffer tank is only about 55°C (131°F). In that case, the domestic hot water will just produce around 55°C (131°F) during that time, which is perfectly sufficient. I thought I would have to lower the setpoint of the domestic hot water as well (for example to 52°C (126°F) / circulation at 47°C (117°F)).
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