Hello everyone,
I am planning to equip our new build with an LWZ 504.
I have noticed that opinions about buffer tanks vary quite a bit.
Currently, I am leaning towards leaving out the buffer tank, since we don’t necessarily need the cooling function through the underfloor heating (it has worked well without it for the past 30 years), and these tanks generally tend to reduce efficiency.
However, I have also read—though not specifically about Stiebel Eltron—that some heat pumps can have issues when using ERR (which is basically required) if there is no buffer tank installed.
What are your experiences and opinions on this?
Best regards,
Roppo
I am planning to equip our new build with an LWZ 504.
I have noticed that opinions about buffer tanks vary quite a bit.
Currently, I am leaning towards leaving out the buffer tank, since we don’t necessarily need the cooling function through the underfloor heating (it has worked well without it for the past 30 years), and these tanks generally tend to reduce efficiency.
However, I have also read—though not specifically about Stiebel Eltron—that some heat pumps can have issues when using ERR (which is basically required) if there is no buffer tank installed.
What are your experiences and opinions on this?
Best regards,
Roppo
Hello!
We have the THZ 504, which is identical to the LWZ.
Since we don’t have cooling, there is no second buffer tank installed. However, I already had the wiring prepared inside the house for this.
The internal storage tank for hot water is sufficient for a bathtub and two showers; so far, there has been no shortage.
We also have ERR, but currently, I keep all rooms fully open because the supply temperature is still very low. Otherwise, I have reduced some rooms.
We have the THZ 504, which is identical to the LWZ.
Since we don’t have cooling, there is no second buffer tank installed. However, I already had the wiring prepared inside the house for this.
The internal storage tank for hot water is sufficient for a bathtub and two showers; so far, there has been no shortage.
We also have ERR, but currently, I keep all rooms fully open because the supply temperature is still very low. Otherwise, I have reduced some rooms.
O
Obstlerbaum2 Oct 2018 10:39Is the heat pump the only heat source? Then the integrated storage tank is sufficient.
Hello!
We also have a heat pump from StiebelEltron: LWZ304.
For a 140m² (1507 ft²) area, we do not use an additional buffer tank. ERR is mandatory and therefore installed, but almost all are set to "off."
A buffer tank might make sense with a photovoltaic system to store excess electricity as hot water.
Cooling was not really necessary this hot summer, at least if you shade intelligently and turn off ventilation during the day.
We also have a heat pump from StiebelEltron: LWZ304.
For a 140m² (1507 ft²) area, we do not use an additional buffer tank. ERR is mandatory and therefore installed, but almost all are set to "off."
A buffer tank might make sense with a photovoltaic system to store excess electricity as hot water.
Cooling was not really necessary this hot summer, at least if you shade intelligently and turn off ventilation during the day.
Okay, so if I understand correctly, from Stiebel Eltron’s side it is not a problem to omit the buffer tank, even though there is an ERR…
We do want to deactivate the ERR, but if there is already a fallback option, it should work, I think.
Otherwise, the heat pump is the only heating source, yes. We do have photovoltaic panels, but we also feed electricity back into the grid. So the best electricity is the one that is not used in the house anyway.
What options do I have, aside from underfloor heating cooling with a buffer tank, to keep the building somewhat temperate in summer?
As far as I understand, the controlled ventilation system with heat recovery only ensures fresh air supply and reuses the heat—it does not provide any cooling function, which can lead to the building getting quite hot in summer when the ventilation brings in outdoor air.
What would be a practical solution here?
Best regards
We do want to deactivate the ERR, but if there is already a fallback option, it should work, I think.
Otherwise, the heat pump is the only heating source, yes. We do have photovoltaic panels, but we also feed electricity back into the grid. So the best electricity is the one that is not used in the house anyway.
What options do I have, aside from underfloor heating cooling with a buffer tank, to keep the building somewhat temperate in summer?
As far as I understand, the controlled ventilation system with heat recovery only ensures fresh air supply and reuses the heat—it does not provide any cooling function, which can lead to the building getting quite hot in summer when the ventilation brings in outdoor air.
What would be a practical solution here?
Best regards
As described, during the "hot" period I turn off the ventilation during the day and switch to "passive cooling ventilation."
This has worked well so far. What happens during passive cooling? There are different options for passive cooling. With the "ventilation" option, the supply air fan is turned off at night (when outdoor temperatures are cooler than indoors), and due to the negative pressure inside the house (since air is still being extracted through the exhaust fan), cool night air is drawn in through the open(!) windows. This has worked quite well.
Alternatively, there is the opposite function: turning off the exhaust fan and turning on the supply air fan --> warm air is "pushed" out of the house.
Additionally, you can purchase and install a "summer cassette." This does not have a heat exchange function and prevents the warm indoor air from warming up the cool night air. However, the summer cassette must be converted back for winter use.
And very important... shading!
This has worked well so far. What happens during passive cooling? There are different options for passive cooling. With the "ventilation" option, the supply air fan is turned off at night (when outdoor temperatures are cooler than indoors), and due to the negative pressure inside the house (since air is still being extracted through the exhaust fan), cool night air is drawn in through the open(!) windows. This has worked quite well.
Alternatively, there is the opposite function: turning off the exhaust fan and turning on the supply air fan --> warm air is "pushed" out of the house.
Additionally, you can purchase and install a "summer cassette." This does not have a heat exchange function and prevents the warm indoor air from warming up the cool night air. However, the summer cassette must be converted back for winter use.
And very important... shading!
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