Hello everyone,
for our new single-family house (about 170sqm (1830 sq ft), brine-to-water heat pump for heating and domestic hot water), we are getting a Viessmann system. Viessmann offers the Natural Cooling Box (NC-Box) as an add-on (around 4000 euros including installation and additional thermostats), which allows cool water to circulate through the underfloor heating in summer (cooled down passively via a plate heat exchanger with the brine). I understand that the cooling capacity is limited by the dew point (and there will be no ceiling cooling). Generally, I hear that the indoor temperature difference is about 3°C (5°F) with or without cooling.
I also realize that temperature perception varies, but nevertheless: Can anyone share first-hand experience with this or a similar system? Is the cooling effect noticeable during summer? How is the electricity consumption? Does the control system work properly?
Furthermore, I read somewhere here in the forum that the NC-Box ALWAYS consumes electricity – even when cooling, for example in winter, is turned off. That can’t be right, can it? Is this nonsense? Maybe a bit of electronics run at 0.25W, but the pump would at least be off, right?
Thanks in advance for any insights!
for our new single-family house (about 170sqm (1830 sq ft), brine-to-water heat pump for heating and domestic hot water), we are getting a Viessmann system. Viessmann offers the Natural Cooling Box (NC-Box) as an add-on (around 4000 euros including installation and additional thermostats), which allows cool water to circulate through the underfloor heating in summer (cooled down passively via a plate heat exchanger with the brine). I understand that the cooling capacity is limited by the dew point (and there will be no ceiling cooling). Generally, I hear that the indoor temperature difference is about 3°C (5°F) with or without cooling.
I also realize that temperature perception varies, but nevertheless: Can anyone share first-hand experience with this or a similar system? Is the cooling effect noticeable during summer? How is the electricity consumption? Does the control system work properly?
Furthermore, I read somewhere here in the forum that the NC-Box ALWAYS consumes electricity – even when cooling, for example in winter, is turned off. That can’t be right, can it? Is this nonsense? Maybe a bit of electronics run at 0.25W, but the pump would at least be off, right?
Thanks in advance for any insights!
An air exchange rate of 0.4 times per hour is generally sufficient to maintain good air quality in a single-family home. Another rule of thumb is approximately 30m³/h (18 cubic feet per minute) per occupant, which is usually even lower than a 0.4 air change rate. This amount of ventilation is enough to keep CO2 levels low during normal use, providing much more consistent air quality than without a ventilation system. I use about 35m³/h (21 cubic feet per minute) per person; increasing the airflow beyond this point does not significantly improve air quality under normal conditions (not during parties).
During parties with about ten times the usual number of people in the house, this is obviously insufficient, but then you can simply open all the windows... For such occasions, an excessively oversized ventilation system offers no real benefits and results in huge energy waste (heat recovery is always less than 100%, plus the electricity consumption of the system for moving this volume of air, high installation costs, etc.). Ventilation systems are also one of the worst options for cooling, as air is known to be a very poor conductor of heat. Active cooling is possible with air conditioning systems, but cooling down with outside air on a permanent basis—even if pre-cooled somewhat through a geothermal heat exchanger—is only feasible during transitional seasons when outdoor temperatures are still relatively low. It will not work during long heat waves when nighttime temperatures do not drop below 20°C (68°F).
During parties with about ten times the usual number of people in the house, this is obviously insufficient, but then you can simply open all the windows... For such occasions, an excessively oversized ventilation system offers no real benefits and results in huge energy waste (heat recovery is always less than 100%, plus the electricity consumption of the system for moving this volume of air, high installation costs, etc.). Ventilation systems are also one of the worst options for cooling, as air is known to be a very poor conductor of heat. Active cooling is possible with air conditioning systems, but cooling down with outside air on a permanent basis—even if pre-cooled somewhat through a geothermal heat exchanger—is only feasible during transitional seasons when outdoor temperatures are still relatively low. It will not work during long heat waves when nighttime temperatures do not drop below 20°C (68°F).
The Daikin system I linked to is an active cooling system that is only integrated into existing ventilation ducts or air handling systems. However, you can forget about it if a ventilation system only provides 0.4 air changes per hour. As you correctly pointed out, air is a poor conductor of heat, so more air needs to be supplied.
Additionally:
Of course, the system should not be undersized to avoid running at full capacity (quieter operation, reserves for when there are fewer guests, etc.). In the example above: 130 m² (1400 sq ft) × 2.5 m (8 ft) = 325 m³ (11,460 cu ft) of room volume. Designing for five times the air volume would mean 1500 m³/h (880 CFM)... which is quite large for a single-family home ventilation system. A typical system with a capacity of 350 m³/h (206 CFM), which normally operates at 130 m³/h (76 CFM), is usually sufficient here.
Of course, the system should not be undersized to avoid running at full capacity (quieter operation, reserves for when there are fewer guests, etc.). In the example above: 130 m² (1400 sq ft) × 2.5 m (8 ft) = 325 m³ (11,460 cu ft) of room volume. Designing for five times the air volume would mean 1500 m³/h (880 CFM)... which is quite large for a single-family home ventilation system. A typical system with a capacity of 350 m³/h (206 CFM), which normally operates at 130 m³/h (76 CFM), is usually sufficient here.
Ok, so 150m² (1,615 ft²) / 2.5m (8.2 ft) = 425/450m³/h (250/265 CFM) airflow should be provided.
With the first developer, where it wasn’t really clear what I meant by "decentralized to centralized," they said the surcharge for the "Pluggit Avent P 310" was €4000. (Airflow range 70 - 300 m³/h (41 - 177 CFM)) and it would actually be too small for the 150m² (1,615 ft²) calculated living area.
As a general addition, the following was noted:
Cross-counterflow heat exchanger made of aluminum with 85.4% heat recovery efficiency
4 ventilation levels, nominal ventilation capacity 230m³/h (135 CFM)
Front control panel + alarm function
Automatic summer bypass
Air volume control with setback periods via a weekly program
Frost protection function
Condensate drain
What I was missing, however, were all the additional ducts that would need to be installed when switching from decentralized to centralized systems?
For active cooling, either air conditioning units or, for example, the Daikin system could be planned. The disadvantage of the central Daikin system is that the device has to cool every room instead of allowing individual rooms to be cooled separately (e.g., 1 bedroom, 1 living room, 1 office).
With the first developer, where it wasn’t really clear what I meant by "decentralized to centralized," they said the surcharge for the "Pluggit Avent P 310" was €4000. (Airflow range 70 - 300 m³/h (41 - 177 CFM)) and it would actually be too small for the 150m² (1,615 ft²) calculated living area.
As a general addition, the following was noted:
Cross-counterflow heat exchanger made of aluminum with 85.4% heat recovery efficiency
4 ventilation levels, nominal ventilation capacity 230m³/h (135 CFM)
Front control panel + alarm function
Automatic summer bypass
Air volume control with setback periods via a weekly program
Frost protection function
Condensate drain
What I was missing, however, were all the additional ducts that would need to be installed when switching from decentralized to centralized systems?
For active cooling, either air conditioning units or, for example, the Daikin system could be planned. The disadvantage of the central Daikin system is that the device has to cool every room instead of allowing individual rooms to be cooled separately (e.g., 1 bedroom, 1 living room, 1 office).
Teemoe86 schrieb:
Ok, so 150m² (1600 sq ft) / 2.5m (8.2 ft) = 425/450m³/h (250/265 cfm) is the recommended airflow.
With the first builder, where it also didn’t seem clear what I meant by "decentralized versus centralized," they said the upgrade cost to the "Pluggit Avent P 310" would be 4000€. (Air volume flow range 70 - 300 m³/h (40 - 176 cfm)) and that unit would actually be too small for the calculated 150m² living area. It depends! A fairly typical design is 0.4 × volume, which means around 170 m³/h (100 cfm) air exchange for a 425 m³ (15,000 cu ft) room volume (and in practice, you usually need even less for good indoor air quality under normal conditions). The P310 can handle that.
Of course, you can't cool with just air exchange, and to cool effectively you need much larger airflow rates, which are well beyond the capacity of standard ventilation systems for single-family homes. For cooling, the required airflow would increase from 170 m³/h to over 1000 m³/h (600+ cfm).
S
Stadtvilla198 Aug 2020 15:08We decided to go with a Viessmann heat pump featuring Natural Cooling. It cost us about €1000 (around $1100) more, which I find reasonable. Since the system has only been running for 3 days and the temperatures have just risen above 30°C (86°F) during the past 3 days, I can’t say much yet.
Our house is built with Ytong blocks and has 36.5cm (14 inches) thick walls without additional insulation. Until now, the indoor temperature in the evenings was always around 21°C (70°F), and even without cooling, we felt chilly sitting on the sofa in the evenings... But the summer hasn’t really been that hot so far.
Of course, this type of cooling can’t compete with an air conditioner, but considering that it practically provides free cooling, it’s impressive. The system only runs a 50W circulation pump, and whether it’s 27°C (81°F) or 24°C (75°F) inside makes a noticeable difference.
Right now, it’s 23.5°C (74°F) indoors and 36°C (97°F) outside. I’m curious to see how things develop over the next few days since it’s supposed to stay above 30°C (86°F) for a while. Of course, I can’t provide a comparison to having no cooling at all...
Our house is built with Ytong blocks and has 36.5cm (14 inches) thick walls without additional insulation. Until now, the indoor temperature in the evenings was always around 21°C (70°F), and even without cooling, we felt chilly sitting on the sofa in the evenings... But the summer hasn’t really been that hot so far.
Of course, this type of cooling can’t compete with an air conditioner, but considering that it practically provides free cooling, it’s impressive. The system only runs a 50W circulation pump, and whether it’s 27°C (81°F) or 24°C (75°F) inside makes a noticeable difference.
Right now, it’s 23.5°C (74°F) indoors and 36°C (97°F) outside. I’m curious to see how things develop over the next few days since it’s supposed to stay above 30°C (86°F) for a while. Of course, I can’t provide a comparison to having no cooling at all...
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