ᐅ Integrated unit Stiebel Eltron LWZ 504 with central supply air system
Created on: 19 Oct 2014 20:20
D
DJCOON
Hello dear forum members,
Through a variety of professional magazines I ordered for our new build in spring 2015, I came across the air-to-water heat pump LWZ 504 from Stibel Eltron. According to Stibel, this unit offers the following:
"The compact LWZ 504 provides all the comfort expected from an energy-efficient house. The system draws energy for pleasant indoor temperatures and hot water from the outside air. Modern ventilation management ensures that the heat stays inside the building. It recovers up to 90% of the heat from the exhaust air. This allows a comfortable, healthy atmosphere to be combined with high efficiency. The demand-controlled inverter technology also ensures high efficiency. It produces exactly the amount of heat currently needed. High performance values can be achieved even at low temperatures. Energy-saving operation is supported by the modern high-efficiency heating circulation pump and excellent insulation of the hot water storage tank. For those who want to be even more independent from rising energy costs, the LWZ 504 can be operated with self-generated photovoltaic electricity using the appropriate accessories (ISG + SEE). The large, intuitive matrix display ensures that the modern technology in the award-winning design is easy to operate."
Key Features
I understand that this great system naturally comes at a price, but I would like to ask the experts among you—air-to-water heat pump owners as well as heating engineers—for advice or experience with such units. Ideally, it would be great if someone already has this exact pump installed in their basement :-)
Thank you in advance for your responses.
Best regards,
Martin
Through a variety of professional magazines I ordered for our new build in spring 2015, I came across the air-to-water heat pump LWZ 504 from Stibel Eltron. According to Stibel, this unit offers the following:
"The compact LWZ 504 provides all the comfort expected from an energy-efficient house. The system draws energy for pleasant indoor temperatures and hot water from the outside air. Modern ventilation management ensures that the heat stays inside the building. It recovers up to 90% of the heat from the exhaust air. This allows a comfortable, healthy atmosphere to be combined with high efficiency. The demand-controlled inverter technology also ensures high efficiency. It produces exactly the amount of heat currently needed. High performance values can be achieved even at low temperatures. Energy-saving operation is supported by the modern high-efficiency heating circulation pump and excellent insulation of the hot water storage tank. For those who want to be even more independent from rising energy costs, the LWZ 504 can be operated with self-generated photovoltaic electricity using the appropriate accessories (ISG + SEE). The large, intuitive matrix display ensures that the modern technology in the award-winning design is easy to operate."
Key Features
- Excellent suitability for new buildings
- Energy-saving inverter technology
- Ventilation with up to 90% heat recovery
- High domestic hot water comfort with well-insulated 235-liter (62 gallon) storage tank
- Compatible with solar systems
- Stable, sound-optimized housing construction
- Built-in high-efficiency heating circulation pump
I understand that this great system naturally comes at a price, but I would like to ask the experts among you—air-to-water heat pump owners as well as heating engineers—for advice or experience with such units. Ideally, it would be great if someone already has this exact pump installed in their basement :-)
Thank you in advance for your responses.
Best regards,
Martin
A
A. Rösner10 May 2019 00:42So.... I didn’t know, or hadn’t read anywhere, that you should only operate a heat pump at a maximum of 50 percent load. We have standard ceiling heights: 2.44 m (8 feet) clear height in the basement and upper floor, and 2.56 m (8 feet 5 inches) on the ground floor. The living area including the “habitable basement,” meaning the area the ventilation system has to handle, is just under 240 m² (2,583 sq ft).
To clarify again, it’s not necessarily the volume of noise but the “sound” – that deep thumping, humming, droning that is simply always there. Especially in the evening, it almost drives me crazy and I just turn off the system. My plumbing company is currently unresponsive... apparently, they don’t know what to do either.
By the way, I’m really only talking about the ventilation system. When the compressor starts up, it sounds like a helicopter... just kidding, but it is seriously loud. I have now set up the heating program so that the heat pump compressor only runs when we are not at home, meaning during weekday mornings and early evenings... how this will work in winter remains to be seen.
To clarify again, it’s not necessarily the volume of noise but the “sound” – that deep thumping, humming, droning that is simply always there. Especially in the evening, it almost drives me crazy and I just turn off the system. My plumbing company is currently unresponsive... apparently, they don’t know what to do either.
By the way, I’m really only talking about the ventilation system. When the compressor starts up, it sounds like a helicopter... just kidding, but it is seriously loud. I have now set up the heating program so that the heat pump compressor only runs when we are not at home, meaning during weekday mornings and early evenings... how this will work in winter remains to be seen.
Sounds like a construction flaw, maybe the installation or some kind of thermal bridge.
240 sqm (2583 sq ft) x 2.50 m (8.2 ft) ceiling height x 0.4/h air exchange rate = 240 m³/h (141 cfm) airflow per hour for nominal ventilation.
That’s too much for the unit if you want to keep noise and energy consumption low.
In cold winter conditions, a heat pump can easily run 24 hours a day to meet the heating demand. That’s when you’re likely to face a problem.
If I’m reading it correctly, the 504 model also only has 6 kW heating capacity. Is the basement heated as well? That wouldn’t be much for 240 sqm (2583 sq ft) of heated area, without wanting to jump ahead to a heat load calculation.
Or do you have very good insulation?
240 sqm (2583 sq ft) x 2.50 m (8.2 ft) ceiling height x 0.4/h air exchange rate = 240 m³/h (141 cfm) airflow per hour for nominal ventilation.
That’s too much for the unit if you want to keep noise and energy consumption low.
In cold winter conditions, a heat pump can easily run 24 hours a day to meet the heating demand. That’s when you’re likely to face a problem.
If I’m reading it correctly, the 504 model also only has 6 kW heating capacity. Is the basement heated as well? That wouldn’t be much for 240 sqm (2583 sq ft) of heated area, without wanting to jump ahead to a heat load calculation.
Or do you have very good insulation?
Is nominal ventilation mandatory? We have less m3/h (cubic meters per hour)... and the humidity is really low.
The THZ 504 delivers over 8 kW (9.5 hp) at A-7/W35.
How is it isolated from the floor?
The system should be installed on its own concrete slab, separated from the main floor slab by a rigid foam insulation board (such as extruded polystyrene). On the sides, it should be decoupled from the screed/floor with at least a “blue screed tape” or similar edge insulation. The ventilation requires two large (rectangular) silencers, connected by flexible ducts leading to the distribution system.
The THZ 504 delivers over 8 kW (9.5 hp) at A-7/W35.
How is it isolated from the floor?
The system should be installed on its own concrete slab, separated from the main floor slab by a rigid foam insulation board (such as extruded polystyrene). On the sides, it should be decoupled from the screed/floor with at least a “blue screed tape” or similar edge insulation. The ventilation requires two large (rectangular) silencers, connected by flexible ducts leading to the distribution system.
We have had an LWZ 504 installed in our KfW 55 house (160 m² (1,722 ft²), two people) since 2017, and it works really well; it is not oversized. We are very satisfied but have not yet tried the cooling function (although it would be ideal right now with the heatwave). However, we are a bit concerned about our beautiful hardwood floor. If anything is not correctly calculated or connected, condensation could form, which would damage the real wood flooring. That is why we are considering adding a dedicated cooling module to the ventilation system. The LWZ can only cool about 2-3 degrees Celsius (4-5 degrees Fahrenheit) above the underfloor heating temperature, so it is not really an air conditioning system.
Regarding noise, I can say that ours is relatively quiet. There is only a narrow dressing room between the utility room and our bedroom, yet we cannot hear it at all there. It has been properly decoupled (floor), and some kind of sound dampers were also installed. Since we have everything on one floor/level, we decided to install a soundproof door in the utility room so that the washing machine, dryer, and heating system are not heard in the living or sleeping areas. And that works perfectly. Anything else would be a disaster as I am very sensitive to noise. Therefore, whatever the issue is with the loud LWZ 504 mentioned earlier, something must have been installed or implemented incorrectly. I also know several others who have this model in their new builds, and theirs is just as quiet as ours.
Regarding noise, I can say that ours is relatively quiet. There is only a narrow dressing room between the utility room and our bedroom, yet we cannot hear it at all there. It has been properly decoupled (floor), and some kind of sound dampers were also installed. Since we have everything on one floor/level, we decided to install a soundproof door in the utility room so that the washing machine, dryer, and heating system are not heard in the living or sleeping areas. And that works perfectly. Anything else would be a disaster as I am very sensitive to noise. Therefore, whatever the issue is with the loud LWZ 504 mentioned earlier, something must have been installed or implemented incorrectly. I also know several others who have this model in their new builds, and theirs is just as quiet as ours.
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