A "Panasonic Mini VRF system U-5LE2E8" was installed on an intermediate roof between two single-family houses near Frankfurt.
The system has the following dimensions: 980 x 370 x 996 (+ 200 vibration dampers) mm (W x D x H).
At maximum output, the system has an air volume of 4,320 m3 / h, the static pressure of the fan is around 15 to 20 Pascal. When planning the acoustic hoods, we assumed a static pressure of <15 Pascal.
By means of the acoustic hood, the noise level is reduced to the neighborhood, the next window is around 7 meters away from the acoustic hood.
Acoustic hood concept
The air inlet is at the rear (condenser side towards the roof). This enables us to achieve an even air flow to the condenser without causing a pressure loss due to excessive air deflection.
The air outlet is on the front side (fan side), front left. A deflector plate was also installed here at the air outlet, which ensures the air outlet speed of 1.4 meters / sec. continues to insulate.
In this way, we achieve a continuous flow of exhaust air without creating an air short circuit. With an air outlet speed of around 1.4 m/sec. hardly any sound is transmitted via the air outlet.
The basic structure of the acoustic hood is based on aluminum system profiles which have the advantage of being light in weight when mounted on the roof. Around the system as well as in the enclosures roof, aluminum sheets were installed as easy-to-open service doors with a thickness of 1.5 mm with internal 50 mm insulation made of closed-cell, semi-rigid and sound-absorbing polyethylene foam sheets (Stratocell Whisper). Due to its sound-absorbing properties, this foam is one of the most innovative materials for sound control in HVAC systems.
The insulation is UV and water resistant and non-flammable. The isolation does not build up bacteria or fungi. And has strong sound insulation across all frequency bands. In this way we prevent masking effects that often occur when eliminating high-frequency sound bands and which lead to an increase in the tonality of the compressor sound.
The insulation is also light and hardly increases the weight of the service doors.
Sound hood dimensions
The acoustic hood has the following dimensions: 1,700 x 1,300 x 1,100mm (W x H x D) / weight including service doors 127 kg. The acoustic hood is made entirely of aluminum and was subsequently powder-coated in RAL color 7016 to match the color of the roof.
Sound reduction between 18 to 20 dB (A)
A total of six acoustic enclosures for six tabletop Heat Pump evaporator modules were created for this project. Since the heat pumps are in series, the air inlet and the air outlet have been moved on both sides.
The cold air is blown out on the side opposite the air outlet so that an air short circuit between the air inlet and the air outlet is impossible. The air chambers are separated by a deflector plate in the middle of the hood. The air outlet going up is deflected by 90° and thus the airborne sound is broken.
The sound reduction on all sides is around 19 dB (A) over the entire frequency band.
The hoods each have the size of: 1'700 x 1'000 x 1'700 mm (L x W x H) and are completely made of aluminum and then powder-coated in RAL color 9003. The systems are freely accessible for service and maintenance work via service doors that are installed around the systems.
The sound hoods were delivered to the construction site in AMSTERDAM pre-assembled.
The picture shows a acoustic enclosure for a Carrier refrigeration system with four axial fans with vertical air flow and an air volume of 28,900 m3/h at the highest performance level.
The system is used to cool the production rooms of a food manufacturer and is in the immediate vicinity of a residential area. Noise complaints from residents led to the system being fitted with a sound barrier.
The acoustic hood offers the following advantages:
Noise reduction over the entire frequency band of -19 dB (A) so that the system also fulfills the maximum permitted sound level for residential areas of 35 dB (A) in the evening and after hours at the next immission location (nearest window to the system). #
The acoustic hood is made entirely of aluminum and powder-coated in RAL color 9006.
Infrared refrigerant sensors with a detection limit of ≤ 10 ppm, which are built into the hood, warn the operator of even the slightest loss of refrigerant. The sound enclosure was delivered to the construction site pre-assembled in 4 parts and set up on the additional concrete foundation built around the system in less than 2 hours.
Therefore, our acoustic enclosures leave our warehouse every day for customers in order to guarantee quiet operation for all possible heat pump models across all performance classes.
Today's strict regulatory requirements regarding the noise emission limits of heat pumps in residential areas lead to increasing planning uncertainty and increased disputes between neighbors.
In fact, heat pumps installed outdoors can only be installed at a distance of 10 to 15 meters from the next neighboring window. With today's compacting construction, distances can hardly be maintained.
Many homeowners are therefore faced with the choice of replacing an old oil heater with a modern one or with a climate-friendly heat pump when they need to change the heating system.
A decision that depends not least on the options for installing a heat pump or the additional options for additional soundproofing.
In this sense, acoustic hoods create planning security and enable heat pumps to be operated in close proximity to the neighborhood.
Silent-Mode Acoustic Enclosure for 2 Panasonic VRF systems during construction for a supermarket.
The sound hood enables a sound reduction of around 22 dB (A) and protects the adjacent residential buildings from noise emissions from the systems.
Enclosure Size: 3'200 x 1'280 x 2'550 mm (L x D x H)
Acoustic enclosure for a Mitsubishi City VRF system installed on a terrace in the immediate vicinity of apartments.
Sound reduction around 25 dB (A).
Enclosure Size: 1'280 x 1'280 x 2'550 mm (L x D x H)