When it comes to central­ized units for home venti­lation, the market trends towards back­ward-curved centrifugal fans. There is a good reason for this: The RadiCal centrifugal fans in the aero­dy­nam­i­cally opti­mized scroll housing from ebm-papst have been specially devel­oped for use in home venti­lation units (Fig. 1).

Figure 1: RadiCal centrifugal fans in a scroll housing opti­mized for aero­dy­namics are avail­able for use in central resi­den­tial venti­lation units, here with an addi­tional Flow­Grid air-inlet grille on the intake side.

This achieves an energy effi­ciency improve­ment of more than 30% in compar­ison to forward-curved fans, which are still widely used in venti­lation units.

The improved energy effi­ciency is based on the combi­na­tion of RadiCal fans with a scroll housing opti­mized for aero­dy­namics. The extremely effi­cient Green­Tech EC motors also contribute towards energy effi­ciency.

The round outlet of the new scroll housing fits directly onto the pipes that distribute the air. This reduces airflow losses in the pipe system. The noise level is also reduced by up to 3.5 dB(A) when compared to a centrifugal blower, as has been confirmed in numerous tests (Fig. 2).

The disturbing tonal noise of a back­ward-curved impeller in a living envi­ron­ment has been signif­i­cantly mini­mized through the combi­na­tion with the opti­mized scroll housing. The tonal propor­tion in the disrup­tive frequency range is reduced by up to 20 dB in compar­ison to conven­tional instal­la­tion condi­tions.

Figure 2: The noise compar­ison shows that the RadiCal in the scroll housing (contin­uous line) is quieter than a centrifugal blower fan (broken line) by 3.5 dB(A).

Further­more, the fan can be mounted very easily in the venti­lation unit via the discharge flange and even combined with the Flow­Grid air-inlet grille, which can be mounted on the intake side. This reduces the turbu­lence caused by fittings in the unit, thus further mini­mizing the noise emis­sions.

Inte­grated volume constancy control

Figure 3: Plug & Play – solu­tion: The blower opti­mized for aero­dy­namics includes a control elec­tronics system as well as sensors to detect the air volume, temper­a­ture, and humidity.

Due to phys­ical factors, the volume flow control in back­ward-curved centrifugal fans is more costly than in forward-curved fans.

However, ebm‑papst has a ready-to-install plug & play solu­tion for this: An impeller manometer posi­tioned in the outlet of the scroll housing (Fig. 3) contin­u­ously records the actual air flow and trans­mits the data to the inte­grated central elec­tronics system of the fan.

This central elec­tronics system adapts the speed of the EC motor to the desired setpoint value, thus regu­lating the air volume (Fig. 4). Thanks to the impeller manometer (patent pending), the air flow can be regu­lated with an accu­racy of +/‑1 % (to the end value) in an air perfor­mance range from 50 m³/h to 500 m³/h (Fig. 5). This is signif­i­cantly more accu­rate than the systems currently avail­able on the market.

Figure 4: The central control elec­tronics of the fan regu­late the air volume depending on the ACTUAL air flow recorded using an impeller manometer posi­tioned in the air flow.

In this appli­ca­tion, a signif­i­cant advan­tage of EC fans is that they retain their high effi­ciency and control accu­racy even in partial-load oper­a­tion.

The inte­grated volume constancy control enables effec­tive home venti­lation without an over­pres­sure or under­pres­sure occur­ring in the living space. This prevents humidity in the walls and unwanted cold air supply from outside.

The addi­tional impeller does not result in any air perfor­mance losses or disrup­tive noise, meaning that the overall perfor­mance of the fan remains unchanged. Even cont­a­m­i­na­tion is not a problem, as has been demon­strated in tests under extreme condi­tions with dust and increased air humidity.

Compre­hen­sive sensor system and commu­ni­ca­tion via MODBUS-RTU

The central elec­tronics inte­grated in the blower offer even more options in addi­tion to the motor control and volume flow control. Through the inte­gra­tion of a sensor in the blower outlet, it is possible to directly record the humidity and temper­a­ture of the supplied air. Further­more, three addi­tional external sensors can be option­ally connected (Fig. 6). There are two analog inputs and one digital input (I2C) avail­able for this. Another 0‑10 V input enables the connec­tion of CO₂ or VOC sensors to record air quality, for example.

With this wide range of options for recording air quality, the venti­lation in living spaces can be opti­mally controlled to provide a pleasant inte­rior climate. Along­side the values detected by the sensors, it is also possible to record the oper­ating data of the motor via the central fan elec­tronics. This enables recording of the running time of the blower in order to deter­mine when the filter needs to be changed, for example. All infor­ma­tion can be commu­ni­cated conve­niently via the MODBUS-RTU inter­face. Alter­na­tively, a 0-10 V inter­face is also avail­able, which the user can use to control the fan speed as desired.

The fan is the intel­li­gent “heart” and central infor­ma­tion source of the controlled resi­den­tial venti­lation system. It is there­fore much more than just a fan that supplies air.

Figure 5: Exam­ples of volume constancy control stages. Thanks to the impeller manometer (patent pending), the air flow can be regu­lated with an accu­racy of +/-1 percent (broken line) in an air perfor­mance range from 50 m³/h up to 500 m³/h.

Perfectly equipped for the EU Ecode­sign Direc­tive

Figure 6: The central control elec­tronics process the signals of the connected sensors, control the motor, and commu­ni­cate all data via the MODBUS-RTU inter­face with the device control of the resi­den­tial venti­lation system.

The RadiCal centrifugal fans in scroll hous­ings are offered in size 190 with various output levels up to 170 W depending on the rated air perfor­mance of the venti­lation units. The series is being expanded to include further sizes and versions. In addi­tion to the EC versions, an AC version without sensors is also avail­able for appli­ca­tions that require less energy.

However, in most cases it may make sense to use the energy-effi­cient EC tech­nology that can be regu­lated as required. This is neces­sary if the inten­tion is to achieve the highest possible energy rating label for the end device.

Since January 2016, the EU Ecode­sign Direc­tive has stip­u­lated that venti­lation units with heat recovery must save as much primary energy as they consume, and must bear the corre­sponding energy label. The require­ments in this regard are set to tighten further in 2018 and 2020.