EC fans for fan coils

Selecting a suit­able fan is no easy task for the producers of fan coils. Besides having the required power, running as quietly as possible and fitting into the housing, the fan drive that is used needs to operate in a way that matches the application’s require­ments, since the drive has a crit­ical effect on energy consump­tion and thus on oper­ating costs. Depending on the appli­ca­tion, other fan char­ac­ter­is­tics can also be impor­tant. For example, when several EC fans are oper­ated in parallel, active power factor correc­tion (PFC) prevents objec­tion­able harmonics and the rele­vant require­ments of EN 61000-3-2 can then be met without addi­tional engi­neering effort.

Fan coils used in offices, hotel rooms or munic­ipal facil­i­ties are often oper­ated in parallel connec­tion. This method of connecting the EC fans that are usually used in these devices for reasons of energy effi­ciency and noise reduc­tion does not fully exclude effects on the grid. The pulsed input current of EC fans gives rise to current harmonics, which strain the supply grid and can cause increased losses due to reac­tive power. In parallel oper­a­tion of multiple EC fans, this can cause the permitted thresh­olds according to EN 61000-3-2 to be exceeded and can have a nega­tive effect on other devices in the system network.

Expen­sive but avoid­able inter­fer­ence suppres­sion measures

A remedy for this problem can be expen­sive. The oper­a­tors need to ensure suffi­cient reac­tive power compen­sa­tion and provide central inter­fer­ence filters, which of course take up space. And space is often in short supply. Since the harmonics also affect the internal supply network, consid­er­a­tion must also be given to adequate cable cross sections. When retro­fitting fan coil units, new wiring may even be neces­sary. However, installing it usually proves diffi­cult or even impos­sible in prac­tice for struc­tural and economic reasons. Of course an external inter­fer­ence filter could be connected to each fan, but such devices are costly and may not exactly match their fans’ motors and are thus only condi­tion­ally adequate.

Figure 1: The EC centrifugal fans are avail­able in single, twin and triple config­u­ra­tions for air perfor­mances of up to 2,500 m³/h in the power range up to 250 W.

Now plan­ners and oper­a­tors can save them­selves all this trouble since the motor and fan specialist ebm-papst Mulfingen has addressed this issue. Now its EC centrifugal fans (Figure 1), which are specially designed for use in fan coil units, are now also avail­able with active PFC. This inte­grated power factor correc­tion converts the pulsed input current of the EC motors into a sinu­soidal current. In the second step, the current is shifted so that it is in phase with the voltage. This signif­i­cantly reduces the harmonic content of the input current. The effec­tive value of the input current is also mini­mized and it is possible in many appli­ca­tions to select a smaller cross-section for the fan supply lines. Figs. 2 and 3 show the same combi­na­tion of motor and fan impeller at the same oper­ating point and with iden­ti­cally adjusted air perfor­mance with and without active PFC. Prob­lems with harmonics and reac­tive power losses are no longer cause for worry thanks to the inte­grated power factor correc­tion, which is perfectly matched to the motors. The require­ments of EN 61000-3-2 are fulfilled with no addi­tional measures.

Figure 2: Without power factor correc­tion (pulsed current curve shown in red): power factor = 0.53. The result: The peaks distort the network. The voltage curve is shown in blue.

Figure 3: With power factor correc­tion (sinu­soidal current curve shown in red): power factor = 0.99. Ideally, the regu­lated current has the same phase as the line voltage. The voltage curve is shown in blue.

Energy-saving and quiet

But the EC centrifugal fans have more to offer. For instance, fan coils are gener­ally oper­ated for extended periods, so high effi­ciency levels gain partic­ular signif­i­cance. The EC fans are also effec­tive in this regard. They work with high effi­cien­cies. Since their Green­Tech EC motors consume up to 70% less energy than conven­tional AC motors, they have a noti­cable effect on oper­ating costs (Figure 4).

Figure 4: The invest­ment in Green­Tech EC tech­nology is already amor­tized in less than two years thanks to its low energy consump­tion. Main­te­nance-free oper­a­tion and long service life reduce life cycle costs even further.

High effi­ciency also means that less heat is dissi­pated. When the fan coil is in cooling mode, dissi­pated heat would mean that addi­tional cooling output is required. In addi­tion, the low motor temper­a­tures have a bene­fi­cial effect on the service life of the ball bear­ings. However, modern EC tech­nology does not provide savings only during full-load oper­a­tion. It is exactly when oper­ating under partial load that EC motors lose much less of their effi­ciency. This means that the energy savings become notice­able even when the fans are oper­ated in low speed ranges, and oper­a­tors quickly notice the bene­fits on the bottom line. The EC centrifugal fans are avail­able in single, twin and triple config­u­ra­tions for air perfor­mances of up to 2,500 m³/h in the power range up to 250 W. All versions are specially designed for low-noise oper­a­tion; they are very compact and can be easily installed as a plug & play solu­tion. The fan is mounted on its exhaust flange and connected using a plug system. The plas­tics used are light, yet durable and sound-absorbing; this combined with aero­dy­namic design allows the fans to operate at very low noise levels.

For different needs

Figure 5: The EC centrifugal fans are ideal for use in fan coils.

Since users should always pay only for the tech­nology they need, in addi­tion to the stan­dard version that can option­ally be equipped with power factor correc­tion, there is also a basic version which also offers all the bene­fits of Green­Tech EC tech­nology and is suit­able for appli­ca­tions in which a PWM signal is suffi­cient for infi­nitely vari­able speed control. There are now effi­cient EC centrifugal fans avail­able for use in various fan coil appli­ca­tions; they can also be used for other appli­ca­tions with similar require­ments (Figure 5). The air curtains in the entrance areas of depart­ment stores or factory halls are an example.