New gas blower impresses with high power density

At the end of the 1980s, gas blowers were already being devel­oped for the modern heating systems known today as “condensing boilers”, which have since become wide­spread due to their very good energy exploita­tion. The gas blowers are arranged upstream of a burner to blow in the gas/air mixture. Like in other appli­ca­tions, the trend in heating systems is also moving towards compact, space-saving devices. Gas blowers of the latest gener­a­tion reflect this. Today, compact “power packs” are on the market that weigh only 20 kg, even in the heavy­weight cate­gory of 1 MW heat output. These impress with their extremely high power density.

Typical pressure/air volume curve for gas blowers for burner controls.

An optimum combus­tion process and low emis­sions for condensing boilers require, for example, the exact mixing ratio of gas and air. The high flow resis­tance of such condensing boilers means that blowers are needed with a steep-gradient pressure/air volume curve. The motor and fan specialist ebm-papst Mulfingen offers suit­able blower solu­tions meeting these require­ments for a wide range of appli­ca­tions. The single inlet radial blowers are installed in scroll hous­ings. The gas blowers’ char­ac­ter­istic features include high effi­ciency, low noise levels, high static pres­sure increase and a compact design, thanks to which they only require a small instal­la­tion space. The bene­fits can be exploited when­ever high heat output is required. The successful line has there­fore been extended to include a new gas blower that is suit­able for heat outputs of up to approx. 1 MW. This means that the gas blowers now cover a power range from 10 kW to 1 MW. Heating appli­ca­tions from detached houses to multi-family homes can thus be realised, and new appli­ca­tions are also possible in indus­trial build­ings.

High-perfor­mance EC motor as driving force

Gas blowers of different power classes cover a wide range of appli­ca­tions.

The driving force behind the new gas blowers is an elec­tron­i­cally commu­tated motor with three-phase power supply. The EC motors of the model series 112 which are inte­grated into gas blowers have already proven their worth in numerous fans and impress with their good noise char­ac­ter­is­tics, simple connec­tions and low energy consump­tion. They work with an effi­ciency of up to 90%, achieving substan­tially higher values than the asyn­chro­nous motors other­wise commonly used in this power class. The resulting energy costs are dras­ti­cally lower, which soon becomes evident in prac­tical appli­ca­tion as the blower usually runs in contin­uous oper­a­tion. This also applies for partial-load oper­a­tion. In this range, EC motors lose far less effi­ciency than asyn­chro­nous motors of the same power, whose effi­ciency, which is already poorer, drops substan­tially further in the part load range.

The different curves illus­trate the power input of controlled AC/EC motors in compar­ison. In all speed ranges, the energy costs for EC motors is much lower that for voltage-controlled or frequency-inverter-fed asyn­chro­nous motors. At the same time, EC motors display impres­sive dura­bility. Their greater effi­ciency does not just mean better use of primary energy. It also means that less heat is lost to the envi­ron­ment, which has a posi­tive effect on the service life of the ball bear­ings employed.

Quiet and easy to control

The different curves illus­trate the power input of controlled AC/EC motors in compar­ison.

Thanks to their design prin­ciple, EC motors also run extremely quietly. This is due in part to the motors’ opti­mised elec­tro­mag­netic circuitry and to the special commu­ta­tion tech­nique. Vibra­tion devel­op­ment and noise emis­sions are thus dras­ti­cally reduced. All of the power elec­tronics are inte­grated into the motors. These are actu­ated by the burner control, either via a PWM signal or with a linear input of 0-10 V, which then controls the blower speed according to the required heat output.

The set values for the speed and thus ulti­mately for the gas volume can be freely varied via the PWM input. If you need to change the speed manu­ally using an adjusting knob, simply connect a poten­tiometer. The neces­sary supply voltage is provided by the inte­grated motor elec­tronics directly via an elec­tri­cally isolated voltage output. The speed control also helps to reduce noise levels and to save energy as the blower only delivers as much gas mixture as is really needed. This constant modu­la­tion minimises above all the espe­cially high losses during the burner start-up phase, which has the effect of reducing emis­sions from the heating system. Natu­rally, the impellers employed in the centrifugal blowers also satisfy the strictest of require­ments. These have been opti­mised in accor­dance with aero­dy­namic criteria, so they also help to ensure smooth running and low noise emis­sions.

Compact and just 20 kg in weight

The blower satis­fies all rele­vant stan­dards for use in both domestic and indus­trial envi­ron­ments, giving it a wide range of possible appli­ca­tions.

The new high-perfor­mance gas blower measure a mere 47 cm high, approx. 43 cm wide and about 40 cm deep along the axis. And because they weight just 20 kg, they can easily be trans­ported without needing tech­nical aids such as fork-lift trucks. This makes instal­la­tion and service far simpler. And if you want to convert the current 750 kW model to the new 1 MW gas blower, that won’t be a problem. The units can be simply inter­changed as the blower inlet and outlet are iden­tical to the current model. The new gas blower works with the same impeller and has almost iden­tical housing dimen­sions. Only in the axial direct does it need a little more instal­la­tion space on account of the higher-perfor­mance motor. Upgrading to a greater output thus entails no major system modi­fi­ca­tions.

The new gas blower design works with speeds of up to 6,400 rpm and needs – thanks to its high power – a three-phase rated input voltage of 400 VAC. A version with a three-phase rated input voltage of 208 VAC is avail­able for the North Amer­ican market. Because the blower satis­fies all rele­vant stan­dards for use in both domestic and indus­trial envi­ron­ments, it also has a wide range of possible appli­ca­tions. They can be found every­where in heating equip­ment and will certainly also be found in future indus­trial appli­ca­tions, espe­cially as suit­able, easy-to-fit gas mixture solu­tions working on different oper­a­tional prin­ci­ples are already on the market for the new blower.