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.
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
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
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 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.