Spec­i­fi­ca­tions, like those defined in the Climate Action Plan 2050, are set down in law with a view to protecting the envi­ron­ment. The overall aim is to reduce carbon dioxide emis­sions by 80 to 95% as compared to the 1990 level. Building heating systems in partic­ular offer great poten­tial for savings. Simply by making consis­tent use of condensing tech­nology and signif­i­cantly increasing the rate at which old heating systems are replaced (6% p. a.), it would be possible to lower the CO₂ emis­sions gener­ated by total power consump­tion in Germany by around 15% by the year 2030.

A prac­ti­cable approach to heating system renewal

TIn theory, house owners can save a lot of money and fuel by using the latest tech­nology in their heating systems. In prac­tice, however, that is asso­ci­ated with a great deal of expense and some­times a lot of construc­tion work. This natu­rally gives rise to a consid­er­able modern­iza­tion backlog, and regret­tably plenty of boilers more than 30 years old are still to be found. What is to be done? Gradual modern­iza­tion, starting with the boiler, then the windows and later on insu­la­tion of the outside walls or attic conver­sion etc., is a solu­tion which reduces the finan­cial burden and is less nerve-wracking in the short term. It does however presup­pose that the new heat source will be able to cope with the different require­ments and always operate effi­ciently.

Picture 1: By way of example, the pressure/air flow graph of the VG 100 shows the broad perfor­mance range of the new gas blowers. (Source: ebm-papst)

Regional building regu­la­tions often addi­tion­ally demand the use of renew­able ener­gies in the event of exten­sive modern­iza­tion. The problem: if base load heat pumps are fitted, these should be designed for a fixed heat output or a fixed heating temper­a­ture to obtain effi­cient oper­a­tion. If condi­tions are altered by later reno­va­tion work, such as further insu­la­tion measures or fitting new radi­a­tors, the heat pump will often operate less effi­ciently, and what was intended as a “saving” will actu­ally make heating more expen­sive.

Such prob­lems can be avoided by using a heating system with scal­able output (picture 1). Oper­a­tion of the heating system in conjunc­tion with thermal solar collec­tors is asso­ci­ated with a fluc­tu­ating heat demand, to which the heating system has to flex­ibly react. Ideally, a heating system should be able to satisfy all these require­ments without any loss of effi­ciency. What form could such an econom­ical and ecolog­ical solu­tion take?

Condensing tech­nology with gas blower

Condensing tech­nology is an extremely effi­cient method of heating. Gas condensing boilers are not just a compact and inex­pen­sive solu­tion, they also offer a scal­able heat output. Thanks to the low heating water temper­a­tures permitted by the design, the condensing units are also ideal for combi­na­tion with other heating concepts such as solar heating and heat pumps. Condensing tech­nology makes use not only of the “normal” heat of the energy contained in the fuel (gas), but also of much of the so-called latent heat of the water vapor contained in the exhaust gas from the combus­tion process.

Its high hydrogen content makes natural gas partic­u­larly suit­able for this. Given an energy content of around 10 kWh/m³ natural gas, this yields up to 3 kW extra heat output with a natural gas consump­tion of 2 m³/h – corre­sponding to a conven­tional heat output of roughly 20 kW. This is obtained solely through the lowering of the exhaust gas temper­a­ture from the stan­dard 150°C to e.g. 40°C and hence 80% conden­sa­tion of the water vapor contained in it (around 1.5 l per m³ gas). As compared to conven­tional systems with an exhaust gas temper­a­ture of 150°C, this repre­sents an up to 15% increase in effi­ciency.

Picture 2: The new RadiMix product range reduces the existing number of gas blower types between 0.5 and 150 kW by a good 20%. (Source: ebm-papst)

This offers many advan­tages, as less fuel is required and a gas condensing boiler is far more compact than a conven­tional boiler. The low temper­a­tures also make exhaust gas ducting less expen­sive. What’s more, modern condensing boilers are elec­tron­i­cally controlled and flex­ibly adapt the burner and pump output to the heating output currently required. This reduces the switching rate of the device and the cooling losses in the inter­vals between the oper­ating phases.

But here again the effi­ciency levels given only ever reflect a momen­tary status and only relate to the current ratio between input and output power. This is however not suffi­cient for the assess­ment of a condensing boiler, as it does not take the standby heat loss into account. In other words, it only calcu­lates the losses occur­ring with the burner in oper­a­tion — and, even then, only at one oper­ating point. A shift in the oper­ating points as a result of different usage or exten­sive modern­iza­tion etc. will render the entire cost-benefit analysis invalid. An answer to this problem is a scal­able burner output which can be achieved with the broad modu­la­tion ranges of the gas blowers used.

These adapt ideally to the instan­ta­neous heat demand without any loss of effi­ciency. The old rule of thumb, that 50% of the maximum heat output as per DIN 4701 is often suffi­cient to cover 90% of the heating energy demand and that many heating boilers are over-dimen­sioned with corre­spond­ingly high standby losses to cover the remaining 10%, thus no longer applies.

Modern gas blower plat­form for outputs from 0.5 to 150 kW

With their broad modu­la­tion range, the new RadiMix gas blowers from ebm-papst Land­shut reduce precisely these standby losses. This means that the blowers can adapt the gas/air mixture quan­tity in a broad range up to 1:15 whilst main­taining a constant quality for optimum, low-emis­sion combus­tion. At the same time, the new RadiMix product range reduces the number of different gas blower types by a good 20% (picture 2).

Boiler manu­fac­turers now require just three versions to cover output levels from 0.5 to 80 kW, and a fourth blower will be coming onto the market next year to fill the gap up to 150 kW. The smallest gas blower, the VG 71, provides a heat output of up to 35 kW whereas the figure for the larger version, the VG 100, is up to 50 kW. The VG 108 with a heat output of up to 80 kW is ideal for large heating systems in apart­ment blocks, for example.

Along­side the vari­able heat output, instal­la­tion has also become more versa­tile, e.g. thanks to 360° motor posi­tioning and hence the possi­bility of connector posi­tioning to suit customer require­ments. In future, the gas blowers will also be avail­able with venturi and gas valve as a perfectly coor­di­nated complete system for partic­u­larly low-emis­sion combus­tion (picture 3).

Picture 3: A lot of plat­form compo­nents can be combined for different output classes. (Source: ebm-papst)

Each blower features a new motor concept, specially adapted aero­dy­namics and isola­tion from vibra­tion devel­oped specially for the blowers to guard against struc­ture-borne noise. The design of the motors with main­te­nance-free ball bear­ings is adapted to the higher air mixture conveying capacity required, for example through the use of a magnet mate­rial with far greater magnetic rema­nence and a completely new motor topology. Depending on the version, this can enhance drive effi­ciency by a good 5%.

Along­side a decrease in air-borne noise, it also proved possible to signif­i­cantly reduce vibra­tion (struc­ture-borne noise) through simu­la­tion and testing with state-of-the-art devel­op­ment tools. As compared to the prede­cessor model, the oper­ating noise dropped by more than 3 dB(A) depending on the blower type. The elec­tronics have also been completely re-designed and now feature optional BUS inter­faces for easy inte­gra­tion into digital systems. Oper­ating states such as output, service status, temper­a­tures, oper­ating voltage and other data processed in the blower control systems can be called up via planned BUS inter­faces (ebm-papst is pursuing the approach of working with the LIN-Bus protocol).

This not only makes incor­po­ra­tion of the blower into the boiler control system easy to imple­ment, it will also permit preven­tive main­te­nance or remote diag­nosis in the near future. Thanks to the use of a cooling concept already success­fully employed in other prod­ucts, the elec­tronics are also located in the cooling airflow, thus making for greater reli­a­bility and a longer service life. A robust motor protec­tive cap perma­nently attached to the housing encloses all the drive compo­nents.