Heating with heat pumps

Today’s heating systems demand concepts based on renew­able ener­gies. ebm-papst delivers low-noise and effi­cient compo­nents.

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With the new version of the F-Gas Regu­la­tion ((EU) 2024/573), which came into force on March 11, 2024, the frame­work condi­tions for these refrig­er­ants will become much stricter; the use of hydro­flu­o­ro­car­bons as refrig­er­ants (HFCs) will be further regu­lated. This means that natural alter­na­tives are the only way forward. However, these are flam­mable in most cases. When devel­oping refrig­er­ating systems and air condi­tioners, house­hold refrig­er­a­tors and heat pumps, manu­fac­turers must there­fore ensure that they only use compo­nents that meet the applic­able stan­dards for handling flam­mable refrig­er­ants.

The F-Gas Regu­la­tion and the phased plan defined within it for reducing CO₂ emis­sions (Fig. 1) means that manu­fac­turers of air/water heat pumps, as well as chillers, evap­o­ra­tors and refrig­er­ated cabi­nets, are increas­ingly using refrig­er­ants with a low global warming poten­tial (GWP), such as the natural refrig­erant R290 (propane, GWP value = 3). However, a low GWP value requires rapid decom­po­si­tion of the refrig­erant when it enters the atmos­phere. This can only be assured if it is chem­i­cally reac­tive, but high reac­tivity typi­cally goes hand in hand with a high level of flam­ma­bility. Special safety concepts are there­fore required to ensure that nobody is harmed if there is a leak in the refrig­erant circuit.

ATEX-approved compact fans for the safety concept

One – albeit rather elab­o­rate – method is the use of restricted-breathing hous­ings that prevent elec­tronic compo­nents and flam­mable atmos­pheres from coming into contact with each other. However, another solu­tion is usually more prac­tical for air/water heat pumps: In the event of a leak in the refrig­erant circuit, ATEX-approved compact fans (Fig. 2) venti­late the housing and prevent a flam­mable atmos­phere from devel­oping. Thanks to the fully encap­su­lated motor and elec­tronics, they meet the require­ments of EN 60079-7, Group IIC, up to T4 and DIN EN 60335-2-40 as stan­dard.

Due to their compact design, the fans require little space for instal­la­tion and can also be used for cooling elec­tronics if required. They can also be used as the main fan for smaller heat pumps, such as those used for floor heating. The ATEX-approved compact fans are avail­able in many vari­ants and in different sizes with edge lengths from 40 to 200 mm and offer high air perfor­mance levels. Thanks to their aero­dy­nam­i­cally opti­mized design, they operate quietly, are energy-effi­cient, and can be used for both intake and exhaust.

Drive design for the main fan in accor­dance with EN 60335-2-40

Even with the larger axial panel and centrifugal fans, which provide the neces­sary air flow over the evap­o­rator in heat pumps, the elec­tronics must not become a source of igni­tion if there is a leak in the refrig­erant circuit. For this reason, ebm-papst has modi­fied the elec­tronic circuits of its fan drives in sizes 60, 74 and 90 so that they comply with EN 60335-2-40 for heat pumps with flam­mable refrig­er­ants. This means that, in the event of a fault, the maximum surface temper­a­ture must be at least 100 Kelvin below the igni­tion temper­a­ture of the refrig­erant used. Propane, which is very suit­able due to its good heat transfer capacity and its low GWP value, has an igni­tion temper­a­ture of 470°C. The elec­tronic assem­blies, which have been tested and certi­fied accord­ingly, ensure that their maximum surface temper­a­ture always remains below 370°C, even if a fault occurs, so that they do not become an igni­tion source.

Fig. 3: Noise levels are partic­u­larly rele­vant at night, when the limits of the applic­able legal regu­la­tions must be observed both inside and espe­cially outside of build­ings. (Image | ebm-papst)

Fig. 4: The powerful, quiet-running AxiTone and AxiEco Plug-In axial panel fans were devel­oped for use in air/water heat pumps and are suit­able for appli­ca­tions with flam­mable refrig­er­ants. (Image | ebm-papst)

Axial panel fans for partic­u­larly noise-sensi­tive areas

Anyone using air/water heat pumps will inevitably have to deal with the issue of noise. Noise levels are partic­u­larly rele­vant at night, when the limits of the applic­able legal regu­la­tions must be observed both inside and espe­cially outside of build­ings (Fig. 3). ebm-papst has devel­oped two fan series for noise-sensi­tive outdoor areas: AxiEco Plug-In and AxiTone (Fig. 4).

Both are also designed for appli­ca­tions with natural and flam­mable refrig­er­ants (EN 60335-2-40) and are partic­u­larly quiet thanks to their special design (Fig. 5 and Fig. 6). While the AxiEco Plug-In in sizes 450 and 500 mm is suit­able for heat pumps that require a large supply pres­sure reserve at the evap­o­rator, the AxiTone in sizes 450, 500 and 630 mm is designed to deliver higher air flows at a lower back pres­sure if the heat pump design requires this. As all compact fans based on the fully encap­su­lated motors are suit­able for use with flam­mable refrig­er­ants as stan­dard, there are many other axial panel and centrifugal fans that are also suit­able for use with heat pumps, as well as chillers, evap­o­ra­tors, and condensers.

Based on many years of expe­ri­ence with heat pump appli­ca­tions, EC motors and their commu­ta­tion elec­tronics, ebm-papst has also devel­oped inverter elec­tronics (Fig. 7) that are suit­able for speed-controlled perma­nent magnet synchro­nous machines (PSM), as typi­cally used in compres­sors. They also reduce noise and simul­ta­ne­ously increase the effi­ciency of the heat pump.

Safety in refrig­er­ated cabi­nets

Natural refrig­er­ants are also used in other refrig­er­a­tion appli­ca­tions, such as refrig­er­ated cabi­nets. The ESM motor (energy saving motor, Fig. 8) set the stan­dard for fan tech­nology in this area several years ago. The compact EC motors are avail­able both as OEM compo­nents for combi­na­tion with the customer’s own fan impeller and as complete plug & play systems with perfectly matching indi­vidual compo­nents. In order to offer a safe cooling solu­tion, the motors and complete systems comply with house­hold appli­ance stan­dard EN 60335-2-89 as stan­dard. This is completely suffi­cient for most refrig­er­ated display cases, as their cooling circuits can handle the refrig­erant filling quan­ti­ties spec­i­fied in the stan­dard, e.g. 500 g for propane. For refrig­er­a­tion circuits with larger filling quan­ti­ties, it may there­fore make sense to split the circuits.