© Leo Dörfler

“Fear has always trumped reason”

Climate protec­tion, effi­ciency and F-Gas Regu­la­tion – Christo­pher Hammel, Tech­nical Manager of SKADEC GmbH, explains the advan­tages of propane as a natural refrig­erant, why concerns are unfounded – and why EC fans are his tool of choice.

How did you become involved with natural refrig­er­ants?

In our parent company, Kratschmayer GmbH, we started looking into the subject years ago. At that time, only a few compa­nies had the use of natural refrig­er­ants on their radar. For us, the goal of pursuing a sustain­able approach was central, so we were looking for a supplier of R290 water chillers. But since we couldn’t find a supplier that met our require­ments, we started devel­oping the chillers ourselves.

Christoph Hammel, Tech­nical Director SKADEC GmbH

Initially, we produced water chillers exclu­sively for our own use within the Group. But then competi­tors also became aware of the machines and wanted to purchase them directly from us. Kratschmayer then decided to found SKADEC GmbH in 2018. This step was neces­sary because spin­ning off the busi­ness unit allowed us to concen­trate fully on the devel­op­ment and sale of water chillers and heat pumps using propane.

Why did you decide on propane?

Propane is a very effi­cient refrig­erant. Combined with its very good ther­mo­dy­namic prop­er­ties, rela­tively low pres­sure rating, good mate­rial compat­i­bility and high volu­metric refrig­er­a­tion capacity, it is possible to create very compact and effi­cient machines over a wide range of appli­ca­tions. It is also ideal for use in heat pumps. Its prop­er­ties can best be compared with those of R22, a refrig­erant that was very popular with older refrig­er­a­tion engi­neers but is now banned. Unlike R22, however, propane has no ODP, so it is not harmful to the ozone layer and has a very low global warming poten­tial of 3.

Have you worked with other natural refrig­er­ants before?

We have had points of contact with all natu­rally occur­ring refrig­er­ants except water. Each of the three has advan­tages and disad­van­tages. Ammonia is highly effi­cient, but toxic and corro­sive to copper mate­rials. CO2 can be used to create systems with very low temper­a­tures, but the oper­ating pres­sures are compar­a­tively high. Hydro­car­bons such as propane are flam­mable. In a direct compar­ison of the points rele­vant to us, such as appli­ca­tion range, handling, and avail­ability, propane provided the best overall package. In addi­tion, one of our refrig­er­a­tion engi­neers wrote his thesis on propane – so it was pretty obvious that we would build on that.

But when people think of propane, they imme­di­ately think of flam­ma­bility.

Fear has always trumped reason in this respect. I don’t want to down­play the risks of propane. Of course caution is required here. The fact is that it is a flam­mable gas. However, you also have to look at the whole thing in perspec­tive. Each of us handles hydro­car­bons on a daily basis, for example when refu­eling. As an example of people’s fear of flam­mable refrig­er­ants, I had a conver­sa­tion with a facility manager of a large corpo­ra­tion. He said: “Oh, propane on the roof? The plant fire depart­ment won’t stand for that!” The inter­esting thing here was that the corpo­ra­tion had a storage facility for large quan­ti­ties of solvents and gases at the loca­tion we were discussing.

“The system we were talking about had a fill rate of less than five kilo­grams. There’s more in a gas bottle for barbe­cues.”

The system we were talking about had a fill rate of less than five kilo­grams per circuit, so with two circuits, the total was ten kilo­grams. There’s more in an 11-kilo­gram gas bottle for barbe­cues. We also recom­mend installing propane systems above a certain fill level outdoors or in specially designed equip­ment rooms. Propane is very volatile, so there can be no propane buildup if the outdoor instal­la­tion is done correctly. We are happy to advise our customers, espe­cially on the impor­tant points of instal­la­tion and system plan­ning. So, a lot of factors have to come together for a poten­tial hazard.

How do you reduce the – albeit minimal – risk in your systems?

It goes without saying that our systems comply with the legal stan­dards and spec­i­fi­ca­tions. The connec­tions in the system are tech­ni­cally sealed for the long term, so leaks are very unlikely. However, if a leak should occur, our safety concept will kick in and ensure that no dangerous situ­a­tion can arise. We monitor the system contin­u­ously with a gas sensor that is coupled with a two-stage system.

“Our machines need highly effi­cient, compact fans that are easy to control.”

Propane ignites at a concen­tra­tion in the air of around 1.7 percent by volume as the lower limit and at around 10.8 percent by volume as the upper limit. When the gas sensor detects ten percent of the lower limit, i.e. of 1.7 percent by volume, the first stage is acti­vated. The machine housing with the refrig­erant-carrying parts is then venti­lated by a gener­ously dimen­sioned ATEX fan, meaning that the escaping propane is discharged directly into the envi­ron­ment in a concen­tra­tion that is not capable of igni­tion. When the 20 percent threshold is reached, all non-ATEX-certi­fied elec­trical compo­nents are de-ener­gized. All safety-rele­vant compo­nents are of course ATEX-certi­fied and remain in oper­a­tion.

You use fans from ebm-papst for your systems. Why?

EC axial fans of the AxiBlade series are extremely effi­cient, even at partial load, and are also quiet.

Our machines need highly effi­cient, compact fans that are easy to control. At SKADEC, we attach great impor­tance to high-quality compo­nents, which is why we use only EC fans from ebm-papst for the air heat exchangers. The AxiBlades used are extremely effi­cient, even at partial load. They are also quiet, which is of course a big plus for heat pumps, espe­cially when used in resi­den­tial areas. To ensure that the systems can run according to demand, the stan­dard Modbus connec­tion is also a great advan­tage. We can eval­uate all the data from the fans, thereby also providing our customers with digital added value. We were impressed by the effi­ciency of the EC tech­nology, and also by the quality of the prod­ucts and excel­lent inter­per­sonal rela­tion­ships. It was just a perfect all-round fit.

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Axial fan AxiBlade

Efiicient, quiet, flexible