For more than 60 years products from our house ensure the right temperatures. Through path- breaking developments in the field of refrigeration and air- conditioning engineering we have gained worldwide recognition.

Our product range covers unit air coolers, fan coils and finned heat exchangers. We only produce at our company located in Gerlingen near Stuttgart.

Fan Coil Units
Air Coolers
Heat Exchangers

Options Industrial

Heat exchangers

Our air coolers are designed for refrigeration applications. Our cooler work efficient in the Standard Condtions according to EN 328, with refrigerants like R404A, R507A or R134a.

If a cooler should be operated outside the limits specified in the catalogues or the selection software, it is possible to adjust the circuiting of the air unit coolers to ensure the operation of the unit.

For different refrigerants e.g. R410A, R407C etc. special heat exchangers are available on request.

Water/ brine heat exchangers

Water connectionUnit air coolers can be equipped with heat exchangers for water or brine operation. Compared to refrigerant heat exchangers the ones for water operation are equipped with threaded fittings, and have an optimised circuiting for water / brine operation. On request the heat exchangers can be prepared for bleeding/ draining.

The maximum allowable pressure for "water" heat exchangers is PS 16 bar.

Regulary used brines are e.g.

  • Ethylene glycol
  • Propylene glycol
  • Temper
  • Tyfoxit

The heat exchanger consists of wide tubes for a minimum of pressure loss, and optimised ciruiting to suit your application.

Flooded evaporator

Every heat exchanger can be equipped for flooded evaporation.


On our unit air coolers we only use high quality fans of well- known manufacturers designed for application in refrigeration. These fans match typical requirements of cold storage.

Due to that the temperature range of the fans is limited to typical refrigeration applications. 

Higher ambient temperatures, more energy-efficieny, explosion-proof, different voltages are exemplary reasons to change the standard fan.

EC fans

Electronically commutated fans are the latest electric motor technology in the market. Due to their higher efficiency than shaded pole and even AC motors, the waste heat of the component is minimized. As an additional feature EC fans are r.p.m. adjustable, only with a minium loss of efficiency.


Streamer attached to fanBy means of the streamer the air throw of cubic air coolers can be increased. An additional feature is due to the removal of the spin generated by the fans, the air is lead straightforward into the room and doesn't touch any surrounding surfaces.

The streamer is available for all standard fans except the diameters of 560 mm. If a custom fan has been incorporated into the unit air cooler the possibility of mounting the streamer has to be checked in advance.

Hingeable fans

Hingeable fanHingeable fans are a good way to remove the electric drive for cleaning and inspection purposes.
Cleaning duty can be done contrary to the air direction by high- pressure cleaner, which is the most effective way. Additional it is much simpler to clean the fan itself.


Due to frost formation on the fins, coolers have to be defrosted regualary to keep their performance. Frost can be removed in many ways.


Heater rods inside a DLKAll Roller industrial air coolers are available as a T- Version. T is the abbreaviation for the german "Tiefkühlung" - low temperature applications. The T- versions differ from the normal air unit coolers in the following ways:

  • Aluminium sleeve tubes inside the heat exchanger in which special stainless steel heaters are incorporated.
  • Heaters for the drain pan that are mounted to the inner bottom sheet of the cooler.

The well-thought-out layout of the heaters ensures a uniform and complete defrost operation.

Defrost safety thermostat

Defrost safety thermostatThe defrost safety thermostat terminates the defrost in case of an failure of the defrost control. A wide range of Roller air unit coolers is already prepared for the installation of the defrost safety thermostat.

Technical data:

Fixed break point,
disconnects +25 °C,
connects +3,5 °C
Contact load at 230 V, 50 Hz:
ohmic Imax 25 A,
inductive Imax 5 A,
Protection class IP 44.
Connection cable 2 cores, 75 cm long.

SI flexible heater

SI flexible heaterThe SI flexible heater is designed to heat the plumbing of the condensate drain. It's available in different lengths to satisfy your application. The SI flexible heater is not designed for contious operation.

Water spray lance

The water spray lance is a very effective way to defrost a cooler, if water is available, and temperatures are near the freezing point. The water spray lance sprayes water into the cooling coil which defrosts the coil block. The water defrost lance is considered to be one of the most energy efficient defrost ways. Because depending on the water temperature only a minimal amout of energy is brought into the cooling chamber. In some application water spray lance might be operated by propylen glycol, to defrost in freezing applications.

Brine defrost

A new innovative solution for defrosting is by brine. In nearly every refrigeration plant there is a huge amount of heat, which is blown into the environment. For example it is possible to install a small hot gas desuperheater that heats up a  brine. Of course you need some kind of hot water storage tank an additional pump and plumbing, but therefore the amount of electric energy can be reduced up to 80 %.

Due to the need of a special design of the heat exchanger inside the heat exchanger it is necessary that we are involved in the planning process. Please call us.

Hot gas defrost

Hot gas defrostHot gas defrost is an either energy saving possibility to defrost the coil block. It is possible to equip the coil with a preparation for hot gas defrost operation. This includes a T at the distributor and a coil at the bottom sheet of the evaporator.

We recommend to lead the hot gas line first to the bottom coil, than to the collector of coil block and go back to the compressor via the T at the distributor.

As there are several possibilities for defrost control and different conditions at the plant there are probably better solutions of a hot gas defrost design.

Defrost help and cover

Shut up and cover

Defrost help and cover is the choice for improving the defrost cycle by fittings. By closing the air inlet with a cover and the fan opening by defrost help, the generated heat stays where it has to be: Inside the air unit cooler. Of course more mounting parts lead to a reduction of the air flow.

There are different ways to handle the reduction of the air flow, please call us when designing.

Heater for fan collar ZH

Fan collar heaterDuring the defrost process it is possible that genearted steam condenses inside the fan collar. After terminating the process the water freezes and prevents the fan from rotating or leads to terrible sounds. If a readjustment of the defrost control doesn't lead to satisfactory results, the heater for fan collar ZH is a simple solution.

The fan collar heater is not combatible with Shut- Up!

Protection against corrosion

If an air unit cooler is defective, corrosion is one of the most possible reasons. That is why in certain cases it makes sense to protect the air cooler from possible damage caused by corrosive environments.

Contents of corrosive environments are for example:

  • Acetic and other organic acids
  • Amines and ammonia compounds
  • Chlorine 
  • Salt
  • Cleaning agents

In corrosive environmets the heat exchanger should be cleaned more often than in neutral environments, depending on the corrosiveness a minium interall of an quarter year is suggested.

Type C

If the complete heat exchanger is varnished by 2 K laquer or powder- coated it's called protection against corrosion type C.

These type of corrosion protection is used at the Co2olers.

Type D

Protection against corrosionThe protection against corrosion type D is a combination of different anti corrosion actions, that lead to sja atisfying result.

First of all the copper tube is protected by a sacrificial anode.

Second the complete heat exchanger ist coated, due to that it is hardly possible for corrosive agents to attack the basic components of the heat exchanger.

The usage of additional material has a negative effect of the performance of the air cooler. When desinging your refrigeration plant, be sure to check the protection against corrosion box in the selection software.

Protection against corrosion type D isn't possible at Co2oler units.

Type E

It's possible to manufacture the complete heat exchanger of copper. This leads to an increse of capacity by about 8 %.

The heat exchanger is then well protected against influences of salt, which is the most common corrosion phenomen at aluminium.

These type of corrosion protection is only possible at fin spacings < 6 mm.

Type F

Fins can be made of prelaquered finstock. Compared to the complete varnished heat exchanger the capacity is a little bit higher, but due to cutting edges the Aluminium is not as good protected as in type C or D.

Type G

Protection against corrosion is a combination of tinned copper tubes, prelaquerd aluminium fins and a varnishing of the two end plates. It is only possible up to a fin spacing of 6 mm.


Different accessories bring the portfolio of cubic air coolers up to a round figure.

Stainless steel casing

Stainless stell casingCasings of the air unit coolers can be made of stainless steel (V2A, 1.4301, AISI 304). The stainless steel casing is superior robust compared to the Aluminium casing.

If you like pure metalic designs the stainless steel casing may also be an option.

Drain pan marine

Drain pan marineWhen the sea is rough, conventional drain pans soon start to spill. Due to the enhancement of the height of the drain pan and multiple drainage, placed according to the specifications, the drain pan marine does a satisfying job.

Insulated drain pan

Insulated drain panThe insulated drain pan avoids the forming of condensate formation at the outer sheet of the drain pan. The application area is at uncommon high temperature differences between evaporation and ambient air temperature.