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 DLK

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.


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. The DLK series is equipped with EC- fans as a standard.

Our standard EC fans, that are incorporated in our products are limited to 2 r.p.m. steps. If you need full infinitely variable r.p.m. control we can supply fans with a 0-10 V input signal to control r.p.m. for DLK/T flatline. At DLK/T EuroLinePlus this option is not available at the moment.


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


T- version of DLKT flatlineMost of the Roller 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.

MS heater rods

MS heater rods are one of the greatest benefits of Roller air unit coolers. These heaters are designed for different purposes around the air unit cooler.

Defrost of air unit coolers

MS heaters in air unit cooler

These MS heater rods can be retro fitted into most of the Roller air unit coolers. They can be simply inserted into the coil. The rods are made of stainless steel and have a special vulcanisation for the appliance in cold rooms.

These type of defrost is designed to work at cooling chamber temperatures near the freezing point, to boost the natural defrost of the ambient and to achieve a complete deicing of the cooler.

We don't recommend the usage of MS heater rods for defrost in low temperature applications.

Air conditioning, dehumidification

AC heaters in DLK flatline

In many Roller air coolers there are already holes to insert MS heater rods in the air outlet to reheat the air. As this is a very use oriented option we are not able to supply saftey installations in case of heat and current supply of these heaters.

A simple protection against touching of the hot surfaces can be supplied on demand.

Defrost safety thermostat

Defrost safety thermostat

The 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.

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.

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 corrosion type DThe protection against corrosion type D is a combination of different anti corrosion actions, that lead to satisfying 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 ceiling type air coolers up to a round figure.

Stainless steel casing

Stainless steel 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 for wall mounted ceiling air coolers

DLK/T with additional drain panCeiling type air unit coolers are in most cases wall- mount able with an additional drain pan. Evaporators can be equipped with the drain pan as an accessory. In case of a water/ brine heat exchanger the intention of a wall mounting should be known in advance to ensure a correct bleeding of the heat exchanger.