FAQ – Frequently asked questions

Here you can find answers to some frequently asked questions. We update this page regularly, if your question is not answered here, please contact us!

What is the EER and how is it calculated?

The EER (energy efficiency ratio) defines the performance figure of a refrigeration machine, i.e. the ratio of the generated refrigeration capacity to the electrical power consumption. The EER of the cold water system varies significantly depending on the design of the device or the operating and ambient temperatures. The overall system must always be taken into account when assessing the value. For example, a water-cooled water chiller usually has a significantly better EER than an air-cooled water chiller. The waste heat must also be dissipated in the condenser of a water-cooled system, if the waste heat can be used for heating or other processes (heat recovery), the system is to be regarded as very efficient. In the case of applications that this is not possible, a dry cooler or well water must generally be used; then, for a correct assessment, the power consumption of the fans and pumps would also have to be included in the calculation.

Does the cold water system have to be protected with filter systems?

An unfiltered chilled water system could cause blockages in the heat exchanger of the chiller or dry cooler. To avoid contamination or to prevent contaminated water from entering the heat exchanger, every water system must be equipped with effective filters. The filters used must filter out all particles with a diameter of more than 1 mm. Filter systems that are used must be checked and serviced regularly. Clogged filters lead to problems with the water volume flow or pump systems.

When do we need performance regulation?

The refrigeration systems are designed for possible extreme operating conditions as well as for the maximum cooling load. These operating states actually only occur for a short time, which means that the refrigeration systems are too large for most of the time. Even the refrigeration points do not always demand the same performance or they are sometimes not in operation. In addition, switching the compressor on / off too often shortens the life expectancy and high starting currents worsen the energy efficiency of the system. A maximum of 7-8 compressor starts per hour are allowed.

In many cases, these conditions require the refrigeration systems to be regulated. Capacity regulation ensures that the compressor usually runs in an optimal range and prevents unnecessary switching on and off of the compressor.

Various power controls that are used

Additional media storage

The simplest and in many cases the most cost-effective variant of power regulation. The medium volume in the system is increased in order to temporarily store the cooling capacity of the chiller and to increase the compressor run times. For this purpose either buffer storage tanks are installed in the circulatory system or the medium pipes are oversized.

Multiple cycles

A very popular variant is to equip the refrigeration systems with several refrigeration circuits and compressors. Individual compressors are switched on / off depending on the cooling load. The intelligent parallel network controller switches individual compressors on and off depending on the running time and temperature of the cooling water. Separate circuits bring system redundancy as an additional advantage, even if a compressor is damaged, the overall system can continue to cool with reduced capacity. This saves valuable time up to the point of repair and protects the operation from a complete failure.

Frequency converter (speed control)

The cooling capacity of a conventional compressor is constant, the motor and crankshaft rotate at constant revolutions. By using frequency converters, the speed can be continuously regulated in a frequency range from 30 to 90 Hz. Depending on the required cooling load, the engine speed is between 900 and 2800 rpm. This means that the output can be continuously adjusted and the refrigeration machine is always correctly dimensioned with regard to the cooling requirement. Motors of frequency-controlled compressors start up in the low frequency range, which also drastically reduces the start-up current.

Hot gas bypass control (precision version)

The very complex variant is used for applications with high demands on temperature stability (hysteresis ± 0.5 K). Using special injection technologies and a control system based on a microprocessor-controlled PID temperature controller, the water outlet temperature is very precisely regulated.

Why should we take out a maintenance contract?

We strongly recommend that you take out a maintenance contract with a customer service center near you. This contract guarantees regular maintenance of the system by qualified personnel who have been trained on our devices. Regular maintenance enables every malfunction to be identified and rectified in good time and the risk of serious damage to be reduced to a minimum. Finally, it should be noted that regular maintenance ensures the longest possible service life of the device. Maintenance work that has not been carried out and / or incorrect installation can lead to the immediate loss of the warranty.

Do you have a 24-hour emergency service?

Yes. A maintenance and emergency service contract is required for this.

Do we need antifreeze for the circuit water?

The circulating water to be used must be designed according to the operating temperatures and year-round ambient temperatures, both operating times and downtimes (e.g. winter) must be taken into account. The system must be specially protected if it is exposed to temperatures below 0 ° C. It may be necessary to protect the cold water system with anti-freeze additives to prevent the pipes from freezing up, even though the system is only running at a minimum of +7 ° C during operation.


Monoethylene glycol Propylene glycol
Active content (volume) Frost protection up to Active content (volume) Frost protection up to
25% -12 °C 25% -11 °C
30% -16 °C 30% -14 °C
35% -20 °C 35% -18 °C
40% -25 °C 40% -22 °C

As a rule, it is advisable to add a 35% proportion of ethylene glycol with inhibitors for corrosion protection to the water. This concentration ensures frost protection down to -20 ° C, at lower temperatures an ice slush is formed that no longer has any explosive effect. If the medium can come into contact with drinking water or food, one based on the toxicologically harmless propylene glycol is preferable. In order to prevent the explosive effect, a 38% share is usually required.

Phase monitoring relay?

The phase sequence relay controls the direction of rotation of the power supply. If the direction of rotation is incorrect (i.e. L1, L2 and L3 are not clockwise), the control is not enabled. If for any reason the phase sequence is changed, the system is switched off immediately. The relays and phase sequence error diode will illuminate.

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Monday to Friday from 8 a.m. to 5 p.m
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We are here to help!

Monday to Friday from 8 a.m. to 5 p.m
Monday to Friday from 8 a.m. to 5 p.m
24h/day (no calls)

Intercom DEEC GmbH
Dieselstraße 11
47228 Duisburg

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Then please contact us right away. Our team of refrigeration and air conditioning experts will be happy to answer your questions.