Defrosting 01.03.2020 09:58 01.03.2020 11:16

The system of protection of outdoor spaces against snow and black ice can take advantage of the Foxtrot system with connected sensors ETOG-55 and heating control of cables in outdoor areas for detecting moisture and subsequent defrosting.

The ETOG-55 sensor is a stainless steel structure, which ensures its high mechanical strength as well as resistance to weathering. When they are dry, the detection metal plates are electrically isolated, but the presence of moisture results in their interconnection. Evaluating the presence of moisture is done by measuring the resistance of the sensor by the respective system inputs.

There is a heating element cast between the detection plates, which slightly heats the sensor, optimizing its function. This feature is required for the humidification of fresh snow, whose electric conductivity is not sufficient. The ETOG-55-55 sensor must be located in the heated part of the space between the heating cables in the place, where humidity usually remains the longest (the bottom part of the surface, or in heavily exposed areas) to be constantly in contact with flowing water from melting snow. But it also must be located so as to be freely exposed to precipitation - i.e. not close to the building or under the overhang of the roof. It must not be installed outside the heated area.

Larger areas can be fitted with multiple sensors, which may be connected in parallel or separately; the second option allows defrosting of individual zones separately.

Connecting several sensors in parallel also increases the reliability of detection of black ice, which may be distributed unevenly; activation of the defrosting system is then more reliable.

Heating of the ETOG-55 sensor has the power input of approx. 2.5 W at 24 V supply. Heating of the ETOG-55 sensor can be connected directly to the DO4 output of the C-IS-0504M module, which is primary intended to power the heating.If the heating of the ETOG-55 sensor is powered from another 24VDC source, it must be switched by other relay output within the system, e.g. by output on the C-IS-0504M module, to which the ETOG-55 sensors are also connected (max. 2 sensors per independent inputs of module) - see the following example of wiring.

In addition to measuring moisture, the ETOG-55 sensor is also equipped with a temperature sensor NTC 12k, which is terminated together with the moisture measurement and heating in a common cable. Temperature measurement helps to control heating of the ETOG-55 probe.

Measurement can also by done by the C-IS-0504M module, which has two inputs intended directly for measurements of conductivity; the measured resistance of the humidity sensor varies from less than 50 kΩ (moisture is present) to hundreds of kΩ (dry sensor).


Fig. 1. The basic wiring of the ETOG-55 sensor, defrosting outdoor spaces



  1. A standard length of the supply cable is 10m, but it can be extended with a separate cable 6 x 1 mm2 (e.g. the JYTY) to several dozen meters (a potentially higher resistance of the cable can be compensated by the system software).

  2. Put a flexible tube (a gooseneck) with the inside diameter of at least 16 mm in the place where the sensor should be located; the ETOG-55 sensor must be at least 5cm from the heating cables, to prevent the heat generated by the cables interfere with the operation of the sensor.

  3. The heating of the sensor can be connected directly to a special DO4 output, or it can be supplied from the source of the Foxtrot system, or from a separate 24 ÷ 27 VDC power supply.