Defrost sensor MK2

Technical data: HBDF-MK2

HBDF-MK2 is a simple solution for automatic defrosting of evaporators. Optimal defrost periods result in energy savings and gain more freezing capacity. Experiences from existing installations show have shown that it can save up to 40% of energy and thereby quickly is recouping its costs. The sensor measures the thickness of ice built up between the fins and it sends a 4-20mA or digital ON/OFF signal to the control systems.

The defrost sensors are based on the capacitive measuring principle, in which an isolated steel wire acts as one conductor. The evaporator fins and tubes act as the second conductor, jointly forming a viable electrical capacitor. Changes in the measured signal occur when ice is built up between the fins, as the sensor is measuring the dielectric difference between the air and ice.

The sensor can be installed in less than one hour, both on new and old evaporators. It can be installed when the system is in operation. Therefore a system shutdown is not necessary. The electronic part is mounted on the evaporator’s frame by using 2 screws. The mechanical part consists of a thin PA12 or PTFE- coated wire, which is mounted between the fins of the evaporator in the air inlet side with special HB Snap-On clips or standard nylon strips. The HBDF-MK2 sensor is available in 3 versions, with a 10m, 20m and 30m wire.

The sensor with a built-in control relay will start the defrosting based on the ice thickness and stop the defrost when the ice is melted and the temperature outside the evaporator tubes rises above 0°C (32°F). Recommended setpoint for stop of defrost cycle is 5-10°C (41-50°F).

After the installation, the sensor should be calibrated/configured to the evaporator by using the HB-TOOL (PC-based software tool), which can be downloaded from our web-site.

Product features

One box start and stop the defrost

Stop the defrost when ice is melted (rising temperature on the evaporator tubes)

Save energy = money on defrost

Gain more capacity

Save energy = save money and reduce the CO2 emission





Power supply
Voltage24 AC/DC + 10%
Max. possible resistance500 ohm
Plug connectionDIN 43650 - 4 pins
Analog output 4-20 mA
Environmental conditions
Ambient temperature-30...+50°C
Refrigerant temperature-60...+80°C
Max. pressure100 bar
Protection degreeIP65
VibrationsIEC 68-2-6 (4g)
Mechanical specifications
Thread connections3/4” NPT & 1" BSP
Material - liquid partsAISI 304 / PTFE
Material - electronic partsCoated aluminium
House typeFront
EMC testEN 61000-2
LED indicationRed LED
ConfigurationPush bottom


Wire lengthOrdering code
10 mHBDF-MK2-10
20 mHBDF-MK2-20
30 mHBDF-MK2-30
HBDF-snapON ClipsOrdering Code
25 pcs. of 8-10 mmHBDF-SnapONClip8-25
50 pcs. of 8-10 mmHBDF-SnapONClip8-50
25 pcs. of 10-12 mmHBDF-SnapONClip10-25
50 pcs. of 10-12 mmHBDF-SnapONClip10-50
25 pcs. of 12-14 mmHBDF-SnapONClip12-25
50 pcs. of 12-14 mmHBDF-SnapONClip12-50
25 pcs. of 14-16 mmHBDF-SnapONClip14-25
50 pcs. of 14-16 mmHBDF-SnapONClip14-50
25 pcs. of 16-18 mmHBDF-SnapONClip16-25
50 pcs. of 16-18 mmHBDF-SnapONClip16-50
25 pcs. of 19-22 mmHBDF-SnapONClip19-25
50 pcs. of 19-22 mmHBDF-SnapONClip19-50
25 pcs. of 22-25 mmHBDF-SnapONClip22-25
50 pcs. of 22-25 mmHBDF-SnapONClip22-50
USB programming cableHBxC-USB