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Installation and calibration manual
HBDF – Mk2 Defrost Sensor
Introduction
The HBDF sensor measures the ice thickness on an evaporator and delivers an analog signal which can be used in a
PLC for controlling the defrost. The sensor is suited for cold rooms, blast freezers and cold stores where temperatures
are below 0°C. If the sensor is used for heat pumps and similar applications where the evaporator get wet special
settings are needed and the installation is more critical to secure success. Please contact HB support before the
installation.
Besides providing input for a PLC, the sensor can also provide other outputs for systems without a classic PLC. The
sensor has these three outputs.
•
Simple analog: Provide a simple analog signal 4-20 mA linear to the ice thickness for a PLC.
•
Smart analog: Provide an analog signal when the specified ice thickness is reached and when defrost can be
ended.
•
Relay output: In this mode the defrost can be controlled by relays based on parameters in the sensor.
The sensor is equipped with a temperature sensor which detects when the ice is melted and the defrost cycle is
complete. This is a smart solution to avoid unnecessary defrost.
The sensor has a M12 interface like other HB-product sensors and is configured by the HB tool. The product consists of
a box, a ground cable, the measuring wire, and a temperature sensor.
The sensor is based on the capacitive measurement principle and reacts on ice and water between the wire and the fins
in the evaporator. This means the wire must be mounted between fins where ice builds up and the fins must be
grounded.
