The differential current measurement method must be used to measure the protective conductor current in units with a frequency converter.
To measure the protective conductor current, the unit must be in operation. All external conductors, including neutral conductors (if available), are guided through a sensitive current measuring clamp (mA range). The measured differential current of all external and neutral conductors corresponds to the protective conductor current of the unit.
Thermo-6 temperature control units are equipped as standard with a frequency converter, which has an increased leakage current of up to 5 mA. If the leakage current exceeds this value during testing with the differential current measurement method, we recommend that you contact HB-Therm customer service.
To measure the protective conductor current in accordance with DIN EN 50678 (VDE 0701), DIN EN 50699 (VDE 0702), the required measuring equipment must be used.
The replacement leakage current measurement method is not suitable for units with frequency converter due to different circuitry of the inverters.
Furthermore, measuring the protective conductor current using the direct method is not suitable for temperature control units, since the unit must be operated in isolation for this measurement.