The RTKSA frost protection controllers have been specially developed for frost protection on the air or water side of hot water heating registers and heat exchangers in ventilation, heating or air conditioning systems. In the event of a sensor break, contact 1-2 is permanently opened and contact 1-4 is permanently closed. Note: Mounting clips, thermowells and protective coils are not included in the scope of delivery and must be ordered separately. Air-side application: The SWK-2-xxx protective coils can be used for temperature measurement of non-aggressive gases in the duct. Water-side application: THK-2-xxx thermowells can be used for temperature measurement in non-aggressive fluids and NTHK-2-xxx thermowells can be used in aggressive fluids.