Insertion heaters cannot be fitted to certain vehicles, e.g. some construction machinery, tractors, trucks, and in exceptional cases passenger cars. For these vehicles the Calix Professional Heater (PH) was developed. The PH works based on a self-circulating principle and is connected to the cooling system outside the engine block using a hose connection (20 mm). The heater is equipped with overheating protection, a thermostat, and a rubber sealing for increased service life and reliability. The heater can be delivered with only an installation bracket, or as a complete kit including the heater, cables, bracket, etc.