Here is the LX H30-R2 3.0KW 1.5 inch heater (L-Shape).
Sensor compatibility: Controlled by the system control box
Required flow rate: Set by a pressure switch, this switch will need to be pressurised, if it runs straight to a big bore out let with no bends, there will be no back pressure and it may not work
Flow detection: Pressure switch built into the heater run on a separate cord
Diameter: 50 mm