Here is the LX H30-R3 3.0KW 1.5 inch heater (T-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 outlet 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
Length: 250 mm
Diameter: 50 mm
Between terminals: 200 mm
Overall length complete: 340 mm