Thermostatic actuator RTN51
Thermostatic actuator RTN51 Thermostatic actuator RTN51 diagram with dimensions


  • Height: 89.5mm
  • Max. diameter: 60mm

Technical data

  • Setpoint setting range: 8...28°C, 50Hz, 210s
  • Perm. medium temperature in the connected valve: 1...110°C
  • Operating medium temperature: 5...50°C
  • Perm. medium temperature: 120°C
  • Perm. sensor temperature: 40°C
  • Use: ITF convectors


  • Union nut: brass, nickel plated
  • Stem: PBT, 30% glass
  • Handle: ABS

Thermostatic Actuator RTN51

Thermostatic actuator RTN51 is used for radiator valves.


  • Self-acting, without auxiliary power
  • Direct mounting with union nut, no tools required
  • Robust construction, maintenance-free, noiseless operation

Mode of operation

The fluid filled sensor responds to deviations from the room temperature setpoint. When the room temperature rises, the fluid inside the metal capsule expands, exerting pressure on the bellows and the stem, which causes the valve to continuously close so that the radiator’s heat output is reduced. When the room temperature falls, the bellows expands, thereby opening the valve so that the radiator’s output is increased again.

The design allows radiator valve operate continuously, thus achieving smooth regulation of hot water flow to the radiator, resulting in constant room temperature according to the room temperature setpoit.

The actuator must not be covered by radiator enclosures, furniture or curtains and it must not be affected by direct solar radiation or air drafts.