NO, NC valves

NO valves

  • Valve is opened when de-energized (Normally Open)
  • The valve stem is fully extended

Radiator valves such as VDN.., VEN.., VUN.., VPD.., VPE.. or VPU.. are normally NO valves.

NC valves

  • Valve is closed when de-energized (Normally Closed)
  • The valve stem is fully extended

Small valves such as V..P47.. are normally NC valves.

Valve and actuator combination

NO function

  • Actuator stem is retracted when de-energized.
  • Valve is open.

NC function

  • Actuator stem is extended when de-energized.
  • Valve is closed.

RTN..

Thermostatic RTN.. actuators control heat demand. They control the water flow by opening and closing the radiator valves.

  • The actuator stem retracts as heat demand increases and steadily opens the radiator valve.
  • The actuator stem extends as heat demand decreases and steadily closes the radiator valve.

STA..

Radiator valves
(NO valves)

STA..
De-energized actuator

  • VDN.., VEN.., VUN..
  • VPD.., VPE.., VPU..

closed (NC function)

SSA..

The electromotive actuator is driven by a DC 0…10 V (SSA61) positioning signal or 3-position signal (SSA31, SSA81). The description of operation in this document applies to the valve versions which are fully open when de-energized (NO).

3-position control signal

  • Voltage at Y1: Stem retracts: Valve opens
  • Voltage at Y2: Stem extends: Valve closes
  • No voltage at Y1 and Y2: Actuator maintains its current position

DC 0...10 V

  • The valve opens / closes in proportion to the control signal at Y.
  • At DC 0 V, the valve is fully closed.
  • The actuator maintains its current position when power is switched off.