Select the Normally Closed (NC) or Normally Open (NO) Actuator?

"For floor heating, the thermal actuators should be open most of the time, so should I use the normally open (NO) type?". Some customers are facing such confusion.

In fact, in the floor heating system, the choice of normally open thermal actuators or normally closed thermal actuators mainly depends on the following three factors:

1. Control requirements:

Normally open thermal actuators (NO, Normal Open): When the control signal (such as the output signal of the thermostat) arrives, the valve is closed. It is usually used in occasions where the valve needs to be closed when the equipment stops heating.

Normally closed thermal actuators (NC, Normal Closed): When the control signal arrives, the valve opens. It is suitable for occasions where the valve needs to be opened when the equipment stops heating, allowing hot water to flow through the floor for heat dissipation.

2. System design:

If the floor heating system is designed to be in a heating state frequently and the heating needs to be turned off only in specific circumstances (such as when the room temperature reaches the set temperature), then the normally closed thermal actuator is a more common choice.

If the system is designed to start heating only when needed and the water flow should be turned off when not heating, the normally open thermal actuators may be more suitable.

3. Safety and energy saving:

Normal closed thermal actuators (NC) usually ensure that hot water flows out automatically when the power supply or control system fails, avoiding low temperature problems caused by system loss of control.

Normal open thermal actuators (NO) provide more precise switch control when the control system is working normally.

In summary, the choice of normally open or normally closed thermal actuators should be determined according to the actual needs of the system, control mode and fault response mechanism. Generally, normally closed thermal actuators are preferred in floor heating systems because they can provide greater safety and system stability in the event of control interruption or failure.