Understanding Normally Open vs. Normally Closed ODE Solenoid Valves

Normally Open and Normally Closed Solenoid Valves

When selecting the right solenoid valve for your system, one of the most important distinctions is whether the valve is Normally Open (NO) or Normally Closed (NC). ODE makes this identification and conversion process straightforward, thanks to their modular magnetic kits and clear body markings.

How to Identify Normally Open vs. Normally Closed

ODE valves are engineered with visual cues that make identification quick and accurate:

• Normally Open (NO):
  You’ll notice groove lines on the body. These physical indicators show that the valve allows flow when de-energized.

• Normally Closed (NC):
  You will see a flush locknut, indicating the valve remains closed when power is removed.

These small differences offer a reliable visual check before installation or servicing.

Converting Between NO and NC Using ODE Magnetic Kits

One advantage of ODE solenoid valves is how easily you can convert an NO valve into an NC valve—or vice versa—by replacing the magnetic kit:

• To convert NO → NC:

  1. Loosen the magnetic kit using a torque wrench.

  2. On a normally open kit, the spring is located on the outside.

  3. Replace it with a normally closed kit, where the spring is positioned inside the plunger.

  4. Tighten back to specification.

The reverse conversion works the same way. This modularity also simplifies repair and maintenance—most issues are resolved simply by replacing the magnetic kit.

Internal Differences: Mechanical Seal vs. O-Ring Seal

• Normally Closed (NC):
  Uses a mechanical seal. This design ensures the valve stays tightly shut when de-energized—ideal for applications requiring safety shutoff or fail-safe performance.

• Normally Open (NO):
  Uses an O-ring on the magnetic kit to maintain sealing. This configuration keeps the valve open without power, reducing energy consumption in systems that rely on constant flow.

Applications: When to Use NO vs. NC Valves

Choosing between NO and NC depends on how your system needs to behave in a power-off or emergency state:

Normally Closed (NC) – Most Common

Use NC when you need the flow to stop when power is removed. Ideal for:

• Hydronic heating and cooling systems (zone isolation)

• Steam or condensate control

• Fuel, LPG, or gas safety shutoff

• Water treatment and RO systems

• Pressure washers and commercial equipment

• Industrial automation requiring fail-safe operation

Normally Open (NO) – Power-Efficient Flow

Use NO when you want flow to continue when power is removed. Ideal for:

• Cooling loops that must stay open during power failure

• Gravity-fed water systems

• Venting, draining, or vacuum applications

• Systems where constant flow is required and shutting off is optional

• Energy-saving applications that avoid energizing a coil for long periods

Clear Stamping for Thread Type and Sealing Material

ODE valves are stamped with:

• Port size

• Thread type (NPT, BSP/GAS, Subplate/flanged)

• Original sealing material (EPDM, Viton, HNBR, etc.)

Since thread type can be difficult to distinguish visually, these markings ensure accurate identification during installation, repair, or replacement.

Need Help Selecting or Converting Your ODE Valve?

Our technical team at Hydronics Depot Inc. is here to help you size, select, repair, or convert your ODE solenoid valves.