Normally Open Piloted Solenoid Valve — Brass, NBR, 2/2-Way

Cematic's normally open piloted solenoid valve made of brass is a 2/2-way solenoid valve designed to control large flow rates with significantly lower electrical coil power than an equivalent direct-acting valve. Its piloted operating principle uses the fluid's own differential pressure to move the main plunger — the coil only activates a small orifice pilot — allowing it to handle 1/2" and 1" diameters with coils of barely 12 VA (220 VAC) or 20 W (24 VDC). Therefore, it is the right choice in high-flow systems where direct action would require high-consumption coils or oversized solenoids.

Its normally open configuration maintains free flow when the coil is de-energized and interrupts it when an electrical signal is received — consequently, it is the standard option when the safe state of the process is continuous flow and cutoff is the exception triggered by the controller.

Direct-acting vs. piloted — when to choose each

This is the most important selection point when specifying a solenoid valve. Therefore, understanding the difference between both operating principles prevents specification errors:

• Direct-acting: The coil moves the plunger directly, without relying on fluid pressure. It operates with zero differential pressure — it can even operate without line pressure. However, for large diameters or high pressures, it requires high-power coils and large solenoids.
• Piloted (this product): The coil activates a small orifice pilot which, in turn, uses the fluid's pressure difference to move the main plunger. Consequently, it can control large flow rates with very low power coils. The necessary condition is a minimum differential pressure of 0.05 MPa (0.5 bar / 10 psi) between inlet and outlet for the pilot mechanism to function correctly.

Therefore, the piloted valve is the right choice when the system always operates with a differential pressure greater than 0.5 bar and significant flow rates need to be controlled with low electrical consumption. If the system can start or operate with zero differential pressure, the correct option is the direct-acting NO brass solenoid →

Operating principle — Normally Open (NO) Piloted

In the de-energized state (coil de-energized): the pilot is open, the main plunger's upper chamber remains at inlet pressure, and the plunger stays in the open position — fluid flows freely. When the coil is energized, the pilot closes, the pressure in the upper chamber drops, and the inlet pressure on the lower face of the plunger pushes it upwards, closing the main passage. When de-energized, the pilot reopens and the cycle restarts.

Construction Materials

• Body: Brass — corrosion resistance for potable water, process water, compressed air, and light hydraulic oils. Compatible with most general industrial fluids at ambient temperature.
• Plunger and pilot: Stainless steel — resistant to corrosion by process fluid.
• Seat seal: NBR (Nitrile) — compatible with water, compressed air, and mineral hydraulic oils up to 80 °C.
• Coil: Encapsulated, IP65 protection — suitable for humid and dusty industrial environments. Low consumption: 20 W at 24 VDC / 25 VA at 110 VAC / 12 VA at 220 VAC.
• Connection: Female NPT thread — industrial standard in Mexico, compatible with steel, copper, and PVC pipes with adapters.

Technical Specifications

Coil voltage and consumption selection

• 24 VDC — 20 W: Standard in control cabinets with PLC and DC power supply. The most common option in new installations. Available in 1/2" and 1".
• 110 VAC — 25 VA: For 110 V single-phase circuits available in the field — the most widespread voltage in industry in Mexico. Available in 1/2" and 1".
• 220 VAC — 12 VA: The lowest consumption of the three options — an advantage in installations with many valves or with restrictions on the control transformer's capacity. Available in 1/2" and 1".

Fluid compatibility

• ✅ Potable water and process water — up to 1.0 MPa and 80 °C
• ✅ Compressed air — up to 1.0 MPa, pneumatic and instrumentation service
• ✅ Mineral hydraulic oils — up to 1.0 MPa, compatible with NBR seal
• ✅ Cooling and HVAC water — HVAC and industrial cooling systems
• ⚠️ Differential pressure below 0.05 MPa: the piloted valve does not operate correctly — use direct-acting solenoid →
• ⚠️ Fluids with suspended particles: install an upstream in-line filter — the pilot orifice is small and sensitive to solids
• ⚠️ Temperature above 80 °C: the NBR seal degrades — consider the high-temperature NO solenoid with Viton →
• ❌ Concentrated acids, chlorinated solvents: use a solenoid with a stainless steel body

Main industrial applications

Medium and large flow rate technical irrigation systems
In sprinkler and drip irrigation installations with working pressures exceeding 0.5 bar, the normally open piloted solenoid valve allows controlling large flow rates per zone with low power consumption coils. In addition, the NO configuration ensures that irrigation continues in the event of any electrical failure of the controller, protecting crops from unscheduled interruptions.

Flow control in HVAC and climate control systems
In hot and cold water circuits for industrial and commercial climate control, this piloted NO solenoid valve controls the flow rate of each zone or fan coil from the central controller. Therefore, it is the standard choice in systems where the hydraulic circuit's differential pressure always exceeds the required minimum of 0.5 bar and low electrical consumption is needed in the coil.

Dispensers and process equipment with high flow rates
In liquid dispensers, industrial washing equipment, and process lines where the required flow rate would exceed the capacity of an equivalent direct-acting solenoid, this piloted valve allows handling the necessary flow rate with a compact, low-consumption coil. Consequently, it reduces the cost of the control system and the sizing of the power supply.

Hydraulic and pneumatic systems with stable pressure
In hydraulic and pneumatic circuits where line pressure always exceeds 0.5 bar under normal operating conditions, this piloted NO solenoid offers a superior flow/electrical consumption ratio compared to direct-acting solenoids. Likewise, the low coil consumption reduces heating of the control system in installations with many simultaneously active valves.

For the complete range of solenoid valves, see solenoid valve collection →

Technical Data Sheet