UNI-D UW-15 DC24V Solenoid Valve

Manufactured by UNI-D (Dingji / Xinda) from Taiwan, Chine, the UW-15 DC24V is a 2/2 way normally closed combined direct-acting diaphragm électrovanne. As a mainstream standard model of the UW series, it features a forged brass body and NBR nitrile rubber seals. It is capable of zero-pressure differential startup, and delivers large flow rate, superior tightness as well as excellent water and moisture resistance. A classic general-purpose component for industrial fluid control, it is widely applied for automatic on-off control of water, compressed air and low-viscosity light oil.

1. Explication du code modèle

Full original model: UW-15 DC24V

UW: Série de produits, 2/2 way combined direct-acting diaphragm solenoid valve. Standard version is normally closed (Caroline du Nord) with waterproof coil design.

15: Nominal diameter and port size, corresponding to G1/2″ (PT/BSPT British taper pipe thread) with a seat orifice of 15 mm.

DC24V: Rated coil voltage, DC 24V with a permissible voltage fluctuation of ±10%.

Optional factory suffixes:

NON: Normally open type (open when de-energized, closed when energized)

D: Solenoid coil with DIN connector (standard version comes with lead wires)

Ex: Explosion-proof coil for flammable and explosive environments

SUW-15: 304 stainless steel body version for corrosive media

2. Principales spécifications techniques (Original Factory Standard)

3. Full Size Model List of UW Series

3.1 Standard Normally Closed Type (Open when energized, Closed when de-energized)

3.2 Normally Open Type (Open when de-energized, Closed when energized)

Add suffix NO to the model number. It shares identical mechanical and electrical parameters with normally closed version, par exemple. UW-15-NO.

Note: Custom voltages including DC12V, AC24V, AC110V, AC220V, AC380V are available for the whole series. Thread types such as NPT and BSPP parallel thread can also be customized.

4. Bobine & Instructions de câblage
5. Polarité: The standard DC24V 2-wire coil has no polarity requirement, wires can be connected arbitrarily. For customized coils with power indicator, follow the marking to distinguish positive and negative poles.
6. Caractéristiques de la bobine: Adopts pure copper enameled wire and stainless steel magnetic tube with Class B insulation. It supports long-term continuous power-on operation and produces no buzzing noise like AC coils.
7. Wiring for DIN Connector Type (Suffix -D): Equipped with standard DIN 43650 Type A connector. Pin definition: Épingle 1 for positive power, Épingle 2 for negative power, Épingle 3 for shielding ground.
8. Protection Recommendation: For DC inductive circuits, connect a freewheeling diode in reverse parallel across the coil to suppress surge voltage and protect control components such as PLCs and relays.
9. Dimensions de montage & Regulations

5.1 Dimensions hors tout (Original Standard for UW-15)

5.2 Mounting Regulations

1. Sens de montage: Horizontal installation with coil facing vertically upward is recommended. Never install the coil facing downward to avoid media ingress and short circuit.
2. Flow Direction: The arrow marked on the valve body must follow the actual media flow direction. Reverse installation will cause poor closure and internal leakage.
3. Inlet Filtration: Install a Y-strainer with no less than 40 mesh upstream of the valve to prevent foreign matters from jamming the diaphragm or scratching sealing surfaces.
4. Maintenance Safety: Do not disassemble the valve under pressure. Cut off power and fully relieve pipeline pressure before any disassembly or maintenance.
5. Applications typiques

On-off control for water circuits in water treatment, water purification and reverse osmosis systems

Air circuit control for pneumatic automation systems, dryers and air compressors

Automatic water control for garden irrigation and musical fountains

Media control for cleaning equipment and food packaging machinery

Cooling water and refrigerant circuit control for air conditioners and refrigeration units

7. Troubleshooting Matrix

8. Modèles alternatifs

Same brand equivalent: UW-15-D (DIN connector coil version, fully interchangeable body)

Domestic compatible models: Airtac 2W050-15, SNS UW-15 (Identical mounting dimensions for direct replacement)

Imported equivalent models: SMC VX2120-02-5G1, CKD AB41-02-5

Structure & Principe de fonctionnement

The UNID UW-15 DC24V is a 2/2 way normally closed combined direct-acting diaphragm solenoid valve, also known as step-by-step direct-acting valve in the industry. It combines the advantages of direct-acting and pilot-operated structures, operating stably within a wide pressure range of 0 ~ 0.7 MPa. Its core feature is reliable startup at zero pressure differential (0 bar). It is a proven and mature solution for fluid control with small and medium orifices for water, air and light oil.

It consists of three major functional assemblies:

1. Electromagnetic Actuator: DC24V pure copper coil, fixed core, movable core and return spring, providing driving force for valve opening and closing.
2. Diaphragm Seal Assembly: NBR diaphragm (with central pilot hole and side balance holes) and main valve seat, serving as the sealing unit for fluid on-off.
3. Valve Body Flow Path: Forged brass body, inlet & outlet flow passages and diaphragm back pressure chamber, forming pressure chambers for media flow.

Complete Working Process

1. De-energized State (Normal Status: Fermé)

The coil loses power and generates no electromagnetic force. The return spring pushes the movable core downward to tightly block the central pilot hole of the diaphragm.

Inlet media flows into the back pressure chamber above the diaphragm through side balance holes, equalizing the pressure on both sides of the diaphragm.

Combined with downward force from the return spring and diaphragm self-weight, the diaphragm presses firmly against the main valve seat. The main orifice is fully closed, cutting off the flow between inlet and outlet.

Higher inlet pressure creates larger downward force on the diaphragm for better sealing, adopting a pressure self-tightening sealing design.

2. Energized State (Valve Opened & Flow Connected)

The DC24V coil is energized and generates steady electromagnetic force, which overcomes spring force and media resistance to pull the movable core upward. The opening process includes two steps:

1. Pressure relief via pilot hole: When the movable core lifts, the central pilot hole of the diaphragm opens first. Media inside the back pressure chamber drains rapidly to the outlet, resulting in an instant pressure drop in the chamber.
2. Main orifice opening: The media pressure below the diaphragm (inlet side) becomes much higher than the back pressure above. Driven by differential pressure and electromagnetic force, the entire diaphragm lifts up. The main orifice fully opens and connects the inlet and outlet flow passages.

> Core principle of zero-pressure startup: When the inlet pressure is 0 bar with no auxiliary differential pressure, the electromagnetic force directly pulls the diaphragm via the movable core to open the main orifice. It does not rely on media pressure, so it is applicable to gravity flow pipelines and non-pressurized water tanks. This is the key advantage over pure pilot-operated solenoid valves.

Operating Characteristics of DC24V Coil

1. Stable suction & faible bruit: DC coil delivers constant current and steady electromagnetic force without fluctuation. It has no 50Hz buzzing noise produced by AC coils, ideal for indoor sites, precision equipment and noise-sensitive applications.
2. Long-term continuous operation: The inrush current equals holding current for DC coils, leading to even temperature rise. With Class B insulation, it can work continuously for a long time.
3. Low control impact: No inrush current upon startup, bringing much lighter load impact on PLC outputs and intermediate relays compared with AC coils, which makes it well suited for automated control systems.