Table of contents
- 2-Way ASCO Solenoid Valve: An Overview
- 3-Way ASCO Solenoid Valve: An Overview
- 2-Way vs. 3-Way ASCO Solenoid Valve: A Detailed Comparison
- 2-Way vs. 3-Way ASCO Solenoid Valve: A Tabular Comparison
- How to Pick the Right ASCO Solenoid Valve from 2-Way Series
- How to Pick the Right ASCO Solenoid Valve from 3-Way Series
- Choose the Right ASCO Solenoid Valve with Control Specialties
- Frequently Asked Questions (FAQs)
A solenoid valve looks simple. It contains a coil, a plunger, and a valve body. Selecting the wrong valve can create costly performance and maintenance problems. A 2-way valve can be the wrong choice when an actuator needs to vent, while a 3-way valve can add unnecessary complexity when all you need is simple on/off flow control.
Following the wrong operating principle can cause another set of problems. A pilot-operated valve may not work where pressure is too low, while a direct-acting valve may not provide the flow capacity you need.
That is why ASCO solenoid valve selection works best as a sequence of decisions, not a catalog hunt. The valve electrically opens, closes, or redirects flow when its coil is energized. The key is narrowing the options based on how your system actually operates.
Quick Answer
Use a 2-way valve to start or stop flow through a single line. Choose a 3-way valve when the circuit needs to pressurize, exhaust, or divert flow, such as operating a single-acting cylinder or piloting another valve. Then select direct-acting when the valve must operate at zero differential pressure, or pilot-operated when higher flow capacity is needed, and sufficient pressure differential is available.
2-Way ASCO Solenoid Valve: An Overview
What is a 2-Way ASCO Solenoid Valve?
A 2-way solenoid valve is the simplest valve in the ASCO solenoid valve lineup. It has one inlet, one outlet, and a single orifice. Its only job is to start or stop flow in one line. It doesn't divert or vent; it just opens and closes. If the line only requires on/off flow control, a 2-way valve is typically the simpler choice.
How Does a 2-Way ASCO Solenoid Valve Work?
When the coil is energized, its magnetic field lifts a plunger. Depending on the construction, the plunger then opens or closes the orifice.
- Normally Closed (NC) valves are often selected when the desired de-energized state is no flow. For fuel-gas or other safety-critical service, verify that the exact valve is approved and rated for the application.
- Normally Open (NO) valves let flow pass until the coil is energized. They suit cooling or purge lines that must keep running during a power outage.
When a 2-way closes, it holds whatever pressure is trapped downstream. It doesn't vent the line. That's an advantage on a shutoff, and a problem on an actuator that has to exhaust.
Industrial Applications of 2-Way ASCO Solenoid Valves
- Water and Cooling Lines: Shutoff for cooling water, washdown, and process water. The 8210 is the go-to for higher flow.
- Compressed Air: Blowoff, drains, and dryer service at plant pressure. Use the 8215 or 8040 on low-pressure lines. See our full range of compressed air system products.
- Fuel Gas Shutoff: NC valves specified for the gas and listed for safety shutoff duty. These are used alongside gas safety systems and flame safeguards from the Fireye range of products.
- Hot Water and Boiler Systems: The 8210HW is built for hot water service on boiler controls and equipment.
- Low-Pressure, Vacuum, and Dosing Lines: Direct-Acting 8262 and 8263 valves for small lines, gravity drains, and metering.
3-Way ASCO Solenoid Valve: An Overview
What is a 3-Way ASCO Solenoid Valve?
A 3-way solenoid valve has three ports and two orifices. The ports are typically pressure, cylinder (outlet), and exhaust. Instead of simply opening and closing, it switches flow between ports, most often to pressurize a device and then vent it. If the downstream side of your system has to exhaust, switch, or divert, you need a 3-way.
How Does a 3-Way ASCO Solenoid Valve Work?
The two orifices work in opposition: when one opens, the other closes.
- In one position, supply flows to the cylinder or actuator.
- In the other position, the cylinder or actuator is connected to the exhaust port, which may vent locally or be piped as required by the application.
ASCO offers three constructions:
- Normally Closed: When de-energized, the pressure port is blocked and the cylinder vents to exhaust. When energized, pressure flows to the cylinder.
- Normally Open: When de-energized, pressure flows to the cylinder. When energized, the pressure port closes and the cylinder exhausts.
- Universal: Any port can be pressurized, so the valve can divert one supply to two outlets or select between two sources. The 8320 is the only one of the three 3-way series covered here that's offered in a universal construction.
Industrial Applications of 3-Way ASCO Solenoid Valves
- Single-Acting Cylinders and Spring-Return Actuators: The valve pressurizes the cylinder to stroke it, then exhausts it so the spring can return. The 8320 suits small cylinders, and the 8316 suits larger ones.
- Piloting Process Valves: A small 3-way valve supplies and vents the air that operates a larger air-actuated valve, such as Fisher control valves and other pneumatic process valves.
- Fast Exhaust: When the return stroke is too slow, the 8321 quick exhaust valve dumps cylinder air rapidly.
- Diverting and Selecting: Universal-construction valves route one supply to two outlets, or switch between two pressures or media.
- Pneumatic Machine Control: Clamping, ejecting, and positioning circuits on packaging and assembly equipment, supplied through your compressed air system products.
2-Way vs. 3-Way ASCO Solenoid Valve: A Detailed Comparison
1. Port Configuration and Flow Path
A 2-way solenoid valve has one inlet, one outlet, and a single orifice, so flow can only move in one path: from inlet to outlet, or not at all.
A 3-way solenoid valve has three ports (pressure, cylinder, and exhaust) and two orifices that work in opposition. That second flow path is the defining difference. A 3-way doesn't just stop flow; it redirects it.
What Happens When the Valve Closes
This is where most selection mistakes happen.
- 2-Way ASCO Solenoid Valve: When it closes, it holds whatever pressure is trapped downstream. That's ideal for a shutoff, because the line stays sealed.
- 3-Way ASCO Solenoid Valve: When it switches, the downstream side vents to exhaust. That's what lets a single-acting cylinder or spring-return actuator return to its home position.
Put a 2-way on that actuator and the trapped air keeps it stroked. The usual result is a "failed valve" service call when the valve itself is fine.
2. Valve Function and Constructions
Both valve types come in Normally Closed (NC) and Normally Open (NO) constructions, but the meaning shifts:
- 2-Way ASCO Solenoid Valve: NC and NO simply describe whether flow passes when the coil is de-energized.
- 3-Way ASCO Solenoid Valve: NC and NO describe which port is connected to the cylinder at rest. A 3-way can also be universal, meaning any port can be pressurized. That lets it divert one supply to two outlets or select between two sources, which no 2-way can do. Of the series covered here, the 8320 is the one offered in a universal construction.
3. Operating Principle and Pressure Requirements
Both types are built in direct-acting and pilot-operated styles, and the same pressure rule applies to each:
- Direct-Acting valves can operate at zero differential pressure, depending on the model. Examples are the 2-way 8262, 8263, 8030, and 8040, and the 3-way 8320.
- Pilot-Operated valves need a minimum pressure differential to shift, but deliver much more flow. Examples are the 2-way 8210 and 8215, and the 3-way 8316 and 8321.
The ranges differ. The 2-way family reaches much larger sizes, up to 3in connections on the 8215, because it's often the main process valve. Most 3-way valves are smaller because their usual job is moving pilot or actuator air.
4. Flow and Sizing
For a 2-way, ASCO solenoid valve sizing is about process flow. You size by Cv (Flow Coefficient) against the required GPM or SCFH and the allowable pressure drop.
For a 3-way, the target is often actuator response/stroke time rather than process liquid flow:
- A small 3-way like the 8320 is plenty for piloting or small cylinders.
- Larger actuators call for the higher-flow 8316.
- When the return stroke is the bottleneck, the 8321 quick exhaust valve dumps air fast.
5. Typical Applications
The 2-way is the workhorse for process media: water, compressed air, light oil, fuel gas, and hot water. That covers cooling lines, washdown, compressed air system products, and burner shutoff alongside gas safety systems.
The 3-way is mainly a pneumatic control valve. It handles single-acting cylinders, spring-return actuators, piloting larger air-operated valves such as Fisher Control Valves, and diverting or selecting flow.
6. Cost, Complexity, and Interchangeability
A 2-way is generally simpler and less expensive for a plain shutoff. Using a 3-way where a 2-way would do adds cost and an extra port to manage.
Interchangeability is limited and must be verified for the exact valve. Plugging the exhaust port of a 3-way lets it act as a 2-way, which can help consolidate spares (confirm the flow rating for that duty). A 2-way can never do a 3-way's job.
Which One is Right For Your Application
The 2-way vs. 3-way ASCO solenoid valve decision comes down to one question:
Does the downstream side need to vent or switch?
If it only needs to start and stop, choose a 2-way. If it needs to exhaust, pilot, divert, or select, choose a 3-way.
2-Way vs. 3-Way ASCO Solenoid Valve: A Tabular Comparison
| Feature | 2-Way ASCO Solenoid Valve | 3-Way ASCO Solenoid Valve |
|---|---|---|
| Body Materials | Brass and stainless steel; aluminum on the 8215 and 8040 for lightweight and low-pressure air | Brass and stainless steel across the 8316, 8320, and 8321 |
| Coil Voltage Options | AC (Alternating Current) or DC (Direct Current) on most series; the 8040 is AC only | AC or DC across all three series covered here |
| Exhaust Port Handling | No exhaust port; nothing to route or silence | Exhaust must stay open, fitted with a muffler or piped to a safe location; blocking it stops the actuator from returning |
| Air Consumption | No consumption beyond the process flow | Exhausts the actuator volume on every cycle, which adds to compressed air demand on high-cycle machines |
| Pressure During Maintenance | Downstream pressure stays trapped when closed; bleed the line before breaking a fitting | NC construction vents downstream pressure when de-energized, which simplifies lockout |
| Typical Installation Point | In-line in the process pipe, often far from the controlled equipment | Mounted close to the actuator or cylinder; short tubing means faster stroke times |
| Seats and Leak Points | One seat; leakage shows up as flow passing downstream | Two seats; a worn seat shows up as continuous air bleeding from the exhaust |
| Common Field Symptom | Won't open (pressure below the pilot minimum) or won't fully shut off | Actuator won't return (exhaust blocked) or constant hiss from the exhaust (seat wear) |
| Rebuild Kit Scope | One seat and disc; pilot-operated models add a diaphragm. The 8263 has a field-replaceable seat | Seals for both orifices, plus a diaphragm on pilot-operated models such as the 8316. |
| Nameplate Series Identification | 82xx and 80xx series (8210, 8215, 8262, 8263, 8030, and 8040) | 83xx series (8316, 8320, and 8321) |
How to Pick the Right ASCO Solenoid Valve from 2-Way Series
| Series | Operation | Sizes | Body Material | Best For |
|---|---|---|---|---|
| 8210 | Pilot-Operated Naturally Close Naturally Open |
3/8in - 2-1/2in | Brass and Stainless Steel | General-service air, inert gas, water, and light oil at higher flow |
| 8262 | Direct-Acting Poppet |
1/8in - 1/4in | Brass and Stainless Steel | Zero pressure Small lines Instrument Dosing service |
| 8263 | Direct-Acting Poppet Naturally Close |
1/4in - 3/8in | Brass and Stainless Steel | More flow without a minimum differential; field-replaceable seat |
| 8215 | Pilot-Operated Naturally Close Naturally Open |
3/8in - 3in | Aluminum | Low-pressure air Inert gas in large lines |
| 8030 | Direct-Acting | 3/8in - 3/4in | Brass and Stainless Steel | Low pressure Vacuum service |
| 8040 | Direct-Acting Naturally Close AC Only |
1/8in - 3/8in | Aluminum | High flow at low pressure Lightweight installs |
| 8210HW | Naturally Close | 3/8in - 3/4in | Brass | Hot water service |
How to Interpret the Above Table
- Line Pressure is Always Above the Minimum, and You Need Flow: Start with the 8210. It's the workhorse for cooling water, washdown, compressors, and pump systems.
- Zero Pressure, Vacuum, or Small Lines: Choose the 8262, and step up to the 8263 when you need more flow. The 8263's replaceable seat is a real advantage on dirty or abrasive service.
- Low-Pressure Air or Inert Gas: The aluminum 8215 covers large lines up to 3in, the 8040 handles small high-flow lines, and the 8030 adds brass or stainless bodies plus vacuum capability.
- Hot Water: Specify the 8210HW rather than a standard 8210 with general-purpose elastomers.
How to Pick the Right ASCO Solenoid Valve from 3-Way Series
| Series | Operation | Sizes | Best For |
|---|---|---|---|
| 8320 | Direct-Acting Poppet Naturally Close Naturally Open Universal |
1/8in - 1/4in | Piloting Small single-acting cylinders In-line piping |
| 8316 | Pilot-Operated Diaphragm Naturally Close Naturally Open |
3/8in - 1in | Larger actuators and high-flow switching Zero-minimum constructions |
| 8321 | Pilot-Operated Quick Exhaust Naturally Close Naturally Open |
1/4in - 3/8in | Dumping actuator or cylinder air fast to speed the return stroke |
How to Interpret the Above Table
- Start with the 8320 for most piloting and small-cylinder work; it's the broadest general-purpose 3-way and the only one of the three offered in a universal construction.
- Step up to the 8316 when the actuator is too large or too slow for an 8320.
- Choose the 8321 when exhaust speed, not supply flow, is the bottleneck.
Choose the Right ASCO Solenoid Valve with Control Specialties
Effective ASCO solenoid valve selection comes down to a few clear decisions. Start with the 2-way vs. 3-way ASCO solenoid valve question: does the line only need to start and stop, or does it need to vent and switch? Then match a direct-acting or pilot-operated design to your line pressure and size by Cv.
Control Specialties, a trusted industrial parts distributor, supplies ASCO 2-way and 3-way series alongside steam pressure regulators, boiler controls, and valve replacement parts. Our team reviews your whole system, not just the valve, before recommending a part.
Are you not sure whether your application calls for a 2-way or a 3-way, or which series fits your pressure and flow? Talk to our experts and share your media, pressure range, flow, voltage, and current part number, and we'll recommend the right ASCO valve based on your specific requirements.
Frequently Asked Questions (FAQs)
What is the difference between a 2-way and 3-way solenoid valve?
A 2-way solenoid valve has one inlet and one outlet and simply starts or stops flow. A 3-way valve has three ports and two orifices, so it can pressurize and exhaust an actuator, pilot another valve, or divert flow.
What does a 3-way solenoid valve do?
It alternately supplies pressure to a cylinder or actuator and then vents it to exhaust. That lets single-acting cylinders and spring-return actuators return home. Universal 3-way valves can also divert or select flow.
How does an ASCO solenoid valve work?
Energizing the coil creates a magnetic field that lifts a plunger. Direct-acting valves open the orifice directly; pilot-operated valves open a small pilot so line pressure moves a diaphragm and opens the main orifice.
Why is my ASCO solenoid valve not opening?
Most often, the pressure differential is below the pilot-operated valve's minimum. Other causes include wrong coil voltage, a burned coil, debris in the pilot orifice, or a worn diaphragm. Check the catalog rating before replacing valve parts.
How do you size a solenoid valve?
Size by flow coefficient (Cv), not pipe size. For liquids, Cv = Q × √(SG ÷ ΔP). Pick the smallest valve whose Cv meets the requirement, and confirm the pressure drop exceeds any pilot minimum.
What is the difference between a 3-way and 4-way solenoid valve?
A 3-way valve controls one side of an actuator, suiting single-acting, spring-return cylinders. A 4-way valve pressurizes one side while exhausting the other, which double-acting cylinders need to extend and retract under air power.
Which ASCO solenoid valve is best for water?
For general water service with steady line pressure, the pilot-operated 8210 is the standard choice. Use direct-acting 8262 or 8263 valves for low or zero pressure, and the 8210HW for hot water.
How do I know if I need a direct-acting or pilot-operated valve?
Choose a direct-acting valve when you need simple, reliable operation, fast response, or performance at low pressure. A pilot-operated valve is better suited for higher flow rates and tighter control when the system pressure is sufficient to operate the pilot.
