Pressure Switch 220V for Compressor — G 1/4″ F × 4 Ports, No Unloader Valve

Introductory Paragraph (Short Description)

A 220V pressure switch (pressostat) with G 1/4″ Female thread and 4 ports — a universal replacement for single-phase piston compressors. Automatically starts the motor when pressure drops below the lower threshold and stops it when the upper threshold is reached. No unloader valve included — if your compressor has a separate unloader valve on the check valve or cylinder head, this model is the right fit. Compatible with Remeza AirCast, MZB, Baikal, Chinese-made units, and most single-phase piston compressors with G 1/4″ thread.

Full Description («Description» tab)

How This Model Differs from the Version WITH an Unloader Valve

This is the most important point when choosing:

When you need the version WITHOUT an unloader valve:

• Your compressor already has a separate (solenoid) unloader valve installed
• A direct-drive compressor where unloading is built into the cylinder head design
• Replacing the switch without modifying the existing circuit in which the unloader valve is connected separately

When you need the version WITH an unloader valve:

• A standard piston compressor without a built-in unloader — choose the G 1/4″ F × 4 version with built-in unloader valve

💡 Not sure whether your compressor has an unloader valve? Call us: +373 22 503-580. An engineer will identify the correct version from your compressor model.

What Is a 220V Pressure Switch and How Does It Work

A pressure switch is an electromechanical device that automatically starts and stops the compressor motor depending on air pressure in the receiver.

Operating principle:

• Inside the housing is a diaphragm connected to the pneumatic system via the G 1/4″ thread
• When pressure drops below the lower threshold — the diaphragm releases the spring mechanism, the contact closes, and the motor starts
• When the upper threshold is reached — pressure compresses the diaphragm, the contact opens, and the motor stops
• The cycle repeats automatically without operator intervention

Two adjusters under the cover:

• Screw P (large spring) — cut-out pressure (upper threshold)
• Screw dP (small spring) — difference between upper and lower threshold (hysteresis)

Example: P = 8 bar, dP = 2 bar → compressor cuts out at 8 bar, cuts in at 6 bar.

Why 4 Ports: G 1/4″ F × 4

Four threaded G 1/4″ ports turn the pressure switch into a compact manifold on the receiver:

• Port 1 — main air supply line to the consumer / hose
• Port 2 — pressure gauge for visual pressure monitoring
• Port 3 — safety valve (emergency pressure relief if the switch fails)
• Port 4 — additional consumer, quick-release coupling, or blanking plug

This arrangement eliminates the need for a separate manifold and consolidates all compressor connections into one point.

Which Compressors Is It Compatible With

By voltage: 220V single-phase compressors only. For 3-phase 380V compressors use the Condor MDR3 series.

By thread: G 1/4″ Female (internal). This is the standard for most compressors up to 2.2 kW.

Compatible models:

• Remeza AirCast LB20, LB24 (single-phase versions up to 2.2 kW)
• MZB piston compressors with direct and belt drive, 220V
• Chinese piston compressors with 50–100 litre receivers at 220V
• Baikal, Aurora, Calibr and equivalents with G 1/4″ thread on the receiver

⚠️ Check before ordering: G 1/4″ thread and R (NPT) 1/4″ thread are different standards. G is parallel (cylindrical), R is tapered (conical). They look similar but are not interchangeable. Most European and Chinese compressors use G 1/4″.

Technical Specifications

How to Set the Pressure Switch for Your Compressor

Step 1. Disconnect the compressor from the power supply and bleed the receiver down to zero pressure.

Step 2. Remove the switch cover (usually 2–4 screws).

Step 3. Locate the two adjustment screws:

• Large screw (P) — upper pressure threshold (cut-out)
• Small screw (dP) — hysteresis (difference between cut-in and cut-out)

Step 4. Turning screw P clockwise increases the cut-out pressure. Anti-clockwise decreases it.

Step 5. Replace the cover, restore power, start the compressor, and verify switching on the pressure gauge.

Typical setting for an 8 bar compressor: P = 8 bar, dP = 2 bar → cuts in at 6 bar, cuts out at 8 bar.

5 Reasons to Choose This Model

1. Universal drop-in replacement with no pipework changes Standard G 1/4″ flange and 4 ports — fits in place of the factory switch on most single-phase compressors without replacing the manifold or tubes.

2. Compact 4-in-1 manifold Pressure gauge + safety valve + supply line + spare port — everything at a single point on the receiver.

3. Simple two-screw adjustment Set the pressure range with no electronic equipment or specialist tools — just a flat-blade screwdriver and a pressure gauge.

4. Suitable for compressors with an external unloader valve If the unloader valve is already installed separately, no circuit modifications are needed — just swap the switch.

5. Low cost — fast replacement with minimal downtime The affordable price allows a spare switch to be kept in stock — when the original fails, the compressor is down for no more than 20 minutes.

Expert Opinion

“This is the most widely-used replacement switch for domestic and semi-professional 220V piston compressors. It’s chosen when the original switch has burned out and a genuine replacement costs several times more. The key question when selecting is whether the compressor has a separate unloader valve or not. If the old switch had a 6 mm side port with a tube running to the check valve — get the version with the built-in unloader. If there was no such tube — this version without the valve is correct. Second point: always check the thread. Chinese compressors sometimes have NPT 1/4″ instead of G 1/4″ — they look the same but a G thread won’t tighten fully in an NPT port. One way to check: if the thread is slightly tapered (narrows toward the end) — it’s NPT; if it’s uniform throughout — it’s G.”

Vitaly Boluchevsky, Chief Engineer at Acvatron SRL, 15 years in the industry

FAQ

❓ What is the difference between a pressure switch with and without an unloader valve? A switch with an unloader valve has a 6 mm side port to which a tube from the compressor’s check valve is connected — after the motor stops, residual pressure from the cylinder head is bled off, making the next start easier. A switch without an unloader valve (this model) suits compressors where unloading is achieved differently — via a separate solenoid valve or built into the head design.

❓ How do I tell whether my compressor needs an unloader valve? Look at the old switch: if a thin tube (usually 6 mm) runs from its housing to the compressor’s check valve — you need the version with the built-in unloader valve. If there is no such tube — this version without the valve is correct.

❓ Does this switch fit the Remeza LB20 220V? Yes, provided the Remeza LB20 in its single-phase 220V version has G 1/4″ thread on the receiver and the unloader valve is realised separately (not via the switch port). Confirm with an Acvatron SRL manager using your compressor’s serial number.

❓ What should I do if the compressor doesn’t stop when the required pressure is reached? Check the P screw setting — the cut-out pressure may be set too high. Also check the diaphragm condition: if the switch is old and has run at maximum pressure for a long time, the diaphragm may have lost its elasticity. In this case replace the switch entirely.

❓ Can this switch be used for a pump or pressure vessel? Yes, provided the voltage (220V) and thread (G 1/4″) match. The pressure-based control principle is identical — the switch starts and stops a pump in exactly the same way as a compressor. Make sure the pump’s running current does not exceed the rated current of the switch contacts.