Air Compressor Pressure Switch 220V 1/4″ F x 4 with Unloader Valve
The 220V 1/4″ F x 4 Air Compressor Pressure Switch (pressostat) is an electromechanical device designed for automatic control of single-phase piston compressor motors. It turns the motor on when pressure drops below the lower threshold and turns it off when the upper threshold is reached, ensuring stable operation of the pneumatic system without constant operator intervention.
Technical Specifications
| Parameter | Value |
|---|---|
| Supply Voltage | 220 V (single-phase, 50 Hz) |
| Connection Thread | G 1/4″ Female (F) |
| Number of Ports | 4 (F x 4) |
| Unloader Valve | Built-in, for ⌀ 6 mm tube |
| Pressure Adjustment | Adjustment screws (main P + differential dP) |
| Body Material | Cast aluminum / silumin |
| Application | Single-phase piston compressors |
| Compatibility | Remeza AirCast, MZB and similar models with G 1/4″ thread |
What is a Pressure Switch and How Does It Work?
A pressure switch (pressostat) is a key component of the compressor control system. The principle is simple: the diaphragm inside the switch reacts to the air pressure in the receiver and mechanically closes or opens the electrical contacts, controlling the motor.
Operating cycle:
- The compressor pumps air.
- Pressure in the receiver reaches the upper threshold → the switch opens the motor circuit.
- The consumer uses air → pressure drops to the lower threshold.
- The switch closes the circuit and the motor starts again.
This cycle repeats automatically.
Why 4 Ports (F x 4)?
The version with four G 1/4″ female ports turns the pressure switch into a multifunctional manifold. You can connect simultaneously:
- Main air line — supply of compressed air to tools or system.
- Pressure gauge — for visual pressure monitoring.
- Safety (relief) valve — emergency pressure release.
- 4th port — quick coupler, drain valve, or plug.
This design eliminates the need for a separate manifold and greatly simplifies compressor piping.
Unloader Valve: Purpose and Connection
The built-in unloader valve is one of the most important features. After the compressor stops, residual compressed air remains in the cylinder head and the line to the check valve. Without releasing this pressure, the motor would start under load, causing high inrush current and increased wear on the windings.
Connection: Connect a flexible tube (e.g. Rilsan / PA12 ⌀ 6 mm) to the unloader valve port. The other end connects to the special port on the check valve at the compressor head outlet. When the motor stops, the valve opens and releases the pressure, allowing the next start without load.
How to Choose the Right Pressure Switch
When selecting or replacing a pressure switch, check:
- Voltage — 220 V single-phase (for 380 V three-phase use Condor MDR3 series).
- Thread — G 1/4″ Female (standard for compressors up to 2.2 kW).
- Current rating — must match your motor’s power and operating current.
- Pressure range — must suit your system’s working pressures.
This model is a universal replacement for Remeza AirCast, MZB, and most Chinese and European single-phase piston compressors with G 1/4″ thread.
Pressure Adjustment
The switch has two adjustment screws:
- P (main) — sets the cut-out (upper) pressure.
- dP (differential) — sets the difference between cut-out and cut-in pressures.
Example: P = 8 bar, dP = 2 bar → compressor stops at 8 bar, restarts at 6 bar.
Important: Always disconnect power and release all pressure in the receiver before adjusting. It is recommended to install an air filter before the pressure switch to protect the diaphragm from dirt.
FAQ
What is a pressure switch (pressostat) and why is it needed? It automatically turns the compressor motor on and off according to the pressure in the receiver, protecting the equipment from overheating and excessive wear.
Which compressors is the 220V 1/4″ F x 4 suitable for? It is suitable for single-phase 220 V piston compressors with G 1/4″ thread: Remeza AirCast, MZB, and most household and semi-professional models up to 2.2 kW.
Why does the F x 4 version have four ports? Four ports allow simultaneous connection of the air outlet, pressure gauge, safety valve, and an additional port. The switch acts as a compact manifold.
What is the unloader valve and how to connect it? It releases pressure from the cylinder head after shutdown for easy restart. Connect a 6 mm tube from the unloader valve to the check valve port.
How do I adjust the on/off pressures? Use screw P for cut-out pressure and dP for the differential. Always adjust with the compressor powered off and pressure released.
Can this replace the original Remeza pressure switch? Yes, provided the thread (G 1/4″), voltage (220 V), and pressure range match.
