How the MDR3 16/20A Differs from the 10 and 11 Bar Versions
In the Condor MDR3 range, three key parameters determine model selection: maximum pressure, thermal protection current, and consequently motor power. The MDR3 16/20A covers the upper range:
| Model | Max. pressure | Thermal protection current | Max. motor power |
|---|---|---|---|
| MDR3 10/6.3A | 11 bar | 4–6.3 A | ~3 kW |
| MDR3 10/10A | 11 bar | 7–10 A | ~5.5 kW |
| MDR3 16/20A | 16 bar | 16–20 A | ~7.5 kW |
| MDR3 16/24A | 16 bar | 18–24 A | ~11 kW |
The MDR3 16/20A is the choice for powerful 3-phase compressors with working pressure of 12–16 bar and motors of 5.5–7.5 kW. These are precisely the parameters found on industrial piston compressors used in laser metal cutting systems, shot blasting, spray painting, and other high-load applications.
How the MDR3 16/20A Pressure Switch Works
A pressure switch is an electromechanical device that closes and opens the compressor’s power circuit depending on receiver pressure. Inside the housing is a diaphragm connected to the pneumatic system via a 3/8″ port. As pressure changes, the diaphragm acts on the spring mechanism controlling the 3-pole contact.
- When pressure drops below the cut-in point (p₁ − Δp) — the contact closes and the motor starts
- When cut-out pressure is reached (p₁) — the contact opens and the motor stops
- The unloader valve (6 mm port) releases residual line pressure after shutdown, enabling easy restart without motor load
Hysteresis (the difference between cut-in and cut-out pressure) is adjusted with a separate regulator (Δp). For a compressor with a maximum pressure of 16 bar, the typical setting is: p₁ = 16 bar, Δp = 2–3 bar → cut-in at 13–14 bar.
5 Reasons to Choose the Condor MDR3 16/20A
1. The only MDR3 model for 12–16 bar systems with a ~7.5 kW motor The MDR3 10/10A is rated for 11 bar — it is physically unsuitable for compressors with working pressure of 12–16 bar. The MDR3 16/20A is a purpose-designed pressure switch for this range, with a diaphragm and spring rated for the corresponding loads.
2. Thermal protection 16–20 A without an external thermal relay The integrated thermal trip automatically disconnects the motor when current exceeds 20 A. This protects motor windings from overheating during difficult starts, prolonged overload, or contactor sticking. No separate thermal relay is needed in the circuit.
3. German quality — the industry standard for industrial compressors across Europe Condor Pressure Control GmbH has been manufacturing MDR series pressure switches for over 40 years. The MDR3 is the standard automation component on factory-fitted piston compressors from Remeza, Atlas Copco, Boge, and most European manufacturers. Contacts are rated for hundreds of thousands of switching cycles.
4. IP54 — works in workshop, factory floor, and outdoor conditions The die-cast aluminium housing with rubber gasket withstands oil dust, water splashes, and vibration — the typical operating environment of a high-power piston compressor.
5. Fast replacement — standard mounting flange The MDR3 16/20A has a standard 3/8″ flange with three additional 1/4″ ports (pressure gauge, safety valve, consumer). Replacement on a live installation takes 20–30 minutes with the right tools.
Which Compressors and Systems Is the MDR3 16/20A Compatible With
By motor power: 3-phase compressors with motors of 5.5–7.5 kW at 400 V
By working pressure: systems with pressure of 12–16 bar
Typical applications:
- Laser metal cutting — 12–16 bar compressors supplying laser heads with nitrogen or compressed air: Remeza LB75, LB100, MZB 16 bar series
- Shot blasting and grit blasting — high pressure for effective abrasive acceleration
- Industrial spray painting — stable pressure of 10–14 bar for high-output spray systems
- Production workshops — centralised compressor stations with line pressure above 10 bar
- High-pressure pneumatic actuators and cylinders in heavy engineering
⚠️ Important: The MDR3 16/20A is designed for 3-phase systems (3Ph + PE, 400 V). For single-phase compressors use the MDR1 series. If your compressor operates up to 11 bar — consider the MDR3 10/10A (the more economical option for lower-pressure applications).
Technical Specifications
| Parameter | Value |
|---|---|
| Type | Electromechanical pressure switch (pressostat) |
| Series | MDR 3 |
| Thermal protection current range | 16–20 A |
| Supply voltage | ≤ 400 V AC, 50/60 Hz |
| Protection class | IP 54 |
| Contact | 3-pole normally closed (NC) |
| Maximum motor power | ~7.5 kW (~10 HP) at 400 V |
| Pressure adjustment range | ≈ 6–16 bar |
| Maximum working pressure | 16 bar |
| Housing material | Die-cast aluminium |
| Maximum ambient temperature | up to 80 °C |
| Connection port | G 3/8″ (main) + 3 × G 1/4″ |
| Unloader valve | 6 mm port (for Rilsan tube) |
| Weight | ≈ 0.69 kg |
| Standard | EN 60947, UL/CSA variants |
| Manufacturer | Condor Pressure Control GmbH (Germany) |
Setting Up the MDR3 16/20A for a 16 Bar Compressor
Step 1. Set the cut-out pressure (p₁) Turn the large spring (main regulator) until the desired cut-out pressure is reached. For a 16 bar compressor: p₁ = 16 bar.
Step 2. Set the hysteresis (Δp) The small spring sets the difference between cut-in and cut-out pressure. Recommended hysteresis for a 16 bar compressor: Δp = 2–3 bar. Result: the compressor cuts in at 13–14 bar and cuts out at 16 bar.
Step 3. Connect the unloader valve Connect the Rilsan tube (6 mm) from the side port of the switch to the compressor check valve. Without this connection, every motor start occurs under pressure — this is a critical installation error.
Step 4. Check the phase sequence Start the compressor and confirm that receiver pressure is rising (not falling). If pressure drops — swap two phases at the MDR3 terminal block.
Expert Opinion
“The MDR3 16/20A is a pressure switch for serious equipment. It’s chosen where 10 bar is not enough: laser cutting, high-power blasting systems, production lines running at 12–14 bar. The most common mistake when replacing it is fitting an MDR3 10/10A ‘because it looks the same’ — and then the diaphragm can’t handle pressure above 11 bar and the switch fails to cut out the compressor in time. The ’16’ in the part number isn’t just a figure: it’s the maximum pressure the diaphragm is rated for. The second point: with a 7.5 kW motor drawing 14–15 A at running load, inrush current can reach 80–100 A — the 16–20 A thermal relay in the pressure switch is not designed to protect against inrush; it protects against sustained overload. For inrush protection, use a separate circuit breaker with a D-characteristic.”
Vitaly Boluchevsky, Chief Engineer at Acvatron SRL, 15 years in the industry
FAQ
❓ What is the difference between the MDR3 16/20A and MDR3 16/24A? Both pressure switches are rated for pressure up to 16 bar. The difference is the thermal protection current: MDR3 16/20A — 16–20 A (motors up to ~7.5 kW), MDR3 16/24A — 18–24 A (motors up to ~11 kW). Choose based on the rated current of your motor: it must fall within the thermal relay range of the pressure switch.
❓ Is the MDR3 16/20A compatible with the Remeza LB75 compressor? The Remeza LB75 has a 5.5 kW motor and working pressure of 10 bar — the MDR3 10/10A is the right fit. Use the MDR3 16/20A if your LB75 or another compressor has pressure above 11 bar (for example, the 12 bar version of the LB75) or a 7.5 kW motor. Confirm with an Acvatron SRL manager by model number.
❓ Why does the pressure switch not cut out the compressor when maximum pressure is reached? Possible causes: incorrect p₁ setting (cut-out pressure set above the compressor’s maximum working pressure); burnt or stuck contacts inside the switch; diaphragm fatigue after years of operation at maximum pressure. In any case — replace the pressure switch.
❓ Can the MDR3 16/20A be used for a pump instead of a compressor? Yes. The MDR3 pressure switch is a universal device for pressure-based control of any 3-phase motor up to 7.5 kW: compressors, pump stations, pressure vessels, industrial pumps. The operating principle and wiring are identical.
❓ Is the MDR3 16/20A in stock in Chișinău? Yes, Condor MDR3 pressure switches are permanently stocked at Acvatron SRL. Same-day collection after payment, delivery across Moldova. Call: +373 22 503-580.
