Comment choisir le bon moteur IE3 / IE4 pour les compresseurs de vis d'ammoniac - 5 conseils incontournables

Choosing the right motor for an ammonia screw compressor isn’t just about specs—it’s about safety, reliability, and peace of mind when failure simply isn’t an option.

What’s the best IE3 or IE4 motor for ammonia screw compressors?
The ideal IE3/IE4 motor for ammonia screw compressors must offer certified energy efficiency, robust anti-corrosion features, precision mounting compatibility, reliable insulation, VFD-readiness, and insulated bearings to prevent electrical damage. Look for CE certifications, epoxy coating, IP55 or higher protection, thermal class F with B rise, PT100 sensors, and proper bearing insulation. Customization is also key—especially in shaft and flange details.

Let’s explore this in more detail with five key points I always double-check before making a motor recommendation.

What level of efficiency does your application demand?

When it comes to ammonia compressors, energy efficiency matters more than ever.

IE3 or IE4: Which efficiency level should you choose for ammonia compressors?
IE3 motors (Premium Efficiency) are great for most industrial uses, while IE4 (Super Premium) is ideal for long-running systems where energy loss adds up. Both reduce heat buildup, help with motor longevity, and ensure compliance with international energy standards like IEC 60034-30-1. Make sure the motor includes a CE certificate and verifiable test report.

Why energy efficiency really matters in ammonia systems

I've had buyers from Chile and South Africa ask me if IE4 is always worth the upgrade. Here's what I usually say: If your compressor runs 24/7—yes. You’ll save power, reduce wear, and cut cooling costs inside the motor panel. But even with IE3, choosing a motor with the right winding and rotor design is half the battle.

A quick comparison:

And always ask your supplier for test reports. I’ve seen some motors labeled IE3 that fail to hit those numbers in real conditions. Certification by TUV or similar bodies is a must.

How do I ensure the motor physically fits my compressor?

Mounting is more than just bolt holes—it's about alignment, coupling, and durability.

Which mounting type and shaft design should you match to an ammonia compressor?
Most compressors use B3 (foot-mounted), B5 (flange-mounted), or B35 (foot + flange). Make sure your motor’s shaft diameter, keyway, and flange thickness are 100% aligned with the compressor’s input. For belt-driven systems, shaft load tolerance also matters. Don’t assume—confirm with the compressor maker.

Avoiding a costly mismatch

We once had a client from Grèce, a long-term refrigeration equipment manufacturer. They placed an order for several IE3 motors for their ammonia screw compressors. They specified B5 flange mounting, but after checking their compressor supplier’s drawings, we noticed a discrepancy—the flange thickness was non-standard, and the shaft needed a longer keyway to fit their coupler properly.

Thanks to their fast response and our flexible production line, we were able to custom-machine the flanges and shafts within a week. No retrofits, no complaints. That small adjustment saved them from a shipment delay during Greece’s peak produce freezing season.

So, always:

• Get the compressor’s technical drawing first
• Verify shaft and flange details with the motor supplier
• Don’t assume "standard B5" fits all B5s—it often doesn’t

Dongchun supports full customization here, down to the last millimeter.

Is the motor built to handle ammonia’s corrosive environment?

You don’t want metal parts corroding in six months. Ammonia is tough on gear—and motors are no exception.

What protection features should a motor have for ammonia compressor applications?
Go for IP55 at minimum—IP65 is even better. Look for a double epoxy coating and sealed bearings (SKF/NSK) with oil seals to block gas intrusion. Ammonia eats away at unprotected metal fast, so these features aren’t “nice to have”—they’re essential.

What I’ve learned from real-world failures

A client in Equateur had motors that began to corrode internally just six months into use. Turned out, the ammonia gas had seeped through unsealed bearings and caused internal rust.

Since then, I always recommend:

• Epoxy coatings, inside and out
• Oil-sealed, shielded bearings from SKF or NSK
• IP65 protection, especially for outdoor or humid rooms

You’ll spend a bit more, but you protect your entire refrigeration system—and your reputation.

Will the motor survive under real working conditions?

Temperature swings, vibration, and humidity all take a toll over time.

What insulation and thermal class is best for ammonia compressor motors?
Class F insulation (with B-class temperature rise) is usually sufficient. But if you’re running in cold rooms or hot outdoor setups, go one level higher. For long-term performance, look for motors with VPI-treated windings and PT100 temperature sensors on both windings and bearings. And don’t forget insulated bearings if a VFD is involved.

Heat and current—two silent killers

That same Greek customer I mentioned earlier? They later upgraded to a VFD-driven setup and started experiencing unexpected bearing noise. We quickly diagnosed the issue: shaft current discharge caused by the inverter. They had forgotten to request insulated bearings.

We fixed it by supplying replacement motors with:

• Insulated bearings to block harmful shaft voltage
• PT100 sensors for early warning before overheating
• Vacuum Pressure Impregnation (VPI) for winding durability

Now they specify insulated bearings on every VFD motor they order—and haven’t had an issue since.

Do you need VFD compatibility for speed control?

Soft starts, energy savings, and variable loads are all good reasons to go with a VFD-compatible motor.

Is your motor VFD-ready? What should you look for?
Check for enhanced insulation (Class F or H), reinforced windings, built-in PT100 sensors, and insulated bearings. Motors should be rated for inverter duty, capable of handling harmonics and voltage spikes. If your compressor speed varies by load, this is non-negotiable.

VFDs are great—but only with the right motor

Another client from Italy had VFDs causing motor failures due to high-frequency voltage spikes. Their motors weren’t inverter-ready—and didn’t have insulated bearings.

At Dongchun, we test all VFD motors under actual inverter load. Here’s what we build in:

• Class F or H insulation
• VFD-compatible windings
• PT100s on windings and bearings
• Insulated bearings as standard for all inverter-duty units

You won’t just save energy—you’ll protect your equipment.

Conclusion

Choosing the right IE3 or IE4 motor for ammonia screw compressors is about the details: protection, fit, efficiency, insulation, and control. Get these right, and everything else just works.