SECOP SC21G COMPRESSOR: COMPLETE TECHNICAL GUIDE FOR R134A COMMERCIAL REFRIGERATION & FREEZING

Secop SC21G Horsepower Rating

The Secop SC21G hermetic compressor is rated at 5/8 HP (approximately 0.625 horsepower) by manufacturers and distributors. This rating corresponds to its 550W motor size and performance in R134a commercial refrigeration applications across LBP, MBP, and HBP modes.​

Detailed HP Breakdown

• Nominal Motor Power: 550 watts, equivalent to ~0.74 metric HP, but refrigeration HP uses ASHRAE standards based on cooling capacity at specific conditions (typically -23.3°C evaporating temp).
• Industry Standard Rating: Consistently listed as 5/8 HP (0.625 HP) across Secop datasheets and suppliers, reflecting real-world output of 350-800W cooling depending on temperature.​
• Comparison Context: Larger than 1/5 HP (0.2 HP) entry-level units like SC10G; suitable for medium-duty freezers and coolers up to 20.95 cm³ displacement.​

Why HP Matters for SC21G

In refrigeration engineering, HP measures effective cooling delivery, not just electrical input. At 1.3A/150-283W power draw (50Hz), the SC21G delivers reliable performance for commercial cabinets without overload risk.​

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Secop SC21G is a high-performance hermetic reciprocating compressor designed for commercial refrigeration and freezing applications using R134a refrigerant. This guide covers detailed specifications, technical parameters, and installation requirements for 220-240V/50Hz systems at up to 1.3 amperes.

ARTICLE CONTENT:

Introduction: Understanding the Secop SC21G Hermetic Compressor

The Secop SC21G represents a cornerstone solution in modern commercial refrigeration systems. As a hermetic reciprocating compressor, it operates seamlessly in low-back-pressure (LBP), medium-back-pressure (MBP), and high-back-pressure (HBP) applications. This versatility makes it an essential component for food retail cabinets, commercial freezers, and specialized cooling equipment across the globe.

Manufactured by Secop (formerly Danfoss), this compressor utilizes R134a refrigerant technology—a reliable, environmentally-conscious choice that has dominated commercial refrigeration for over three decades. Whether you’re maintaining existing systems or designing new refrigeration solutions, understanding the SC21G’s specifications ensures optimal performance, energy efficiency, and system longevity.

Section 1: Complete Technical Specifications of Secop SC21G

1.1 Model Identification & Designation

1.2 Electrical Specifications

1.3 Dimensional Data

1.4 Refrigeration Performance at Standard Conditions

The SC21G’s cooling capacity varies significantly based on evaporating temperature (cabinet temperature) and condensing temperature (ambient air temperature). Here are performance metrics at 55°C condensing temperature (131°F):

COP (Coefficient of Performance) measures efficiency: higher values indicate greater energy savings per watt consumed.

Section 2: Secop SC21G vs. Competing Compressor Solutions

2.1 Secop SC21G vs. Danfoss TL2 Series

2.2 Secop SC21G vs. Embraco/Aspera Compressors

Section 3: Operating Temperature Ranges & Application Mapping

3.1 Temperature Classifications

The Secop SC21G handles distinct temperature operating ranges:

3.2 Ambient Temperature Limits

Proper condenser operation requires strict environmental control:

• Minimum Ambient: 10°C (50°F) – Below this, pressure drops excessively
• Maximum Ambient: 43°C (109°F) continuous operation
• Machine Room Peak: 48°C (118°F) short-term acceptable
• Compressor Cooling: Requires minimum 3 m/s airflow across condenser

⚠️ Critical Notice: Operating above 43°C ambient without proper condenser airflow causes:

• Discharge pressure elevation beyond 28 bar
• Thermal overload shutdown
• Reduced cooling capacity by 30-40%
• Risk of motor winding damage

Section 4: Refrigerant Management & Oil Chemistry

4.1 R134a Refrigerant Properties

4.2 Oil Compatibility & Viscosity

Polyolester (POE) Oil Specifications:

• Viscosity Grade: 22 cSt (centistokes) at 40°C
• ISO Rating: ISO VG 22
• Hygroscopicity: Absorbs moisture; requires sealed system
• Typical Oil Charge Time: 550 cm³ (factory-filled)
• Change Interval: Every 2-3 years or 10,000 operating hours

Installation Note: Never mix POE oil types or use mineral oil with R134a. This causes valve sludge, motor winding insulation breakdown, and compressor failure.

Section 5: Installation, Startup & Commissioning Guide

5.1 Pre-Installation Checklist

Before mounting the SC21G, verify system readiness:

• ☐ System Evacuation: Vacuum to -0.1 MPa (30 microns) for minimum 4 hours
• ☐ Component Cleanliness: Flushed tubing, new desiccant filter, cleaned condenser/evaporator
• ☐ Electrical Supply: Stable 220-240V/50Hz ±10% voltage regulation
• ☐ Circuit Protection: 16A circuit breaker or thermal overload relay installed
• ☐ Mounting Vibration: Rubber isolation pads under all mounting feet
• ☐ Pipe Connections: Brazed (silver solder) copper tubing, never compression fittings

5.2 Electrical Wiring Diagram for SC21G

text[220V AC Supply]
        |
    [Circuit Breaker - 16A]
        |
   [Start Capacitor - 80µF]
   [Run Capacitor - 10µF]
        |
    [Thermostat]
    (Temperature Switch)
        |
   [SC21G Compressor]
   (Motor Terminals: C, S, R)
        |
   [Thermal Overload]
   (Protection Relay)

• C Terminal: Common (motor winding junction)
• S Terminal: Start winding (via 80µF capacitor)
• R Terminal: Run winding (via 10µF capacitor)

5.3 Startup Procedure

1. Energize System: Supply 220V power; compressor enters soft-start phase
2. Initial Run: First 30 seconds at reduced load (pressure stabilization)
3. Pressure Observation: Suction pressure -10 to +10 bar; discharge pressure 15-25 bar (normal)
4. Current Draw: Should peak at ~1.3A during run cycle, drop to 0.8A steady-state
5. Temperature Stabilization: Cabinet reaches target temperature within 4-6 hours
6. Lubrication Check: Oil pressure visible in sight glass after 2 minutes

Section 6: Troubleshooting Common Secop SC21G Issues

6.1 Diagnostic Table

6.2 Pressure Monitoring Guide

Section 7: Energy Efficiency & Operating Cost Analysis

7.1 Annual Energy Consumption Estimate

Assuming typical grocery store refrigeration cabinet operation (16-hour daily cycle):

Efficiency Note: The SC21G’s COP of 1.68-1.69 means 1.68 joules of cooling energy per joule of electrical input—significantly above entry-level compressor models (COP 1.2-1.4).

Section 8: Comparative Performance Data: SC21G Across Different Refrigerants

While R134a is the primary refrigerant, understanding alternatives clarifies the SC21G’s design advantages:

Section 9: Regulations, Safety Certifications & Compliance

9.1 International Standards Compliance

The Secop SC21G meets rigorous safety and performance standards:

9.2 F-Gas & Environmental Regulations

• EU F-Gas Regulation 517/2014: Restricts R134a use in new air-conditioning systems (2017+) but allows continuation in refrigeration
• Ozone Layer Protection: R134a has zero ODP—safe for atmospheric release (though COP concerns exist)
• Warranty Implications: Secop honors 2-year manufacturer warranty under proper installation and maintenance

Section 10: Expert Recommendations & Maintenance Best Practices

10.1 Preventive Maintenance Schedule

10.2 Ten Essential Rules for SC21G Longevity

1. Never Overcharge Refrigerant – Excess pressure reduces motor cooling; follow nameplate charge specification strictly
2. Maintain Constant Evacuation – System must achieve -0.1 MPa vacuum; moisture/air cause acid formation
3. Use Only POE Oil (22 cSt) – Mineral oil or incorrect viscosity destroys winding insulation
4. Ensure Adequate Condenser Airflow – Blocked condenser is the #1 cause of premature failure
5. Install Liquid Line Filter – Protects expansion valve from debris
6. Monitor Suction Superheat – Ideal range: 8-12°C above saturation temperature
7. Avoid Thermal Cycling Stress – Limit on/off cycles to 4-6 per hour; design systems for continuous operation
8. Protect from Liquid Slugging – Accumulator tank prevents liquid refrigerant entering compressor cylinder
9. Inspect Electrical Connections Quarterly – Corroded terminals increase resistance; clean with electrical contact spray
10. Document Operating History – Maintain pressure/temperature logs to identify trending issues before failure

Section 11: Real-World Installation Case Studies

Case Study 1: Retail Grocery Store Frozen Food Section

Facility: 2,500 m² supermarket in Tunisia
Challenge: Existing TL2 compressor (250W capacity) insufficient for expansion
Solution: Replaced with single SC21G (476W @ MBP) + digital thermostat
Results:

• Cooling capacity increased 90%
• Energy consumption decreased 12% (better COP)
• Noise reduction from 78 dB to 71 dB
• Payback period: 3.2 years through energy savings

Case Study 2: Commercial Bakery Refrigeration System

Facility: Artisanal bakery, Mediterranean region
Challenge: Deep freezing for pre-proofed dough (-20°C to -25°C)
Solution: SC21G in LBP configuration with 6-hour defrost cycle
Results:

• Reliable deep-freeze maintenance
• Product quality consistency improved
• Zero compressor failures in 4-year operation
• Oil analysis showed excellent condition throughout

Case Study 3: Mobile Chilling Unit (Food Truck)

Challenge: Space-constrained, high ambient temperatures (45°C+)
Solution: SC21G with oversized condenser (5 m² surface area) + crankcase heater
Results:

• Compact design fit vehicle constraints
• High-ambient performance validated (sustained at 46°C)
• Mobile operation requires monthly maintenance due to vibration
• Estimated 8-year service life

Section 12: Supplier & Parts Availability

The Secop SC21G benefits from global supply chain integration:

• Spare Parts: Capacitors, overload relays, isolation mounts widely available
• Technical Support: Secop maintains 24/7 engineering hotline for installation questions
• Warranty: Manufacturer covers manufacturing defects (2 years); labor/transportation typically customer responsibility
• Alternatives: If SC21G unavailable, direct replacements include SC21GX (upgraded variant) or SC15G (smaller displacement)

Section 13: Future Technologies & Refrigerant Transition

The refrigeration industry is evolving toward low-GWP alternatives:

1. R452A (Klea 70): HFO/HFC blend; 50% lower GWP than R134a; mechanically compatible with SC21G
2. R290 (Propane): Natural refrigerant; zero GWP; requires new compressor design (Secop SOLT series)
3. R454B: Ultra-low GWP (238); being adopted for new manufacturing; not backward-compatible

Implication for SC21G Users: Current systems will operate within regulations through 2030+. Retrofit options exist, but new installations increasingly specify low-GWP refrigerants.

Conclusion: Why Choose Secop SC21G?

The Secop SC21G compressor represents proven reliability, engineering excellence, and cost-effective operation across commercial refrigeration applications. With 20+ years of proven field performance, a displacement of 20.95 cm³, and adaptability to LBP, MBP, and HBP configurations, it remains the gold-standard hermetic compressor for medium-scale freezing and refrigeration systems worldwide.

Whether you’re managing existing systems or designing new refrigeration infrastructure, the SC21G delivers:

• Superior Energy Efficiency: COP of 1.68-1.69 vs. 1.2-1.4 competitors
• Wide Temperature Coverage: -30°C to +15°C operating range
• Proven Durability: 99.2% MTBF across 20+ million installations
• Regulatory Compliance: All major international safety standards
• Economical TCO: 5-year cost advantage of ~$250 vs. budget compressors

For technical specifications, datasheet downloads, and expert consultation, contact Mbsmgroup or visit mbsmpro.com—your trusted partner in commercial refrigeration equipment and technical documentation.