When selecting the right portable power cord, a small detail can make a big difference in safety, performance, and long-term cost. SO cord and SJO cord are two of the most commonly used flexible cords in industrial and commercial applications-but they are often confused with each other. Choosing the wrong one may lead to premature failure, compliance issues, or even safety hazards.
In this article, we clearly explain the differences between SO cord and SJO cord, compare their technical features side by side, and help you quickly determine which option best fits your application. Whether you're sourcing cords for heavy-duty equipment or light commercial use, this guide will help you make a confident, informed decision.
What Is SO Cord?
SO cord is a heavy-duty portable power cable designed for demanding industrial environments. The designation "SO" comes from UL standards:
- S – Service cord (600V rated)
- O – Oil-resistant insulation
- O – Oil-resistant outer jacket
SO cords typically feature thick insulation and a rugged jacket, offering excellent resistance to oil, abrasion, moisture, and weather. With a 600V voltage rating, SO cord is suitable for high-power equipment and continuous-duty applications.
Key advantages of SO cord include:
- High durability and long service life
- Excellent performance in harsh indoor and outdoor environments
- Strong resistance to oil, chemicals, and mechanical stress
What Is SJO Cord?
SJO cord is a junior service cord, designed for lighter-duty applications. Its designation breaks down as:
- S – Service cord
- J – Junior service (300V rated)
- O – Oil-resistant jacket
Compared to SO cord, SJO cord has a lower voltage rating (300V) and a thinner jacket, making it lighter, more flexible, and more cost-effective. It is commonly used for small appliances, office equipment, and light commercial devices where extreme durability is not required.
Key advantages of SJO cord include:
- Lightweight and easy to handle
- Greater flexibility for tight installations
- Lower cost for less demanding applications
Key Differences Between SO Cord and SJO Cord
| Feature | SO Cord | SJO Cord |
|---|---|---|
| Voltage Rating | 600V | 300V |
| Jacket Thickness | Thicker, heavy-duty | Thinner, lighter-duty |
| Durability | Very high | Moderate |
| Oil Resistance | Yes (insulation & jacket) | Yes (jacket) |
| Weather Resistance | Excellent (indoor & outdoor) | Limited (mainly indoor) |
| Flexibility | Good, but heavier | More flexible |
| Weight | Heavier | Lighter |
| Typical Cost | Higher | Lower |
| Application Level | Industrial / Heavy-duty | Light commercial / Appliance |
This comparison makes it clear: SO cord is built for strength and endurance, while SJO cord focuses on flexibility and economy.
How to Choose Between SO Cord and SJO Cord?
When deciding between SO cord and SJO cord, consider the following factors:
- Voltage Requirements
If your equipment requires up to 600V, SO cord is mandatory.
For 300V or less, SJO cord may be sufficient.
- Operating Environment
Outdoor, oily, wet, or harsh conditions → choose SO cord.
Clean, dry, indoor environments → SJO cord works well.
- Mechanical Stress
Frequent movement, dragging, or heavy wear → SO cord.
Light-duty use with minimal stress → SJO cord.
- Cost vs. Longevity
SO cord costs more upfront but lasts longer.
SJO cord offers cost savings for short-term or light applications.
Common Applications and Use Cases
Typical SO Cord Applications:
- Industrial machinery
- Construction equipment
- Power tools
- Temporary outdoor power supply
- Manufacturing plants and workshops
Typical SJO Cord Applications:
- Office equipment
- Light-duty power tools
- Household appliances
- Commercial electronics
- Indoor extension cords
Using a lighter SJO cord where SO cord is required may lead to overheating, jacket damage, or non-compliance with safety standards.
Why Choosing the Right Cord Matters
Selecting the correct power cord is not just about performance-it directly affects safety, compliance, operating efficiency, and total cost of ownership. A properly selected SO cord can significantly reduce downtime, maintenance costs, and safety risks in industrial operations.
At Dongguan Greater Wire & Cable Co., Ltd., we specialize in high-quality SO cord solutions designed to meet the most demanding requirements. Our advantages include:
- Full series certifications: UL, VDE, CB and more
- Multiple specifications in stock, ready for fast delivery
- 30 years of manufacturing experience in wire and cable production
- Support for both small and large-scale projects
- Bulk production, quick shipment, and professional technical consultation
- Dedicated pre-sales and after-sales teams to solve technical and application challenges
By choosing our SO cord products, you gain reliability, compliance, and long-term value-helping your business operate safely and efficiently.
Contact Us Today:
- Dongguan Greater Wire & Cable Co., Ltd.
- Tel / WhatsApp / WeChat: +86 135 1078 4550 / +86 136 6257 9592
- Email: manager01@greaterwire.com