Well, we all know you have your parkas, pea coats, or even your 80’s stylish windbreakers but do you know the difference between the jackets on your wire? Choosing a cable jacket for your wire can be just as important as choosing a jacket for the snow, the rain, or even one to protect you from a fall on your motorcycle. There are many different types of jackets used for the outside of the wire, all helping it stay protected from different elements. It could be oil, fire or even the nasty weather.
Materials
Let’s start with the material used for wire jackets. They can go mainly into two categories: the Thermoplastics and the Thermosets. Thermoplastics are more popular as they are lower in cost to produce and lighter in weight. Thermosets are more flexible and offer heat resistance. The most commonly used is PVC which is part of the Thermoplastic category. It offers great flexibility for your cord and are typically used for general purpose wire. Next we have silicone rubber which offers great flexibility and heat resistance up to 2500°. Silicone rubber belongs to the Thermoset category.
Jacket Types
If you take a look at any wire, they should be labeled with the jacket type and size of the wire. It may say something like SJT, SJ or SO and all those letters stamped on the wire mean something different. S always stands for stranded, SJ stands for junior service and T stands for thermoplastic. O stands for oil-resistant compound. P stands for parallel and denotes flat wires. S indicates a 600 Volt Service cord and SJ indicates 300 Volt Service.
SJT stands for Stranded Junior Thermoplastic, and are generally used at 300 volts. It is rated for -20 to 150 degrees Celsius. SJT are appropriate when both flexibility and durability is required. Common uses include portable hand tools, medical equipment, and office machines.
SVT stands for Stranded Vacuum Thermoplastic, and are used at 300V. It is rated for 60 degrees Celsius, and resists oils, water, acids and ozone. It is used for 2 pronged devices, such as vacuum cleaners, food processors and office equipment.
SJ stands for Stranded Junior Service, and is rated for 300 volts. It is rated at 60 degrees Celsius. SJ is very similar to SJT wires, only without the thermoplastic coding. It has excellent flexibility in low temperatures, but should not be subject to acid, grease, oil or solvents. Common uses for the SJT are portable tools and small motors.
And SO stands for stranded oil-resistant compound. It has extra hard service flexible cord and is rated for 600 volts and rated at 60 degrees Celsius. SO wires are ideal when power is needed in harsh environments, and durability is key. They are often used on construction sites.
Here is a quick summary of the jacket types for visual learners:
| Name | Full Name | Voltage | Degrees | If you’re looking for… | Don’t mix with… | Common Uses |
| SJT | Stranded Junior Thermoplastic | 300V | -20-150 degrees Celsius | Flexibility and durability | Portable hand tools, medical equipment, office machines | |
| SVT | Stranded Vacuum Thermoplastic | 300V | 60 degrees Celsius | Durability | Vacuum cleaners, food processors, and office equipment | |
| SJ | Stranded Junior Service | 300V | 60 degrees Celsius | Flexibility | Acid, grease, oil, solvents | Portable tools and small motors |
| SO | Stranded oil-resistant compound | 600V | 60 degrees Celsius | Durability | Construction sites | |
| SPT | Stranded parallel thermoplastic | 300V | Flexibility | Outdoors | Lamps, irons, household items |
Round wire vs. Flat wire
Another question that often comes up is round wires vs. flat wire. Here is a quick chart to summarize the difference:
| Rounded Wire | Flat Wire | |
| Jacket Types | SJT/SJ/SVT | SPT-1/SPT-2/HPN |
| Look | Typical circular wire, surrounded by conductors | Flat appearance achieved by conductors sitting parallel to each other |
| Flexibility | Good | Excellent |
| Uses | Outdoor | Indoor only |
Flat wires are denoted with the P in the title, to indicate parallel structure of the wires. Conductors are situated next to each other, giving it the flat appearance. They are much more flexible, and easy to situate than rounded wires. However, they are to be used only indoors. Rounded wires come in a variety of jackets, and can be used for outside work as well.
Quail Electronics has also provided a chart documenting how these different wires look, available here. If you still have any questions regarding which jacket type is necessary, are sales department would be more than happy to assist you!
By Clark Cable
Clark briefly entered the lucrative world of jacket designing. His goal was to integrate stylish coats with electric jacket types to bridge the gap between wires and high fashion. Some of his more famous designs were the Pea-VC coat, and the moto-circuit jacket. Unfortunately, demand for his products eventually fell, forcing Clark to retire from the fashion industry once and for all.