Selecting the right cables for the correct environmental conditions is essential to ensure the cable’s expected life span will not be affected. The use of cables installed in environments with harsh conditions and high ambient temperatures outside of their designed temperature range can result in premature and often expensive failures.
What is High-Temperature Wire?
Often defined as a wire with a temperature rating of 150℃ or higher, high-temperature wire can also refer to temperature ratings as low as 90℃. These high-temperature wires are commonly constructed of an annealed, tinned copper, copper-plated, or nickel-coated copper conductor, insulation, and in some cases may include an additional jacket of fiberglass braid or K-fiber material.
The two key components that are used to ensure that high-temperature wires are suitable for their intended application are the wire’s temperature rating and ampacity.
Temperature ratings are defined as the maximum continuous temperature that a wire can withstand during its lifetime. If the temperature rating of a cable is not suitable for the environment and ambient temperature in which it is installed, the cable's lifespan could be affected.
Ampacity is the maximum current that an insulated conductor can safely carry without exceeding its insulation and jacket maximum temperatures. If undersized, the cable may be compromised by the load exceeding the temperature rating of the cable.
There are many popular high-temperature wires available. Some of the most popular types include SF-2, SFF-2, SRML, and Silicone Rubber Wires. How do you know which one is right for you? To make this decision, you must consider the industry standards and specific needs of your high-temperature application, from its maximum temperature to its flexibility requirements.
What is SF-2 Wire?
SF-2 wire has a soft annealed stranded tinned copper conductor per ASTM B33, silicone rubber insulation, and a fiberglass braid jacket that is treated with a high-temp finish. These cables are available in a wide range of colors, the most common colors being black and white for 18AWG-10AWG and just black for 8AWG-750MCM. SF-2 has a temperature rating of 200℃ and is designated as a fixture wire by the SF-2 rating.
These wires are also approved for use as equipment wire or appliance wire through the CSA SEW-2 rating. Additionally, 18AWG -14AWG SF-2 wires are UL dual-rated and meet the UL 3071, UL 3074, UL 3075, or UL 3231 standards for appliance wire. Braidless versions of SF-2 wire are available, but they meet different UL specifications.
What is SFF-2 Wire?
SFF-2 wire also has a soft annealed stranded tinned copper conductor per ASTM B33, silicone rubber insulation, and a fiberglass braid jacket treated with a high-temp finish. A more flexible version of SF-2 wire, SFF-2 wire gains its flexibility from a higher strand count within the conductor. Similar to SF-2, SFF-2 wires are available in a variety of colors, with black and white being the most common for 18AWG-10AWG wires, and just black for 8AWG-750MCM wires. However, with other colors available upon request.
This cable also has a lower temperature rating than SF-2, only being able to withstand temperatures up to 150℃. It is CSA approved as SEWF-2 equipment and appliance wire. All SFF-2 parts between 18AWG and 14AWG are dual-rated as UL appliance wire meeting UL 3070, UL 3101, or UL 3278 standards. Braidless versions of SFF-2 wire are available, but they meet different UL specifications.
What is SRML Wire?
SRML wirehas a stranded tin-plated annealed copper conductor that conforms to ASTM B33 standards,an extruded silicone rubber insulation, and a non-fraying, fiberglass braid with a glossy high-temperature finish. The temperature ratings for SRML wired vary depending on the size. 4AWG conductor strands or larger are rated for 200℃, while 6AWG strands or smaller are rated for 150℃.
Additionally, 6AWG and 8AWG wires are rated for 150℃ UL or 200℃ non-UL. Like SFF-2, SRML cables feature higher strand counts for more flexibility. These wires are available in versions that are dual-rated and meet UL 3070, UL 3231, or UL3278 standards
What is Silicone Flexible Cable?
Silicone flexible cable is typically constructed of multiple tinned copper conductors that are stranded in multiple layers, a Besilen® EI2 insulation material, and Besilen® EM9 jacket material. Some versions of Silicon rubber cable include an inner jacket material of Besilen® EM9, a tinned copper braided screen, galvanized steel wire braiding armor, or many other variations to suit the needs of specific applications.
The temperature ratings for this type of cable range from 150℃ to 200℃ depending on the construction. Silicone rubber cables are great for use in applications where extreme temperatures, strong UV rays, and mechanical wear and tear break down other types of cables.
Now that you are familiar with some of the basic differences between these popular types of high-temperature wire, you should be able to better identify the right wire or cable for your application. To learn more about SF-2 wire, SFF-2 wire, SRML cable, and Silicone Flexible Cable, and to see full product specifications, visit the high-temperature wire section of the Allied Wire and Cable online catalog.