Allied Encyclopedia – High Temperature Wire: SF-2, SFF-2, SRML

Allied EncyclopediaThere are a lot of high temperature lead wire options on the market, and the sheer number of products and standards can make choosing the right wire difficult. In this Allied Encyclopedia, we will introduce you to three popular types of high temperature wire: SF-2, SFF-2, and SRML.

SF-2 wire, SFF-2 wire, and SRML wire are all UL-rated high temperature lead wires which may be used in automotive motor lead applications or electrical equipment in high temperature environments. They share similar constructions featuring tinned copper conductors, extruded silicone rubber insulation, and overall fiberglass braids with a high-temperature finish. Silicone rubber is used because of its stable, non-reactive properties and its ability to perform over a wide temperature range. The cables’ fiberglass braiding provides tensile strength, heat resistance, and resistance to moisture, fungus, and chemicals. SF-2 wire, SFF-2 wire, and SRML cable are all rated to 600 volts, and have maximum temperatures of 150°C or 200° C.

So far, SF-2 wire, SFF-2 wire, and SRML cable are all sounding pretty much the same, so how do you know which one is right for you? This is where you must consider industry standards, along with the specific needs of your high temperature application, from its maximum temperature to its flexibility requirements.

SF-2 wire is rated to 200°C. The SF-2 rating designates it as fixture wire. It is also approved for use as equipment wire or appliance wire through the CSA SEW-2 rating. In addition, parts from 18 AWG through 14 AWG are UL dual-rated and meet the UL 3070, UL 3074, UL 3075, or UL 3231 standards for appliance wire.

SFF-2 wire is a more flexible version of SF-2 wire. It gains its extra flexibility from its higher strand counts. It also has a lower temperature rating than SF-2, and may only be used up to 150° C. It is CSA approved as SEWF-2 equipment wire and appliance wire. Like SF-2, the SFF-2 parts between 18 AWG and 14 AWG are dual-rated as UL appliance wire. Parts meet UL 3070, UL 3101, or UL 3278 standards.

Our third high temperature lead wire product, SRML wire is available in versions that are dual-rated and meet UL 3231, UL 3070, or UL 3278. The temperature rating for SRML depends on the wire size. Parts with 4 AWG conductor strands or larger are rated to 200°C, while those with 6 AWG strands or smaller are UL rated to 150°C. Like SFF-2 wire, the SRML cable features higher strand counts for flexibility.

Now that you are familiar with some of the basic differences between these popular types of high temperature wire, you should be well on your way to identifying the right wire or cable for your application. In addition to the options listed above, braidless versions of SF-2 wire and SFF-2 wire are available; however these meet different UL specifications than the ones discussed here. To learn more about SF-2 wire, SFF-2 wire, and SRML cable, and to see full product specifications, visit the high temperature wire section of the Allied Wire & Cable online catalog.

About awcwire
Allied Wire & Cable is a value-added manufacturer and distributor of electrical wire and cable, tubing, and more. We are a family owned and operated company, serving a wide range of industries, including the military, automotive, aerospace, and telecommunications markets. Allied is headquartered in Collegeville, PA. Additional locations can be found across the US, in Phoenix, AZ; Bedford, NH; Pewaukee, WI; Rochester, NY, Tampa, FL; and Mt. Juliet, TN. For more information on Allied, visit our main website at

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