Allied Encyclopedia – RHW and RHH Cables…and their Dual USE-2 Ratings

Allied EncyclopediaRHW and RHH – We see these letter designations on all kinds of cable products, whether it’s when we’re choosing a cable and placing an order, or when we’re reading the stamp on a cable in front of us. But why are they there? What do those letters mean?

Well, the code is a way to identify the cable, its ratings, and how it can be used. You just need to decode the letters to understand the cable.

For RHW and RHH cables, this is what we need to know:

  • R = Rubber Insulated
  • H = 75°C
  • HH = 90°C
  • W = Moisture Resistant

Now, if we put those meanings together, we can figure out what kind of cable we have.

RHW = rubber insulated cable, good up to 75°C, moisture resistant

*Note: If cable is rated as RHW-2 wire, conductor temperatures must not exceed 90°C in wet or dry locations.

RHH = rubber insulated cable, good up to 90°C

You may see RHW and RHH cables marked with a USE-2 rating as well. The USE-2 label indicates that the cable meets the National Electrical Code (NEC) specifications for underground service entrance cable. USE-2 cable is designed for direct burial in environments with maximum temperatures of 90°C, wet or dry. It is often used in solar cable applications to connect grounded photovoltaic modules.

Although cables that carry multiple ratings may be used in different applications, be sure to check that the way you are using the cable (as USE-2, as RHW, or as RHH cable) matches up with the specifications you are following. For example, if you are using the cable as USE-2 or RHW-2, the conductor temperature may not exceed 90°C in wet or dry locations. If it is being used as RHH cable, the conductor temperature may not exceed 90°C in dry locations.

Learn the meanings of the letters on your cable jacket and follow these simple rules, and you should have no problem finding an appropriate cable solution for your application.

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 Merrimack, NH, Tampa, FL, Pewaukee, WI, and Las Vegas, NV. For more information on Allied, visit our main website at

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