Why are ampacity markings not permitted on UL Listed wire and cable, and not shown in UL wire and cable Standards?
The ampacity of a wire or cable is the amount of current that the wire or cable can transmit without exceeding its rated temperature. An ampacity marking on a wire or cable or a reference to a specific ampacity for a wire or cable in a UL wire or cable standard is not feasible since ampacity varies according to the actual conditions under which the cable will operate. These conditions include the ambient temperature, installation environment e.g. free-air, conduit or directly buried in the earth. The National Electrical Code provides two methods for the cable user to determine ampacity for a cable based on the installation conditions.
The ampacity of a wire or cable is the amount of current that the wire or cable can transmit without exceeding its rated temperature. An ampacity marking on a wire or cable or a reference to a specific ampacity for a wire or cable in a UL wire or cable standard is not feasible since ampacity varies according to the actual conditions under which the cable will operate. These conditions include the ambient temperature, installation environment (e.g., free-air), conduit or directly buried in the earth. The National Electrical Code provides two methods for the cable user to determine ampacity for a cable based on the installation conditions.
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