What is the temp rating on wire?
The higher a material’s heat resistance, the less likely it will deteriorate in higher temperatures. The most common conductor temperature rating is 90°C, but conductors can be rated as low as 60°C or as high as 1,200°C for some special purpose wire and cables.
How does temperature affect ampacity?
In order words, as temperature changes, the ampacity of a conductor changes. Increase in ambient/surrounding/medium temperature can significantly limit the current carrying capacities of cables. As cable temperature increases, its resistance increases thereby reducing the amount of current that can be carried.
What temperature is Romex wire rated for?
Southwire® Romex® Brand SIMpull® NM-B (nonmetallic-sheathed) cable may be used for both exposed and concealed work in normally dry locations at temperatures not to exceed 90°C (with ampacity limited to that for 60°C conductors) as specified in the National Electrical Code.
How do you calculate ampacity of a wire?
Ampacity can be calculated by dividing the Wattage by the rated voltage. The quotient is the expected Amperage of the circuit.
What is ampacity of wire?
Ampacity is the maximum current that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. Current is measured in amperes or “amps.” You must use the correct size wire for the current (load) requirement of the circuit to prevent the wire from overheating.
How does temperature affects the maximum ampacity of a wire?
An increase in temperature rating of the compounds and/or an increase in conductor size will increase cable ampacity. Conversely, an increase in ambient temperature will decrease ampacity.
How does temperature affect current carrying capacity?
Increasing the conductor size increases the current carrying capacity. Similarly, the higher the temperature resistance of the insulating material, the higher the ampacity or current carrying capacity. A 90°C rated insulation will have a higher current carrying capacity than a 70°C rated insulation.
What is the maximum operating temperature of TW insulation?
90°C
Wire Insulation Temperature Limits
| Maximum Operating Temperature (ref. NEC table 310-16) | ||
|---|---|---|
| Insulation Types | Insulation Types | Insulation Types |
| 60°C (140°F) | 75°C (167°F) | 90°C (194°F) |
| TW, UF | FEPW, RH, RHW, | TBS, SA, SIS, FEP, |
| THHW, THW, THWN, | FEPB, MI, RHH, |