Improper wire jumper wire

[David K. Lee]

Is it okay to use two different wire sizes on a jumper to a breaker? The breaker is a 20amp with #12 wire on the circuit. There is a jumper wire connected to the #12 wire that is a #14 wire which is connected to the breaker. I believe you need to correct wire size. One electrician told me it was okay and the other said #12 wire should be used on the jumper. Looking for your opinions

[Terry a. Russell, jr]

should be a #12

[Robert Meier]

The OCPD needs to be smaller or equal to the size listed in 240.4(D) of the NEC. Except for certain installations (not this one) #14 can not be protected at 20 amps.

240.4(D) Small Conductors. Unless specifically permitted in 240.4(E) or (G), the overcurrent protection shall not exceed that required by (D)(1) through (D)(7) after any correction factors for ambient temperature and number of conductors have been applied.
(1) 18 AWG Copper. 7 amperes, provided all the following conditions are met:
(1) Continuous loads do not exceed 5.6 amperes.
(2) Overcurrent protection is provided by one of the following:
a. Branch-circuit-rated circuit breakers listed and marked for use with 18 AWG copper wire
b. Branch-circuit-rated fuses listed and marked for use with 18 AWG copper wire
c. Class CC, Class J, or Class T fuses
(2) 16 AWG Copper. 10 amperes, provided all the following conditions are met:
(1) Continuous loads do not exceed 8 amperes.
(2) Overcurrent protection is provided by one of the following:
a. Branch-circuit-rated circuit breakers listed and marked for use with 16 AWG copper wire
b. Branch-circuit-rated fuses listed and marked for use with 16 AWG copper wire
c. Class CC, Class J, or Class T fuses
(3) 14 AWG Copper. 15 amperes
(4) 12 AWG Aluminum and Copper-Clad Aluminum. 15 amperes
(5) 12 AWG Copper. 20 amperes