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Effects of Emissivity and Number of Copper Busses on Ampacity

Data here show how higher emissivities improve ampacity. Multiple busses also affect ampacity in a nonlinear relationship. Ampacity may be raised by increasing heat dissipation through the use of convection cooling or surface treatments.

Number of 1/4 x 4 in. Busses* Ampacity, Amp
  30 °C Rise 50 °C Rise 65 °C Rise
  Emissivity Emissivity Emissivity
  0.15 0.4 0.7 0.9 0.15 0.4 0.7 0.9 0.15 0.4 0.7 0.9
1 1100 1250 1400 1600 1500 1700 1900 2000 1700 1950 2200 2300
2 1900 2050 2200 2300 2550 2750 2950 3100 2950 3200 3400 3600
3 2500 2700 2850 3000 3400 3600 3850 4000 3950 4200 4500 4600
4 3100 3300 3450 3600 4200 4400 4700 4800 4900 5100 5400

5600

 

*1/4 in. spacing. Ampacities of bus bar systems of other configurations must be calculated, taking into account size, spacing, number of bus bars and overall skin-effect ratio.

 

Table courtesy of Copper Development Association Inc. (www.copper.org)