Current load

Permissible current load of the cable by cross-section

The same cable can carry different currents when installed outdoors and in the wall. In open laying, heat dissipates freely, while in a pipe or under plaster, there is nowhere for it to go — that's why the allowable current is lower. Below are the guidelines according to the Electrical Code for copper and aluminum.

Copper cable

Cross-sectional area, mm²	Open circuit, A	In pipe / in wall, A
1,5	23	19
2,5	30	27
4	41	38
6	50	46
10	80	70
16	100	85
25	140	115

Aluminum cable

Cross-sectional area, mm²	Open circuit, A	In pipe / in wall, A
16	75	60
25	90	75
35	115	95
50	145	110

The tables are approximate, according to the Electrical Code for normal conditions (ambient temperature around +25 °C, cable laid separately). The current is reduced if several cables are laid nearby in a bundle, especially if it is hot, and even more so for outdoor installation in the sun. Copper is preferred: for the same cross-section, it holds more and is more reliable in connections.

How to convert current into power and select the cross-section for the load - in the section Cable cross-section by power and current.

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