Summary 30 Amp Circuit

30 Amp Circuits

  1. A 30A circuit breaker with an unknown load, uses the 80% rule. This means the voltage drop calculations are done assuming a 24A Load.
  2. The feeder circuit to the post uses the 3% rule, meaning the circuit must handle 24A with a voltage drop of only 3.6 Volts. 120V Feed can drop to 116.4.  A 125V Feed can drop to 121.4V
  3. Looking at cable ampacity, 1% VD, CEC Table D3 Appendix 6, We can calculate  the wire size and distance which will deliver the 24A
Wire 1% Dist(M) 3% Dist(M) FT
#10 6.2M 18.6M 61
#8 9.9M 29.4M 96.5
#6 15.7M. 47.1M 154.5
#4 6.2M 24.9M 245
#3 31.4M 94.2M 309

Summary of Available Current at various distances of #10, #8 and #6 Cable

Distance

Cable

Amps(5%)

Amps(10%)

100Ft

#10

25

##

200Ft

#10

12.5

25.0

300Ft

#10

8.3

16.67

200Ft

#8

19.23

###

300Ft

#8

12.82

25.64

400Ft

#8

9.61

19.23

300Ft

#6

20.41

###

400Ft

#6

15.3

30.6

500Ft

#6

12.24

24.48

### Indicates that the wire can carry more than current than the circuit breaker allows.

 

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