50 Amp Circuits

• A 50A circuit breaker with an unknown load, uses the 80% rule. This means the voltage drop calculations are done assuming a 40A Load.
• The feeder circuit to the post uses the 3% rule, meaning the circuit must handle 40A with a voltage drop of only 3.6 Volts. 120V Feed can drop to 116.4, A 125V Feed can drop to 121.4
• Looking at cable ampacity, 1% VD, CEC Table D3 Appendix 6, We can calculate  the wire size and distance which will deliver the 40A.

Wire	1% Dist(M)	3% Dist(M)	FT
#8	6.2M	18.6M	61
#6	9.8M	29.4M	96.5
#4	15.6M	48.8M	153.5
#3	19.7M	59.1M	309

Summary of Available Current at various distances of  #8,#6 and #4 Cable

Distance	Cable	Amps(5%)	Amps(10%)
100Ft	#8	38.46A	##
200Ft	#8	19.213	38.46
300Ft	#8	12.82	25.64
100Ft	#6	###	###
200Ft	#6	30.61	###
300Ft	#6	20.41	40.81
100Ft	#4	###	###
200Ft	#4	###	###
300Ft	#4	32.25	###

Amperage available at various cable sizes and distances at 120V

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

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