oceanobob
Member
- Location
- central coast California
- Occupation
- electrical and industrial contractor company owner
Time to run some electrical outlets at 120VAC: would like to run as a Multi Wire Branch Circuit (MWBC).
Having difficulty with the circuit breaker (CB) selection since the two pole breaker has the slash rating (120/240) but the three pole breaker does not. This has been confirmed by the salesrep at the supply house in contact w mfg and available literature.
Original idea was to have two sets of 'three hots and one neutral' for ea string w a #10 copper stranded conductor THHN in 3/4" EMT (thinwall) with one 20a CB Circuit Breaker with three poles for each set. Total thinking is/was six hots and two neutrals and two three pole circuit breakers.
But with the limitation of the 120/240 label for the CB looks like I need to go with 6 hots, three neutrals and three two pole circuit breakers. EMT limit getting close with 9 number #10s but OK.
Derating at 70% of the 90C 10's value is 28 amps (fyi number 12's at 21 amps but I'll prolly use the 10's) - this checks out.
Otherwise this plan now seems valid, yet am unable to understand why the three pole breaker is not available slash rated?
Having difficulty with the circuit breaker (CB) selection since the two pole breaker has the slash rating (120/240) but the three pole breaker does not. This has been confirmed by the salesrep at the supply house in contact w mfg and available literature.
Original idea was to have two sets of 'three hots and one neutral' for ea string w a #10 copper stranded conductor THHN in 3/4" EMT (thinwall) with one 20a CB Circuit Breaker with three poles for each set. Total thinking is/was six hots and two neutrals and two three pole circuit breakers.
But with the limitation of the 120/240 label for the CB looks like I need to go with 6 hots, three neutrals and three two pole circuit breakers. EMT limit getting close with 9 number #10s but OK.
Derating at 70% of the 90C 10's value is 28 amps (fyi number 12's at 21 amps but I'll prolly use the 10's) - this checks out.
Otherwise this plan now seems valid, yet am unable to understand why the three pole breaker is not available slash rated?