EDIT:
I just used the NEC ampacity rating of the wire to size the 2 pole breaker for the feeder. Going back this AM and rereading what I posted yesterday I should have posted a 2 pole 60 amp or a 2 pole 70 amp breaker. It could even be a 2 pole 50 providing the wire lug size is big enough for #4 copper or #2 Al (aluminum) wire.
Example Square D is listed at,
@ audiozenology
I called 4 large wholesale houses this morning and none of them stocked the steel armor MC cable.
Remember in the OP’s case his average load is around 7 amps. #4awg copper is rated for 70 amps (60 degree C, 140 F) and 85 amps (75 degree C, 167 F, THHN/THWN)
(There are factors that may apply for the adjusted ampacity rating of the wire.)
The circuit is through one of the feeder’s two hot legs and the feeder’s neutral conductor, a 7 amp load is insignificant in the scheme of things in my opinion.
Jim
jea483,227 posts
12-22-2019
1:57pm
Sub Panel Feeder:
If it were me I would feed the sub panel with at least #4awg copper or #2awg aluminum conductors. I would oversize the equipment grounding conductor as well.
If the electrician used #4 copper, (or #2 aluminum), he could use a 2 pole 70 amp, or a 2 pole 80 amp, breaker at the main electrical panel.
I just used the NEC ampacity rating of the wire to size the 2 pole breaker for the feeder. Going back this AM and rereading what I posted yesterday I should have posted a 2 pole 60 amp or a 2 pole 70 amp breaker. It could even be a 2 pole 50 providing the wire lug size is big enough for #4 copper or #2 Al (aluminum) wire.
Example Square D is listed at,
35A - 70Ahttps://www.se.com/us/en/faqs/FA237923/
- 1 wire per lug: (1) #8 - #2 AWG Aluminum or Copper
@ audiozenology
If you are in a major city, I don’t think you will have too much trouble finding steel armoured cable. Most of the major electrical distributors will stock it, though maybe not in their branch outlets, so you may have to order today, deliver tomorrow.You would think so. But unless there is a demand for steel armor MC cable, Electrical Wholesale Houses, today anyway, don’t stock items that just take up self space.
I called 4 large wholesale houses this morning and none of them stocked the steel armor MC cable.
My brain is starting to go into Christmas shutdown mode, so I am not sure I am 100% accurate when stating that using 120/240 will create unbalanced current which could cause ground injection. Assume I am wrong, but please check my work.Not sure I follow, please explain.
Remember in the OP’s case his average load is around 7 amps. #4awg copper is rated for 70 amps (60 degree C, 140 F) and 85 amps (75 degree C, 167 F, THHN/THWN)
(There are factors that may apply for the adjusted ampacity rating of the wire.)
The circuit is through one of the feeder’s two hot legs and the feeder’s neutral conductor, a 7 amp load is insignificant in the scheme of things in my opinion.
Jim