Can I use both rigid and flexible conduit for a conduit run between my main panel and sub panel? Also, for running 220V between, what size conduit do I need for #6 or for #4 wire? As I understand the tables, 1" is sufficient for #6 and 1 1/4 for #4. Correct? Thanks.
Yes you can use flex and regid conduit in combination but do use approved connectors.
Now to the conduit verses the number of wires and the size that will be allowed to put in the conduit. Here is per say from the the NEC code on Conduit verses size and number of wires allowed by the NEC code.
[2 -- # 6 wires] and [1 -- # 8 ground wire] in 1" conduit. [3 --- # 6 wires] in 1" conduit. [2 --- # 4 wires] and [1 -- #6 Ground wire] in 1 1/4" conduit. [3 -- # 4 wires] in 1 1/4" conduit.
If you would like , e-mail me your breaker and load rating of what your running to and i can check it out to make sure your doing good on the conduit and wires of the job requires and not read about it in the Newspaper about what went wrong. If your using #4 and #6 your running some heavy equipment or load of some kind here.
Restrictions on flex conduit are it has limited grounding conductor ampacity, so don't use it as a ground wire and run a ground wire inside the conduit instead. Another restriction is that flex cannot be installed where subject to physical damage. Cable has this same restriction, so usually flex conduit and cable can be used in the same places in a residence.
Others have replied on the minimum size for your conduit, and such. May I suggest that you consider going one or two sizes over the minium? Bigger conduit makes pulling wire easier, especially if you have a long run, or lots of bends. And also be aware that after 360 degrees of bends, you need some relief, like pull elbow. If you are running with PVC conduit, or if you use flex, you will need to run a ground wire in your conduit along with your hots and neutral. What is the size of the breaker that you will be protecting your sub panel with?
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