I want to feed 240V 30A from a new 30A breaker in my home main electric panel to a new subpanel in a adetached shed. The electric feed I want to use for the new subpanel is (4) 10awg THWN wires (R/B/W/G) to be fed from a new 240V 30A circuit breaker in my home main load center, and then through 60' of conduit across my basement and underground to the new shed subpanel. The subpanel would have (2) 120V 20A breakers for light and outlet circuits – as well the capacity for a 240V 20A future breaker for a compressor outlet. I will separate neutrals and grounds in the subpanel, and will ground the shed subpanel and shed circuitry devices with a new ground rod at the shed.
I have (4) questions :
-
Will a new 8-slot, 125A Square D 125A subpanel with a 125A main breaker that I want
to use for a subpanel and disconnect in the shed satisfy NEC code requirements ?
(I want 2nd opinion on early advice saying SuI'll have to swap out 125A main for 30A main)
And if so, can you please point me to the applicable NEC code section(s) ? -
Will I need two ground rods at the shed ? or just one ?
And if so can you point me to the applicable NEC section(s) ? -
Wiring in the shed will be with (3) 12awg THHN wires (B/W/G) in 1/2" EMT. IF I run
the three wires for power from a 20A breaker in the subpanel to a light switch near
a cornner shed door, can I run the switched wires part way back to the light in the
same EMT conduit ?
And if so, the applicable code section(s) ? -
Any other advice anyone can offer on this plan to provide electricity in my shed ?
Thanks for any help.
Best Answer
You seem very wrapped up chapter and verse of complying with NEC. You're missing the point. We are not serfs to electricity. We are the masters of this technology. Electricity works for us. Bare compliance is for slumlords. Make electricity wonderful!
#1 mistake is getting the smallest panel that will serve immediate needs. This creates a nightmare later when you want to add more stuff. More spaces are a trivial amount of money, so while we certainly are interested in saving you money, chintzing out on panel spaces is not the place to do that. Go BIG or go home. Bye bye 8-space. Hello 30-space.
And if you want to save some money, avoid "QO". Eaton CH is just as good and just as compact at 2/3 the price for the breakers.
Yeah, people get sucked into this mistake all the time. They get told to use a main-breaker panel as an outbuilding subpanel, but don't understand why they're doing that, and they make too much out of the main breaker, like "shouldn't that match or something?"
You do not need any main breaker at all in the subpanel. (NEC nothin'.nothin').
The only purpose of using a main-breaker panel is to provide a "main disconnect" as required in outbuildings per (NEC 225.31).
However... if you plan to carry the feeder some distance within the building before it gets to the subpanel, you will need a separate disconnect near the entry point. If you do need that separate disconnect, then this satisfies 225.31 fully, and you do not need a main breaker at all at the panel.
Needless to say, saying you need to downgrade to a 30A breaker is utterly laughable advice, the person is just "making stuff up".
Two needed unless you can get free services from an electrician.
You can evade this requirement if your electrode tests out as having good conductivity to earth; however the cost of doing this test is a great deal more than driving a second ground rod. Other code calls out a minimum 6' distance, but more is better.
You can't use green wire!
I would suggest "red". Green is reserved for safety ground, but you don't need to wire that if it's EMT pipe.
As far as how many wires / can you do that switch, again can't prove a negative. Certainly any number of wires or circuits are allowed in conduit, if you're willing to pay the derate in 310.15(B)(3)(a)...
However all related conductors must be together in the same conduit.