I have some questions about proper grounding and specs for a subpanel in a shed. Here’s an overview:
Distance from the main panel (at the house) to the shed is about 110’. Using 10/3 wire. At the main service panel = a double-pole 20-amp breaker (two 20-amp breakers with the switches connected). Only using 20 b/c of the long run from panel to sub.
At the shed: Subpanel for 4 circuits, but plan is only for two 20-amp circuits (or a 15 and a 20). Two 8’ ground rods, 6’ apart, connected with #6 copper wire.
These are my questions:
Grounding at the shed Part 1 - what is the proper connection for the #6 ground wire at the shed? To the neutral buss bar?
Grounding at the shed Part 2 - What happens to the ground that’s coming from the main panel (the bare wire in the 10/3 “feed”)? Just leave it disconnected at both ends (at the sub and main panels)?
4.At the shed, should I get a subpanel with a main breaker, one switch that will shut the whole thing down? That seems like overkill if there are only 2 circuits, but I’ve seen conflicting information depending on if it’s a subpanel in the house or detached (this is detached), and depending on how many circuits are at the subpanel.
5.GFCI – if there’s an outdoor outlet at the shed, does the outlet need to be GFCI, or the breaker, or both?
Thanks very much for any guidance you can provide. I live in North Carolina, FWIW.
If you only need two circuits, why put a sub panel in… Pull the 10/3 to a junction box and branch out your two circuits. What’s the reason for putting in the panel?
With the exception of outbuildings containing only one branch circuit, electric systems at detached buildings require a separate grounding electrode system (GES), which is commonly a grounding electrode. See attachment for wiring illustration. One illustrates a 3 wire feeder and one illustrates a 4 wire feed.
I’m confused. If it’s wired as a sub-panel, where does it state that a “main breaker” is needed. The disconnecting means is at the main panel. Why is a sub-panel in a shed any different from a sub-panel in an attic?
Is there a definition for “separate structure” for this rule? The reason I ask is for future clarification if the two buildings are connected by a covered breezeway to avoid the “detached” designation of the building.
A “main breaker” is not what’s required. A disconnect for the structure is what’s required. It does not necessarily need to be located within the sub panel.
You can have multiple sub panels in a detached building, but the building must have a disconnect that will disconnect all ungrounded conductors at (or near) the point where the feeders from the service enter the structure.
Below is not in the IRC but is applicable by reference. I learn something every day.
“225.31 Disconnecting Means. Means shall be provided
for disconnecting all ungrounded conductors that supply or
pass through the building or structure.
225.32 Location. The disconnecting means shall be in-
stalled either inside or outside of the building or structure
served or where the conductors pass through the building or
structure. The disconnecting means shall be at a readily
accessible location nearest the point of entrance of the con-
ductors. For the purposes of this section, the requirements
in 230.6 shall be utilized.”
Thanks to all respondents on this thread from 01/2014… 2 years ago! Nonetheless, I found it very constructive. Special thanks to Joe Funderburk for the 2 excellent diagrams he provided that helped me visualize this.
