According to Calvin Henry-Cotnam :
chester ) said...
You can only have one circuit going to the shed.
Is that a code thing? I need two circuits, and was planning either to do
two 12g wires running from two 15A breakers, or a larger wire (I guess
based on above post 10g for a 240V/30A circuit),
You can have as many circuits as you wnt in the shed, but do you really
want to pay for multiple home runs back to the main panel?
Henry, given electrical codes, you should specify the cable configuration,
not (just) "conductor count", otherwise, the person might be tempted to
use multiple cables. Which can lead to trouble.
The code frowns on running multiple cables to outbuildings, because they
want to minimize the number of things you have to kill to completely
kill the building's power. Ie: _one_ breaker (or tied breaker pair).
With that in mind:
Regarding grounds: You will _require_ a ground. The wiring nomenclature
we use below (eg: "14/2") is wire size/current-carrying-conductor-count.
Which does NOT include ground.
In Canada, you ALWAYS have a ground wire. Ie: in Canada a 14/2 will
actually have three strands of copper - two insulated (the "/2") and
one uninsulated (not mentioned explicitly). In the US, the ground
isn't always assumed, so there is such things as 14/2 with only two
conductors and no ground. To be sure of things, we're using the
Canadian convention, and in the US, tack on "with ground" to the wire
designation to be sure.
Here are the options I would consider:
Single 120 V circuit: home run to main panel has two 14 ga (for 15 A) or
two 12 ga (for 12 A) plus ground
Using 14/2 or 12/2 respectively.
Two 120 V circuits: home run to main panel has three 14 ga (for 15 A) or
three 12 ga (for 12 A) plus ground wired to a double
pole breaker
Using 14/3 or 12/3 respectively.
One 240 V circuit: home run to main panel with either two (if no neutral
is needed) or three (if neutral is needed) 14 ga (for
15 A) or 12 ga (if 20 A) plus ground wired to a double
pole breaker
For 240V, if you need a neutral (120V/240V circuit for four wire devices _only_),
14/3 or 12/3 as above. For 240V _without neutral_ (240V tools _only_) 14/2 or
12/2 respectively.
Combinations of more circuits: go with a sub panel in the shed; the home
run consisting of three conductors plus ground wired
to a double pole breaker, and rated to hande 125% of
your worst-case load (i.e.: a 10 ga home run should be
protected by a 30 A breaker, but should only be loaded
to 80% of this value, or 24 A).
This will be a single cable "wiresize/3". Ie: "10/3" for Henry's 30A example.
Note as well, detached outbuildings with a subpanel USUALLY need their own
grounding system (ground rods etc), and do NOT need a ground wire in the
panel feed. You will need to consult a local inspector to be sure.
Note: Generally speaking, the third option (A "240V" or "240V/120V" circuit)
is rarely useful. Neither of which permit 120V devices (outlets or lighting),
they're really only useful if the shed will contain ONLY 240V or 240V/120V
devices (can't even mix 240V-only and 240V/120V devices), and usually only
one at that (ie: a shed containing only your 240V water pump, and you plan on
using flashlights for maintenance... ;-).
[Strictly speaking, while hanging 240V-only or 120V-only devices off a
240V/120V circuit _can_ be made to work, it's almost always a code violation,
sometimes potentially hazardous or dangerously confusing, and should be avoided.]
Generally speaking, if the shed only needs lights and a few outlets,
a single 120V circuit (first example) is the best approach. This
is more-or-less the minimum (and most common) "Garage arrangement".
If you plan on anything more substantial, a subpanel (last example)
is usually the best approach. Unless you know that you need only
two circuits, will never exceed it, and don't need 240V.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
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