I am planning on building a large shed in the backyard, and am planning
on running electrical to it. I am getting a couple of books in on wiring
a house (including one called “Wiring a House”…) but would also be
interested in feedback from experienced electricians.

I have a few questions.

First, how is the easiest way to figure out what I have coming into the
house. My panel says 120/240AC 200 Amp, and I really have to believe
that is what is coming on, but I would like to confirm i have 200A. Does
it say on the meter? My bill? Or do I need to call the electric company?

Second, is there an easy, straightforward method of calculating current
“usage”, or load on the main panel? I am guessing the books will go into
this, but I wouldn’t mind getting some other input on this. I am
assuming I will have enough to add a 120V/15A dedicated for an electric
wall heater, and then one 15A circuit for the shed, since I recently
removed an electric stove in the house (replaced with gas), but I want
to confirm.

I was thinking it might be nice to have a sub-panel in the shed, with
the two circuits. Is there an advantage to this? I was thinking I could
feed the shed with 10g, and then have a 50A panel in the shed, instead
of running two separate wires for the circuits. My plan would be to hook
the feed wire to a GFCI breaker in the main, and then have two 15A
standard breakers in the sub. Is 10g enough for this load on an ~80ft
run (underground)? How would I wire it into the main panel? With one
single 50A breaker, or 2 25A, or some other way. Using 10g 2 w/g or 10g
3 w/g? I have not looked into how to wire a sub panel, so excuse my
ignorance.

Again, just looking for a base before I get my books.

Just wanted to note something about your comment regarding amperage. Do you
have 200A? Huh?

Amperage is a matter of how much you draw, not how much is directed to your
house. Your main breaker is probably rated to a max of 200A (and probably
so is your panel), nothing more. If you try to pull more than 200A, you'll
getit until you pop the breaker or fry something.


"chester" wrote in message
...
I am planning on building a large shed in the backyard, and am planning
on running electrical to it. I am getting a couple of books in on wiring
a house (including one called “Wiring a House”…) but would also be
interested in feedback from experienced electricians.

I have a few questions.

First, how is the easiest way to figure out what I have coming into the
house. My panel says 120/240AC 200 Amp, and I really have to believe
that is what is coming on, but I would like to confirm i have 200A. Does
it say on the meter? My bill? Or do I need to call the electric company?

Second, is there an easy, straightforward method of calculating current
“usage”, or load on the main panel? I am guessing the books will go into
this, but I wouldn’t mind getting some other input on this. I am
assuming I will have enough to add a 120V/15A dedicated for an electric
wall heater, and then one 15A circuit for the shed, since I recently
removed an electric stove in the house (replaced with gas), but I want
to confirm.

I was thinking it might be nice to have a sub-panel in the shed, with
the two circuits. Is there an advantage to this? I was thinking I could
feed the shed with 10g, and then have a 50A panel in the shed, instead
of running two separate wires for the circuits. My plan would be to hook
the feed wire to a GFCI breaker in the main, and then have two 15A
standard breakers in the sub. Is 10g enough for this load on an ~80ft
run (underground)? How would I wire it into the main panel? With one
single 50A breaker, or 2 25A, or some other way. Using 10g 2 w/g or 10g
3 w/g? I have not looked into how to wire a sub panel, so excuse my
ignorance.

Again, just looking for a base before I get my books.

MrC1 wrote:

Just wanted to note something about your comment regarding amperage. Do you
have 200A? Huh?

Amperage is a matter of how much you draw, not how much is directed to your
house. Your main breaker is probably rated to a max of 200A (and probably
so is your panel), nothing more. If you try to pull more than 200A, you'll
getit until you pop the breaker or fry something.


I have a main panel rated for 200A. However, I am not absolutely certain
the house is wired for that, FROM THE STREET. For example, say my house
was wired in the 50s for 100A, or 60A maximum. And the main panel, but
not the wiring to the house, was changed. I am sure it has happened
somewhere by a DIY or bad electrician. I dont want to draw more than
what the system can handle, because I dont want to "fry" something.

i.e. So while 200A might not be "directed at my house", I want to make
sure that from the street to my house is set to handle 200A of DRAW. I
can't belive it isn't, but I want to make sure.

According to chester :

MrC1 wrote:

Just wanted to note something about your comment regarding amperage. Do you
have 200A? Huh?

Amperage is a matter of how much you draw, not how much is directed to your
house. Your main breaker is probably rated to a max of 200A (and probably
so is your panel), nothing more. If you try to pull more than 200A, you'll
getit until you pop the breaker or fry something.

I have a main panel rated for 200A. However, I am not absolutely certain
the house is wired for that, FROM THE STREET. For example, say my house
was wired in the 50s for 100A, or 60A maximum. And the main panel, but
not the wiring to the house, was changed. I am sure it has happened
somewhere by a DIY or bad electrician. I dont want to draw more than
what the system can handle, because I dont want to "fry" something.

The panel is rated for 200A. Which means you can draw up to 200A safely
(subject to limitations of individual circuits) if the main breakers
are rated that high.

What is the main breaker rating? It could be less than 200A. That's
the true determining factor of how much you can pull from the street.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

chester wrote:


MrC1 wrote:

Just wanted to note something about your comment regarding amperage.
Do you
have 200A? Huh?

Amperage is a matter of how much you draw, not how much is directed to
your
house. Your main breaker is probably rated to a max of 200A (and
probably
so is your panel), nothing more. If you try to pull more than 200A,
you'll
getit until you pop the breaker or fry something.


I have a main panel rated for 200A. However, I am not absolutely certain
the house is wired for that, FROM THE STREET. For example, say my house
was wired in the 50s for 100A, or 60A maximum. And the main panel, but
not the wiring to the house, was changed. I am sure it has happened
somewhere by a DIY or bad electrician. I dont want to draw more than
what the system can handle, because I dont want to "fry" something.

i.e. So while 200A might not be "directed at my house", I want to make
sure that from the street to my house is set to handle 200A of DRAW. I
can't belive it isn't, but I want to make sure.


The wires between the electric utility and the main breaker (this
includes the electric meter) are the only wires than have to handle
200A. These should be very large copper wires or enormous aluminum
wires (I don't recall the exact minimum sizes for 200A).

You can only have one circuit going to the shed. If 120V/20A is
sufficient, you can directly bury a strand of UF cable and it only has
to be covered 12 inches if it is protected by a GFCI at the house. If
120V/20A is not enough, you probably want to run at least a 240V/30A
circuit to a small subpanel (it has to be rated for "service equipment",
but almost all of them are) and split it into smaller circuits at the
shed. This larger circuit would have to be run in conduit and/or be
buried a lot deeper, (or run it overhead with UF or triplex or quadplex
cable) but it would not need GFCI protection at the house. (You will
want GFCI outlets installed in the shed.)

Overhead wiring is more trouble than it sounds like (don't ask me how I
know this) so I recommend buried cable if at all possible.

Best regards,
Bob

"chester" wrote in message
...


MrC1 wrote:

Just wanted to note something about your comment regarding amperage. Do
you
have 200A? Huh?

Amperage is a matter of how much you draw, not how much is directed to
your
house. Your main breaker is probably rated to a max of 200A (and
probably
so is your panel), nothing more. If you try to pull more than 200A,
you'll
getit until you pop the breaker or fry something.


I have a main panel rated for 200A. However, I am not absolutely certain
the house is wired for that, FROM THE STREET. For example, say my house
was wired in the 50s for 100A, or 60A maximum. And the main panel, but not
the wiring to the house, was changed. I am sure it has happened somewhere
by a DIY or bad electrician. I dont want to draw more than what the
system can handle, because I dont want to "fry" something.

i.e. So while 200A might not be "directed at my house", I want to make
sure that from the street to my house is set to handle 200A of DRAW. I
can't belive it isn't, but I want to make sure.


Most local utility companies will come out and let you know....most will
also upgrade the feed to the home in SOME areas at no cost provided proper
permits have been pulled and inspections made on the panel box when
upgrading by a licenced electrician.
Here, all thats required if the service to the home, GOING INTO THE PANEL is
not up to the panels capacity, (ex: 60A service to the powerhead going into
a 200A box), is a permit and the local utility will upgrade the line at no
cost to the homeowner.

The wires between the electric utility and the main breaker (this
includes the electric meter) are the only wires than have to handle
200A. These should be very large copper wires or enormous aluminum
wires (I don't recall the exact minimum sizes for 200A).

Yeah they are BIG aluminum wires.


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), and doing it like you
describe below. At any rate, I am burying them, and was going to run
some PVC conduit anyway. It is not that expensive, and looks like it
just snaps together. Gonna rent a trench digger, I think. And I will use
a GFCI at the house to be on the safe side, and in the shed too, I
suppose. But woiuld GFCI in the house not be required if I was running a
subpanel and had GFCI in the shed?

Thanks for your help.

If 120V/20A is
sufficient, you can directly bury a strand of UF cable and it only has
to be covered 12 inches if it is protected by a GFCI at the house. If
120V/20A is not enough, you probably want to run at least a 240V/30A
circuit to a small subpanel (it has to be rated for "service equipment",
but almost all of them are) and split it into smaller circuits at the
shed. This larger circuit would have to be run in conduit and/or be
buried a lot deeper, (or run it overhead with UF or triplex or quadplex
cable) but it would not need GFCI protection at the house. (You will
want GFCI outlets installed in the shed.)


Overhead wiring is more trouble than it sounds like (don't ask me how I
know this) so I recommend buried cable if at all possible.

Best regards,
Bob

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?

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

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

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

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).

--
Calvin Henry-Cotnam
"Never ascribe to malice what can equally be explained by incompetence."
- Napoleon
-------------------------------------------------------------------------
NOTE: if replying by email, remove "remove." and ".invalid"

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.

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.

Well in the US, most wiring is labeled 12/2 with ground. 12/3 witll have
3 insulated wires, with a bare gound, "in my experience". I am sure
there are exceptions.



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.

Well, I need two circuits, and that is it I would anticipate. I need one
for ruunnning lighting (one over head flourescent, and one other
probably incandenscent). Probably also a TV and /or a cumputer. The only
big draw I could imagine adding to this circuit is a excercise tredmill.
I have no idea what the draw is on those, so I guess I will need to
check. The other circuit will be a dedicated circuit to run an in wall
electric space heater, set to run at 15A/120V. I have two in the house,
in added-on rooms, and they work well.
I will look into the 30A subpanel, but would lean on just running two
12/2 w/ground out through some pvc conduit as the easiest option.

Thanks for the input.

According to chester :

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.

Well in the US, most wiring is labeled 12/2 with ground. 12/3 witll have
3 insulated wires, with a bare gound, "in my experience". I am sure
there are exceptions.

I only mention it because the "with ground" is implicit in Canada (you
can't buy wiring suitable for residential wiring without it), and AFAIK,
you can still buy wire without it in the US, so the "with ground" should
be stated to be absolutely sure you get what you want.

Well, I need two circuits, and that is it I would anticipate. I need one
for ruunnning lighting (one over head flourescent, and one other
probably incandenscent). Probably also a TV and /or a cumputer. The only
big draw I could imagine adding to this circuit is a excercise tredmill.
I have no idea what the draw is on those, so I guess I will need to
check.

AFAIK, they're usually under 10A.

I will look into the 30A subpanel, but would lean on just running two
12/2 w/ground out through some pvc conduit as the easiest option.

As a personal preference (and I think preferred by codes), I'd do
this with a single 12/3 NMW (or UF) and tie-barred breaker, and just
inside the shed I'd split it into two 12/2 branches. You sometimes save
a bit of money, and it's a little easier to install.

Buried PVC conduit? You don't have to with NMW (UF), tho, the burial depth
requirement is a little deeper. You'll need to check for what the burial
requirements are in your area. You shouldn't use ordinary NM/NMD regardless.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

As a personal preference (and I think preferred by codes), I'd do
this with a single 12/3 NMW (or UF) and tie-barred breaker, and just
inside the shed I'd split it into two 12/2 branches. You sometimes save
a bit of money, and it's a little easier to install.


I think I see what your saying. Have two (15A?) tied breakers sharing
neutral and ground, with separate hots? That sounds like the best
solution. GFCI is code I assume for the breakers.
thanks

moose wrote:


As a personal preference (and I think preferred by codes), I'd do
this with a single 12/3 NMW (or UF) and tie-barred breaker, and just
inside the shed I'd split it into two 12/2 branches. You sometimes save
a bit of money, and it's a little easier to install.


I think I see what your saying. Have two (15A?) tied breakers sharing
neutral and ground, with separate hots? That sounds like the best
solution. GFCI is code I assume for the breakers.
thanks


At the shed, you'll split the circuit into two branches. One goes to
your electric outlets, and the first one gets a GFCI to protect
everything downline from it. The other goes first to the lights
(without a GFCI) and then to any specialty outlets you might have (like
a freezer that your don't want on a GFCI), and *then* another GFCI
outlet and more convenience outlets if you want.

GFCI devices are cheaper than GFCI breakers (especially if you'd need a
2-pole GFCI breaker), and you don't want a GFCI on some things (lights,
freezers, maybe a sump pump, etc.)

Check on adding a supplemental grounding electrode at the shed and
connecting it to the ground wire at the first J-box.

Bob

According to zxcvbob :
moose wrote:

As a personal preference (and I think preferred by codes), I'd do
this with a single 12/3 NMW (or UF) and tie-barred breaker, and just
inside the shed I'd split it into two 12/2 branches. You sometimes save
a bit of money, and it's a little easier to install.

I think I see what your saying. Have two (15A?) tied breakers sharing
neutral and ground, with separate hots? That sounds like the best
solution. GFCI is code I assume for the breakers.

Yup.

I was thinking of saying something about GFCI. You _should_ have
it (tho, it might not be explicitly code-required, depending on what
the floor is, external outlets etc).

GFCI breakers are expensive. Bob's solution is better:

At the shed, you'll split the circuit into two branches. One goes to
your electric outlets, and the first one gets a GFCI to protect
everything downline from it. The other goes first to the lights
(without a GFCI) and then to any specialty outlets you might have (like
a freezer that your don't want on a GFCI), and *then* another GFCI
outlet and more convenience outlets if you want.

The above might be a bit confusing. Basically, you put a GFCI in passthru
mode on both branches (MUST be downstream of where the neutral splits).
You just might want to put a few unprotected outlets _upstream_ of one or
both of the GFCIs for things you can't afford to trip (like a freezer).

Note: I believe electrical code can be pretty picky, so you may need
to use non-duplex (_single_ outlet) receptacles for them, and they
must feed "fixed" equipment (like a freezer). Not general purpose outlets.

[I'd probably GFCI the lights. Depends on whether anything in the
shed is going to be "dangerous". I wouldn't GFCI _all_ of the lights
in a workshop with power tools, for example.]

GFCI devices are cheaper than GFCI breakers (especially if you'd need a
2-pole GFCI breaker), and you don't want a GFCI on some things (lights,
freezers, maybe a sump pump, etc.)

Check on adding a supplemental grounding electrode at the shed and
connecting it to the ground wire at the first J-box.

You only add supplemental grounding electrodes to outbuildings that
have a subpanel. Not necessary for a single circuit (the dual breaker/
multi-wire branch counts as a single).
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

OK you have been -very- helpful. One last question:

Is it OK to put that heater, which requires a dedicated 15A/120V circuit
(if memory serves), on the tied breakers circuit? I would think not, but
I admit I don't know a lot about tied breakers.
thx again.

chester wrote:
OK you have been -very- helpful. One last question:

Is it OK to put that heater, which requires a dedicated 15A/120V circuit
(if memory serves), on the tied breakers circuit? I would think not, but
I admit I don't know a lot about tied breakers.
thx again.


Put it on one leg of your 20A circuit, and put almost everything else on
the other leg and the heater will be very happy. (this would work with
a 15A circuit too, but with a higher chance that you will trip the
breaker occasionally if the heater is not the only thing on its leg of
the circuit)

Bob