This weekend, my new shop walls are going up, and I need to start thinking
about how to wire it. Ideally, this is what I want to do:
1 120V circuit for machines (many, many plugs)
1 220V circuit for hard core machines (a few plug)
1 120V circuit for lighting
1 120V circuit for any dust collection
The last circuit there would probably just be 1 whip across the floor
joists to plug in a ceiling-mounted collector unit, so that's trivial and
could even come off a circuit in the next room.
I plan on this shop being used for a hobbyist but I'm also thinking of
resale of the home, especially if the potential buyer is any kind of
handycraftsy person. Is 4 circuits too much? How many outlets would you
recommend, and is that 220V line really necessary? I have no current
plans for 220V machines but that doesn't mean I may not get them
eventually. Is it really necessary to have the lights on their own
circuit (this was recommended to me repeatedly, but nobody could tell me
Lights on separate circuit? YES. If a machine blows a circuit, you
won't be in the dark.
15 amps Lights
20 amps (115) outlets around wall
20 amps (230) table saw
20 amps (230) dust collection (future)
20 amps (115) garage door opener, outdoor lights
20 amps (115) A/C, heater outlet
+ 3 open spots in sub-panel for anything in the future.
That depends - are you with the code enforcement division? ;^)
I put it all in and ran it all in smurf tube so I could change it later
if necessary. My shop has OSB walls so I can screw the conduit and
outlets in where ever I need them.
Heh, no. I've done a few really tiny wiring projects (install a GFCB, for
example), I'm just trying to guess if I can do all this on my own. I did
took a few home electricity classes in high school, but that was 10 years
As long as you have clear access the wiring part is rather easy.
Check your local library for books on home wiring. There are likely some
available which will get you acquainted with what you are going to do.
If you aren't currently using 220V you can hook it up as 110 in the
That way when you have a need for 220 all you need is a new breaker and a
Leave a bit of slack in the main panel so that you can rewire if that
Your plan seems sound enough. Watch the amperage on the
circuit you have for machines; 20amps is my suggestion. I have
a couple 20-amp circuits for machines which is not overkill given
that I could easily have the compressor cut in (loss of pressure)
if I started using a saw. Given the number of lights I have, I have
two 15-amp circuits for lights. However, part of the reason for
two circuits was to simplify the wiring.
As to the *potential* for 220V, it's trivial to convert that to/from
120 *if* you have sufficiently-sized wire (move the white to/from
hot, change to/from ganged breakers).
Good start. I'd check that "many, many" receptacles bit, though. IIRC, NEC
limits 110 volt circuits to a max of 8 outlets per. If I even think 2 tools
will be used on the circuit at one time, I add another circuit.
I'd guess your dust collector is a 110 volt. Many are 220. Make sure.
I'd also, if possible, run a second 220, or at least make sure there's space
for the breaker. If you have no current 220 equipment, figure out how long you
expect to stay in the house. If it's 5 years or more, and you keep woodworking,
you'll want 220 gear at some point.
Lights are put on their own circuit for a simple reason: if you're feeding wood
to your table saw and the saw binds, you will be glad the lights are on another
circuit when the saw breaker blows.
"We have a firm commitment to NATO, we are a *part* of NATO. We have a firm
commitment to Europe. We are a *part* of Europe."
Electrical circuits are like clamps, you can NEVER have too many.
The following are some general guidelines for a distribution system.
Use two (2) dedicated 20A ckts for lighting.
If you loose one, you still have the other.
Yes, you want 240V circuits, lots of them.
Your table saw will be much happier on 240VAC as opposed to 120VAC.
How about a decent air compressor and/or a dust collector, they both like
Forget 15A circuits.
Use 20A c'bkrs and #12 AWG wire as a minimum for 120 VAC distribution.
Even though this shop is in your basement, consider adding a 60A panel fed
from the main panel and dedicated to your shop.
Panels, c'bkrs and wire are relatively inexpensive. Labor is expensive;
however, it is the job unknowns that really drive up the cost of the
S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
Is lights on their own circuit _necessary_? No. *GOOD*IDEA*(tm)? hell yes.
why? what happens to the lights if "something else" sharing the circuit
overloads and causes the breaker to blow?
The _first_ thing you need to do is consult the electrical code requirements
for your locale. each 220 outlet may _have_ to be on a separate circuit,
just for starters..
As for 4 circuits being "too many", I've got _ten_ circuits in my *kitchen*.
(one for lights, one for stove, one for refrigerator, one for dishwasher,
and _six_ circuits for the outlets.) Admittedly, I've got a -lot- of
counter-top appliances, and running several at the same time _is_ likely
e.g. electric skillet, microwave, toaster, bread machine, and blender.
I'd recommend at least 3 220 circuits. each with a single outlet.
(Note, if you don't have 220 use _currently_, you can put a single
'split' duplex outlet in the box, and have 2 120VAC outlets -- until
you need the 220u)
Then I'd add _at_least_ two 120V outlets, -- put *lots* of outlets
around the walls, and alternate which circuits they're on. (you may need
to run, for example, a vacuum and "something else")
*ANY* chance that 'more than one' person might be working in the place
_at_the_same_time_ ?? If "absolutely not" (even in the future, after
you've sold the place), then go ahead and wire to support *only*one*
device in use at any time.
Other things to think about, that may affect electrical needs:
Air conditioning? Dehumidifier?
There may be something in some locale where the IBEW has a strangle hold on the
code officials but there is nothing in the NEC about this.
One thing that wasn't mentioned but may be implied. If these circuits are
exposed, they should be in conduit. I know some AHJs are fairly lax in
providing physical protection and allow Romex on running boards in utility
As an inspector I would see a wood shop, where you are handling large pieces of
lumber, as a place requiring physical protection for the wiring.
If this shop has a concrete floor, some AHJs might ask for GFCI protection in
the 15 & 20a 120v receptacle circuits. (citing the same dangers you have in a
garage or basement) That would be a stretch tho.
AND? What's the above suppose to mean?
For your information... the IBEW has trained more electricians in Canada and
the USA than any other group could hope to imagine.
IN FACT, the IBEW has the only REAL training program for electricians.
Not enough IMO, if there is any possibility that more than one person will be
working in the shop simultaneously. I recommend two 20A 120V circuits at a
minimum for machinery.
Again, probably not enough, if there is a possibility of two people in the
shop at once. Two 30A 240V, or one each 20A and 30A, is better.
Good idea. Lights should never be on the same circuit as the receptacles that
power your machines. Example: the first time I used my table saw after moving
into our current house (workshop in basement), I unknowingly plugged it into a
receptacle on the same 15A circuit as the overhead lights. The instant I
turned it on, the fluorescent lights dimmed to the approximate brightness of a
birthday candle. NOT a good thing.
You may in time decide that a 240V dust collector would serve your needs
better. So anticipate that need, and run *both* 120V and 240V circuits.
OK, wait a second here. Ceiling-mounted units are dust *filters*, not
collectors. You really should have one of *each* IMO. (That subject has been
beaten to death in this ng. Check Google for all the gory details.)
Four circuits is not enough IMO -- you can *never* have "enough". Yes, the
220/240V line is necessary. Having the lights on a separate circuit is not
required by Code, but as I noted above it's sure a good idea.
My shop contains a table saw, dust collector, shaper, lathe (all 240V),
bandsaw, radial arm saw, drill press, belt/disc sander, spindle sander,
jointer, grinder, planer, mortiser, scroll saw, air filter, two exhaust fans,
and a variety of portable power tools (all 120V). SWMBO and the kids (15 and
12) are woodworkers too, so it's not unusual that we have the dust collector,
the air filter, and two or three machines running at once.
We have six circuits in the shop:
The lathe and the dust collector share a 20A 240V circuit.
The table saw and shaper share a 30A 240V circuit.
Bandsaw, drill press, air filter, scroll saw, and mortiser share a 20A 120V
Radial arm saw, jointer, and planer share a 20A 120V circuit. (I know it seems
that this overloads the circuit, but the shop is kinda small, and its layout
prevents the use of more than one of these at a time.) The grinder and sanders
are on this circuit as well.
Lights are on a 15A 120V circuit.
Exhaust fans are on a 20A 120V circuit.
Portable tools usually get plugged into the same circuit as the air filter.
sometimes the same circuit as the lights.
Doug Miller (alphageek-at-milmac-dot-com)
Save the baby humans - stop partial-birth abortion NOW
I have two circuits for lights (there's a little more than lights
on these circuits, including garage door openers) and found
it very convenient to have THREE switches for the lights,
three banks of fluorescents. Means I can turn on some,
most, or all, depending on what I'm doing. Didn't see the
advantage of turning on all nine 2-bulb, 4-foot, fixtures just
to fetch a screwdriver or somesuch.
Oh, and earlier I mentioned the number of circuits I have
in my garage/workshop but overlooked another circuit
for my 10,000BTU window air conditioner [gloat!]. On recent
100+ degree days (Wednesday, Dallas/Fort Worth had
a record 109 for the date!) my shop was a comfy 77.
Helps to turn the A/C on in the morning, when the ambient
is 80+/-, and to have insulated the walls and garage doors
(my ceiling, though, is still just a 1/2" layer of drywall, no
insulation in the attic).
"Bruce Garland" <BRuce> wrote in message
Fairly common rules for shop wire guage sizes:
10 ga for the 30 amp circuits
12 ga for the 20 amp circuits
14 ga for the 15 amp lighting circuits
Note that some locales now require nothing smaller than 12ga throughout,
even on your lighting circuits.
I used all 12 ga in my shop, except for my 220 circuits, where I ran 10
guage on the 30 amp circuits and 12 on the 20 amp circuits.
I tend to believe what my electrician, who has 50+ years of experience, and
the city electrical inspector tell me, as far as what is required. :)
Locale is in the suburbs, outside of Chicago.
'Standard' here is BOCA building code (not NEC), 1997, with two lines of 'over-
rides'. One forbids any new aluminium wire, and I don't remember, off hand,
what the other one is.
Circuits above 20A capacity, *are* limited to single outlet. I was planning
to put 30A circuits in my new kitchen, so I could have 2 1500 watt devices
in use on a common circuit. No can do, so I've got 6 circuits worth of
kitchen outlets instead.
12 ga is rated for 20A. This is adequate for a 'true' 3 HP load at 120V,
or 6 HP at 240.
Assuming, as well, that you're not using anything bigger than 20A breakers,
If you have _really_ long runs, it's recommended to go one size larger than
needed. Going 'larger than needed' also cuts down on the losses in the
wiring. The cost difference between 12 ga, and 10 ga, is relatively small,
and -- especially if you're doing the work yourself -- the labor cost is
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