The whole key to this is what the supply is like. If you have a good
stiff 120V supply with a short cord, you likely would see zero
difference between 120V and 240V wiring. Once the voltage gets to the
motor the motor cannot tell whether it's 120V or 240V, anyway. The
voltage goes through the same windings (just differently) Each winding
sees exactly 120V regardless of how the motor is hooked up.
However, the wires outside the motor are all the difference. If your
120V supply is a long way from the panel and you have a long motor
cord, and god forbid it's a 15A circuit, your saw is going to jump to
life like a racehorse out of the gate when it's wired (and supplied)
It is not, however, because there's something magic about 240V or the
motor. It's about double the current draw at 120V and four X the
percentage of voltage drop that makes the difference.
And there're no heat issues, no energy savings, no magic pill. Stiff
supply, no difference. Long runs, 240V usually makes a difference.
On Wed, 20 Feb 2008 07:12:30 -0800 (PST), Airedale
How many horsepower does the table saw generate? Another way of asking
is how many amps does the table saw draw at 110 volts, both on start
up and under load?
If you were looking at a 1.5 HP table saw, or the amps are at 15 or
under, you'd probably be OK with a 110 volt circuit, 20 amp circuit
breaker, 12 gauge wire.
At 2 HP or more, or over 15-18 amps current draw, you really are going
to want a 220 volt circuit, as the alternative is a 30 amp 110 volt
circuit and 10 gauge wire, which doesn't make a lot of sense to put
Regardless you want to dedicate this circuit to the table saw.
If you ever want a dust collector for your saw, or other heavy duty
tools, the subpanel others have suggested is going to save a lot of
money over time.
This question comes up at least every other week.
Yes, you need 240V in the shop if you are going to do any serious work
involving stationary power tools.
To do the job so that you get the biggest bang for the buck, install a
2P-60A sub feeder in the house panel, a 12/24 ckt, 125 MLO sub panel
with a 2P-60A main, in the garage and #4 feeder wire in a new
conduit. (1-1/2" plastic will make pulling the wire a lot easier).
(Yes you can save a couple of $'s with #6AWG, but I like #4AWG,
especially when you only do this job once)
Find an electrican who wants to pick up a few extra $'s and work with
You do the grunt work under their direction, they make the hook ups.
Advantage of 220: Less voltage loss in the circuitry. Thus more of the
power that are buying (at a not so cheap price these days) gets wasted
heating the wiring.
Disadvantage of 220: Costs lots to install in old work. But only an
electrician would know how much more (depends on whatever else needs to be
\the very least..
Once upon a time, I wanted to install an electric oven in my kitchen which
needed a 60 amp circuit. The existing oven only needed a 40 amp circuit,
was what was in the house. So, I called an electrcian to get an idea. He
quoted a very high price because he would need to replace the wiring. It is
involved in old work that runs the cost up. The cost of the wiring, etc.,
is almost incidental. I am talking about making changes to an existing
It certainly would not cost me very much to install a 240v circuit in my
garage because there is already a 240v line inside the wall.
So the electrician comes out and quotes me $780 to run the new line. I
am blown away at how much it would cost for that.
Because we are planning on moving in about 5 years, I wasn't willing
to put that much money into the place for something I won't be reaping
the benefits of in the long run.
Instead I had him switch over an existing line in the garage from 15
Amps to 20 Amps. The only other thing that runs on that are a couple
of shop lights. Those don't draw too much amperage so I figure I'll be
Since the existing line was run with 14 gauge wire, they beefed it up
to 12 gauge. That whole little fiasco cost me $275.
You guys have any similar experiences? I am left thinking to myself
that I got into the wrong industry!
Around here the homeowner can get a permit to do electrical work as long
as it's inspected by the power utility. (Once nice thing about this is
that the inspector is then available for code interpretation questions.)
Shortly after buying my house I installed a new subpanel in the garage
and added a whole bunch of outlets (120 and 240V, various amperages),
overhead lighting circuits, unit heater circuit, etc.
If you have the skills to do it yourself, it's *much* cheaper.
OK, so to "beef up" the existing line from 15 to 20 amps, he had to pull
wire. What he pulled was probably "12-2 plus ground" if it was nomex
type. If it went in conduit, he just used the old wire to pull in the
new, into the same conduit.
He could have pulled in 12-3 and given you a 240 volt, 20 ampere circuit
just as easily, and you'd have double the capacity for something like
20% more wire cost and the cost of the other pole breaker.
Why the 60 ampere circuit was so much was really related to a single
thing. To run a 60 ampere circuit, you need heavy guage wire (costs
considerably more per foot) and it's a royal PITA to pull in the heavier
wire, compared to 12 guage. If you are running in existing conduit,
there wouldn't have been enough room inside the conduit to hold the wire
(plus the air space required by code) for the heavy guage wire for a 60
ampere circuit. It's not the fact it was 240 volts, but it is directly
related to the amount of current you are trying to carry.
Without knowing how far you were running from panel to outlet, it's hard
to determine if you were being overcharged. On the other hand, if you
ingore the wire cost, what's the hourly rate where you live for an
electrician? I bet it was a large portion of the cost involved,
particularly as you got the 120 volt circuit for only $275...
On Thu, 21 Feb 2008 08:51:35 -0800 (PST), Airedale
$780...Ouch! My house was setup for a 220v outlet for an electric
stove. Since I have a gas stove and gas clothes dryer, I had a choice
to take one of these for my shop 220v circuit. I decided to take the
stove 220v and wired that into the subpanel in my shop. I left the
220v laundry alone because I thought electric clothes dryers are more
popular than electric stoves. Plus a gas stove (unlike a clothes
dryer) would be left with the new home owner. I paid an electrician
$50 to inspect and test my wiring.
Exactly so. It is the labor involved in old work. Whether it's 240V or 120V is
almost irrelevant; it costs hardly any more to install 240V in old work than
it does to install 120V in old work. The cost is not a "disadvantage of 240V"
as you called it; the cost is a disadvantage of old work. That electrician
would have charged you very nearly the same to install a 60A 120V circuit.
Doug Miller (alphageek at milmac dot com)
On Wed, 20 Feb 2008 07:12:30 -0800 (PST), Airedale
I'm going to be a bit of a contrarian on the subpanel. Nothing
against the idea, just might be overkill depending on your plans.
My 400 square foot shop started with a single 20 AMP 110 V circuit
pulled from the main panel and a lighting circuit that came by
extending an existing, underutilized, lighting circuit from the
carport. For years this worked fine.
I then added several 220 tools and ran a second circuit from the main
panel to handle 220.
I only run one tool at a time or occaisonally, one running on the 220
circuit and one on the 110 circuit. I've often worked with a friend
and the single 110 circuit was able to run my RAS and Jointer, with
the table saw running on the 220 circuit as we rapidly processsed a
lot of lumber for glue up.
Never any tripping or voltage drop problems.
My advice, if you have even a remote plan to make the garage a real
shop and are going to be drawing lots of power in the future, the the
60 amp minimum subpanel is probably a good idea. Particularly if you
plan to be there for a while. If not, you may be just adding a lot
of electricians cost.
Now, that said, I'm planning a shop expansion, doubling the size and
connected load and will put in a 60 Amp subpanel. Primary reason is
the addition of a dust collection system and having an air compressor
on random start feeding shop air. But it took me 15 years to get to
the point I need the additional power.
Look past your connected load to your diversity factor. Connected
load is not important if very little is operating at any given time.
It may be that pulling the wire for the second circuit in the existing
conduit is your most cost effective approach.
I agree Frank. I operated most of my equipment on a 15 amp circuit for
almost 20 years, I still do. I added 220 when I had to, my cabinet saw only
runs on 220. Fortunately that enabled me to go with a honken band saw and a
stationary planer. The Performax drum sander needs to be plugged into the
single 20 amp circuit as it an the DC are too much for the 15 amp circuit.
Typically I can run the DC, large router, radio, lighting, and fan on the 15
amp circuit, but shut a tool down quick if the compressor starts up. LOL
I'm a fan of the sub panel. It gives you the flexibiltiy you need
without having to make long runs from the main panel (Of course,
nobody's mentioned yet that the main may be nearly full already, so that
means a suh-panel anyway if you want more than a single 240 volt circuit..)
In my shop, which is manned only by me, I've got the following on 240
volts: 3HP wood lathe, 3HP cabinet Saw, 5hp wide Belt sander, air
compressor, 18" bandsaw, dust extractor and two different electric
welders. Correct, I can't run them all at the same time, but to run the
drum sander, I need to have the dust extractor running or I die from the
dust, and the compressor has to be able to run periodically to keep the
belt moving (it oscillates back and forth under air power. No air, and
it won't even start...) There's a bunch of other 120 volt tools too,
but most don't contribute heavily to the total running load of the shop.
As I'm not willing to run back and forth and turn the air compressor on
and off, it's always enabled when I'm in the shop and could start at any
time. (Gettin' lazy in my older age.) Anything that generates
significant dust or shavings (Cabinet saw, Lathe, Belt Sander, Planer)
also requires the dust extractor at the same time or I spend more time
cleaning than working. If I'm putting a finish on a bowl on the lathe,
I often spray lacquer, so the compressor runs fairly often while the
lathe is running in this mode. Add a few normally forgotten loads and
it's easy to add up to a sub-panel making sense, even in a much smaller
My Shop is 28 x 32 feet (though half is taken up by "temporary storage"
as we build our house) and has four 30 amp 240 volt circuits, 2ea 50 amp
240 volt circuits for the welders (opposide ends of the shop, it just
worked out that way) and all of the 120 volt circuits are 20 amperes
each, with most 120 volt circuits feeding only one or two outlets.
Filled a 28 slot breaker panel. Some days, I could still use a few more
outlets, but have some 10 guage extension cords for odd machine placement.
If you are really only going to run one thing at a time, and never plan
on any expansion, you may be able to squeak by on only a few circuits,
but having lived with inadequate capacity for over half of my life, it's
just no longer worth it anymore to try to "get by". It's like some of
the power tools. I "GOT BY" with an old Craftsman almost-contractor
type saw with a 1.5 HP motor on it for years, but spent a bunch of
wasted time waiting for it to recover or by sawing really slow in hard
woods. Moved to a good 3HP 240V Cabinet saw and the difference is
amazing. If I could only have done it years ago my frustration with
table saws would have dropped a long time ago and I would have gotten
more work done in the same time.... Seme thing with electrical service
capacity. Just getting by with minimum was frustrating and wasted a lot
of time that could have been put to productive work (or more recreation!)
"thinks I can use the existing conduit to add in another line if it is
just 110. "
It appears you are hesitant to do your own electric. But the cost
differential (contractor vs self-install) will be significant for many
folks - certainly for me!
However, if you already have a conduit line running 110 into the
subject area and the electrician indicates he could add another
circuit through that same conduit run (which involves using one or all
of the existing wires in that conduit to pull a string through ther
conduit and then tying that off to the new group of wires and pulling
them back through.
So, if it were me, I'd look at the conduit run and see if I couldn't
fit a sub-panel at the point it enters the subject space. (You can
mount them recessed into or on the wall surface) and check the specs
to see the largest gauge wire one might pull through the existing (I
am assuming tubular) conduit run and the max amp that gauge wire would
carry. If you can fit 10/3 you could do your 220VAC and if you can fit
8/3 even better - more amps.
You put a 15 Amp breaker in for the existing circuit and add breakers
for the 220 for the saw and another breaker or two for additional tool
circuits as suggested elsewhere in the thread.
If what your electrician saw was a straight run through an existing
conduit from you main panel to your garage, its as if you have a small
entension cord (in there) and need to replace it with a larger
extension cord. How simple is that?
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