My shop is located in the basement. Last year, we converted our hot
water and range to natural gas, and as a result, I have these two nice
junction boxes from the original 220 just waiting to be tapped with a
nice big 3HP TS or something.
I was wondering if I could simply plug a 1PH 3HP power tool into one of
the available boxes, or is there something more that I should be aware
BTW, saving about $20/month on electric bill so far, so I figure I'll
break even when I'm 93.
220 lines come in different amperages as you will likely find out when you
try to match up the plug on the tool to the receptacle on the wall
(different amperages use different shaped plugs). You need to make sure that
the amperage required by the tool matches what the line is designed to
supply. If the tool needs more amps than the line was designed for then you
will need to run larger wires as well as replace the breaker and receptacle.
If the tool needs fewer amps than the line was designed for then the wires
should be fine but you may need a different breaker and receptacle.
When I was running a new 220 line for my tablesaw I was told by an
electrician of long experience that I should not use a breaker and wire any
larger than was necessary for the saw. I think his logic was along the lines
of: if the saw motor gets overloaded you WANT the circuit breaker to trip to
protect the motor. I realize this flies in the face of the way most
household circuits work -- most of the loads on a typical 15A 110V household
circuit are well below 15A -- and I cannot fully reconcile that discrepancy
beyond saying that when running a dedicated circuit why not set it up so
that it protects the motor and the rest of the electrical components of the
tool as much as possible. Beyond that, all I can do is tell you what the
electrician told me. If presented with the situation at hand I do not know
if he would suggest installing a smaller breaker.
I may be misremembering his reasoning or he may have been wrong. He worked
as an electrician for a number of decades but that does not mean he is
perfect. What's more likely is that I am misremembering his reasoning.
there are reasons to not oversize wires. they are things like bigger
wire costs more and is harder to install. they are not things like
bigger wire interferes with the ability of the circuit breaker to do
The reason my electrician gave for not oversizing the circuit was not the
extra cost or difficulty of pulling the wires. But as I have now said over
and over, all I am telling you is what an electrician of long experience
told me. If you don't like what he said, so be it.
There are plenty of electricians who have no business reason to understand all
the intricacies of article 430.
A lot of the finer points are really for designers and engineers, not
installers. That is one reason why the manufacturer's instructions are usually
the best guide.
In the given situation, making a sub panel out of the range circuit may be the
best choice, even if it only can serve 240v loads. (assuming no neutral is
available and he wants to use the existing wire)
Then he could install the NEMA 6-20 recomended by most machine manufacturers on
On 14 Oct 2004 04:07:16 GMT, email@example.com (Greg) wrote:
I had the same dilemma.
As a new woodworker and needing a garage wired for power tools, I read
the manuals and realized I had two choices. I could try to figure out
where I wanted the nightmare of 10A/120, 15A/120, 20A/120, 15A/240,
and 20A/240 or just go with 20A/110 and 20A/240 and let the breaker
protect the wiring and box.
Supposedly, setting the breaker size to the motor, protects the motor
from power surges. Being that the cost to run outlets galore in a
mobile shop for ever possible combination would break the bank, I took
my chances and went with all circuits at 20A in both voltages.
On Wed, 13 Oct 2004 13:48:57 -0400, loutent wrote:
Sounds like you hit a gold mine! Electric WH heaters generally require a
30AMP circuit and electric ranges are usually on a 50AMP circuit. If this
is the case, you could put a subpanel on the end of the range circuit and
expand from there for all your WW needs.
"It has been a source of great pain to me to have met with so many among
[my] opponents who had not the liberality to distinguish between
I had a similar situation, an unused 50A 220V circuit just sitting in
my basement. Currently I am running a 2hp tablesaw from this circuit
(with the appropriate recepticle/plug for 50A). I want to add a 220V
powered dust collector now.
So is there a difference between installing a subpanel and then
reinstalling 2 220V recepticles of lesser amperage and just wiring
another 220V recepticle from the 220V recepticle that is currently
running the tablesaw? The combined amperage would still be far less
than 50 in either case. Is there some reason that each 220V
recepticle should be on an individual circuit?
Hope this is not too dumb of a question.
The real issue is protecting the smallest conductor in the circuit from a
short. The overload protection in your motor equipment should protect the
That all said, a sub panel with the proper breakers is the safest way to go and
the only legal way if you are installing 15-20a receptacles.
With 50a at your disposal you can install a pretty big sub panel as long as you
know you will have load diversity (NEC speak for "not to much going at once")
If you don't have a neutral and a ground this can only be a 240v panel, no
Typically a water heater is run on a 30A circuit (10 gauge wire) and a
range on either a 50A (old) or 60A (new) circuit. The 50A was often
wired with 6 gauge aluminum and may not have a neutral; the 60A with 6
You could certainly run a 3HP motor on either of those. If you insist
on using the installed receptacles, you'll need to build a converter
cable, but it's not a great feat to put in the receptacle of your
choice with a little effort.
Really, everything is there; it's just a matter of safely mating the
machine to the service.
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
Congrats on the conversion to gas, I think you'll like it. No reason
not to use these boxes. You might want to install 220v outlets in
convenient locations (and then some more!) in your shop. A 220v DC is
Thanks everyone for the great info - seems like I'm ok to go for a new
TS & DC - now just to decide on them!
BTW-we never run out of hot water with our gas heater - sometimes we
did with the electric. Cooking with gas is WAY better (another hobby!)
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