On the subject of running 3 conductors + ground. What might you want to
run on from there? Someday you may want some 110 at that location.
Planning to go back to the panel or just tap into what you've got. I
don't think many have kicked themselves because they ran too large or
too many conductors the first time. No law against installing a fused
switch or breaker at the location if the device needs more protection.
That is simply not true. You only need to provide conductors to serve the load
plus a grounding path. If you have a neutral load on a 240v circuit, you need 4
wires or a raceway system that provides the grounding path and 3 wires.
Otherwise 3 are fine. The only issue is reidentifying the white wire to another
color in a 2 wire plus ground cable.
White green and grey are reserved, any other color is OK for the ungrounded
On 24 Aug 2004 16:41:47 GMT, email@example.com (Greg) wrote:
Greg -- Thanks for that. Based on your other posts in this thread, I'll
accept that. *Maybe* it is a local code where I live. Or, maybe I just am
wrong about it, even locally. When I had a new circuit put in 20 years ago
for a hand-me-down elec dryer that only needed 2+ground, the licensed
electrician (whom I trusted) said I neeed 3 + ground. Maybe (or maybe not)
he was just looking out for me for when I would get a new dyrer.
Or, maybe I am thinking about rules for home appliances that require they
be configured for 2 hot and a neutral, plus ground...
The timer(s) and any lights/buzzers etc in your dryer, even one that old,
probably required the neutral (3 + ground) for 120v operation. For most wREC
purposes when adding 220 circuits for a saw, etc, 2+ground should meet any
code in the country (US) as long as the hot wires are properly marked on
both ends and correctly sized for the load.
The dryer had been built in the mid 50's. Even when I retired it in the
late 80s it still worked. It had a motor, a belt, and a heating element.
Belt and element got replaced every few years. The timer was spring loaded
and when it stopped the dryer it rang a bell. It was like one of those
basic cheap white plastic counter-top timers, with some contacts added. It
was gone from the alley an hour after I put it out there for what was
supposed to be a city pick up a few days later. As long as belts and
heating elements were available, that thing would probably still be
Swingman is on target. The cases of ranges and dryers were allowed to share the
current carrying grounded leg of the power cord from WWII until 1996. It was a
way to save copper for the war effort.
They finally decided the war was over and required that these 120v loads
required a separate wire. That may be where the idea that all 240v circuits
require a neutral come from. It is only true if there is a 120v load along with
the 240v load.
They assume most ranges and dryers will use 120v lights, clocks and motors so
that is the standard but there are still a lot of "cook tops" with pure 240v
loads and they are still legal on a 2 wire+ground wiring method.
The same will be true if you have a piece of pure 240v shop equipment.
The only reason I can think of to pull the neutral is if you think you may want
a local work light at the machine. I have seen this question asked here a few
times. The cost is minimal so it is your choice.
Agreed. I put a 240 v 30 amp plug into my garage, and I researched the
topic of '3' vs '2'. The Elecrical code in Alberta, Canada, requires
3+ground for dryers, otherwise '2' is fine and meets code. Since my garage
is no place for a dryer, the 2+ground is fine. My electrical inspector
agreed. However for a dryer, remember the extra neutral, since even a
functional older machine will be replaced when people move. An outdated
dryer plug may be hard to upgrade after the drywall is in, so the code
requires the extra wire for dryers. I don't know of many shop tools that
require the 120/240 option. For my shop, it would be easy to pull extra wire
through the conduit, and the run is only 7 feet. If thr run were more
complex, I might have brought in the three-wire cable, just to give more
You didn't say what the current ratings were for each of them.
If you do this you need to realize that anything that you hook to a 30 amp
breaker needs to be capable of handling 30 amps. In other words all of the
wiring, outlets, switches, etc. to your saw and your dust collector needs to
be rated at 30 amps as well. That means #10 wire minimum. The reason for
this is that the wiring needs to be able to handle a short circuit anywhere
in the circuit up to the rating of the circuit breaker that's feeding it. If
you use smaller wire and hardware a short circuit will result in a fire and
a wood shop is one of the last places that you want this to happen.
I strongly recommend that you put each one on their own breaker which is
sized correctly for their full load ratings and wiring. If you bought a sub
panel without adequate space you should consider replacing it with a bigger
You again are confusing overload current and short circuit current. A 500'
piece of #14/2 will still operate a 40a breaker with a bolted fault.
Shorts are not the problem.
If that was true you couldn't plug an 18ga lamp cord into a 15/20a circuit.
I agree that 2 separate circuits is the best way, but you are wrong to say
everything must be 30a. It only has to be 30a up to the receptacle. After
that, 20a is okay, assuming the machines are less than 20a. (In fact,
rereading the code, I am not even sure if the receptacle has to be 30a,
though it seems prudent.)
I am the original person who posted this. I have the Grizzly G0444Z 220
volt table saw and the Grizzly 220 volt G1029Z dust collector. Both are
rated at 12 amps each. What I would like to do is have them both on the
same circuit. I was confused as to using a 30 amp brkr with 10/3 wire. I
thought 12/3 with a 20 amp brkr would handle it if I turned each on
separately and let it get up to speed before turning on the other. It
appears that the best solution would be to wire them separately on their own
circuit. It is somewhat confusing to me.
Thanks again for your help.
Congrats on your choice of equipment. I too wonder, why couldn't you use
the 30 amp circuit as a branch circuit, run it into a subpanel with two 20
amp breakers, and the run your 2 220v 20amp outlets from there.
2X12amps$amps, well within the 30amp breaker's operating range. Just
don't start 'em both at the same time.
Your scheme will work fine and be perfectly legal (with the normal
disclaimers about it being installed correctly and all that...)
However there are two reasons to consider having two 20a circuits.
1) Grizzly is apparently a bit careless in their motor design and is
concerned that it can suffer damaging overloads under some circumstances
(perhaps a stalled motor?). They believe the damage is less likely on a 20a
breaker than on a 30a breaker. This should not be an issue, but presumably
they have had problems.
2) It is preferable not to have 20a components (cordsets, outlets, plugs) on
a 30a circuit. It is legal, and is comparable to having a 10a lampcord
plugged into a 20a circuit. It is done all the time, but is undesirable.
I think that is as clear as it gets. Use two circuits if you can; one if
you can't. Use 4wire if you want, but since you have other circuits
available for 120v, there is little point to it.
If you look at the Article 430 rules for 2 motors on one circuit and they are
12aFLA you come up with an ampacity of 27a so 30 is the "right" solution
125% of the biggest added to the other one.
Assuming he will have the DC come on with the saw I don't even see Grizzly's
concern being an issue. There will only be 6a "left over" with both on a 30 and
one on a 20 would have 8a left over.
Since the saw will be started unloaded and a DC doesn't really draw much power
until it really starts moving air I doubt inrush will be that big a problem.
That's utter nonsense. There are loads of 1 and 2 A devices that are
INTENDED to be plugged into such circuits, such as answering machines,
clock radios, electric toothbrushes, coffee grinders, night lights,
speakers for your computer, caller ID boxes, battery chargers, and
myriad other small appliances and devices. There is no necessity nor
provision for anything other than standard 15 or 20 A circuits for
To repeat, so perhaps you will understand: the circuit breaker is to
protect the wire, not the load or device. There are no 1, 2, 5, or
other small circuit breakers to do as you're alluding to in your
If you believe there is something improper about plugging a 5 A device
into a 30 A circuit, you should recuse yourself from dispensing any
further opinions in electrical threads.
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
From the text of your post to which I had responded:
"Preferable not to have" and "undesirable," your words, are virtually
synonomous with "improper" in the context of your message. So, yes,
that sounds to me like you think it is improper.
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
Is it English or reason that you have problems with?
1) What does "synonomous" mean? There is a word "synonymous" in English; is
that what you mean? Probably not, since it would be an incorrect usage.
2) If there are more than one way to do something, one way will probably be
"preferable" or "desirable". That certainly does not make the other ways
"improper"; now does it?
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