Any 240v woodworking equipment need a neutral?

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Doug Miller wrote:

No they're not! Only in TN-C systems. There are several other ways to arrange things, and the others are just as popular.
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Toller wrote:

Same as anywhere else. It's not the voltage, it's the number of phases.
If you use single phase (and "domestic" always does) then you need a neutral. This isn't because you "need" it as a consumer, just because it's the convenient way to tap a supply transformer for a single phase output.
If you use multi-phase (i.e. three phase), then you don't need and don't use a neutral. There's just little point to it.
If you choose too low a consumption voltage in designing a system-wide standard (i.e. 110V) then it becomes necessary to also provide a high "high power domestic" feed of twice this, hacked together by using opposing phases of a two phase supply. You don't even need neutral here either. It can be useful though for loads that are easily split in two (i.e. heating elements) and is naturally provided if the "double voltage" system is already providing a neutral connection to the supply transformer's centre tap.
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Explain that a little further, if you would please. Here in the US, 3-phase power *does* have a neutral. The voltage is (typically) 208V phase-to-phase, and 120V phase-to-neutral.
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Doug Miller (alphageek at milmac dot com)
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Doug Miller wrote:

That's not a 3-phase system, it's a combination of 3-phase and single phase. Only the single phase component needs the neutral to supply power, but because it's also bonded to the local earth it's supplied as well. It's sometimes used for the provision of separate heating elements on each phase, also with electrode boilers so as to limit potential difference between the water and earth.
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How do you figure that? The three phases are tapped off a rotary generator at the power plant, 120 degrees apart, with the neutral as earth ground. Any one of the three phases can be used separately, of course, but there's no "combination" present.

Might be different in the UK, but there isn't a separate "single phase component" in North American three-phase power distribution -- 120V devices are powered by using any one of the three phases, and a neutral which is bonded to earth ground.
208V devices use any two of the three phase conductors, or all three, and no neutral.
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Doug Miller wrote:

That's what I'm telling you. Both systems are wired through similar cabling, but the neutral only gets used when it's supplying a simgle phase device.
And the "208V 2 out of 3 phases" unbalanced systems are an abomination unto the hallowed memory of Tesla.
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OK, we're on the same page now. You confused me with your reference to it as a "combination" of 3-phase and single-phase -- that's not the way I see it.
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Doug Miller (alphageek at milmac dot com)
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Doug Miller wrote:

That is correct. That configuration is visible at the transmission lines. The very basic reason for that, is the attainable rpm of either 2 or 4 pole generators. 4 Pole being the choice of large diameter (1800 RPM turbines, lest the turbine blade-tips break the soundbarrier.)
r
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Robatoy wrote:

What does any of that have to do with the use of 3 phase transmission, or 3 phase transformers?
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Everything. Try working out the rpm at 60 Hz and pole structure with 4 or 5 windings.
Is any of it relevant to the topic at hand? Nope.
r
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Or with running a 240V circuit in your basement?
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Anything that has just a 240V motor does not need a neutral. But accessories such as lights do. As electronic controls on tools will become more common, I would expect more of them to need neutrals.
Just because you run 4-wire cable does not mean you have to install the much more expensive 4-wire outlets; those can be retrofitted when needed.
Side remark: What everyone calls neutral (on a 120/240V circuit), the electrical code calls the grounded conductor. What everyone calls ground, the electrical code calls the grounding conductur. The difference is small, but crucial.

If you don't want to do it twice, then run 10/3 (with ground!) now. Even better, in a few places where you might want to add high-powered tools (such as a 5HP table saw), run 8-3 instead; the cost is only a little higher. Ideally, you should run conduit (3/4" EMT is better, as it is easier to pull #10 and #8 wires through it); but installing conduit in an existing stud wall is a big pain, and flexible conduit is really hard to pull through. While you are at it, terminate all 240V cables in extra-deep metal 2-gang boxes (not plastic), with mud rings. Then you can later replace the single-gang mud ring with a 2-gang mud ring, and install larger outlets: trying to squeeze a 50A 4-wire 240V outlet into a single-gang box is either impossible or very hard, and certainly violates code.

If you mean by this that you can use 10/2 with ground wire, and then at the device end use the ground as both a neutral and a ground, you are absolutely wrong. Yes, they may be connected at the breaker box, but by no means on all breaker boxes (read the electrical code, in many cases they have to be isolated from each other). Deliberately running current through the safety grounding wire is extremely dangerous, bordering on suicidal. Extremely bad advice.
While we are at it: I would recommend GFCIs for everything in a shop, in particular if the shop has a concrete floor, is in a basement, or has any risk of getting wet. 2-pole 220V GFCI breakers for the electrical panel are inexpensive and easy to find.
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Don't skimp. Do it "Right" the first time. Use 10/3 with ground and be safe; safer; ready for change, not sorry.
Also, the circuit can be used to pull a 110/120 outlet as well.
Do it to "code" and you will not be sorry.
I know the cost of wire is nuts nowadays, but the old rule "do it right the first time" has proven itself may times over to be the best advice.

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If he were to do it "right" the first time, he'd use 10/2 w/g.

If you were to wire a separate 110v outlet from this (instead of using a 4-pole receptacle), you'd be in violation of code, since the breakers are handle-tied (which would prevent one from being able to disconnect the 110v circuit without also disconnecting the 220v circuit).

While this is generally true; doing to the specific requirements of your jurisdiction is better.
scott
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wrote:

Sorry, he's right about that, and you're mistaken. There's nothing in the Code that prohibits that.
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Doug Miller (alphageek at milmac dot com)
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Please cite the code that calls for 10/3. Code is quite happy with 10/2. This is the second time you've referenced "code". Do you know what the code says?

the
And right would be 10/2.
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While one may wire a circuit for a specific tool, the circuit doesn't know hat. Not might others who subsequently own that circuit (as when they purchase the home).
Circuits installed in homes are, therefore, just 110/120VAC or 220/240VAC circuits terminated with breakers and receptacles that would appear to indicate the design amperage but in no way indicate which "tool" the installer initially had in mind when adding the run out to the portion of the home the installer might have used for a workshop or sauna - who knows?
I bought a hoe that saw its share of homebrew re-wiring all of which may well have minimally served the installer at the moment but had seen adapted to serve uses beyond the limits a strict interpretation of the electrical codes I'd come across in dealing with several inspections and inspectors in South Florida over the years.
As I cannot find the NEC on-line (save in offers to sell me a copy for sixty bucks or so), I've been unable to find and cite the advice recalled from various and sundry wiring projects involving City Electrical Inspectors who were able to quote me the relevant code at the time.
So, I may well be advocating over kill in insisting that OP consider running 10/3 out to his shop to support a motor that only demands two hot conductors and an equipment ground to actually operate (indeed, will do so without running the equipment ground others have chimed in to support installing).
Part of my issue, aside from exculpation clauses in insurance policies an the potential liability to a subsequent purchaser under law, was the practical matter of expending the additional cash to cover the cost of the neutral conductor out to the intended outlet in anticipation of the one constant all reasonable wood workers can agree upon - change.
As, if and when I can find the code book, I shall look up a residential 240VAC circuit and report what I find verbatim (since no one else seems to have access to the code to do so not withstanding the ad hominid attacks in response to my prudent suggestions herein.
So for those vociferous folks who would find me so fallible and my advice to go with 10/3 rather tan 10/2) so offensive, ignorant and objectionable as to warrant attacks on my credibility, intelligence and motives, let me agree to disagree an leave it there.
I must admit that the insurance and legal points made were a bit "out there" in the sense that such cases seldom arise unless the loss of life is significant and the pockets of the liable party are obviously deep.
But, in my defense, we were notified that the crack in the pane of the window in our garage would result in the cancellation of our policy if not corrected in two weeks! Good thing they had not inspected my electrical wiring eh?
Before one blithely assumes he is "covered" by his homeowners, perhaps a review of what happened to all those folks in Louisiana an the Gulf Coast after the Hurricane. Disputes over whether rising water or wind-driven water caused the damages with the majority of the insured walking away with little or nothing despite their coverage. Talk about your exculpation clauses!
What if the motor of the intended device would operate upon two twelve's - would that be OK as well?It would be less expensive.
I suspect the OP has long since abandoned reading this thread as I should and will forthwith as my intent was not to antagonize those with as much time on their hands as I but to offer well-intended advice to a fellow carpenter the result of which could not be assailed as unsafe, dangerous, nor imprudent only unnecessary.

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Equipment is typically provided by its manufacturer with a plug that is appropriate to that equipment -- a plug which prevents connection of that equipment to a receptacle that is not suitable.

You'll excuse me, I'm sure, if I smile a little bit here, as your previous posts don't indicate any degree of familiarity at all with the NEC, or indeed with residential wiring practices in general.

Right here: http://nfpa-acs-01.gvpi.net:8080/rrserver/browser?title=/NFPASTD/7005SB
Read to your heart's content, and try to back up the silly claims you've been making.

You didn't just insist that he "consider" it -- you insisted that it was required by Code.

You haven't cited any of those, either.

That won't be necessary -- simply citing the relevant article and section will do, since all of us have the same access to it on-line that you do.
Again, the full 2005 NEC is at http://nfpa-acs-01.gvpi.net:8080/rrserver/browser?title=/NFPASTD/7005SB

You haven't made any "prudent suggestions" -- just uninformed claims about supposed Code requirements that do not in fact exist.

You've ruined your own credibility by making unfounded and erroneous claims about phantom "requirements".
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Doug Miller (alphageek at milmac dot com)
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Great applet. It could benefit from a search engine however!
Thanks


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One other point: Insurance.
If there's a fire, etc. and the investigation uncovers your home-brew cost-saving electrical work, your insurance company can simply deny your claim because you promised them you would never install electrical without a permit, licensed contractor and appropriate inspections.
A missing neutral would be hard to disguise!

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