220 wiring question for saw & dust collector

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.

Reply to
toller
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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.
Reply to
Greg

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 those devices.

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 statement.

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.

- - LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

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Reply to
LRod

"Your scheme will work fine and be perfectly legal". That sounds to you like I think it is improper?

Reply to
toller

Lew - your point is well taken and it has never been disputed in any of the recent threads on this topic. However - the discussions have not been about what NEC is intending to do. The electricians (or seemingly so) in the group keep referencing NEC and the fact that NEC intends to protect the wire not the device. The points that have been made about protecting the motors represent the *owner's* concerns. Not everything in the world of electricity is covered by NEC's interest. Owners have other interests besides their house wire. To date, I've not heard any of the electricians argue that the statements about properly sizing a circuit to the load is improper. The owner is concerned for his saw motor. It appears from the Griz literature that he should be. Maybe there is an error in the Griz literature, but to repeat that NEC only cares about wire insulation really does nothing to further understandings in these threads.

Reply to
Mike Marlow

I addressed that and pointed out 2 12a motors on one 30a circuit will actually provide MORE protection than one on a 20a. The reality is the NEC does talk about protecting the motor. That is the overLOAD protection that should be integral to the equipment. If your overloaded motor is tripping the wall breaker you either have the circuit overcurrent device sized TOO SMALL or the overload protection is not working. The overload should trip first if things are sized "properly".

Reply to
Greg

I am confused after reading all the replies. So folks what should I do for my Grizzly 12 amp saw & 12 amp DC, go with (2)

220 separate 20 amp breakers 1 for each device using 12/3 for each, or go with 1 220 30 amp breaker using 10/3 cable and putting them both on the same circuit? Thanks again.

Reply to
Jim

Your choice, either way will do fine and both are legal. A am still not sure why you want 12/3 or 10/3. You can use 2 wire with ground. Just reidentify the white with some black tape.

Reply to
Greg

I msut have missed the earlier messages but I would use two 20 amp circuits. Two 12 amp motors starting at the same time would probably trip a 30 amp breaker. Thats assuming the 12 amps is running amps as oppossed to starting amps. See NEC 430 for code requirements for motors.

MikeM

Reply to
Mike M

Read my LIPS:

Overload devices provide that function.

Reply to
Lew Hodgett

Use a 2P-30A c'bkr and #10 AWG for each device.

Eliminates any inrush problems and keeps the voltage drop down.

Reply to
Lew Hodgett

Aha - my apologies Greg - I missed that when you first posted it. I've been following the threads on this pretty closely but then again sometimes earthlink (sometimes...???) drops posts along the way.

Reply to
Mike Marlow

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.

- - LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

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Reply to
LRod

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?
Reply to
toller

[snip]

My understanding is that code requires 3 + ground even if the device does not. Others here seem more qualified for a definitive answer on this.

Reply to
igor

"toller"

This is why I wired my entire house with the same 4 ga wire coming in from the utility pole. Using similar logic, one thing led to another. Works great now, but I have yet to get to changing my lamp cords to 4 ga. I'll get there, though. Safest house on the block.

- Nate

Reply to
Nate B

Geez, how many angels can dance on the head of a pin? Do you realize that you're coming across as something of a wanker with this kind of hair splitting do you not? Something that is improper is something that one shouldn't do. Something that is undesirable is something that one shouldn't do. Regardless of the exact terminology you use, it appears that you believe that plugging one's desk lamp, answering machine, or other small, low powered device into a 20 amp socket is something that one shouldn't do. If you believe otherwise then you should clarify this rather than arguing that your words mean something other than most people will percieve them to mean.

Reply to
J. Clarke

undesirable.

Are you a moron, or do you just play on the internet? If you have no circuit breakers in your house, then yes, you would have to wire the whole house in with #4. You have a breaker box that enables you to use smaller wires, since they are protected by breakers. But you probably knew this already and were just being childish.

Reply to
toller

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 conductors.

Reply to
Greg

If the issue is room, here is an idea you might consider: For the "standard" circuits (such as lights, hand tools, etc.), if your box is capable/proper for such things, consider using a couple of double-circuit breakers -- that is, 2 20 amp breakers in the space of a normal-sixed breaker. (RIght now, I cannot recall the name for these things.) That can help you with the space concern. I don't know why one cannot use as many as will actually fit in a box, but there is a limit as to how many circuits, not just breakers, one is supposed to have in a box. Maybe it has something to do with the amount of wire you can have in a box -- code talks about this.

BTW, if you do go this route and use two sets of double breakers, I suggest (though I cannot tell you that the theory and/or code supports this) that you put them in the box so that they are on opposite sides of the 220 -- for example, put one in right above the other (at least that is how it works in Square D boxes).

[Warning: Digression.] HTH. Either way, this is an interesting thread you started. One of the things I love about this NG is that there is some real expertise around here on all sorts of subjects. I would not be surprised (notwithstanding all of the refs to SWMBO) that if someone asked what's a good snack to eat while working in the shop, there would be recipes flying about. Or, if someone asked whether Iran's nuclear program is a threat, a group of woodworker/physicists would have at it. Then there would be someone telling a story about this great cake he makes by putting the pan on a steam pipe down at the nuclear plant. (Or is that "nucular", Mr. President?) Myself, I always try to help here on software and other computer stuff.

Along this same train of thought, anyone remember a long-ago Sat Night Live routine about the ultimate hardware store? It's just a series of people coming in asking for stuff. First the basics, such as nails. "Is that finishing nails or common?" Then less and less typical stuff - but every time the guy had it in stock. Maybe it was on the third shelf in the back behind the new flame throwers, but they had it. Then, someone comes in and asks for a chocolate violin. "Is that light chocolate or dark chocolate?" If you didn't hang out a lot in real hardware stores as a kid, that skit must have made no sense whatsoever. But for me, it was a great moment. -- Igor

Reply to
igor

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