Electrical help: 20 amp vs 30 amp

[Leon]

Yeah I agree and did not make the install modification permanent in the event that I do ever move or have an inspection.

[toller]

Whats the last water heater you saw connected to a 30a 120v line? It has to be 240v; he just thought the 2nd hot was a neutral. (However, it does suggest he shouldn't be doing any of this himself.)

[LRod]

On Fri, 7 Jan 2005 16:01:46 -0800, "Slowhand" >> describing your situation. You actually have a copper, 10 gauge (3

All that is true, and I'm sure as an old sparky you remember when a

240V circuit was just the two hots; the ground wire is a relatively new (40 or 50 years?) requirement.

In any event, I'm also sure you will agree that in a 240V circuit that will supply only a motor or a heater, there won't be any neutral because there is no neutral in a 240V circuit.

Now I am fully aware that dryer circuits are now required to be four wire, that one may no longer use the ground for the neutral path needed for the 120V parts of a dryer circuit which the NEC permitted as a special use. But that's an exception. I think that may also be an exception in range circuits, but for water heaters, table saws, planers, jointers, dust collectors, ACs, etc., all that's required is three (and electrically, all that's needed is two), and neutral isn't one of them.

Your example of the 120V receptacle is simply a variation of a multi wire circuit which looks just like a 240V circuit everywhere along the circuit except at the loads. But a neutral IS needed in a multiwire circuit. It isn't in a 240V circuit excepting the dryer/range applications.

- - LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

[Leon]

So do you still maintain, There is no neutral in a 240V circuit (North America)?

[Leon]

Actually I saw one 5 years ago on a small 10 gallon tank.

[Duane Bozarth]

Of course, the other outlet needs to be wired to the same ampacity of the breaker to protect that wiring as well as the original...otherwise, one would have an unsafe condition in that section of the circuit. I was agreeing w/ the load of the saw as not being an excessive load w/ the dryer for short periods, especially since one has to be there to operate it...

[Leon]

Yes, and it is. I think we are seeing eye to eye here Duane... Thank you.

[loutent]

Thanks for the help everyone.

Since I already have the double 30 amp breaker and the 10 g wire with hot,hot,ground, I am going to use it as soon as I get to the Borg to get the proper outlet and plug.

Nothing like an electrical question to stimulate discussion - especially in a woodworking group!

Lou

[LRod]

What I'm trying to say (and apparently unsuccesfully) is that

*electrically* there is no neutral or need for a neutral in a 240V circuit in North America. All that's needed for a 240V load to work is the two hots. Period.

The ground is a safety requirement that was added to the NEC several years ago. It isn't electrically required for a strictly 240V load to work (North America). In some other locations with solely 240V service, it may be that they have a 240V and a neutral. Probably not, but I don't know. But in North America, that's not how 240V works.

The "neutral" is a safety requirement that was added to the NEC recently to alleviate the anomalous situation (elsewhere prohibited) in dryers and ranges where the ground had previously been permitted to perform the duties of a neutral as in a multi wire (2 x 120V/shared neutral) circuit. That is, there were some 120V things going on in the machine that is fed by a 240V circuit.

So, in the strictest sense of the words, yes I suppose you could say that there is a neutral in [certain] 240V circuits (North America). But it's not electrically necessary in order to run most 240V loads.

- - LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

[Dave]

A 20 amp two pole breaker is worth about 15 bucks. Although I agree in principle that the system should run fine on the 30 amp circuit, I wonder whether your warranty would still hold if something happened. The internal wiring on their machine will not be of adequate gauge for 30 amps of current. In the owner's manual they will say that they want a 20 amp circuit, not a 30 amp circuit. Sure, Grizz should have designed the system to internally trip with excess current. But if you blow the motor and Grizz find out that 30 amps were running through the wires, they might find cause to blame you for some of that problem. Changing the breaker is a one-minute job. Cheap insurance.

Dave

[Doug Miller]

Please turn off HTML before you post again. Thank you.

No reason at all to think that. He has a 220V table saw that needs a (minimum) 20A circuit, and he's asking if it's OK to hook it up to a 30A 220V breaker. No mention of 110 anywhere.

No he doesn't. He already has a 220 breaker.

Wrong. He needs a three-wire cable (hot, hot, and ground). The table saw, being a 220V device, doesn't need the neutral.

Wrong again. The gauge of the wire is determined principally by the rating of the breaker protecting it. For the 30A breaker that the OP says he has, the

*minimum* wire size is 10ga copper (or 8ga aluminum) regardless of the distance from the breaker to the equipment. In residential applications such as the OP's, it is *highly* unlikely that the load can be far enough away from the breaker as to require a heavier gauge of circuit conductor.

Well, at least *that* is good advice.

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter by sending email to autoresponder at filterinfo-at-milmac-dot-com You must use your REAL email address to get a response.

[Phisherman]

No. No.

[Doug Miller]

Not if it used to power a water heater like he said. He's probably looking at black-white-bare and thinking he's seeing hot-neutral-ground, when in fact it's really hot-hot-ground on a 220V circuit.

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter by sending email to autoresponder at filterinfo-at-milmac-dot-com You must use your REAL email address to get a response.

[CW]

If you blow the motor and there was 30 amps running through the wires, it would indicate a defective motor.

[Roy Smith]

Which is why you're supposed to wrap some red tape around the white wire in the boxes at both ends, to indicate that it's a hot conductor.

[Slowhand]

Hey, I'm not old. (38). ;-) As long as I've been sparkin (wired my first house in 1992), it's been two hots and a ground.

I have a buddy who's a electrical contractor who pretty much taught me enough to be dangerous. I'm still not sure why electricity works the way it does. I just do what I've been taught. SH

[Leon]

I am not disagreeing with that statement, "There is no need for a Neutral in a 240V circuit in N America." But some what recently there is that 4th wire being used. My house does not have the 4th but the newer ones do. Previousely you indicated that there was NO Neutral in a 240 circuit. I was just trying to clarifiy what the 4th wire was exactly.

[LRod]

It's a neutral. That doesn't contradict my original statement given in my previous post. It performs a function that most closely resembles a multiwire circuit.

The best way to think of all of this is to not think of "neutral" and "240V" in the same breath (I think I may have mixed a metaphor there).

"Neutral" only has meaning at 120V. If there is a neutral wire in a

240V circuit it's because there is some 120V load in the appliance that's being powered. NEC no longer permits the ground wire to perform that function (and rightly so) in new construction. That's why you see 4 wire "240V" circuits.

- - LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

[LRod]

Please. You should refrain from offering electrical advice. I'm sorry if that hurts your feelings, but your reply does not reflect the slightest bit of reality with regard to electrical theory, engineering, or legal requirements.

- - LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

[Leon]

Ok, I think I am see what you are saying now....Thanks