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Old 05-04-2011, 03:27 AM   #16
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Originally Posted by thesmackdown View Post
Nope, both welders are single phase. The breakers look to be standard 30A breakers. Is that not going to work?
Wait a second. Do you have a 30A 2-pole breaker (takes up two spaces and has the handles tied together), or do you have two separate 30A single pole breakers? If the former, then you're fine. If the latter, then you need to change it to a double pole breaker.

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Old 05-04-2011, 09:46 AM   #17
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Originally Posted by mpoulton View Post
Wait a second. Do you have a 30A 2-pole breaker (takes up two spaces and has the handles tied together), or do you have two separate 30A single pole breakers? If the former, then you're fine. If the latter, then you need to change it to a double pole breaker.
Hmmm...I assumes they were two seperate circuits but I wonder if both breakers are used and the same outlet. I will pull the outlets today and clear this whole mess up!
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Old 05-04-2011, 09:54 AM   #18
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I think the OP is a little confused about 240 volt circuits.
A 240 volt circuit requires a connection to each leg , don't use the term phase when describing the connects, and hence, the current circuit is a 240 volt circuit. Residential wiring is either single phase 240 or single phase 120.
The welder that this circuit will support requires 240 volts and a 6-50 connection. There is no neutral (white wire) required.
To wire this circuit will require a two pole breaker with a red and black wire connected to the breaker and a ground connected to the ground bus.
The first posting says the current circuit is wired with 10-3 so I'm assuming there is a neutral to the current plug. His new welder doesn't require a neutral so if he tries to use the current wiring, he will have to cap the neutral in the first box.
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Old 05-04-2011, 10:00 AM   #19
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Originally Posted by a7ecorsair View Post
I think the OP is a little confused about 240 volt circuits.
A 240 volt circuit requires a connection to each leg , don't use the term phase when describing the connects, and hence, the current circuit is a 240 volt circuit. Residential wiring is either single phase 240 or single phase 120.
The welder that this circuit will support requires 240 volts and a 6-50 connection. There is no neutral (white wire) required.
To wire this circuit will require a two pole breaker with a red and black wire connected to the breaker and a ground connected to the ground bus.
The first posting says the current circuit is wired with 10-3 so I'm assuming there is a neutral to the current plug. His new welder doesn't require a neutral so if he tries to use the current wiring, he will have to cap the neutral in the first box.
Yes I was confused - thanks for clearing it up!
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Old 05-04-2011, 10:38 AM   #20
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Quote:
Originally Posted by a7ecorsair View Post
I think the OP is a little confused about 240 volt circuits.
A 240 volt circuit requires a connection to each leg , don't use the term phase when describing the connects, and hence, the current circuit is a 240 volt circuit. Residential wiring is either single phase 240 or single phase 120.
The welder that this circuit will support requires 240 volts and a 6-50 connection. There is no neutral (white wire) required.
To wire this circuit will require a two pole breaker with a red and black wire connected to the breaker and a ground connected to the ground bus.
The first posting says the current circuit is wired with 10-3 so I'm assuming there is a neutral to the current plug. His new welder doesn't require a neutral so if he tries to use the current wiring, he will have to cap the neutral in the first box.

Maybe my fault on phase, I think of them as phases but I'm inclined to think that it would be better for me to not explain myself and just go with the terminology

Alright I can't entirely help myself as an engineer, I swear if I stopped there I'd have trouble focussing the rest of the day. Apologies in advance.

Correct me if I'm wrong, but AC electricity is a sine wave that goes positive then to zero then to negative then back to zero and repeats, each cycle from zero-positive-zero-negative-zero is a cycle and in the US the frequency of these cycles is 60 Hertz meaning 60 cycles per second. So what is happennng is that the POCO pushes 120 volts on one hot leg, the neutral is a return path that is otherwise a constant zero, so the potential is the difference between the 2 wires and thus 120 volts.

Two hot conductors go to a typical residential service, these each are at 120 volts, but they are 180 degrees out of phase so that when one hot is at it's peak positive the other is at its peak negative. So for 240 appliances they use both hots and the potential difference between the two is 120 + 120, so it's equivalent to single phase 240 volts.

In industrial applications something different is done where the term phase is more correctly used because motors with multiple phases are using the different phases so different segments of the windings are charged differently at any given instant... 3 phase would have 3 hot wires each out of phase by 120 degrees.

For real fun, anyone else ever wire a Lionel train layout with multiple transformers and different power blocks on the tracks? Lionel trains use an 0-20 volt AC supply to the track which is different than many other gage model trains that usually use DC power. It's interesting because the trains generally don't care about polarity, but the plugs for the transformers don't have a larger prong for the hot than the neutral. What this means is that if you have 2 transformers on isolated adjacent track sections, when your train crosses the insulator it's shorting across your house wiring's neutral to hot if both transformers have opposite polarity. One of the transformer's plugs needs to be turned around.

Sorry for the sidetracking, and thanks for bearing with me so I can have a clear head!
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Old 05-04-2011, 12:29 PM   #21
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This is just to respond to WillK and is not directly part of this thread.
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So for 240 appliances they use both hots and the potential difference between the two is 120 + 120, so it's equivalent to single phase 240 volts.
Yes, in a sense, it is 120 VAC 2 phase power. The problem is that nothing uses 2 phase 120V AC. Show me a single device that requires two 120 volt connections that are 180 deg out of phase and requires a common.
If you eliminate the common you loose the difference in phase angle between the two hot leads.

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Old 05-04-2011, 02:35 PM   #22
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remember that a neutral is not a zero. It is a center tap. The only reason we talk about it being a zero reference point is because we ground it. If allowed to float it would have 120v, and it still does in theory, but be cause it is bonded to earth, there is no difference in voltage between and grounded metal object, therefore we say its a zero volts.
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Old 05-04-2011, 05:12 PM   #23
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Originally Posted by a7ecorsair View Post
This is just to respond to WillK and is not directly part of this thread.
Yes, in a sense, it is 120 VAC 2 phase power. The problem is that nothing uses 2 phase 120V AC. Show me a single device that requires two 120 volt connections that are 180 deg out of phase and requires a common.
If you eliminate the common you loose the difference in phase angle between the two hot leads.
Most ranges and dryers do. They have both 240V and 120V loads internally. This is a 120/240V connection - two hots, neutral, and ground. This is NOT the same thing as two phase power. Two phase does exist and was used in some very early systems. It consists of either two or four hots with 90-degree phase angles.

http://en.wikipedia.org/wiki/Two-phase_electric_power

The U.S. residential power system is "split phase" - a single phase source with a center tap. The real test is this: can you derive the power from a single phase connection using a transformer, or not? If you can, then it is single phase. If not, then it's polyphase. 120/240V split phase power is derived from a transformer with a single-phase primary and a center-tapped secondary. Thus, it's single phase.
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Old 05-04-2011, 06:40 PM   #24
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Actually, I didn't expect to come out of this any less confused about it. To my pleasant surprise, I think it actually makes more sense to me now. Thanks!
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Old 05-04-2011, 07:30 PM   #25
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I want to change the plugs to 50 amp plugs and also change the breakers to 50 amp - I read somewhere that as long as I marked the outlets "For Welder Use Only" it was acceptable by code. Is this ok?
You can use a breaker that is larger than the normal breaker for a specific wire size for a welder that has a limited duty cycle. The outlet does have to be labeled "For Welder Only". See NEC 630 for additional details.

You should calculate the current at max output AND the duty cycle at that output in order to decide if your wire is large enough to run the welder at full output. See NEC 630.11 (A). Due to the difference in the design of welders, it would be best to ask the manufacturer for the correct breaker size. As stated above the breaker size can be larger than the normal breaker for a specific size wire, but you must see NEC section 630 for the calculations for duty cycle and breaker size limitations. AND THE OUTLET CAN ONLY BE USED FOR THE WELDER IT WAS DESIGNED FOR.

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Old 05-05-2011, 09:59 AM   #26
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Quote:
Originally Posted by mpoulton View Post
Most ranges and dryers do. They have both 240V and 120V loads internally. This is a 120/240V connection - two hots, neutral, and ground. This is NOT the same thing as two phase power. Two phase does exist and was used in some very early systems. It consists of either two or four hots with 90-degree phase angles.

http://en.wikipedia.org/wiki/Two-phase_electric_power

The U.S. residential power system is "split phase" - a single phase source with a center tap. The real test is this: can you derive the power from a single phase connection using a transformer, or not? If you can, then it is single phase. If not, then it's polyphase. 120/240V split phase power is derived from a transformer with a single-phase primary and a center-tapped secondary. Thus, it's single phase.
A dryer or electric range is not a single device. These units have motors, elements, clocks, etc. none of which individually require the two hots and the neutral to operate. In theory it can be looked at as 120 two phase but in application we only use it single phase.

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