O/T Electric wireing

To have either 120 or 240 volt NEC code proper circuits, you need to run 4 wires: 2 hots, Neutral (white grounded conductor), Equipment Ground (green/bare grounding conductor)

ALSO in the event you want to set up a sub panel in a garage fed from say the main panel in the house, you need to run the 4 wires PLUS at the sub panel the Neutral Buss and the Ground Buss MUST BE SEPERATE AND ISOLATED unlike at the main service where they are bonded together and also bonded to a grounding electrode (such as a made ground like a driven ground rod).

The safety equipment ground (grounding conductor) is used ONLY to provide a low impedance circuit path for fault current back to the main panel to clear the fault by tripping a breaker. The Neutral (grounded conductor) is used to carry the normal return current to operate the load.

John T Nordhoff, retired EE in Indiana

Nowwwww 3 phase can be either Wye (which is usually earth grounded) or Delta (which is usually floated although I have corner grounded them).

A 3 Phase 4 Wire Wye circuit carries 3 hots, a Neutral, and an equipment ground. At the service entrance the Neutral and Ground busses are bonded, same as in the 1 Phase 3 Wire home system. Typical of voltages are 208 Y 120 or 480 Y 277.

A 3 Phase 3 Wire floating Delta circuit carries 3 hots and an equipment ground (has no Neutral). Typical of voltages are 240 or 480. There can also be a hot or high leg 120/240 volt 3 phase 4 wire Delta configuration in which one transformer has a center Neutral which is earth grounded and off that transformer one gets 120 volt single phase (2 legs) or 240 volt single phase.

Hope this helps yall

John T (retired electrical engineer who designed secondary power distribution systems)

The only way to run a legal, code compliant 220/110 circuit today is with 4 wires. No electrician worth his liabiity insurance will do it any other way.

John T

VADAVE, there are instances where 3-wire 240 volt installations are still appropriate, as long as you don't try to tap 120 volts off of them. Dryers & ranges come to mind, where everything runs on 240 volts, and are wired with two hot legs and a safety ground. An air compressor with a 240 volt motor is another example.

The issue comes in when you try to connect to the center tap, which is actually what is grounded. When two conductor (ungrounded) outlets were commonly used, there was no separate grounding (safety ground) conductor, and the neutral (groundED conductor) and safety ground (groundING conductor) were in fact one and the same. Only two wires (hot & neutral) were run to the individual outlets.

With a three conductor grounded outlet, as currently required, a third wire is provided as a safety ground. This wire is not allowed to carry load current, only fault current, which is why it must be isolated from the neutral except at one point. If it were connected to neutral at any other point, then it would carry part of the load current and would not provide shock protection under certain fault conditions. This is also why the safety ground wire is allowed to be smaller than the current carrying conductors, as it only carries current in a fault condition.

As John pointed out, a four wire installation does not indicate three-phase power, although there are three phase installations that only use 4 wires. These are analogous to the 3 wire single phase installation, i.e., single phase 240 volt is 2 hot wires & safety ground. A delta three phase connection is 3 hot wires and a safety ground. A wye three phase connection is 5 wires, 3 hot plus neutral plus a safety ground. Note that 2 hot wires does not indicate two phases, but indicates only that neither of the wires is a neutral.

Maybe clarify things a little...

Keith

We may just be having trouble communicating also. YOURE ABSOLUTELY RIGHT that your home "service" panel only has 3 wires ran to it from the transformer, being 2 hots and one Neutral often configured as whats called twisted Triplex Cable of the 2 insulated hots wound around the bare center Neutral. Its called 120/240 volt Single Phase 3 Wire "Service". At the service entrance YOURE ABSOLUTELY RIGHT the Neutral Buss and the Equipment Ground Buss in the panel are tied together, and at either the meter base or the panel the Neutral is bonded to earth ground via a driven ground rod or metal water pipe etc.

WHERE YOU MAY NOT BE READING ME AND WHATS CONFUSING is that once you leave that main panel with a 120 volt branch circuit, it has 3 wires being 1 Hot, 1 Neutral, 1 Equipment Ground. If you ran a 240 volt branch circuit, it also has 3 wires, 2 hots and 1 Equipment ground.

HOWEVER if you ran a circuit to a sub panel, YOU MUST RUN 4 WIRES BEING 2 hots, 1 Neutral, 1 Equipment Ground. LIKEWISE, if you run a circuit (like to an overhead buss duct) and you need to obtain BOTH 120 volt and 240 volt taps, YOU AGAIN NEED 4 WIRES. You CAN NOT use the equipment ground as the Neutral even though the device would still function. The Neutral (grounded conductor) carries normal circuit return current while the equipment ground (groundign conductor) is intended to carry ONLY FAULT CURRENT.

Thanks for the fun discussion, were making progress it sounds like its just the english language which we are havign trouble with lol

Take care yall

John T

Some will suggest just using the ground wire because 'it goes tot he same place' but the ground wire does a different job than thew nuetral wire, and interchanging them like that makes all metal surfaces on all your electrical devices _hot_ if something should go wrong - a short, etc. Not a good idea.

Turning your ground wire into a nuetral wire by changing the ground busses around is possible, but that leaves you without a ground wire, which isn't to code or real good either.

--->Paul

An example here would be somebody using a drill under the kitchen sink. A fault between the motor windings and the drill case (assuming its not a double insulated one) would make the case hot with respect to the plumbing, which is connected to earth. You're doing really well to get the resistance of a single ground rod down to less that a few 10's of ohms, so there will be some resistance in the path back from the pipe to the ground rod to the neutral buss in the breaker panel. 120 volts across 20 ohms is 6 amps, well below what will pop a breaker but many time higher than the current necessary for a fatal shock.

A safety ground wire will have a lot less resistance, and would therefore carry the fault current back to the breaker instead of the current flowing through a hazardous path. Without the safety ground wire, the drill would operate normally even though the case is at 120 volts above ground.

Gound fault interrupters in high risk places such as kitchens & bathrooms add another layer of protection against fault conditions that don't blow breakers. A ground fault interruptor monitors the current in the hot & neutral leads, and opens the circuit if there's ever a difference. Any difference in current means that some of the current is flowing in a fault path somewhere instead of returning on the neutral.

Codes are in place for a reason, and even though that reason may not be intuitively obvious, I can gurantee you that the codes are based on well thought out engineering practices.

Keith

You need a dedicated neutral, all the way back to the fuse/breaker box, and MUST have the outlet protected by a 15 or 20 amp fuse/breaker.