240v Single Phase GFCI - Wiring Issue

Your electrician is confused. You can bring the neutral to the last J box or not run it at all. The 240v GFCI will still function fine with nothing but a line to line load. Personally I would not even connect to the neutral on the load side of the breaker. The line side pigtail will still need to be connected.

I have some difficulty understanding your situation in detail from what is written. Also, my professional experience to cover your situation is limited.

I presume you are not talking about an Edison ±120V line when you say 240V. I think of a hot 240V conductor, a neutral conductor, and a protective ground conductor. I do not understand why you should need a fourth wire.

In my small greenhouse, using 120V submersible pumps, I have had problems with GFCI trips when the pump turns off. I have attributed that to voltage spikes when inductive current is interrupted. The armature to ground insulation on these pumps seems to be poor. That is making it tempting to remove the GFCI protection and rely on the ground connection for protection, but I am chicken to do so. If you have really good insulation from armature to ground I would certainly use GFCI.

It may be worth your while to hire a PE for an hour or two who is competent in this field.

Bill

In many parts of the world, 240 V. means one hot wire (at 240 V above neutral, one neutral wire, and a protective earth or ground connector). 3 wires do the job. This is not necessarily the case in the USA.

A typical US setup for 240V would be (TWO HOT wires (each 120 V. to neutral - 240V. between them), a NEUTRAL (may or may not be required) and a PROTECTIVE GROUND conductor.

Typically, devices that require dual voltage 240/120V require a neutral wire (because it carries current), thus 4 wires instead of 3.

You might want to research the US code requirements for a 240V hot tub installations The specifications are detailed and strict and it sounds possibly that it may be applicable to your setup.

Siemens makes a 1 or 2 pole GFI circuit breaker that may be of interest to you: It is expensive, but it will probably do the job.

Your electrician is just plain wrong about how a GFCI detects ground leakage current. In a GFCI assembly all of the current carrying conductors of the circuit pass through a sensing coil. As long as the total current running through the conductors that are intended to carry current remains equal the coil does not have nay current induced into it. That is because the current flowing out to the load by any normal pathway is equal to the current flowing back to the load by any normal pathway. If the flow of current in both directions remains equal the magnetic field created by the two flows cancels each other out. With no net magnetic field passing through the sensing coil no current is induced into the coil for the sensing circuit to detect. If the currents flowing in the conductors enclosed in the sensing coil get out of balance for any reason the magnetic fields they produce no longer cancel out and a net magnetic field is then passing through the sensing coil. That induces a current flow in the sensing coil which the sensing circuit detects. When the current in the sensing coil exceeds the value for which the sensing circuit is designed the sensing circuit trips the mechanism that opens the current carrying conductors.

The value for which the circuit is designed varies with the purpose of the device. Some GFCIs are designed to protect people others are designed to protect equipment.

Since your load is 240 volts no current will flow on the neutral conductor and there was no reason to install it. Installing it does no harm beyond the waste of the material and labor but it also does no good.

The GFCI breakers pigtail does need to run to the neutral buss in the panel in which it is installed because the sensing circuit operates off of the 120 volts available between one of the two ungrounded current carrying conductors; i.e. the hot wires; and the neutral point of the supply transformer. In your case only the GFCI itself needs the 120 volt supply. The load can be successfully supplied through just the two ungrounded current carrying conductors as I've already stated.

A simple test should provide your electrician of the proof of this as long as the particular type of GFCI that is installed in your project is the kind that is meant to protect people. With the breaker closed and the panel energized but with no conductors connected to the GFCI breakers terminals he should test between both hots, each hot and the neutral, and between either hot and ground/earth at the GFCI breakers terminals. The test should be performed using a solenoid or Wigginton type tester which is commonly called a Wiggy. The solenoid in the Wiggy will draw around nine milliamperes of current to move the indicator to the proper voltage level. Since the current drawn by the tester exceeds the trip point of the sensing circuit in a GFCI that is designed to protect personnel it should trip the GFCI that you have installed there. Point out that it trips with the only points being tested being either of the ungrounded current carrying conductors and the Equipment Grounding Conductor / safety earth. A Wiggy can not draw current from a conductor to which it is not connected. So even with no current flowing in the neutral the GFCI can still perform it's protective function.

-- Tom Horne

"This alternating current stuff is just a fad it is much too dangerous for general use." Thomas Alva Edison

| Back came the electrician who said he had to install an '...additional | conductor...' to meet the codes for | a 240v GFCI. So he ran a new additional wire from the panel all the | way to the dedicated box. He put in | a new breaker on the panel, apparently of the GFCI type. However he | said he could not connect the | device to the service box as it only has a 3-wire tail cord. So he | left - and we're still down.

There is no requirement for an additional conductor on a GFCI protected circuit. There does need to be a neutral connection available for the GFCI breaker itself, but that would be in the breaker panel where the circuit originates.

A US-style 240/120 dual voltage circuit consists of 4 wires: ground, hot A, hot B, and neutral

A US-style 240 single voltage circuit consists of 3 wires: ground, hot A, hot B ... and no more than that

A GFCI breaker for 240 volts is a 2-pole device. It plugs into TWO slots in the breaker panel. Some brands have a double handle with a bar between them and some brans just have a single handle. They also have a TEST button.

It will also have, inside the panel, an extra wire covered with white color insulation. This wire is connected to the neutral bus bar. It is used for TWO purposes:

1. It supplies a way for the GFCI breaker circuitry to have 120 volt power to operate. The internal circuitry will operate via ONE of the two hot lines it gets from the connection behind the breaker, and that neutral. It's the same circuit as used in the 120 volt single pole breakers, so it needs the 120 volts and needs that wire to be connected to the neutral bus to function correctly.

1. It is connected through the breaker to the neutral terminam on the breaker. There are 3 terminals on this 2-pole breaker and one of them is the neutral. For correct operation in a circuit which uses a neutral for dual voltage operation (240/120) the neutral passes through the same current sensing transformer inside the breaker as the two hot wires.

If a GFCI protected circuit uses a neutral conductor, that neutral MUST be connected to the neutral terminal of the breaker. Normal circuits would just connect the neutral to the neutral bus bar.

However, a circuit does NOT have to have a neutral. If the load uses only a single voltage and that voltage is 240 volts, it would not be attached to a neutral.

| I called the manufacturer, and they say that ALWAYS with 240v Single | Phase one "...only uses | 3 poles, not 4' and that the "netural and earth ground' are tied to | the same point on the system.

The manufacturer is correct.

| However, the electrician then points out that the way a GFCI works is | by detecting the differential | between the Neutral and Earth, ('leakage?") and that if the system end | ties them together then the | GFCI is of total uselessness.

He is partially correct.

A GFCI runs ALL of the current carrying conductors (hot plus neutral for

120 volts, and two hots plus neutral for 240 or 240/120 volts) through a special kind of transformer (called a current transformer, abbreviated CT). These wires run together. If the total current going IN and the total current going OUT are the same, the CT will sense ZERO current combined (since the IN and OUT currents cancel each other's magnetic fields when inside the CT). What a GFCI device does is detect if some of the current going through one way is going back by some means other than these wires. One such way is the ground wire (the green one if insulated) since that wire is NEVER connected through the GFCI. Another such way is ground itself. If a person touches a hot wire while standing on concrete with bare feet, they will get a jolt of current. It won't be a lot of current like a short circuit would be. It could be as low as 8 milliamps and be enough to cause heart fibrilation and kill the person contacting the wire. A normal circuit breaker or a fuse would never sense this. But a GFCI is specially designed to do this by means of detecting whether all the current going out TO the load comes BACK through the same wires. If not, it is referred to as a leak, and the GFCI breaker is supposed to shut it off if the amount is somewhere between 2mA and 6mA (nominally 5mA).

Devices operated in water, such as a submersible pump, usually require GFCI protection because the water itself can contact the wires if there is a leak. That water could then be energized without format a path to ground until someone touches the water and then they die.

If there is no neutral wire in the load (there isn't for devices that need only 240 volts), then a neutral wire does not need to be run in the circuit at all.

The two HOT wires will still be protected because they pass through the CT together inside the 2-pole GFCI breaker. If there is a leakage, the total current IN and total current OUT will be different on those two HOT wires and the breaker will detect that and trip (if the leak is more than the threshhold the breaker operates at ... around 5mA for people protection).

BTW, the 60-amp GFCI 2-pole breaker from Square-D does NOT have a neutral terminal. So it cannot be used on dual voltage circuits. It must only be used for 240-only single voltage circuits. It still has the pigtail to get 120 volts to operate on. I believe it is the case that at this high amperage, the larger wires sizes cannot fit 3 wires through the CT. But the point here is that it is NORMAL to operate a 240-volt circuit WITHOUT a neutral wire there at all. Typical 15-amp and 20-amp 240-volt outlets do not have a neutral connection (NEMA type 6-15R and 6-20R).

| SO back and forth they go - and I am still down and out! | | Any help and/or guidance / clarification / education would sure be | appreciated!

Do NOT pay for the extra work and material for the neutral wire that was added because it was not needed.

The wires from the pump will have 2 hots and a ground. The ground will either be bare or covered in green insulation. The 2 hots will be covered in black and/or red insulation (in certain extreme cases you may see blue or even brown). The 2 hots are to be connected to the 2 hots in the box just as they were before when things worked. Nothing is connected to the neutral (the wire with white insulation).

So, in summary, the electrician is the one who has it wrong. This circuit does not need a neutral. A GFCI will operate fine on a circuit without a neutral, as long as it has a connection to the neutral for itself.

If you were to install the GFCI breaker remotely, such as near the pump, then yes, a neutral wire IS NEEDED up to the point of the breaker so it can connect its white pigtail to it.