[harum]

Hello, we have a 50 Amp 240 VAC circuit with a single outlet in the garage area pulled there by previous owner for an electric dryer. There are no plans on our part on installing an electric dryer or any other 240 VAC appliances in that area.

My question is if it is acceptable to use one of the poles of this never used 240 VAC circuit for powering 120 VAC devices and keeping the other pole isolated? Would it be just a matter of installing a split-circuit receptacle, i.e. using both hot wires?

Thanks, h.

[harum]

Would this scheme work? First, break brass connecting fin at the "hot" side of receptacle; then connect the red wire to one brass "hot" terminal and the black wire to the other; then connect the "neutral" wire to one of the silver terminals.

The top and bottom halves of the outlet will be powered by different hot wires with 120 VAC. The "neutral" wire will be shared, which is acceptable because the "red" and "black" current would be of opposite phases.

[ma0641]

How do you plan to connect a wire rated for 50 amps to a 15 or 20 amp outlet. If you put a 12 or 14 on for a pigtail you would need to change the breaker. Why not put in a small subpanel, leave the 50 amp breaker and you could have 240 and 120 VAC circuits.

[harum]

I still haven't been able to locate the main shut-off switch that powers off the main panel: there is no visible switch at the roof where the service enters the house or around the panel. I have been doing some electrical work switching off individual breakers rather than main power.

With the breaker for this particular circuit off, when I touched the "neutral" wire with the "ground" wire in one of the kitchen outlets, there was always a small spark between them. In contrast, touching the "hot" wire with the "ground" does nothing. My power tester shows no voltage in any of the wires. Is this something to expect? What is the explanation for this? Is this because the "neutral" wire in the outlet, even with the breaker off, is still continuous with the city service "neutral" (with some non-zero potential), and it is the "hot" wire that is interrupted by the breaker?

[hkstroud]

50 Amp 240 VAC

No, a 240V circuit has no neutral.

With the breaker for this particular circuit off, when I touched the "neutral" wire with the "ground" wire in one of the kitchen outlets

What does a circuit in the kitchen have to do with a 240V circuit to the garage?

when I touched the "neutral" wire with the "ground" wire in one of the kitchen outlets, there was always a small spark between them

That indicates an open neutral on that circuit.

is the "hot" wire that is interrupted by the breaker?

Yes.

[harum]

No, a 240V circuit has no neutral.

Do you mean the current goes through the water pipes to the ground and doesn't return to the city line? I thought that I have three wires: -120VAC, +120VAC and the "neutral" "returning" wire. Or are you talking about home service in Europe?

Those are two different circuits. I put two questions in the same thread.

[donf]

You know just enough to be really dangerous. :) I suspect that if the receptacle is up high on the wall it was for a welding unit and not a dryer. Also, for this type of circuit testing, use a Multi-meter and check for 240 Vac between both hot pole on the receptacle.

If you have zero volts across the hot poles, then the breaker may be off or have already been removed. If it has been removed already, then pull the entire circuit.

There are two 240 Vac receptacle configurations. A Three wire, 2 hot conductors and one Neutral / Ground" wire. The four wire configuration has 2 hot conductors, a Neutral conductor and a Ground conductor.

The three wire configuration is no longer an acceptable configuration. It has been replaced with the four wire. The 3 wire configuration came about as a method to save on the use of copper during WW II. The problem with this configuration is that "Neutral", which is a current carrying conductor is connected to the frame ground of the appliance and the Ground is then used to transfer the return current back through the circuit to the panel board.

What you are going to have to do is trace the cable from the receptacle to the panel board and to the breaker. The breaker should be fairly easy to find. It will be a double pole breaker 40 or 50 amp breaker. Once you have identified the breaker, turn it off and then remove the breaker and the entire circuit .

[hkstroud]

Those are two different circuits. I put two questions in the same thread.

OK, while that was not very smart thing to do, you got two answers.

1. You said you have a 240V circuit to the garage.
If you have a 240V circuit you have no neutral.

2. If you get a spark when connecting a neutral to a ground wire, you probably have an interrupted neutral.

Not smart present two different problems in one thread because it is difficult to convey all the aspects of one problem to someone remotely over the internet, much less two. Only creates confusion. If you are going to do that, state "I have a second problem" so that everyone knows you are talking about a different problem.

Don is correct that if this is a 50 amp circuit it is most likely for something other than a dryer. Dryer circuits are most often 30 amps.

If your garage circuit has 3 wires, two hots (black and white and ground) you have a 240V circuit. If it has 4 wires (black, red, white and ground) you have a 240/210V circuit. How many holes or slots does the receptical in the garage have, 3 or 4?

[harum]

You know just enough to be really dangerous. :)
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What you are going to have to do is trace the cable from the receptacle to the panel board and to the breaker. The breaker should be fairly easy to find. It will be a double pole breaker 40 or 50 amp breaker. Once you have identified the breaker, turn it off and then remove the breaker and the entire circuit .

Thanks for the answer. The receptacle is 30-40 in. above the floor. The breaker is off, because I turned it off. I have assumed that this 240 VAC circuit is otherwise in good shape and ready to use. It runs all the way from the main panel (the panel is without any sign of the main shut-off switch) in a metal sheath in the crawl space.

The outlet was made for electric dryer, I know it. This is an old house with a small 100 A main panel, and I am reluctant to remove a ready-to-use circuit.

Maybe the best solution is to substitute a 20 A breaker for the old 50 A and split the outlet, one receptacle per "hot" wire -- this way, I will have two extra 20 A receptacles.

Yes, there are only three wires, i.e. there is no ground. But the circuits like this are still legal, i.e. one doesn't have to pull new 4-wire lines.

[donf]

Thanks for the response. It seems as if you are set on doing it your way.

If this is a true 240 Vac circuit, you will only have two hot legs and ground. That tells you that you have no Neutral (White). Without a Neutral, you cannot create 120 Vac circuits.

You cannot use the Ground wire as a Neutral.

You would be much safer in just abandoning the existing circuit and creating two new circuits.

Technically what you want to do is called a Multiwire circuit. Two hot wires each with their own breaker sharing the Neutral.. However, the risk here is that if you ever have a Neutral failure, you would be putting 240 Vac across each receptacle.

[harum]

Thanks again. Yes, putting this line to use will take some tweaking. No "neutral" means that I will have to pull one or two new lines.

[hfcarson]

And when you pull these additional wires, you know they need to be in the same raceway or part of the same cable assembly?
So, now that your pulling some new wires, why not pull the correct new circuits you wanted and leave the 50 amp circuit and outlet for the future? Do it once and do it right...

[harum]

and when you pull these additional wires, you know they need to be in the same raceway or part of the same cable assembly?
So, now that your pulling some new wires, why not pull the correct new circuits you wanted and leave the 50 amp circuit and outlet for the future? Do it once and do it right...

Well, I will definitely leave the 50 VAC line intact for future use, i.e. when I upgrade to 200 A main board. It is a perfectly working circuit, but of not much use at this point.