I have voltage leaking between two wires!


Yes, there is a difference. The hot wire (black in the US) carries 120VAC to an electrical load such as your TV or a lightbulb. Most of that voltage is dissipated across the load, so that the voltage on the neutral line (white in the US) is very close to zero, but still AC. The key point is that the neutral serves as the return path for the electrical current to the service panel: current into the load has to match the current out. For example, a 60W light bulb will draw about 500mA of current, and that 500mA will be carried in on the hot wire and out on the neutral.

The ground lead, on the other hand, normally never carries current. It is there to provide additional safety. For example, if the hot wire comes loose in a device and touches a metal part, anything connected to that metal is now energized at 120VAC. If you touch any exposed metal, you could get a shock. On the other hand, if the device is grounded, when the hot wire touches the metal, the circuit breaker will...

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Step 1: unplug the bandsaw until you have this all sorted out.

Step 2 should almost certainly be calling an electrician.

If you want to investigate further, I'd check the outlet and the saw separately.

Re the outlet, you're right to think that there should be 0 volts between the ground from your 110V outlet and the ground from your new 220V outlet. If you find voltage between them, you have a seriously flawed ground (and almost certainly should call an electrician.)

As for the two hot wires on your 220 line, there's a 90%+ chance that they should each read 110V to ground, but have opposite polarity so there's 220V between them. It's unlikely that you have 220V leg and a neutral, as your earlier test proposal suggests.

[EDIT: After re-reading your other thread again, it occurs to me I may have misunderstood your meaning on the outlet testing, due to the strange color coding on both ends. The building ground should really be green, not white, although...

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I have 4 questions about measuring voltage and the nuetral wire. I have worked alot installing fixtures, baseboard heaters plugs etc. I always shut the power off at the panel before I do any work. I think I understand how things work. I just want to confirm. Here we go. These are things I have kind of always wondered about.

From what I understand a voltage meter measures the difference between two points. For instance, a 110V outlet, if you touch the leads to the Black and White wire it reads 110V. This is because there is a 110V coming from the hot (Black) but the nuetral (white) has no power (0 volts). The difference between those two wires is the difference between 0 volts and 110 volts. Am I right about this - does it measure the voltage difference between two points?

Now if I have a circuit (say baseboard heater) that is 220. It has two hot wires and a ground and maybe a neutral. Each hot wire is bringing in 110V. If I measure across the hot wires (black and red)...

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I think I'm in over my head

. Really disappointed. I went to the brand-new headquarters of my volunteer ambulance service tonight, and nothing that I had planned worked out. So frustrating.

The plan was this: there's a security system at our building made by Rosslare. My goal was to hookup a keypad where someone can type in a code, and the door will unlock. The keypad part is done and is working great. The wiring guy gave me two wires that go into the "brains" of the security system. He said when you "touch" those two wires together for just a second, the door will unlock. So when the user enters the correct code, I need to touch those wires together for a second.

So first I thought I could use a relay, which worked, but then I thought I was overcomplicating things, and I thought I could use a "simple" transistor. So I tested the transistor with an LED - when I applied power to the "base", the LED lit up. I thought, great! This will work!

When I got to...

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WARNING - This page is NOT intended to tell you how to make high voltage wires safe. It is intended only to show you how I do high voltage wiring to prevent losses along the wire path from the power supply to the final destination. These techniques have not been used by me above 75kV. Working with high voltages is extremely dangerous. Use this information at your own risk.

Use insulated wire

Bare wire (e.g. bare copper wire), if it is at high voltage with respect to ground, will leak electrons. Electrons from the wire will attach themselves to molecules in the surrounding air, ionizing the air. This means you will have a lower voltage at your destination than you could otherwise have. This is the reason for using insulated wire instead. You'll have less leakage.

How much insulation you need depends on how high the voltage. For voltages such as I work with, 10kV and higher, you should use special high voltage wire. That's not to say you shouldn't use it...

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