Grounding Rod

[joe]

[joe]

oops, don't know how that happened, meant to paste this link.

[Pop]

.... I think the name actually dates back to WWII or maybe even earlier. A "Megger" measures Meghohms, and thus the name for its use as in "megging a line". I used them a lot in the service to look for insulation breakdowns in aircraft wiring. You apply the megger, which was basically a high voltage generator, crank it up, and measure the voltage at which current flows, and then the current, and the readout would in meghohms. It was a tiny scale, very hard to read, and you usually got to use it in the mid day tropical sun, inside a hell hole somwhere in one of the aircraft fuselage.

Just for grins, I jumped onto Google and the first place I tried turned up one very similar to the ones we had:

Megger is the actual name of the instrument: try a search on Google and you'll find lots of hits for "megger". They've taken a much more modern design and application of course, but the concept of all of them seems to be the same: measuring current flow at specified voltages and reading out the reults, in resistance or impedance, whichever the case may be.

It was a surprise to me to see a megger used for ground rod testing, but I did see a couple of links for that purpose too, though I didn't open them. I would have thought it more of a high current test, but apparently not, which I can sort of see, because the two opposing phases coming into a building each add or subtract for total current, depending on the phase, but I can't argue with facts, eh? Earth grounds are "interesting' to say the least.

HTH,

Pop

[William.Deans]

Greetings,

Everyone here says that #6 is the size ground that you need. I think that it is important to point out that you actually only need a #8. The problem is that #8 wire is so small that if you use it you must protect it from physical damage by placing it into a proper conduit or by purchasing an armored grounding cable. I often use a #8 ground when there is no lug which can accept a #6 ground. Please note that just because a #6 ground will fit doesn't mean the connector is rated for it! This would be a code violation.

Hope this helps, William

[George E. Cawthon]

[George E. Cawthon]

Thanks!

[Bill Davis Jr]

Thanks for the replies all.

Never heard of a megger before. Learn new things everyday.

Bill

[Rick]

Next subject-"growlers"....

[~^Johnny^~]

[CL (dnoyeB) Gilbert]

I thought municipal power was 3 phase?

[G Henslee]

Yeah? Where?

Shit your drawers again ya old bastard...

[Pop]

"~^Johnny^~" wrote in message news: [e-mail]...

....

That's true; it isn't really two "phases" per sae. There are two wires coming to the house from the transofrmer on the pole, and the literal phase of the voltage/current is 180 degrees out of phase in each wire. When one wire is at max voltage in above ground, the other is at max below ground. Technically it's called split-phase since it's a transformer generated relatioship where each wire is

180 degrees out of phase with the other.

Here's a page that does a decent job of describing how it comes oritinally as 3 phase (120 degree phase related) and becomes a split-phase derived sigle-phase power. That's why so many people refer to it as two-phase. There ARE two "phases", but ... it's derived from single phase by splitting that phase.

HTH,

Pop

[~^Johnny^~]

[HorneTD]

The power to most homes in North American practice is single phase 240 volt that has been center tapped to derive 120 volts from it. That system is called an Edison circuit and that is why it is used here. It was developed for use in converting Edison Electrics DC three wire circuits to AC. No matter what anyone tells you it is only single phase. The clearest evidence of which is that there is no way to wire a motor to it that will make the motor turn without the motor having a starting capacitor. The power on the supply side of the transformer that supplies most homes here is often three phase but only one phase is used to supply each transformer.

[Don Young]

I agree with single phase but not that all AC motors have starting capacitors. There are series motors, repulsion induction motors, split phase motors, shaded pole motors, and probably others which start and operate on single phase power without capacitors. Except for the series motor, they all do use some sort of system to develop an out of phase magnetic field for starting. Once running only a single phase field is required. Incidentally, a 180 degree out of phase field, even if derived by phase shifting rather than inversion, will not start an induction motor. There are two phase motors which operate with a 90 degree out of phase power source but they are rather specialized. Don Young