[rescue] SGI goodies anyone?

Robert Darlington rdarlington at gmail.com
Sat Oct 16 02:56:54 CDT 2010

In regards to 3 prong outlets, make sure you do it to code.  Either run a
ground line to that 3rd prong OR use a GFI (sometimes pronounced GFCI).
There is no requirement to attach a ground line to a GFI outlet and that's
the only way that I know of to safely and legally switch to a three prong
outlet without running a ground line.  GFI's use a simple transformer
circuit to compare the current between hot and neutral.  If they go out of
balance by 5mA or less they trip and cut off power.  Kirchoff's Current Law
basically says what goes out has to equal what comes in.  If the current
coming back is not the same as what goes in, you know you have current going
where it should not be and the GFI trips.  You can chain regular (cheap)
outlets downstream to protect those outlets as well.

Also, avoid running grounds to copper water pipes when possible.  It can be
a bad time for plumbers when they cut a pipe and become a path to ground.

Jeff, take a look at the meter outside your house.  Chances are it's modern
(if you pay an electrical bill, it's a modern meter) and was upgraded at
some point in the last 50 years.  Utility companies know that demand rarely
goes down and that it's cheaper to run a cable once.


On Sat, Oct 16, 2010 at 1:12 AM, Rick Hamell <hamellr at gmail.com> wrote:

> On 10/15/10 11:55 PM, Jeff Cole wrote:
> > On 10/15/2010 8:27 PM, Robert Darlington wrote:
> >> Every home in North America (with I'm sure a small handfull of
> >> exceptions)
> >> is wired for 240 volts at 50 amps or greater.
> >
> > Pretty sure my place falls into the exception category. Built in 1932 or
> > so. I do wonder if it didn't have electricity when built. There's a lamp
> > in the dining room that was very obviously a gas lamp converted to
> > electric later on.
> >
> > I'll have to take some pictures of the original electrical panel. It's
> > very old. Over the years, it's been added onto. There's an older fuse
> > box with the screw in fuses, a modern fuse box, and a separate circuit
> > for the dryer.
> >
> > Save for the bathroom and the kitchen, the whole house is 2 prong
> > outlets. I'm looking into getting a couple 3 prong outlets installed
> > around the house just for the sake of convenience and safety.
> Check that those are grounded. You can get a little tool to test that
> for under $10 at any hardware store.
> I used to live in a house that was the exact same way, but none of the
> power was actually grounded, it was "grounded" to the back of the plug.
> I lost a bit of hardware due to a storm, back when UPS were expensive
> and the not practical for the number of machines I had on hand.
> --
> Rick Hamell
> Linkedin Profile - http://www.linkedin.com/pub/6/946/27
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