RE: NANFA-- Electricity and thinking aloud...

Shane Graber (
Thu, 26 Jun 2003 13:41:54 -0400

> First question: Are iron support I-beams typically used as
> the earth ground
> for a house?

No, earth ground for a house is thru a 8' length of copper bar that should
be driven into the ground outside your house where the electricity comes in.
IIRC, code now for new houses is that you actually have to have two ground
rods out a couple feet away from your house. It looks like a piece of rebar
driven into the ground with a copper wire coming off of it and that's
attached to your electrical box. That's where all of your outlets should be
grounded to thru the neutral and ground wire.

> If I connect from the tank to the I-beam with a multimeter...
> I get about 50
> volts (which would shock the snot out of about anything) in each tank.
> However, I'm not sure which way the current is going. If
> there's stray
> voltage on the I-beam from other circuits, well, that sucks
> to send into the
> tank.

I have a feeling you're getting a false reading here as your I-beam isn't

> If I connect to a metal object (like a strip light frame)
> from the tank, I
> find about 7 volts in each tank. However, I'm suspicious
> that since these
> objects are plugged into the same circuit I worked on, that
> the voltage is
> just fluttering off into some nebulous void, or more specifically, not
> getting removed from the tank. Not a good ground, and
> possibly only pulling
> 7 vots off the 50 that are really in the tank.

What you might be seeing is an induced electrical current from your
lighting. I see it with my halides on my reef. No lights on, no electrical
current in my reef. Halide on, +5 VAC in the tank. As far as I've been
able to tell it's an induced electrical current due to EM field off of my
halide. Reference was ground in my GFCI. Ground wire from GFCI connects to
copper bus in the electrical panel and the copper bus is connected to my
copper grounding rod outside the house.

> Second question: Can a false ground be created by screwing in a metal
> object (like a heat sink for a vho ballast) into unconnected
> wood on the
> frame of the house?

Probably not likely. Wood is a pretty poor conductor of electricity. The
wood would have to be pretty wet to carry much of a current or voltage.

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