This is a LONG subject, but let me give you a couple of things to check
concerning this one outlet.
Disclaimer: This advice is SPECIFIC to USA wiring codes. Non-USA, MOTM'ers
please ignore.
1. turn electricity off to outlet.
2. pull outlet and actually check the wiring. Are there 3 separate wires to
the outlet? There should be. I have seen 3 prong outlets added to 2 wire
systems by simply installing a new outlet and either leaving the ground
disconnected or even worse, connecting the ground terminal to the neutral
connection buy putting those 2 together.
Here is a quick check for isolated ground that you can do with your digital
voltmeter with the power turned on. Use caution, this is 120 volts.
Connect something to the outlet that uses a fair amount of electricity. You
may find a regular lamp will work, but the effect will be easier to see with
something like a blow dryer, heat shrink gun, toaster, or something that
uses more electricity.
When you turn this device on, you will experience voltage drop in the wiring
to the outlet. You can measure that. For example, measuring hot to ground,
you may find 122.3 volts with the device turned off and 121.5 with the
device turned on. You are seeing a voltage drop of 0.8 volts. Something
like that is normal. Take the same measurement on the neutral to ground.
As you turn the device on and off, you should see the same change in voltage
between neutral and ground. Maybe before, your neutral to ground voltage
was 0 or 0.1 volts (depends on other loads on that circuit). When you turn
your load on, you should see that neutral to ground voltage increase to 0.8
(or whatever you measured as voltage drop on the positive side). This shows
that the voltage drop in the neutral is the same as the hot, and NO drop in
the ground.
If you get an identical change in voltage on the neutral and hot compared to
ground, then chances are your isolated neutral on that circuit is OK.
I will do a long blurb on house grounding soon. But, basically, you can
only have ONE ground at the house for proper lightning protection. If you
have multiple grounds, they need to be bonded together with BIG wire. I
don't know about Paul's situation. But, phone company grounds to water
pipes is the single most common grounding error I see made and has no doubt
burnt up a lot of modems. :)
Surge protectors - I don't use them. There is almost nothing in the way of
man made induced spikes on your electrical system that will make it through
your transformer and cause you any grief. I have almost never seen anything
like this. Most damage is caused by lightning. Those varistors in power
strips are most likely not going to save you.
I have one piece of advice for protection - disconnect , period. That is
the best way. I have ONE electrical circuit going to my studio (a heavy one
personally installed). I installed a $35 switch on the wall next to my
electrical box that turns this circuit off and disconnects it from the
electrical system. I only turn it on when I am using the stuff. I don't
use it during storms. So, try to arrange your stuff so it can be
disconnected or unplugged when not in use. I know this sounds cliche'.
But, unplugging when not in use is the best thing you can do.
Larry Hendry
----- Original Message -----
From: sucrosemusic <sucrosemusic@...>
The great thing about living in a house from the 1700s is the
wonderful electrical system. Who knows when it was installed! I
know a lot of the outlet in my house are not grounded... since
they're two prong... ewww. Also, though my outlet is 3 prong, I
don't know if I trust it. What's a good way to check? Should I put
a voltmeter from one of the AC lines to the ground, and then the
other AC line to the ground, to check to see if I get voltage both
ways? Eh. I'm not doing this tonight! ::laughs:: Man. An
electical nightmare, my house is. Toasted, I fear my gear will be.
Yoda, I will be speaking like tonight.
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