On 4/4/2011 12:22 PM, TexasRF@aol.com wrote:
> In a typical sub panel, is the buss bar that is used to common the
> neutral leads insulated from the box chassis? I have installed a
> couple of sub panels through the years but never paid any attention to
> that.
All panels are built with a neutral bus that is insulated from the steel
enclosure. In most, there is a large bonding screw that shorts the
neutral bus to the enclosure. If the neutral bond is not permitted,
this screw must be removed. Not all electricians know that this
matters, but it is critical. Indeed, extra neutral-to-ground bonds are
one of the most common wiring mistake in buildings.
An easy way to sniff for this is with an AC voltmeter that has a good
low volts scale. Connecting the meter between ground and neutral any
where in the system except at the bonding point, you should see some
small voltage, typically less than a volt or so. If you see zero,
there's a neutral to ground short close by.
73, Jim Brown K9YC
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