No, the white wire is neutral, the GREEN wire is
ground. (Black obviously is hot. For two wire polarized
plugs, I've always used the mnemonic "black hot shorts"
to remember that the skinny blade is hot and the flaired,
wider blade is neutral.)
Per code, bonding of the neutral (white) and ground (green) wires
should occur only at the building entrance, as you pointed
out. That is where to locate your main surge suppressor
device (preferably an in-line device). At the sub-building,
I would suggest a shunt-type suppressor. Depending on its
distance from the main panel, you could tie the grounds
together or create a new ground system; for lightning suppression
purposes, this distance is on the order of 50~75 feet*. For important
stuff like a good TV, computer, or ham gear, you should consider an
outlet-mounted protector with a proper grounding system. Most outlet
surge suppressors merely tie back to the ac power ground via the green
wire and therefore are more suited to 60-Hz transients than those
created by lightning. While the most damage-causing component in
a lightning strike is at dc, because of the fast rise times (on the order
of a few microseconds), you will have components up into the VHF
range with the ability to cause problems if they aren't taken to ground
as quickly as possible. The (in)famouse #6 wire, while adequate at
60-Hz, is just too inductive and has a fairly low ampacity for lightning
ground purposes; the best is wide copper strap or if you must go the
round member route, #2/0 is probably the smallest to use.
Realize that devices providing lightning-induced surge suppression
such as PolyPhaser products are not designed from the point-of-view
of suppressing line (switching) transients. For this reason, you should
consider
such a product for protecting your computer and ham gear. These
type suppressors are contained in most good quality UPSes such as
those from Best and APC.
Typically, by the time a "distant" lightning-induced surge (transient) gets
to your outlet (or even oftentimes your service entrance), it has been
reduced in level (but stretched out timewise) by the inductance of the
power wiring. This is what saves the "bacon" of most suppressors. The
dynamics of a "close" hit is what separates the men from the boys in
suppressors. The other issue is that a nearby (or even fairly far away)
lightning
strike can induce "significent" surge current in the house wiring, which is
why the suggestion for additional protection at the outlets.
*) This tie should utilize wide copper strap. There will probably be
differences
of opinion on this topic.
73,
Bob AA0CY
----------
From: alsopb[SMTP:alsopb@gloryroad.net]
Sent: Sunday, October 24, 1999 6:43 AM
To: towertalk@contesting.com
Subject: [TowerTalk] MOV mains surge protectors
Guys,
Here's an interesting question. On an
outbuilding, it is normal to keep the neutral and
grounds separate and have them only tied together
back
at the main entrance cable in the house.
If one want's to install one of those main panel
MOV surge protectors in the outbulding, where does
one connect the WHITE (ground) wire to. It would
seem that one wants it directly to go to ground
rather than the neutral. Connected to the
neutral, the surge has to go all the way back to
the house to find a ground. Seems like that would
be nearly useless.
Anybody have authoritative advice?
73 de Brian/K3KO
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