[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: Lightning and neutral grounding



Roy you are correct in your observation about the electrical neutral is already 
tied to the electrical ground and therefore your equipment which is also tied 
to your SPG (single point ground) is also tied to the electrical ground but 
there's a difference.  I've argued the next point with many many licensed 
electricians and electrical engineers and they all agree that one may not use 
the neutral as a ground. Never, never.  It's against the NEC. Don't touch it; 
you may invalidate your homeowner's insurance.  I do know from working with 
three phase power here at the plant that the neutral can develop a current on 
it and that's why you don't want to tie anything to it.  Also the small ground 
wire that connects to your receptacle and is run back to the service entrance 
panel can be of a high impedance and that fact would prevent the two grounds 
from rising and falling together during a surge event.  (Notice I said surge 
event, which also includes direct hits, but most often, results from nearby 
strikes.)  That's why you need a larger wire to connect the two; a wire that is 
of a very low impedance so you don't get a potential diffence between the two 
grounds.  Finally, during a direct hit, this wire may be carrying a lot of 
energy, which one doesn't want inside of the house.  I'm no expert, just an 
avid reader and learner and my personal experience has been of no problems even 
though two years ago lightning hit and blew up a neighbor's tree within 300 ft. 
of my stuff.  It blew out the 30 amp fuse to the electrical in the barn and 
nothing happened to all the radio gear.  And, some was in operation at the 
time.  I never disconnect!  Read the Polyphaser articles.  If not then ask 
yourself (not you Roy) can your equipment take a 30 amp surge?!  Phil  KB9CRY
> I also have the same problem.  Service entrance is on the north side of the 
> house, the radio antenna ground is on the mid west side of the house and TV 
> antenna ground is mid way between on the west side also.  All are grounded 
> by 8 foot ground rods and connected together by a #8 solid copper wire.
> 
> I have a 240 volt three conductor line from the service entrance breaker 
> box to the shack desk where I have a small panel fused disconnect box. 
> With one lever on the side of the box I disconnect the entire desk from the 
> 240 line.  There I split the phases to supply 120 volts (each fused) to the 
> various pieces of equipment for load balance purposes.  The neutral is 
> carried, of course, to both phases on the desk.  Inside the 120v lines 
> carrying the Hot and Neutral lines, there is also the third wire, a ground 
> wire.  This ground wire goes all the way back to the entrance box where it 
> is tied to the service entrance ground along with the neutral.  So, the 
> ground wire and neutral wire both go to ground at the entrance box.
> 
> If the shack equipment has three conductor AC power leads, the ground lead 
> is usually connected to the equipment chassis.  This ground is carried via 
> the metal chassis to the braid conductor of any coax cable coming from the 
> antennas to the shack equipment.  If the antennas are connected to an 
> external ground rod, haven't you already connected the neutral conductor to 
> ground at a point other than the entrance ground?  I see no way of avoiding 
> this if the house ground wires are tied to the equipment chassis.  If this 
> is the case, why not connect the ground wire on the radio desk phases to 
> the 240v neutral conductor at the desk instead of taking a separate ground 
> lead all the way back the the entrance panel?
> 
> I see this as the reason for, very definitely, connecting the external 
> ground rods together with a heavy, low inductance conductor.  Have I 
> misunderstood this?  I am not arguing for tying neutral leads to ground at 
> any point except at the entrance box.  I just don't see how you avoid 
> having it happen as described above.  Can you?
> 
> Jon Ogden wrote:
> > NO! NO! NO!!
> > 
> > Do NOT mess with the NEUTRAL!!!!
> > 
> > You tie your GROUNDS together.  This means you tied your tower, surge, and
> > shack grounds to the electrical service ground.
> > 
> > The neutral should ONLY be tied to ground at the service panel which it
> > already is.
> > 
> > on 3/11/03 1:17 AM, Greg D. at ko6th_greg@hotmail.com wrote:
> > 
> > 
> >>So the question:  I believe everything is done more-or-less
> >>correctly, EXCEPT that I need to tie the neutral of the electrical
> >>plug in the shack to the same grounded bar that the arrestors are
> >>bolted to.  "Neutral" is "white wire" side of the plug.  (The hot
> >>side is black, as in charcoal, which is what happens to your
> >>finger if you touch it...).
> > 
> > 
> > Please don't do this.
> > 
> > 
> >>I can't depend on the service entrance
> >>ground to be at the same potential as the ham ground during a strike,
> >>since they are too far apart.
> > 
> > 
> > You are correct here.  That's why you tie all grounds to the service
> > entrance ground via a network of ground wires.
> > 
> > 
> >>The safety ground (green wire) is
> >>left alone.  This means snaking a heavy wire from the lightning
> >>arrestor mounting bar, into the wall, and over to the electrical
> >>outlet box, and attaching it to the neurtal side of that wall plug.
> >>I don't need any other sort of lightning arrestor on the power line,
> >>other than a good "surge protector"; our electrical service has an
> >>underground feed.
> > 
> > 
> > Please again no.  There can be AC voltages present from netural to ground on
> > an AC line.  Neutral is not ground.  Don't run the lightning protection
> > ground lines through the house.
> > 
> > If your tower is roof mounted run several, heavy braided ground lines (good
> > surface area) from the tower to the earth.  As an alternate you can use some
> > big, arc welding cable.  Avoid sharp bends and turns.  Each line from the
> > roof goes to its own ground rod.  Then connect all ground rods together
> > (outside) via #4 copper wire or copper strap.  Additionally, you need ground
> > rods every 16 feet.  All should be interconnected.  Everything gets tied to
> > the electrical service ground.
> > 
> > 73,
> > 
> > Jon
> > NA9D
> > 
> > -------------------------------------
> > Jon Ogden
> > NA9D (ex: KE9NA)
> > 
> > Citizen of the People's Democratic Republik of Illinois
> > 
> > Life Member: ARRL, NRA
> > Member:  AMSAT, DXCC
> > 
> > http://www.qsl.net/na9d   <- Updated on 1/22/03!!!
> > 
> > "A life lived in fear is a life half lived."
> > 
> > 
> > ----
> > Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> > Not an AMSAT member? Join now to support the amateur satellite program!
> > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> > 
> 
> 
> -- 
> 73, Roy -- W0SL
> 
> E-Mail: rdwelch@swbell.net
> Home Page: http://home.swbell.net/rdwelch
> 
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT member? Join now to support the amateur satellite program!
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home