I knew that it was better for all the ground rods to be connected in a ring but assumed that if they were all connected to a central point differences in potential wouldn't be a problem.

Faisal Imtiaz wrote:
When you have multiple grounding rods at a site (e.g. for a tower ground, there 
should be a ring around the tower base, with multiple ground rods, they should 
all be connected together, i.e ring, and different tower legs should be 
connected to the different ground rods.... (don't forget the guy wires too...)

Split grounding is when the different grounding rods are not connected to each 
other...
Most common issue is that there is an Electrical ground (ground rod) which is 
not connected using a heavy gauge copper wire to the other (tower or shelter) 
grounding rods.

In a split ground situation, if you were to connect an ohm meter to these two 
different ground(s) you will see high resistance...and in many cases if you 
were to connect a volt meter, you can actually get a reading of a few volts 
flowing thru the two different grounds.  In Hot Weather, when one side of the 
split ground gets wet, the voltage increases, and goes thru the electronic 
equipment (flowing in the wrong direction) causing Ethernet port damage at the 
very least and blowing equipment totally at the most.

Regards.

Faisal Imtiaz
Snappy Internet & Telecom
7266 SW 48 Street
Miami, FL 33155
Tel: 305 663 5518 x 232

Help-desk: (305)663-5518 Option 2 or Email: supp...@snappytelecom.net

----- Original Message -----
From: "CBB - Jay Fuller" <par...@cyberbroadband.net>
To: af@afmug.com
Sent: Wednesday, December 30, 2015 11:53:07 AM
Subject: Re: [AFMUG] WISP insurance
What is split grounding?

Faisal Imtiaz wrote:
one of the most classic examples of a 'split ground' situation is when
you loose gear with rain during hot days (first rains after dry
season). Because there is rain involved most folks chalk this off to
'Lightning' ... in reality it is not, it is due to Tower Ground, Bldg
Ground and Power Ground being at a different potential causing current
to flow thru the ground wires etc.

:)

Faisal Imtiaz
Snappy Internet & Telecom
7266 SW 48 Street
Miami, FL 33155
Tel: 305 663 5518 x 232

Help-desk: (305)663-5518 Option 2 or Email: supp...@snappytelecom.net

------------------------------------------------------------------------

     *From: *"George Skorup" <geo...@cbcast.com>
     *To: *af@afmug.com
     *Sent: *Wednesday, December 30, 2015 12:15:33 AM
     *Subject: *Re: [AFMUG] WISP insurance

     For about a month at one site during the summer (maybe last year,
     I don't remember, too much shit in my head), we got a bunch of
     popped fuses and surge suppressors. Our local 911 dispatch joined
     the site months before and we didn't have any problems. We finally
     figured out that the grounding sorta got split. Everything was
     still interconnected, just not optimally. So we all made sure that
     everything was tied to a single point, aka R56. No more issues. We
     do still get some popped fuses once in a while, but that's mostly
     Chuck's surge suppressors clamping on nearby lightning strikes.
     I'd rather have that than dead or degraded ethernet ports.

     It was also a very wet spring and then things dried out. We've
     noticed this pattern for >10 years. If the soil is pretty dry for
     a lot of the year, we lose more gear. Which brings up another
     point. Up to a couple years ago, we had a site where we'd lose
     everything 2-3 times per year. The power company came out and ran
     a load test at our transformer. 20A is all it would do. The ground
     rod at the pole/transformer was almost completely gone. I think
     they said there was maybe 2 feet left and they pulled it out by
     hand. Of course it was probably 40 years old.

     On 12/29/2015 10:28 PM, Jaime Solorza wrote:

         When I wear  my SCADA hat grounding takes a front seat.   We
         take great care to insure we follow sound methodology and take
         no short cuts.  I have shared many posts on how we do it...
         basically all of it hinges of Franklin method.  Those who know
         me, know I don't pull punches...if we were getting hit allot I
         would post it.  Yes we have had hits and lost equipment but it
         is extremely rare. Consider that one SCADA network alone has
         over 500 sites with elevated tanks, towers and masts all with
         yagis, sectored and omni antennas with heliax cabling.  Wisps
         around here get more hits.  I will share some links you might
         find useful.

         On Dec 29, 2015 8:08 PM, "Faisal Imtiaz"
         <fai...@snappytelecom.net <mailto:fai...@snappytelecom.net>>
         wrote:

             I thought about commenting, walked away,  but decided to
             comment at the risk of offending someone, but it would be
             worth it if the point being made and the information being
             shared was understood properly..

             So here goes... Joshaven took the time and provided a
             farily accurate, detailed post on how to do grounding
             properly, and the potential issues when it is not proper.
             There is a lot of good information in there.....

             Glen I don't know if you realize what you did with your
             replies .... while sounding dismissive you actually have
             described the exact thing that Joshaven was trying to
             point out, as to what happens when grounding is not proper !

             'Grounding' is not just running some copper wires to be
             visually satisfying.... your statement about  'it is
             grounded pretty well...'  followed by .. I have lost
             equipment there is an Oxymoron....

             Grounding when done correctly will protect your equipment
             from having the type of damage you are describing.... and
             yes there are some ways to measure and determine if your
             grounding is proper !


             BTW, Audio affects of a Lightning strike,  shaking stuff
             etc etc is due to sound waves generated.. (sort of a mini
             explosion)... makes for great sound effect, but has
             nothing to do with electrical damage to equipment.

             :)


             Faisal Imtiaz
             Snappy Internet & Telecom
             7266 SW 48 Street
             Miami, FL 33155
             Tel: 305 663 5518 x 232 <tel:305%20663%205518%20x%20232>

             Help-desk: (305)663-5518 <tel:%28305%29663-5518> Option 2
             or Email: supp...@snappytelecom.net

             
------------------------------------------------------------------------

                 *From: *"Glen Waldrop" <gwl...@cngwireless.net
                 <mailto:gwl...@cngwireless.net>>
                 *To: *af@afmug.com <mailto:af@afmug.com>
                 *Sent: *Tuesday, December 29, 2015 6:02:24 PM
                 *Subject: *Re: [AFMUG] WISP insurance

                 Forgot to mention, this was one hell of a storm.

                 Lightning from *several* miles away shook my home
                 enough that the dishes rattled, the TV moved, cabinet
                 doors opened and closed, etc, for upwards of 45 seconds.

                 I’m honestly surprised we only lost one tower in that
                 storm. I was preparing myself for putting up at least
                 a couple of replacement towers over my Christmas break
                 instead of goofing with the wife and kids. We got
                 lucky and only lost some electronics.
                 *From:* Glen Waldrop <mailto:gwl...@cngwireless.net>
                 *Sent:* Tuesday, December 29, 2015 4:57 PM
                 *To:* af@afmug.com <mailto:af@afmug.com>
                 *Subject:* Re: [AFMUG] WISP insurance
                 It is grounded pretty well, couple of ground rods,
                 tower is grounded and the copper goes to the top,
                 tallest point for quite a ways out there. The strike
                 also blew out the neighboring transformer (didn’t hit
                 my equipment directly).

                 I have not been tying in my electrical ground with my
                 tower ground. I do believe I’m about to change that.
                 I do have a few other towers where the electrical
                 ground is tied into the tower ground which is also
                 tied to a copper wire (6 or 8, depending on what I had
                 at the time) the entire length of the tower, bolted to
                 the tower at the top and bottom.

                 Those have also been struck.

                 One of my most recent ones ran up the ethernet cable,
                 fried the equipment at the top. POE on the ground
                 survived, UPS survived and the surge suppressor
                 (10/100M fusible link essentially) survived. The only
                 radio to survive the strike was the only one I had
                 forgotten to install a suppressor on. They were all
                 replaced of course. The only equipment I’ve seen
                 survive an actual lightning strike without a hiccup is
                 the RB600. Everything else seems to die within 6 months.

                 It appears the surge went through the ground (which
                 we’ve gone over several times) into the surge
                 suppressor, into the ethernet and blew out the radios.

                 Any speculation on that would be awesome. The only
                 thing that makes sense is that maybe the static was
                 close enough to hit the electrical ground and go up
                 the tower, but we’ve checked the ground rods and
                 copper, bolts, etc.
                 *From:* Joshaven Mailing Lists
                 <mailto:lis...@joshaven.com>
                 *Sent:* Tuesday, December 29, 2015 1:18 PM
                 *To:* af@afmug.com
                 *Subject:* Re: [AFMUG] WISP insurance
                 Kinda off topic... Insurance of another type (avoidance)
                 I often find locations where the grounds are hooked up
                 to the tower ground which includes one or more ground
                 rods… but what often goes unrealized is that the
                 system is also grounded to another system through the
                 utility company… and the tower and the utility company
                 may not be properly bonded.  So the lightning finds
                 the big tower, and thinking it is a lightning rod…
                 uses some of the path to ground through rods at the
                 base of the tower but then also uses the path through
                 the equipment to get to the power utility ground…. and
                 pop goes the radio and router and such… Just don’t be
                 that guy that connects the big lightening rod to the
                 utility power ground through your router...
                 Your equipment should be surviving lightning strikes.
                 Large towers can be struck multiple times per month
                 and equipment can be on them for years without any
                 damage at all.  The fact that you lost equipment says
                 that the strike was either direct to your equipment or
                 you have a grounding issue that made your equipment a
                 better path to ground.
                 At some sites commercial radio engineers will even
                 bring in a beaded cable from the tower and spread it
                 across the floor to set all equipment on just to be
                 sure that the ground panes are entirely bonded.  The
                 reason that equipment blows is that the difference in
                 positive to negative current is out of range.  When
                 you get a lightning strike and things are not well
                 bonded then you can have variances between grounds in
                 the order of thousands of volts which will make your
                 equipment pop like a fire cracker…  if your ground is
                 at 10,000v (relative to an average earth voltage) and
                 your equipment is at 10,024v then the potential
                 between them is 24v.  It is like a bird setting on a
                 high voltage line… somehow they don’t “feel” the high
                 voltage… The trick to surviving a lightning strike is
                 to bond all grounds well so ground is constant and
                 then to have your power level referenced from that
                 ground.  This way if the earth ground or the tower
                 ground or anything else has a sudden change then your
                 equipment changes with it and remains relatively the
                 same. After bonding your grounds properly so that you
                 don’t end up with thousands of volts difference
                 between two grounds like your power company ground and
                 the tower that your equipment is mounted to… then you
                 can install good surge equipment that will handle
                 current overages in the event that you need it.
                 The thing to keep in mind when grounding your
                 equipment is that you don’t want your equipment to
                 experience a situation like 0v for negative, 24v for
                 positive and 50,000v for ground.  If your equipment
                 ground plane floats with a strike then it won’t even
                 know that it experienced a surge. Just like a boat
                 going over shallower and deeper water — who knew
                 unless they had a fish finder running?
                 During a strike, you don’t want a 5,000v on the
                 utility ground while you have a 25,000v on the tower…
                 If the cable between the two (or patch of earth
                 between rods) won’t handle the surge or the impedance
                 is too high then your equipment will possibly have two
                 grounds with two very different power levels so the
                 power will transfer from your shielded cable through
                 your router chassis to the utility power until a
                 something pops.  The bottom line make the tower,
                 earth, & utility power all the same and properly
                 ground your equipment to that and you’ll survive most
                 strikes perfectly fine.
                 if you want some good reading google the terms:
                 “copper.org <http://copper.org> lightning”  they have
                 some great write-ups with pictures of the good, bad
                 and ugly.
                 Sincerely,
                 Joshaven Potter
                 Google Hangouts: j...@g2wireless.co
                 Cell & SMS: 1-517-607-9370 <tel:1-517-607-9370>
                 supp...@joshaven.com <mailto:supp...@joshaven.com>

                     On Dec 27, 2015, at 10:31 PM, Craig House
                     <cr...@totalhighspeed.net> wrote:
                     2 in a year?  We had 7 last night.

                     Sent from my iPhone

                     On Dec 27, 2015, at 21:22, Glen Waldrop
                     <gwl...@cngwireless.net> wrote:

                         We’ve had another lightning strike, at least
                         the second one this year.

                         I’ve got this feeling that our insurance
                         company is probably going to start to get a
                         little difficult in the near future.

                         Who do you guys recommend?

                         I’ve read about a few that cover everything,
                         CPE, tower equipment, towers, labor, etc... I
                         imagine those probably cost roughly what we
                         bring in a year, but...
                         Thanks guys.





Reply via email to