| grounding and lightning protection recommendations See attached, it is a digram of our tower site.
We just took lightning hit to our tower all of our equipment is dead. And of course Fedex is closed today. Doh. Learned two things today, always have backup units, and don't skimp on the grounding  Luckily we learned this only with 7 subscribers.
Not only is all of our equipment at the tower dead, but our UPS is dead, and the person who lives at the tower ("Mr. Smith") site lost his router and computer as well. Double Doh.
Anyway, we have ordered all the replacement equipment and we are going to replace his computer, but now we have to get to the issue of grounding the tower properly and putting lightning protection in place.
Right now the tower is grounded with an 8 ft. grounding rod (10 guage copper wire connects the grounding rod to the tower). The equipment on the tower is grounded merely by means of being bolted to the tower.
For the shielded Cat5 we have wrapped the drain wire around the wires inside the shielded RJ45 plug to carry the shield through from the radio to the PoE. That is per manufacturer recommendation. The only exception is where indicated on the drawing (where the shielded Cat5 goes from the tower to inside the house and to "Mr. Smith's" router). There we couldn't use shielded plugs because his off-the-sheld cable/DSL router wouldn't take the shielded plug.
Any recommendations would be greatly appreciated.
I imagine we should have our UPS on a dedicated circuit inside his house, that would probably help for starters to isolate his equipment from ours. The only reason we have the UPS inside his house is because we didn't think the UPS could take the variations between heat and cold. Otherwise we would have just gotten a small power pole and meter put in at the tower.
Note the tower and his house are separated by about 150 ft. or more. The AC power and shielded Cat5 run underground in PVC pipe to the tower.
Thanks for any help you guys can provide.
Note that the "NOC" is 10 miles away (the Trango is the backhaul) where our main Cisco router, T1 line, monitoring computer, etc. is. None of that is reflected in the drawing.
Ben |
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lutfulPremium
join:2005-06-16
Ottawa, ON Reviews:
 ·TekSavvy DSL
| said by bcbuie:the tower and his house are separated by about 150 ft. or more. The AC power and shielded Cat5 run underground in PVC pipe to the tower. The "exposed" section of cable could pick up voltage surge from lightning miles away. So, you need separate CAT5 8-pair surge protectors at both the top and the base of the tower.
Often just grounding to the tower metal is OK if concrete base is usually wet and conductive. You can google for HAM and lightning for expert advice on "single-point" grounding. |
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| reply to bcbuie
Re: grounding and lightning protection recommendat Look up Motorola R-56 standards for grounding.
Any jumpers you have using 10 gauge should be also replaced with 6 AWG Cu as well.
FWIW If your tower gets blasted directly with lightning, there is nothing thats going to be able to stop it from blowing crap up. What you really need to worry about is static from near-by strikes. This is preventable by using proper grounding techniques as well as good spike arrestors. For our sites we use Transtector brand stuff as well as Polyphaser for our coax runs.
FWIW we have been doing radio related stuff for over 25 years.....live and learn. |
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| reply to bcbuie
You can use fiber converters to connect the PoE to the switch and from the switch to your customer. That will totally isolate your customers equipment and protect some of yours. |
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robbinPremium,MVM
join:2000-09-21
Leander, TX
kudos:1 | reply to bcbuie
Re: grounding and lightning protection recommendations You don't show any ground wires or ground rods on your diagram. You also don't show any lightning protectors (you should have multiples). Could you elaborate on what you have already done? I saw what you wrote in your first post, but am not sure what to make of it. It appears that you just pounded in one 8' rod at the base of the tower and connected it to the tower and considered everything grounded. Did I miss something? |
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| reply to bcbuie
Re: grounding and lightning protection recommendat No, you didn't miss anything, all we have is an 8 ft. ground rod and have the tower grounded to it.
That is why I am asking for recommendations.
Thanks,
Ben |
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nwnPremium
join:2004-03-05
Centerville, IN | 
Tower Grounding |
The theory is that with a large enough ground grid, the energy can be dissapated before there is a strike. Don't know if that is what happens, but this has worked for me.
Also, all cables that run up the tower have surge suppression on them. Keep that induced voltage as low as possible.
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Scott |
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pointrowPremium
join:2003-09-23
Poplar Bluff, MO | we have done this also but we ran a ground wire from the perimeter ring to the breaker box. just to tie everything together. learned that from the old school. |
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| reply to bcbuie
I didn't mention the tower is 170 ft. tall.
Do all the guy wires act as grounding points at all?
Another thing, how do you keep the tower from basically being a huge lightning rod? It is by far the tallest structure (by a good margin) in a 5 mile radius, and the only metal structure of any height within a 5 mile radius (no cell towers or anything).
It just amazes me that with the tower only being up less than 2 months it already took a direct lightning hit, or at least it sure seems like it did.
What would be signs that the tower took a direct hit vs. just having taken a hit close by?
Is that grounding rod grid designed to actually deter lightning from hitting the tower at all?
Ben |
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| reply to bcbuie
Also, what about AC power going between his house and the tower? The UPS I assume only protects in one direction, i.e., it is protecting the tower equipment from surges and spikes from his AC power. But what about the other direction?
Ben |
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lutfulPremium
join:2005-06-16
Ottawa, ON Reviews:
·TekSavvy DSL
| said by bcbuie:what about AC power going between his house and the tower? The UPS I assume only protects in one direction UPS surge protection is usually designed for low-level surges that come through the Hydro protection circuit - most likely the warranty will be void if you run AC cable outdoors.
Look at this Transtector brochure for a visual on how to protect a home at the cable entry point.
»www.transtector.com/Documents/NE···hure.pdf |
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nwnPremium
join:2004-03-05
Centerville, IN | reply to bcbuie
The tower being a lightning rod is not necessarily a bad thing. As long as it is the tower and not your antennae. I think it is Alvarion that has a white paper about how to help protect the antennae. It is an informative read.
Surge protect all wires. Have a common ground. Use BIG wire for ground. 10AWG is not big. 2AWG is getting big. There is a difference here between safety grounding and lightning bypass grounding. Search the archives. Lots of discussion on this very topic.
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Scott |
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 John GaltForward, MarchPremium
join:2004-09-30
Happy Camp
kudos:3 | reply to bcbuie
Re: grounding and lightning protection recommendations Good discussion with some pictures:
»www.swssec.com/grounding.html
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A is A |
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public
join:2002-01-19
Santa Clara, CA | reply to bcbuie
Re: grounding and lightning protection recommendat said by bcbuie:I didn't mention the tower is 170 ft. tall. Do all the guy wires act as grounding points at all? Another thing, how do you keep the tower from basically being a huge lightning rod? It is by far the tallest structure (by a good margin) in a 5 mile radius, and the only metal structure of any height within a 5 mile radius (no cell towers or anything). It just amazes me that with the tower only being up less than 2 months it already took a direct lightning hit, or at least it sure seems like it did. What would be signs that the tower took a direct hit vs. just having taken a hit close by? Is that grounding rod grid designed to actually deter lightning from hitting the tower at all? Ben The expected happened. Of course the tower is a lightning rod. You must mount and protect your equipment in such a way that when the lightning current flows through the tower the protection can handle the effects.
One very good ground rod will give you 5-10 ohms. That means during a typical strike the tower base is up to 300 kV above ground. Can your protection handle that??
Read some of the earlier threads. All of this has been discussed many times before. |
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a1_AndyPremium
join:2005-12-29
Oshawa, ON Reviews:
 ·WIND Mobile
 ·Rogers Hi-Speed
3 edits | reply to nwn
gif |
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a1_AndyPremium
join:2005-12-29
Oshawa, ON
2 edits | reply to nwn
If all is lost anyway, Maybe try something like this?
oh and the grounds are separate to prevent interference.
Then give your client a wifi modem and you won't be responsible for his computer. |
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public
join:2002-01-19
Santa Clara, CA | reply to a1_Andy
Your omni acts as a lightning air terminal and will be blown to bits during each strike.
The so called arrestors are probably just small surge suppressors not capable of carrying the strike current.
Read some of the earlier threads on grounding and protection. |
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a1_AndyPremium
join:2005-12-29
Oshawa, ON Reviews:
·WIND Mobile
·Rogers Hi-Speed
4 edits | 10,000 hits is what my omni is rated for I heard, Now I don't want to test it. But yes I am not the highest on the tower so I have only taken near hits. I guess it wouldn't hurt to add a lighting rod of some sort to be safe if I was alone on the tower.
»Re: Hit by a lightning yesterday!
I read the thread its good.
So are the Gas tube 1,000V +/-20%, max 5,000amp no good? |
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| reply to bcbuie
Thanks for everyone's help, and special thanks to John Galt for contacting me directly.
We will implement a combination of:
1) surge surpression on the PoE going up the tower and on the coax in between the antenna and the radio
2) a heavy-duty grounding grid for the tower as described here and by John, with very heavy-duty ground wire
3) disconnecting "Mr. Smith's" home from the system completely; we will get power at the tower (either via a power-pole or solar) and put everything at the base of the tower and serve Mr. Smith via wireless. One less thing to worry about
Thanks again,
Ben |
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nwnPremium
join:2004-03-05
Centerville, IN | Mr. Galt's advice is always worth following.
Sounds like a good plan.
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Scott |
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