We have suffered large amounts of lightning damage (mostly current passing through our cat-5 cable, much like the cat-5 cable is picking up the static electricity like a radio antenna) and it’s fried more than one radio - including the pins in the radio.
We have recently rewired a very prone tower using 2 300SS modules - one at the bottom of the tower in our building near the hub and the other at the top of the tower near the radios - the theory being if surge passes through our cable, it’ll be stopped at either end.
WE GOT FRIED.
pix at http://www.cyberbroadband.net/damage2006
A few questions…
1) is 2 300SS’s a bad thing?
2) could the blown chips on the radios you see have been caused by an overloaded or fully charged drill battery or reverse polarity? (we have used drill batteries for testing successfully in the past)
3) What advice can you give us?
Thanks,
Cyber Broadband
Cullman Alabama
I’m a partner with the previous poster. We also need to mention that there are 3 ground wires. Two ten foot runs to the electrical ground serve two 300ss’s in our service room. One for the SM cat 5 cable and one for the AP cat 5 cable. The other ground is 200 to 300 feet long going bonded to same electrical ground and serves two daisy chained 300ss’s at the top of the tower. In a nutshell, each cat 5 cable has 2 300ss’s and is served by a 10 foot ground at one end and a 200 to 300 foot ground at the far end. Both runs are 10awg stranded cable.
does the tower have a lightening rod ?
what else is on the tower ?
this tower is a rural water tower with nothing else on it. we’re it.
Am I reading that you ran a ground wire up the tower? If so it needs to be 0awg, you really should not run a ground up the tower anyways as it may give the current another path causing an arc on the way down.
This is what I have read on various forums and google about a proper tower ground I am in no means an expert on grounding. If someone has corrections to what I say correct it!
Iideally you should have three ground rods, the ground rods will need to be in a sort of triangle and be twice their length from each other, if you have 8 foot ground rods they need to be 16feet from each other, the ground rods should be bonded together with a circular ground loop and then attached to the tower. You should use some solid 4 or 6 awg here .
So bond the towers ground to your electric ground with some 2 or 4 awg. and use the tower “as the ground wire” for the two surge suppressors at the top. I think with a 250 foot run of 10awg you are not accomplisihing anything whatsoever so far as grounding is concerned. Also stranded does not have the same capacity as solid when a strike is concerned. All your ground points need to be at the same potential, or as close as you can get them.
bm
i too have a simliar set up gnd ring and rods out try isolating your gear from the tower with rubber mounts.
milbrath wrote: Am I reading that you ran a ground wire up the tower? If so it needs to be 0awg, you really should not run a ground up the tower anyways as it may give the current another path causing an arc on the way down.
You are correct. We actually have two grounds. The one that ran up the tower and a shorter run in our equipment shed. Both connect to the electrical ground.
This is what I have read on various forums and google about a proper tower ground I am in no means an expert on grounding. If someone has corrections to what I say correct it!
Iideally you should have three ground rods, the ground rods will need to be in a sort of triangle and be twice their length from each other, if you have 8 foot ground rods they need to be 16feet from each other, the ground rods should be bonded together with a circular ground loop and then attached to the tower. You should use some solid 4 or 6 awg here .
So bond the towers ground to your electric ground with some 2 or 4 awg. and use the tower "as the ground wire" for the two surge suppressors at the top. I think with a 250 foot run of 10awg you are not accomplisihing anything whatsoever so far as grounding is concerned. Also stranded does not have the same capacity as solid when a strike is concerned. All your ground points need to be at the same potential, or as close as you can get them.
Unfortunatly, we are not in a position to change the grounding of the water tower so we are stuck with using the electrical grounding post.
bm
Ahh it’s a water tower.
Ground the Surge Suppressors to the water tower. A water tower will be grounded, it pretty much can’t help but be well grounded. Find someting welded to the structure you can clean the paint off of, say the back support of the ladder, if the handrails are welded to the structure you could use them. Usually there is also a small ladder going to the top and may also be directly attached to the structure via a weld, and attach your much shorter grounds there. Use some solid 6 or 8 to to the surge suppressors. Use 10 awg on short runs, client radios… longer runs need thicker stuff. Stick with solid as compared to stranded
Then bond your electrical ground to the water tower. By attaching a 4-6 solid awg to the metal structure at the base. This should make everyting at pretty much the same potential.
I will also ask, do you have a lightning arrestor between the AP & antenna?
Will that stop a direct hit, NO! But should handle static farily well. I assume you are using sheidled cat5.
Again don’t take my word on this, that’s just how I’d do it. Someone else may have a better suggestion, and if they do, that will be my new method.
BM
jay wrote:
1) is 2 300SS's a bad thing?
2) could the blown chips on the radios you see have been caused by an overloaded or fully charged drill battery or reverse polarity? (we have used drill batteries for testing successfully in the past)
In heavily prone lightning areas we have suggested the use of a 2nd 300SS. As energy is quickly taken down the tower to ground it is natural to have a small amount flow up. In most cases a floating 300SS at the top will protect the radios from that energy. The cable length from the AP/BH at the top of the tower to the 300SS should be <10'. Also, the rest of the cabling should be tested and the drain wire must be properly terminated to the shielded connectors. If you have any cable loss you might find it difficult to pass data if set to 100Mbps. If you are having trouble passing data then force the radios to 10 Mbps until you can have the cabling fixed/replaced.
Can you post pictures of the plastic housing of these radios?
There is some concern on your grounding. The tower should be checked and validated against your local electrical standards.
Where are your radios on the tower, at the top? Can you post a picture of the tower?
Regarding your second question, if the battery put out greater than 65V then yes it could have caused similar damage. What voltage was the battery? I havent seen a drill battery over 24V but never looked for one larger.
We recently dealt with a static issue on a water tower for some non-canopy radios equipment. Another contractor installed the radio equipment, we just maintain it now.
What we did after replacing the radios, was install some Andrew ground kits on the coaxial cable from the antenna to the radio, and tied that to the railing around the top. The paint was scraped and cleaned down to bare steel, and holes were made for bolts. Burndy conductive grease was applied and the connector was grounded. The NEMA enclosure for the injectors and other equipment was also grounded using #4 stranded. In addition, Polyphaser bulkhead connectors were installed on the coax just prior to it passing into the enclosure that houses the radio, and grounded to the same point as the ground kits using #6 stranded.
Inside the radio housing we installed some Citel RJ-45 spike supressors to protect the ethernet just before it come into the radio and just after the power extractor. These were also installed inside the NEMA enclosure just before the cable runs into the injectors.
After this, another storm rolled through of the same intensity and someone else equipment got bit, but the stuff we maintain kept on ticking.
If you would like to learn the proper technique for grounding a radio communication’s site I would suggest seing if you could get your hands on a Motorola R56 Manuel. All the work I do for Motorola R56 is a requirement. Also I sent Jerry and VJ a Canopy wiring and installation guide that has some pretty good info in it. I dont know why it is not on this site but I will try to get it up on the net this weekend.
The canopy wiring document is a good refrence guide. You are right it should be on the website.
R56 manual, can you download it or does it have to be purchased ?
I think you can get it in print form or on CD. I have it in print. It’s about 4 inches thick. I will get you the part no.
You have to buy R56 training manuals. We have it on PDF and in print at the office as the type of work the other side of the house does requires us to be in compliance with “Mother Motorola”.
And besides that, some of our customers on that side of the house get pissy if their stuff is not R56.
mmm… any idea how much it costs… I don’t know how much benefit there is in investing in them… will have to see an index or content of the manuals…
well first of all do not use the original ground rod of the electrical system i had trouble with ac noise feeding back into the 300ss causing problems go ahead and drive another ground rod.
in other words think of it this way if you hook your 300ss to the breaker box ground rod you are basically hooking it up to the nuetral wire going to the transformer which is twisted with a total of 220 volts ac just waiting for a surge from the transformer. as well as injecting small amounts of ac ripple into it.
i been hit once it was last week got my 900 apc but i fixed it myself the symptom was everytime i plugged in a psu it would blow the psu in about 5 mins so i replaced the surface mount diode beside the ethernet jack which was shorted and the step down voltage regulator p# LM2596S-ADJ but let me warn you these are hard to get off and we just happen to have the kinda of equipment to replace them here for i to tv repair also.
this unit got hit basicaly floating i did have a 300ss on it but not grounded yet i hadn’t had time but guess what it was on a water tank too.
also moto i heard some of you BH’s had fuses in them would it not be effecient to put a small pico fuse between pin1 input on the regulator and pad to suffice as a small break point for a little more surge protection?
There are a few problems with your grounding setup;
First you have too long of a run ran; 200 feet is way to long to ground on a tower, if there is a nick in the sheath it could arc with the tower.
Second, you should use a true earth ground as much as possible, this will reduce the path the electricity would travel to actually get to a grounding point.
Third, I am not 100% sure on this, but I think that the motorola 300SS only grounds the poe pins on the RJ45, ( 4-5 , 7-8 ). This means that there is a possibility for a high voltage current to go through the data pins on the ethernet and cause damage on the tower mounted equipment as well as any switches or routers that you have at the site as well. I know that transector makes a product that does provide some grounding on all data pins as well as the poe pins, not sure on the model number.
Try Polyphaser IX-2H2DC48/W for a 48V PoE unit. I have gotten these to work with canopy. You have to change around the pairs to get it to work properly but it works.
Yes, there are pictures available of the damage at :
http://cyberbroadband.net/damage2006/
i will post back with more responses later.
jay fuller
cyber broadband inc
I didnt see any pictures of the damaged plastics. Do you have pictures of the outer plastic shell?