Topic: Weather station grounding

[Koolkid1935]

I have a question regarding grounding our weather station and tripod in the event of a lightning strike.  The house's existing ground rod is fairly difficult to get to since the landscape around it was brought up 4 feet and thus burying it (not a good situation, but it is what it is).  My question is, can I or should I drive another 8' rod just for the weather station and tripod or try and get to the existing ground rod and ground to it?  If you need pictures of the tripod and proposed location for the new rod in relation to where the existing rod is, just ask and I will go take some.

[racenet]

The ideal situation would be to use the same grounding point. If you can't, then use another rod, as close as possible to the other rod.

Just to clear the air on the whole thing. Grounding your station will do nothing with a direct strike. That is not what the grounding is used for. Is used to discharge static build-up, which will hopefully prevent a strike to the grounded equipment. If it receives a direct hit, grounded or not, it and anything directly attached to it is burnt toast.



Bob

 

[Koolkid1935]

Thanks for the info.  What about something like this that has a relatively low clamping voltage? http://www.metrix.net/cat-5-lightning-arrestor-p-23.html

It sounds like once it gets above the clamping voltage on that pair it acts like a fuse and breaks the connection between the incoming and outgoing pair.  I realize that lightning has massive amounts of voltage and current, but would this at least help out a little bit?

[Jim18655]

The ideal situation would be to use the same grounding point. If you can't, then use another rod, as close as possible to the other rod.

Just to clear the air on the whole thing. Grounding your station will do nothing with a direct strike. That is not what the grounding is used for. Is used to discharge static build-up, which will hopefully prevent a strike to the grounded equipment. If it receives a direct hit, grounded or not, it and anything directly attached to it is burnt toast.



Bob

 

Drive a new rod if you must, but all grounding systems must be connected together per the "National Electrical Code".
250.58 -Common Grounding Electrode.
 Where an ac system
is connected to a grounding electrode in or at a building
or structure, the same electrode shall be used to ground
conductor enclosures and equipment in or on that building
or structure. Where separate services, feeders, or branch
circuits supply a building and are required to be connected
to a grounding electrode(s), the same grounding electrode(
s) shall be used.
Two or more grounding electrodes that are bonded together
shall be considered as a single grounding electrode
system in this sense.

250.60 Use of Air Terminals. Air terminal conductors and
driven pipes, rods, or plate electrodes used for grounding
air terminals shall not be used in lieu of the grounding
electrodes required by 250.50 for grounding wiring systems
and equipment. This provision shall not prohibit the required
bonding together of grounding electrodes of different
systems.
FPN No. 1: See 250.106 for spacing from air terminals.
See 800.100(D), 810.21(J), and 820.100(D) for bonding of
electrodes.
FPN No. 2: Bonding together of all separate grounding
electrodes will limit potential differences between them and
between their associated wiring systems.

Run a piece of #6 copper between the two systems and your new rod should be a minimum of 6' from the old one. Ideally it should be at least twice the length of the rods apart - 16' for 8' rods.
You might think this is overkill until you have a lightning strike and the insurance company comes out to settle your claim. I worked with person who was a maintenance man in several factories for over 30 years. He cleaned his oil burner and several months later had a fire because of the furnace. The insurance company fought his claim for over 2 years because he wasn't a qualified oil burner technician.

Jim

[GvlSkywarnNCS]

FWIW the subject of lightning protection is still controversial. You have to remember the power involved from the spark that just jumped through possibly miles of air, which is about as good an electrical insulator as there is!

As a Ham radio operator I've heard lots of stories of lightning strikes and have lost a few radios myself from a nearby strike(should have unhooked the ungrounded antennas before leaving home, my fault). I also lost half of the AC appliances in my house in another instance when lightning struck a nearby tree then jumped to the wiring coming from the power pole. You could see the burn mark on the tree stop at the level of the wire. The only effective grounding system I know of for tower structures is a series of buried radials hooked to a horn gap like the commercial broadcasters use- and even that that isn't 100% certain.

The NEC advice already listed is good but bonding to the house wiring ground may not be a good idea in every case. If there is nothing in common between the two(such as with a wireless WX station on a mast, or coax from a radio that will be unhooked outside of the structure)making this bond will only ensure that a strike will enter your house wiring where it can wreak havoc unless the strike was dissapated completely before getting to your house ground! But if there's any commonality- bond the grounds. Transmitters and amplifiers can do strange things due to ground loops from bonding but that's another topic in itself.

Generally you want a minimum of three 8 ft. grounding rods about 6 feet apart in a triangle, all bonded together with the first rod as close to the protected mast/tower as possible using solid copper 6ga wire and non-corroding brass connections. The rod spacing should be somewhere between 3/4 and 2 rod lengths apart, closer serving better for dry soil and farther serving better for wet soil. Get solid brass rods, the brass plated steel ones you usually see at RS and such will corrode over time and they will introduce a resistance differential between your house ground if they're bonded together. The strike will seek the least resistance so the majority of it will be directed to the solid brass rod at your house which kind of defeats your intent.

If the lightning makes it as far as entering your house, all bets are off and as always your best and sometimes only protection is a good insurance policy. Even if all you can manage is a single ground rod it is a lot better than nothing because most lightning damage is from near-hits and a single rod will usually handle that.

[Mark / Ohio]

Welcome to the forum GvlSkywarnNCS! 

[ncpilot]

With all the pathways into one's house from a remote strike, let alone more direct strike, I'm not sure I understand this fascination with grounding as a means of lightning "protection"... unless it's necessary for the proper operation of the electronics themselves, why fool yourself?

I'm not trying to be argumentative, but I've followed this line of thought for many years in other forums, and no one has been able to show any benefit from any low end type of protection, e.g. a wire to a ground rod. As some in this forum (and others) have pointed out, to get any degree of confidence you'd need a commercial grade protection system, which isn't cheap, and from all of my research, is primarily intended to save the structure, not anything inside the structure.

[port1]

   Marc is right.  No argument taken.
A direct hit means your equipment is a gonner.  That ground rod will best serve static discharge and some missive, stray voltages.
A commercial systems costs thousands, and is meant to protect thousands of dollars worth of equipment.  And there is a difference between grounding and "earthing", another set of concepts meant for another discussion.

Bottom line is this:  It's not a bad idea to add a ground rod and copper wire to your station, but if lighting hits it directly, kiss your station goodbye. 

Henry

[GvlSkywarnNCS]

Agreed on the direct hit- everything will be toast Yet the better your ground and surge supression system is, the lower your chances for non-direct hit damage. Me? I take more chances that I should I guess because I'm renting and won't be here for too much longer if things go as I hope they do. Once I'm permanantly located you can bet your bippy that all my stuff will be very well grounded- probably enough to take a direct hit. I'll be working with a broadcast engineer on that- he definately knows about this subject since his antennas get direct hits all the time 

BTW, an older wooden apartment building here in Greenville SC took a direct hit this afternoon with expected results- all ashes  At least only some unattended pets died and nobody else got hurt. My usual daytime Skywarn NCS did a good job handling that report- I was listening at my workplace when that report came in. One of those "WOW!" events 

Phil

[port1]

Agreed on the direct hit- everything will be toast Yet the better your ground and surge supression system is, the lower your chances for non-direct hit damage. Me? I take more chances that I should I guess because I'm renting and won't be here for too much longer if things go as I hope they do. Once I'm permanantly located you can bet your bippy that all my stuff will be very well grounded- probably enough to take a direct hit. I'll be working with a broadcast engineer on that- he definately knows about this subject since his antennas get direct hits all the time 

BTW, an older wooden apartment building here in Greenville SC took a direct hit this afternoon with expected results- all ashes  At least only some unattended pets died and nobody else got hurt. My usual daytime Skywarn NCS did a good job handling that report- I was listening at my workplace when that report came in. One of those "WOW!" events 

Phil

Yup...that's a good description: "toast".
I concur.  Way too powerful, unless you spend thousands.
Tough to guarantee "complete" protection.
Good Luck there...
But in the end, just have fun!
This hobby of ours is too cool for anything other than fun. 

Henry

[Koolkid1935]

Bought quite a few feet of #6 while we were in Billings a few days ago.  Everyone's suggestions so far have been very helpful and insightful - never knew there was so much involved in something that originally sounded so easy.  What I will probably end up doing at least for now is running it from our existing ground rod up to the tripod just to get something there.  From what I gather and from what common sense dictates something is better than nothing.

I wanted your opinion on something else too.  I was trying to figure out how to ground the tripod while also grounding the surge protector.  The lady at Lowes suggested running the #6 up to the tripod, having it pass through the clamp and then onto the surge protector on one continuous shot of wire since they are both at the same location.  It sounds like a good idea to me but still wanted to put it out there for your thoughts on it.  If that sounds like a good idea my next challenge is getting the #6 terminated in the housing.  It comes with #12 cable (a couple feet worth) with bare wire on one end and a spade connector on the other.  The spade end is what terminates in the surge protector housing as well as the surge protectors themselves.

[port1]

  The lady at Lowes was correct.  That method is known as bonding.  Go for it. 

Henry