Grounding Tripod Antenna Question

[northwoodsradio]

Greetings. I have recently installed three TV style tripods on top of my metal shop roof at about 30 feet up. I have LMR 400 coming off all the tripods down to lightning arrestors that is grounded with 8 gauge wire.

My question is, should I look at running a ground wire from each of the tripods on the metal shop roof to a ground or tie them together? I guess in the past I have not grounded tripods on my roof, but I was wondering if this should be done. Yes I do know it’s required by NEC. If so, I do have an electrician schedule to come out to do other work and I could have it done to ensure it’s done properly.

Thoughts?

 

[mmckenna]

Well, NEC is always a good idea.
The idea is to get everything at the same potential. The tripods sitting on the roof may not have the best path to ground without a proper downlead.

If it was me, I'd certainly do that. Towers usually get well grounded, even though the antenna at the top gets connected to coax that passes through a lightning protection device.

Be wary of anyone that tells you to ignore code or to skip doing these sorts of safety things. Some think that because they are lucky, they are skilled. Eventually luck runs out….

 

[cavmedic]

Not sure I’d trust an electrician to properly
ground an antenna mounting system.

I understand you won’t be looking for an R56 install, but very few sparkies I’ve come
across understand what needs to be done and have the basic tools to test the ground resistance after the fact.

Their answer is to just throw in multiple ground rods because a few hundred bucks for a ground resistance meter is too expensive, but will spend thousands on Milwaukee Packout gear.

 

[prcguy]

Here is one of many sites that have easy to understand antenna and mast grounding to code.

https://www.mikeholt.com/files/PDF/Radio_and_Television_2014NEC.pdf

 

[northwoodsradio]

Well, NEC is always a good idea.
The idea is to get everything at the same potential. The tripods sitting on the roof may not have the best path to ground without a proper downlead.

If it was me, I'd certainly do that. Towers usually get well grounded, even though the antenna at the top gets connected to coax that passes through a lightning protection device.

Be wary of anyone that tells you to ignore code or to skip doing these sorts of safety things. Some think that because they are lucky, they are skilled. Eventually luck runs out….

I agree. NEC is the standard. I was planning on doing it and I can sleep better at night knowing it is too.

My plan was to run wire from each and then follow the side of the metal roof to a ground.

Would it make sense to tie them together with with a continuous line or do each tripod separately?

I have always grounded my towers at the base, kinda new to the tripod thing again.

 

[mmckenna]

For lightning protection, you want the straightest/shortest run you can get. Avoid sharp bends, also.

I'd run a ground lead as straight as possible down to a rod.
By code, all rods must be bonded together, bonded to the electrical ground rod, and all your lightning protectors.

 

[northwoodsradio]

For lightning protection, you want the straightest/shortest run you can get. Avoid sharp bends, also.

I'd run a ground lead as straight as possible down to a rod.
By code, all rods must be bonded together, bonded to the electrical ground rod, and all your lightning protectors.

Straight is going to be tricky it will have to bend or curve at least once to go down the wall to the ground. I was looking at enclosing in conduit where I can to hide it. Is conduit okay to conceal?

 

[prcguy]

Straight is going to be tricky it will have to bend or curve at least once to go down the wall to the ground. I was looking at enclosing in conduit where I can to hide it. Is conduit okay to conceal?

Ground downleads in conduit is not ideal for lightning protection and is probably worse than sharp bends as it chokes off the conductor and makes it less appetizing for lightning. Concealing ground wires in conduit is sometimes required by code where the wire is accessible but grounding per NEC is for human safety and not necessarily for lighting protection. For that you might study the Motorola R56 grounding standards and it may turn out you can’t really protect from a direct lightning hit unless you hire a company that specializes in this and pay lots of $$.

 

[mmckenna]

Straight is going to be tricky it will have to bend or curve at least once to go down the wall to the ground. I was looking at enclosing in conduit where I can to hide it. Is conduit okay to conceal?

Bends are almost always required.
If required, you want them to be a sweep, not a sharp bend. Sharp points become a place where lightning likes to jump off.

Like prcguy said, you need to be careful with conduit. Using metal conduit can act like a choke and reduce the effectiveness.

Where we've done this at work, we use either PVC, or a grounding bushing at each end.

 

[northwoodsradio]

Ground downleads in conduit is not ideal for lightning protection and is probably worse than sharp bends as it chokes off the conductor and makes it less appetizing for lightning. Concealing ground wires in conduit is sometimes required by code where the wire is accessible but grounding per NEC is for human safety and not necessarily for lighting protection. For that you might study the Motorola R56 grounding standards and it may turn out you can’t really protect from a direct lightning hit unless you hire a company that specializes in this and pay lots of $$.

Thanks for the input. That makes sense. That’s the goal with being on provide property is the lightning protection. I will research more into this standard and make some informed decision on how to design it. Thanks for the info! This very helpful everyone!

 

[northwoodsradio]

Bends are almost always required.
If required, you want them to be a sweep, not a sharp bend. Sharp points become a place where lightning likes to jump off.

Like prcguy said, you need to be careful with conduit. Using metal conduit can act like a choke and reduce the effectiveness.

Where we've done this at work, we use either PVC, or a grounding bushing at each end.

Thanks! That makes sense. I could certainly run them off my back side of the shop to ground by running a clamp then wire across the metal shop roof of my lean too side then straight down to ground and would be hidden from the main side.