Listed Question, Black Hole

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dereckbc

dereckbc

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Now that I have your attention, I stumbled into a big black hole during a Bonding & Grounding class I gave recently at a hamfest. A relatively large class, I knew several attendees professionally and personally as they are both Hams and electrical contractors I have worked with for decades,

As I covered article 810, exceptionally 810.57 requiring a listed ADU, John, a contractor I have worked with for decades, interrupted and informed me it was BS. He was right. Impossible to comply with. There is no such thing as a Listed ground block or ADUs used by radio operators. I was stunned and asked how we got away with it for decades and hundreds of inspections. No one checks or cares when a PE stamp is involved, I own the responsibility if something happens. No UL-listed ground blocks or ADUs are manufactured for radio operators I am aware of.

Walking into any box store or supply house, you will find hundreds of ground blocks and ADUs for CATV using 75-ohm coax and “F” type Coax connectors stamped with UL-452. Radio transmitter and receivers do not use “F” type CATV Coax Connectors, operate at much higher power levels, and is 50-ohms.

I use high-end Industrial equipment from manufacturers like CommScope and PolyPhaser, who make HEMP-rated ADUs for the military and all ADUs for cellular and commercial users. They have all kinds of listings, standards, and certifications. All have CE, MIL-STD, and IEC ratings; none have UL. I know CE will not cut the mustard, perhaps IEC?

Not sure if there is a correct answer or not. I know I have to change course material and am not comfortable saying, ignore the code, do not pull a permit, buy a quality ADU, and do the best you can. It is impossible to comply.

Any Inspectors out there. All comments are welcome.
 
Maybe you can explain it a bit more for us unfamiliar with Article 810:

(2020) section 810.57 doesn't use the word "listed." I do see some general language in 810.6 and 810.7 that require "antenna lead-in surge protectors" and "grounding devices" to be listed. But 810.57 is about an "antenna discharge unit" that "drains static charges from the antenna system."

So seems like you could use a listed surge protector (if required) with an unlisted ADU. What am I missing? Draining static charge seems like a different function from surge protection (from lightning?)

Cheers, Wayne
 
wwhitney said:
Maybe you can explain it a bit more for us unfamiliar with Article 810:
Click to expand...
OK, good idea.
wwhitney said:
(2020) section 810.57 doesn't use the word "listed." I do see some general language in 810.6 and 810.7 that require "antenna lead-in surge protectors" and "grounding devices" to be listed. But 810.57 is about an "antenna discharge unit" that "drains static charges from the antenna system."
Click to expand...
OK, working from 2011 in my area, but I looked and realized where I went wrong, reading something into the code that is not there. You are correct; the; word LISTED is not there. So, where did I go wrong?

810.57 is in Section 3 of article 810, additional requirements for transmitters, and this is where I and many others get sidetracked. Back up to Section 2 810.20, and you get this:

(A) Where Required. Each lead-in conductor from an outdoor antenna shall be provided with a listed antenna discharge unit.

This is for a receiving antenna like a TV; it makes no sense why one requires listed and the other does not. Considering a Radio transmitter is a separately derived source like an Inverter generates up to 500 Volts AC @ 3-amps. Amateurs operate up to 1500 watts. The more demanding, dangerous,s and stress on equipment is the transmitting antenna system.
wwhitney said:
Draining static charge seems like a different function from surge protection (from lightning?)
Click to expand...
No, sir, the same thing. The ADU is the same thing all services like Telephone, CATV, Internet Service Provider, and SATV use to comply with 250.94 IBT bonding requirements to the Service. For example, CATV and Telco call a NID or Network Interface Device. Either Gast Tube, Carbon Block, MOC, or SAD devices to arrest any static or lightning charge to earth before it enters the premises. TV and radio coaxes are treated the same way and called ADUs.

Many antennas used for transmitting are not DC grounded. The center conductor is isolated from the shield going straight up the tower, emerging from the coax as a single insulated wire at the top of the tower, screaming at the clouds, Pick Me! It needs both static and lightning protection. FWIW some of the HEMP-rated ADUs are rated for 100Kva @ 30mJ.

HEMP = High altitude nuclear explosion Electromagnetic Pulse, making lightning look like a static carpet discharge.
 
dereckbc said:
OK, good idea.

OK, working from 2011 in my area, but I looked and realized where I went wrong, reading something into the code that is not there. You are correct; the; word LISTED is not there. So, where did I go wrong?

810.57 is in Section 3 of article 810, additional requirements for transmitters, and this is where I and many others get sidetracked. Back up to Section 2 810.20, and you get this:

(A) Where Required. Each lead-in conductor from an outdoor antenna shall be provided with a listed antenna discharge unit.

This is for a receiving antenna like a TV; it makes no sense why one requires listed and the other does not. Considering a Radio transmitter is a separately derived source like an Inverter generates up to 500 Volts AC @ 3-amps. Amateurs operate up to 1500 watts. The more demanding, dangerous,s and stress on equipment is the transmitting antenna system.

No, sir, the same thing. The ADU is the same thing all services like Telephone, CATV, Internet Service Provider, and SATV use to comply with 250.94 IBT bonding requirements to the Service. For example, CATV and Telco call a NID or Network Interface Device. Either Gast Tube, Carbon Block, MOC, or SAD devices to arrest any static or lightning charge to earth before it enters the premises. TV and radio coaxes are treated the same way and called ADUs.

Many antennas used for transmitting are not DC grounded. The center conductor is isolated from the shield going straight up the tower, emerging from the coax as a single insulated wire at the top of the tower, screaming at the clouds, Pick Me! It needs both static and lightning protection. FWIW some of the HEMP-rated ADUs are rated for 100Kva @ 30mJ.

HEMP = High altitude nuclear explosion Electromagnetic Pulse, making lightning look like a static carpet discharge.
Click to expand...

Some of this is accurate, some isn’t,

Chapter 8 is special. As explained in chapter 1 of NEC chapters 1-3 apply to “everything”. Chapters 4-6 modify chapters 1-3. In chapter 8 though you ignore chapters 1-3 including a Listing requirement unless it is called out specifically.

Lightning protection systems aren’t even NEC. They fall under a strange brew of the LPI standard, NFPA 780, and UL or some other NRTL for some parts.

And the comment about using devices such as GDTs is way off base here. A GDT has a very low voltage MCOV rating. That’s great if your signals are under 50 V like in receivers but not good in high power transmitters. If you are transmitting 50 Watts to a 50 ohm load, what is the Voltage?

As far as HEMPs go those ratings are ridiculous. One consideration you need is what is the CFO (critical flashover voltage) of your coaxial feeder? Because at some point your feeder IS the surge protection.
 
810.6 conflicts under general requirements added in 2014 again say LISTED ADU's, and 810.57 contradicts the language used.
 
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