Antenna mast grounding
- Thread starter michaelr
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bphgravity
Senior Member
- Location
- Florida
See section 810.21 of the NEC, specifically part (F).
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
I believe the answer is that the access point for the LV installer would need to be accessible without opening a high-voltage cabinet.
Mike Holt said:
An accessible bonding point must be provided at service equipment or the disconnecting means of separate buildings or structures for communications systems. The point can be any one of the following:
(1) An exposed, nonflexible metallic raceway.
(2) An exposed grounding electrode conductor.
(3) An external connection approved by the authority having jurisdiction.
FPN No. 2: Communications systems must be bonded together. Figure 250?134
? Antennas/Satellite Dishes, 810.21
? CATV, 820.100
? Telephone Circuits, 800.100
Author?s Comment: The bonding of all external communications systems to a single point minimizes the possibility of damage to the systems from potential (voltage) differences between the systems.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Amazing, isn't it?michaelr said:
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
What percentage of the direct digital TV dishes are correctly grounded and bonded? Has anyone ever seen one done per the NEC?
Just the one's at my home, and that's because I did them.tom baker said:
The AHJ here doesn't do any inspection on any residential LV wiring.
Usually, I see the mast and the coax shield grounding block bonded to a nearby exterior light fixture, or sometimes a hose bib.
BTW, the common consumer-grade coax cable ground blocks are not "discharge units" specified in 810. All they do is provide a means to ground the shield, which is all that's required for coaxial cable.
georgestolz said:
This is for a pumping station telemetry radio, all of my equipment is mounted inside the control cabinet already. The ground distribution block is in there as well. My question was can I just ground everything (mast, discharge unit) right at that point, which ultimately goes to the grounding electrode system?
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Where's the main disconnect for the building? I believe it's supposed to be terminated there.
Disclaimer: I've never worked on what you're working on.
Disclaimer: I've never worked on what you're working on.
810.21(F) lists potential bond points quite clearly. Essentially, equipment ground (such as the ground block in the control panel Michael speaks of) is never used as a bond point. The path created by the antenna and lead-in discharge grounding conductor is always taken as directly to earth as electrically possible... and that means never through equipment or an equipment grounding conductor. Though equipment grounding may provide a low impedance path to earth ground, the slight resistance that it does have to the grounding electrode system could elevate bonded equipment enclosures and such to damaging if not fatal voltage levels when an attempt to dissipate thousands of volts is in progress.georgestolz said:
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
michaelr: I design, install and maintain water SCADA equipment, and have converted to radio. It took me a while to come to understand art 810 and 820.
What your objective is is to create a single point ground. You can use the cabinet to do this, as long as you meet the requirements in 810 and 820.
I install the antenna outside on a 21 ft stick of sch 40 water pipe. its hinged at the base, the coax runs inside it and via a C conduit body into the building. The impusle supressor is mounted just inside the building, its bonded outside via a 2 AWG BCS to the mast and a ground rod, and this is bonded to the building ground system.
the mast can be lowered to the ground via a portable winch. Inside the building I change to a flame retardant coax, I use LMR400.
This system keeps the antenna off the roof and is very clean. I have seen a lot of SCADA radio systems and almost all are poorly installed and wrong.
PM me and I can email you some pictures.
Most of the system integrators get the installations wrong as well.
What your objective is is to create a single point ground. You can use the cabinet to do this, as long as you meet the requirements in 810 and 820.
I install the antenna outside on a 21 ft stick of sch 40 water pipe. its hinged at the base, the coax runs inside it and via a C conduit body into the building. The impusle supressor is mounted just inside the building, its bonded outside via a 2 AWG BCS to the mast and a ground rod, and this is bonded to the building ground system.
the mast can be lowered to the ground via a portable winch. Inside the building I change to a flame retardant coax, I use LMR400.
This system keeps the antenna off the roof and is very clean. I have seen a lot of SCADA radio systems and almost all are poorly installed and wrong.
PM me and I can email you some pictures.
Most of the system integrators get the installations wrong as well.
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