For those who have done Cellular equipment installs. A Master ground bar is installed where a halo ground ring bonds all the equipment together with antennas and metal platform. The drawings requires a master ground bar so everything is terminated at one location. The platform is a floating platform on top of roof and the only ground on equipement will be the one insite the electrical panel. Normally on other projects i have seen that a ground rod or building steel with a EGC/stinger going straight to master ground bar. Is there a requirement in NEC or a lightning issue with Master ground bar? or some other standard i can look up for this type of application.
grounding
- Thread starter mannyb
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- Licensed Electrician
The NEC requires a grounding electrode system, in this case probably a conductor to the building steel. Lightning protection is a whole different thing and is not in the NEC.
The rooftop shelter that I worked on had lightning protection done by a specialized contractor who tied into the building's existing lightning protection system.
The rooftop shelter that I worked on had lightning protection done by a specialized contractor who tied into the building's existing lightning protection system.
the skid will be a floating skid on roof. The skid will have a panel for equipment and a master ground bar for halo or single point grounding. I was just wondering where the Master ground bar gets its potential. Would I or could I run a ground from panel to master ground bar of ground or run a seperate GEC from service entrance straight to Master ground bar.
when we construct towers in raw land the grounding is never an issue because everytihing is tied together with service. I am just trying to be proactive with any problems or is this something i should bring to A and E attention.
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- Licensed Electrician
The GEC needs to go from the panel to the GES uninterrupted so no reason to use the master ground plate.
Ours was sitting on floating i beams and posts that cut into the roof and welded to the structural steel so a simple tag to the steel with a cad weld was all that was needed.
Ours was sitting on floating i beams and posts that cut into the roof and welded to the structural steel so a simple tag to the steel with a cad weld was all that was needed.
FionaZuppa
Senior Member
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- AZ
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- Part Time Electrician (semi retired, old) - EE retired.
i would use the biggest copper you could from panel egc down to building ges, and make sure the ges is good, perhaps even checking (suggest) that there are some ground rods. i would then also take a few smaller coppers from the gnd ring bonded to panel egc (or to the egc bus bar) and perhaps bonded directly to the bigger copper that goes from panel to ges. why? because you are not asking about NFPA lighting system, thus i would at least try to be lightning conscious and give multi path from ring to egc and a fat copper from egc to ges. just make sure whatever bonding is done has proper metal-to-metal interface because you want to minimize corrosion from dissimilar metals, etc. NEC required this way or required, no, but considering the application i would perhaps do it this way.
The Master ground bar is needed so all the equipment ,antennas, antenna mounts, electrical panel, and metal structures lead back to MGB for single point grounding. The metal skid is a floating skid that will sit on roof. The MGB is attached to skid. Rather than relying on EGC inside the feeder to panel. Is it desirable to have separate EGC to master ground bar from building ground rod or a totally separate ground rod or ground bus inside main distribution panel. Its normally required to have 5ohms or less for telecom grounding.
FionaZuppa
Senior Member
- Location
- AZ
- Occupation
- Part Time Electrician (semi retired, old) - EE retired.
equip to MGB is just that side of it. would i then bond that MGB to the panel egc, yes. would i bond the MGB to GES, yes. perhaps one bond from MBG to panel EGC, and then if possible multiple bonds from MGB over to GES, preferably different locations on the GES.
since electrical ckt's use the egc that comes up into a panel its probably a good idea to bond MGB to that egc. HOWEVER NOTED - if all the gear "grounding" is isolated chassis ground/bonding, then i would not tie that to panel EGC, i would take that to GES only. some gear use metal shell case isolated from the internal circuitry, a way of creating a isolated metal "shield". if stray voltage hits that shell it does not hit the internals. so verify is the MGB is for isolated metal shells of the gear, or if the metal shells of the gear are (any one of them) internally connected to ckt EGC.
i only suggest it this way because it seems there will not be a lightning arrest system installed.
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- Licensed Electrician
So you should bond everything together but make sure that certain parts of the bonded parts between the two systems don't overlap? That makes no sense.
- Occupation
- Licensed Electrician
All that matters is that everything else is done to spec and to code. There is nothing different that happens just because the shelter is on a roof instead of on the ground.
FionaZuppa
Senior Member
- Location
- AZ
- Occupation
- Part Time Electrician (semi retired, old) - EE retired.
no. thats not what i am saying. if the gear has isolated cases (frames, whatever) then i would not take that bonded stuff (aka MGB) over to EGC at panel, i would take it directly over to GES only. if however the gear cases are internally tied to EGC then i would take the external bonding (MGB) to both EGC in/at/on panel and GES. in all cases i would use multiple bond wires from MGB to GES.
in other words, if the MGB is a fully isolated bond (not connected to EGC by way of internals) then do not bond MGB over to EGC at panel. the EGC is typically bonded to GES at some point, but if the cases are fully isolated then i see no good reason to connect MGB to panel EGC, just take it as close to earth as you can. why? because if there is a lightning strike why have a zero ohms path directly into the panel? the multi wire from MGB to GES is a better way while at the same time the MGB would essentially be tied down to EGC via EGC/GES bond some place in the building. its more of a path thing then anything else, etc.
just my view of it.
- Occupation
- Licensed Electrician
Which is going to be tied to the A.C. EGC in the panel.
It's required by law and by good sense.
It's unavoidable in a properly wired system.
A lightning strike is to be expected. The whole point of all hundreds of bonding connections that are made in cell site is to keep everything at the same potential.
It's hoodoo voodoo superstition.
FionaZuppa
Senior Member
- Location
- AZ
- Occupation
- Part Time Electrician (semi retired, old) - EE retired.
well, we all hopefully know that equi-potential has nothing to do with amps, right.
there is no good reason to create a amps path for lightning from tower gear to an electrical panel.
- Occupation
- Licensed Electrician
Whatever point you are trying to make would be easier to understand if what you said made any sense.
FionaZuppa
Senior Member
- Location
- AZ
- Occupation
- Part Time Electrician (semi retired, old) - EE retired.
its very ez.
if i want to create a path for lightning AMPS, even if the "system" is not something you find in NFPA docs, you create a path away from things the best you can. creating a near zero ohms path for lightning AMPS directly into an electrical panel is not a good idea. having a few paths over to the GES helps get lightning AMPS into the earth w/o having to pass through an electrical panel and down any ckt/feed wires.
with the way electrical equipment is made these days, its all best effort, etc.
does that make sense, or do i need to make a diagram
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