I am the Chief Engineer for KMA radio. I am having a bit of a battle regarding grounding requirements at our new Transmitter site. I want to follow the grounding recommendation of article 250.50 and 250.52 and 250.58. Which to me basically states that all ground systems should be bonded together and to the point of electrical entry (supply side). Since we are a broadcast site we use 4 inch copper strap and multiple ground rods to form our station ground for all our equipment. My electrical contractor says the inspectors won't allow us to bond the electrical and station ground together at any point. They claim the electrical ground and neutral needs to isolated from our station ground. I understand the need to isolate the neutral after the main entry point but shouldn't the neutral be bonded to all existing grounds at the point of electrical entry (supply side). I am confused why our inspectors are contradicting the NEC code?
Broadcast Transmitter Site Grounding
- Thread starter mbrockm
- Start date
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brian john
Senior Member
- Location
- Leesburg, VA
They are not reading the NEC properly and are WRONG. No matter what you do all grounds will be common either accidentally or intentionally. You are better off and code compliant when they are intentionally bonded together.
Ask them how they are isolated?
Well I design tower grounding for about 35 years and your EC is full of PoPo. Your AC service, Tower radials, and building ring are all bonded together to for a grounding electrode system.
The only dispute or topology is where the AC Service gets bonded. Some bond the service from the MGB inside the shelter in a Single Point Isolated Ground Plane, or bond to the building ground ring in a multi or aka integrated ground plane. Either way it is all bonded.
Your EC does not understand what ISOLATED means. In the radio and telecom sector Isolated means:
All equipment racks are installed electrically isolated from the building ground plane. In other words when you set the equipment in place you install isolator pads underneath the equipment racks so it makes no electrical contact with the floor, and use isolator bushings in the floor anchor bolts isolated so they do not make electrical contact with the equipment frame.
Next the power plant return buss and frame in DC systems is bonded to the Master Ground Bar.
The equipment racks are bonded to the MGB.
All this is done to make a true Isolated Single Point Ground Plane. All this is done so there is only one single point ground. Being such no external currents can flow through the equipment.
If you need some advice or consulting drop me a line via PM and I will help you out and direct you to some resources and reference material.
The only dispute or topology is where the AC Service gets bonded. Some bond the service from the MGB inside the shelter in a Single Point Isolated Ground Plane, or bond to the building ground ring in a multi or aka integrated ground plane. Either way it is all bonded.
Your EC does not understand what ISOLATED means. In the radio and telecom sector Isolated means:
All equipment racks are installed electrically isolated from the building ground plane. In other words when you set the equipment in place you install isolator pads underneath the equipment racks so it makes no electrical contact with the floor, and use isolator bushings in the floor anchor bolts isolated so they do not make electrical contact with the equipment frame.
Next the power plant return buss and frame in DC systems is bonded to the Master Ground Bar.
The equipment racks are bonded to the MGB.
All this is done to make a true Isolated Single Point Ground Plane. All this is done so there is only one single point ground. Being such no external currents can flow through the equipment.
If you need some advice or consulting drop me a line via PM and I will help you out and direct you to some resources and reference material.
Last edited:
cadpoint
Senior Member
- Location
- Durham, NC
I'd get an independant Antenna Engineer involved!
What inspectors are you talking of?
This is the National Archives and Records Administration search engine: Here
Note that it's in title 47 which I'll assume is the correct place.
I used a simple term search using; ""FCC GROUNDING RULES"" which will revealed better results than I saw at the FCC web site.
What inspectors are you talking of?
This is the National Archives and Records Administration search engine: Here
Note that it's in title 47 which I'll assume is the correct place.
I used a simple term search using; ""FCC GROUNDING RULES"" which will revealed better results than I saw at the FCC web site.
- Status