Grounding Do's Don'ts & Why Part 3

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KF5LJW, Mar 19, 2012.

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  1. KF5LJW

    KF5LJW Ham Member QRZ Page

    Thanks I appreciate it and please forgive my very late response. For the last 3 months have been very busy relocating to Oklahoma and starting a new company for my Son. Just now got my desktop hooked back up and on the internet. If it makes you feel better, this is my first post in 3-months.

    Very common problem, especially problematic with older construction. New construction today brings in all services (CATV, water, gas, telephone, etc...) at the same point which makes things really easy to bond properly and follows best practices. In other words make Single Point Ground very easy to establish. Ideally that is where you the ham operator want to set up shop. Unfortunately we hams screw that up by insisting putting up shop on the other side of the house now making it almost impossible to create a Single Point Ground. It can be done but requires a lot of expense using an Isolation Transformer and AC Power Distribution Panel to create a new Ground Reference Point.


    So what is a ham operator to do? The answer is quite simple, you have to compromise and accept the fact it will not be ideal. You can make it safe, but still higher risk compared to a SPG. Here is what I mean. In order for current to flow there has to be a Entry point and an Exit point, aka 2 nodes with a Potential Difference (voltage) across the 2 nodes. I bring this up because it should help you and others to understand what a Single Point Ground (SPG) is and how it works. With a SPG, no external fault currents can flow because it has no where to go or exit. Get your noodles wrapped around that, and you are well on your way to understanding what is going on and how to deal with it.

    So now you have you AC Service on one side of your house, and tower and coaz entry on a different side making it impossible to create a SPG. You have 2-ground rods for the AC service assuming it was built to Code on one side of your house, and some more rods on another side making up your tower and station ground. You now have a BIG PROBLEM on your hands. In a nutshell you are not in compliance with electrical codes. You cannot have two Ground Electrode Systems aka GES. Good way to get yourself killed and burn up your equipment and home. You created 2 NODES for lightning current to flow through. Have you figured out what is connecting the 2 NODES, or bringing them into close proximity for a FLASH OVER.

    Your radio, DC Power Supply, widgets, gadgets, gizmos, whizbangs. bells and whistles like a desktop or laptop all use power and interconnected. That power comes from your AC Service. In the Branch Circuit (wall receptacle) there are two wires connected to the AC Service Ground; A white colored conductor called Grounded Circuit Conductor aka Neutral, and a green wire called Equipment Ground. Those two wires, especially the green ground wire are bonding the two Ground Rod System together and asking for big trouble. If lightning were to hit your tower or AC service, the fault current will split into two directions, One to earth, and through your hose wiring to the other ground on the other side to the other ground it sees. Bang you let the magic smoke out of your equipment, and burn up your house wiring. God forbid you are there, get in the path, and BANG you let your magic smoke out and meet your maker. Understand the problem now?

    This is where code saves your skin. Thou Shall Not have two GES. Thou Shall Bond All Electrodes Together to Form a COMMOM GES. This does not make a SPG, it is a compromise. At a minimum you would run a bare, solid, tinned #6 AWG as you proposed to make that bond. Even better make a Ground Ring like a data center or communication facility would use. What that does is creates a SHUNT which takes the lion's share of current around you and away from your home and equipment. It will NOT Shunt all the current, there will still be some current flowing through your equipment and wiring in the event of a fault. However the impedance of the Shunt will be much lower than the impedance of your equipment and house wiring keeping fault current flowing through your equipment to tolerable levels most of the time. Not ideal, it is a compromise.


     
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  2. KF5LJW

    KF5LJW Ham Member QRZ Page

    By code, even old code is required to be used, and yes that is what I would do and you are required to do by code. You verify by physical inspection and looking. You start at the AC meter and find the path used for earth. Keep in mind it may not be a physical wire, it can be the conduit. If you recall in my last reply I said: "The grounded circuit conductor and ground are connected together". Thje bond between the two by code MUST BE MADE at the SERVICE DISCONNECT DEVICE. It must be permanent so as to never be disconnected even if the Meter is pulled or of Disconnect Switch is Operated. Neutral and Ground Must always be bonded together and at ONE SINGLE POINT ONLY.

    So look for a wire or conduit at the meter base going to earth like a cold water pipe or ground rod. At your Main Breaker Panel measure the voltage between N-G, and you should see 0 volts. Also measure voltage between L1 to N, L1 to G. They should be the same 120 volts. Repeat on L2 to N, and L2 to G should be 120 volts. L1 to Lz should be 240 volts. Lastly measure voltag eat a receptacle between N-G should be 0 or very close to 0 volts. If you have a very heavy load, you will see up to 1-volt difference between N-G becaus eof voltage drop on the Neutral conductor with current flowing.
     
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  3. KD5NDQ

    KD5NDQ Ham Member QRZ Page

    Thanks for the reply Dereck. I have electrician coming out this week to look over what I have and what I want to do, and hopefully be able to put together a good solution to this. He came recommended by the city building inspector. I would rather have someone that does this for a living put their eyes on it rather than trusting myself with what I think is "good enough".
    73's
    KD5NDQ
    Bob
     
  4. KF5LJW

    KF5LJW Ham Member QRZ Page

    Excellent idea and worth every penny. Us hams have a tendency not to comply with electrical codes and is a huge significant oversight. Not only does it put you at risk, it also can render a radio useless on the RX side, and get you on your neighbors chit-list on the TX side. Most comes from a lack of understanding, and us ole farts who say, that is the way I have always done it (WRONG) from the beginning.

    Now with that said electrical contractors have a different POV. By that I mean meeting minimum code requirements. Just the nature of the biz and the bidding. process to win contracts to keep food on the table. What hams need to do sometimes is exceed code requirements to make a performance spec. 1 very good example would be RF Radials for a vertical antenna. This is one area where hams and electrical contractors really go WRONG and fail to understand the code and basic electrical principles. A sparky (electrical contractor) would tell you that you only need to bond the Tower to the Ground Electrode System aka GES. A ham wil tell you that you need RF radials constructed of insulated wire. Who is right and who is wrong?

    Well both have different POV's, but 9 times out of 10 the Sparky is more right. Yes you need radials to make the antenna work correctly. The Sparky does not give a crap about that. What Sparky cares about is life and property safety. By code he knows the Tower must be bonded to the GES, and it should be. Where hams go wrong is they do not want the Tower or Radials bonded to the GES which is a huge mistake asking for big trouble both operational and safety. That mistake is compounded by using insulated radials thus giving up really good lightning protection out of ignorance and the good ole boy network that says: 'That is the way we always do it crowd".

    So here are some tips to get you and your spark on the same page and can talk the same language.

    Ask him to inspect the AC Service Ground Electrodes. That would be ground rods, water pipes, rebar in concrete, building steel ect... Ask home to make sure it is up to code and properly bonded and up to current code.

    Have him look at the Main Breaker Panel and inspect for proper Neutral to Ground Bonds and Equipment Ground Conductors. Tell him you do not want Jack Leg Grounds. A Jack Leg Ground is where the Neutral and Ground are bonded downstream from the service disconnect. Just about every older home with a 3-wire electric dryer has a Jack Leg Ground. Neutral and Ground are bonded at one point only and no othjer bonds allowed downstream. He will know what it means and to look for.

    Lastly tell him you want to extend the GES to wherever you want the coax to enter, and code minimums are not enough. Otherwise being a contractor he might suggest a #10 tacked to the side of the house. You do not want that. Meets code, but not acceptable. What does work, meets and exceeds code is what you want to do. Sink a rod at the entry point, and use 6 AWG buried to the nearest GEC access point. That might very well be the Cold Water Pipe. You will also want a means to connect to the ground rod like a ground bar on the outside wall he would call a Inter-System Bonding Buss. That would allow you to install a Antenna Discharge Unit outside, and bring in a Station Ground into the shack.

    Hope that helps. Feel free to ask questions.
     
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  5. KG5WKO

    KG5WKO Ham Member QRZ Page

    What may be my biggest problem is distance from ham shack to utility box is 121 feet if I cannot get access thru wall. If I have to go the long way around what issues with feedback issues on tuning or simply a good wire to recommend? Since I will break up run with two or three rods is this just new ham worry about nothing and run it and enjoy? I am surprised how many locals do not have anything resembling a decent ground system and complain about noise! I have a tilt over and collapse during violent storms any way but they forget electrostatic build up, surging in ac lines and not good at all.
     
  6. KF5LJW

    KF5LJW Ham Member QRZ Page

    No issues. As for the cable use #6 AWG solid bare tinned copper.

    You are touching on the most common mistake ham radio operators make. Some where back in time hams got the idea that their radio system ground should be ISOLATED. Problem is hams have no idea what that means. Heck you would be surprised how many electricians and equipment manufactures have no clue what that means. Anyway some how folks thing utility ground is dirty and noisy. Nothing could be further from the truth. Ignorance compounds on itself.

    So here is the real dirt on the subject. Try this for yourself some time. Get a couple of long nails, rods, or pipes. Drive them into the ground say 20 feet apart. Now take a AC Volt meter and read the voltage. Surprise surprise surprise Sgt Carter you got a voltage. Where is it coming from? Simple it is coming from the electric utility and mother nature. Utilities are allowed to use dirt as a conductor and they use dirt as a Return Conductor called Multi-Grounded-Neutral aka MGN. So in effect you have current flowing through dirt and dirt is a poor conductor which has resistance. The voltage you are seeing is a result of current passing through resistance. If you look at the frequency will be 60, 120, and 180 Hz.

    What do you call an unwanted voltage and current? By any definition would be NOISE right? So here is what happens when you fail to understand Isolated Ground and where it goes wrong. You have your AC Service ground at one end of a building, and you drive say a ground rod, two or three on another side of a building with the thought of an Isolated Ground. Sounds good right? Wrong dead wrong.

    Your radio and all the gizmos and gadgets get their power from the AC Service. From your main breaker panel you have a branch circuit which carries a Equipment Ground conductor or the 3rd green wire that is bonded to the chassis of all your equipment. So in effect when you connect that so-called Isolated Ground to your radios and gizmos, you have now bonded the two ground together putting all your equipment right in a series path. You just created a entry and exit point for current to flow. All that noise and external faults will flow through your equipment.

    Under normal operation, that may or may not be a problem and you are taking your chances. However if lightning were to ever strike nearby, all that fault current flows through you equipment and house wiring. That will cause equipment failure, burned house wiring, possible fire, injury, and or death. There is no up side and a critical mistake. All caused by ignorance and not complying with electrical codes.

    The fix is easy, you comply with electrical codes by Bonding all Electrodes together to form a common Ground Electrode System aka GES. When you do that you shunt all that around you, your equipment, and house wiring keeping the lion's share outside where it belongs.

    Only question left is what is an Isolated Ground? A completely different subject and topic. All I will say is it comes from the same place, the common GES.
     
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  7. KG5WKO

    KG5WKO Ham Member QRZ Page

    Thankfully, I am spared even worrying about long ground as a bit of politics and building owner a neat sowing room has moved me to room ten feet away from Home AC Panel. I agree with you and Derek and remember I am using a tilt over as not having a pole 25 feet up in any lightening storm regardless of grounds but did not grasp other issues as started out here. Station panel ground mast grounds and bonded to ac ground. TNX for patience all
     
  8. WA5VAH

    WA5VAH XML Subscriber QRZ Page

    Thanks so much for all of your answers in this series. They are very helpful. I have a few questions.

    Background: I need to bring antenna cables into my house on the south side to a second-story room. The AC service panel for the house is on the northwest corner. The total distance between the two entry points is approximately 100 ft. The southwest corner of the house is about 85 feet from the AC service panel. The coax cables will enter the second story about 10 feet above ground level. So, I will place an 8' ground rod directly below this point which is approximately 15 feet from the southwest corner of the house. I plan to place several Antenna Discharge Units outside of the house 10 feet above this ground rod and connect them to the ground rod below with a straight piece of #12 solid copper clad steel wire. I have quite a bit of #12 AWG solid copper clad steel wire I got from the telephone company approximately 50 years ago.

    If I understand the NEC 810.21 correctly it says that I can also use a #17 copper clad steel wire (or larger) for bonding between the ground rod at my station entry point and the house ground which is approximately 100 feet away. I would also like to use the #12 AWG solid copper clad steel wire to bond the two grounds together. Am I correct in using this wire for bonding the two systems together?

    I also understand that I should put an 8 ft ground rod every 16 ft or so on the bonding wire between the two grounds. Is that correct?

    When the bonding wire between the ground rods goes around the southwest corner of the home is there a minimum radius that I should use for the wire?
     
  9. KF5LJW

    KF5LJW Ham Member QRZ Page

    Again I apologize for a late response.

    You are correct, you can use 12 AWG solid copper clad steel wire to meet NEC minimum code requirements. Keep this point in mind, NEC is bare minimum requirements, NOT best practice. It is important to under the difference. If you were to look at any industry Practice, they meet minimum NEC requirements, but more times than not, they exceed NEC requirements to meet performance specifications. NEC is minimum SAFETY requirements, and do not necessarily meet operation requirements. Example instead of using 17 AWG copper clad steel would be #6 AWG solid tinned bare copper wire. That meets and exceeds NEC requirements. 12 AWG copper clad steel would not be my choice.

    Yes with a caveat. NEC requirement is minimum 6-feet without regard to rod length. Best practice if you use two or more ground rods is 2X or more rod length. So if you use 8 foot rods, minimum 16 feet distance. You can 17, 20, or 30 feet. Just nothing less than 16-feet.

    Minimum is 10X conductor diameter. Easy answer is 12-inch radius for 90 Degree bend.

    Final comment. For the coax going to second floor, Route cable up from from ground elevation even if that means routing it down to dirt before going up. Example bring the coax down from the tower straight down the dirt close as possible, and bond the shield. Run coax around house as close to ground elevation as you can until you bet to the point where it needs to go straight. Bond shield again to ground electrode system along with ADU where the coax bends to go up to second floor entry point. Additionally if you want a Station Ground, run a ground wire with coax from the ground rod where the coax goes up
     
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  10. WA5VAH

    WA5VAH XML Subscriber QRZ Page

    Dereck,

    Thank you so much for your answers. Your comments are very helpful.

    I also put the ground wire going up to the second story inside a PVC conduit to protect it. I read somewhere that is a good idea as well.

    73,
    Bryan
    WA5VAH
     

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