Grounding Do's Don'ts & Why Part 1

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KF5LJW, Feb 27, 2012.

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  1. WA9SVD

    WA9SVD Ham Member QRZ Page

    Here's a funny part (since fixed, I believe.) The neighbor was doing some home improvements, and this may or may not be related. but shortly thereafter, I noticed that turning on the microwave oven made the window fan run FASTER! Measured outlet voltage was 125 Volts (a bit on the high side already) but when the microwave switched on, the voltage went to 134 Volts A.C.! I assume there was a bad ground/neutral somewhere that was the electric Co. problem, but after a couple of weeks, it was corrected.
    Since I'm in a rental house, I have NO idea how the original house and addition are wired, and I'm a bit afraid to even ask.
     
    WA7DAU likes this.
  2. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    SVD:

    That usually is an open neutral which then puts the wiring in a series/parallel situation. That is, all of the circuits on one leg of the 240 VAC are then put in series with the other leg. As the load changes on one leg, the voltage on the other leg varies.

    Several years ago, squirrels actually chewed through the neutral coming from the "pole pig" at the back corner of my lot. The lights in some rooms started getting brighter or darker which definitely indicated a problem with the neutral. I went outside and looked at the service drop. The neutral was definitely open.

    An open neutral is a Class "A" fault for any electric company and the company will get a serviceman out to repair the drop as soon as possible. In my case, it took less than an hour between the time I called the company and the repairman showed up to repair the open neutral.

    Glen, K9STH
     
    K4AGO likes this.
  3. KF5LJW

    KF5LJW Ham Member QRZ Page

    OK what you describe is classic loose or high resistance neutral connection. When a neutral is completely open you get some really out of balance voltages, and it all depends what is connectedto each leg and using power at any moment in time. It is a major cause of fried equipment like stereos, TV.s computers, refrigerators, etc. I have personally seen where L1 voltage measured 60 volts L1-G and 180 volts L2-G.

    This is exactly why the NEC required the the cold water pipe to be used an electrode. In the event you lost your service neutral, the return current to the transformer would then flow to your cold water pipe, out to the water meter, onto the water main, to you neighbors cold water pipe, and return through your neighbors neutral wire to the service transformer.

    However using the cold water is outdated. It is still required, but for different purposes. Water companies did not like the electric utility using their pipes as conductors, and caused several fatalities and injuries from electrocution. What was happening is people neutral would open and never noticed by the owner as everything still functioned properly. When Mr Plumber or Water Utility comes to work on your pipes and removes the meter or breaks the continuity, the circuit path is open and full 240 VAC potential across the open pipe or meter electrocuting your plumber or utility company personal. To combat the problem water utilities now install a insulation bushing at the meter. So now the first thing a plumber will do is measure the voltage from the water meter to your house cold water pipe. If they see voltage, they stop and have the owner make repairs to their electrical system before they will return, or have the electric company pull your meter.

    Well today that makes a problem. Without the cold water pipe continuity, and if you loose your service neutral, something expensive is likely to get fried.
     
  4. K9KJM

    K9KJM Ham Member QRZ Page

    So hurry up with part 2 to FULLY explain to the average ham how to properly ground and bond systems! The stated intent of this post to explain how it all works has already gone horribly wrong with the nit picking so far!
     
  5. W8JI

    W8JI Ham Member QRZ Page

    No, thank you for agreeing with me. :) :)

    I was trying to clarify the location of the common point rule. The confusing part was saying the RF ground needed to be common connected with other grounds, when that requirement is only that shields and grounds should be bonded at the building entrance. This gives the impression they are the same everywhere and anywhere, and they are not:

    It is important to understand RF grounds and audio grounds often have to be isolated from safety and lightning grounds at various points in the system. It is really just at the building entrance, we must be careful to not have shields and grounds rise differently. But there absolutely are many cases, in the antenna system or equipment, where we must isolate. One of the most common problems with audio hum and noise is grounding the shield of shielded audio cables at multiple points. Many antenna systems cannot have the RF ground or counterpoise bonded to the mast, boom, or cable shield. On the desk, RF grounds should not be isolated. Outside the entrance, they can be and sometimes must be isolated.

    73 Tom
     
    Last edited: Feb 28, 2012
    KR3DX likes this.
  6. K5AMT

    K5AMT Ham Member QRZ Page

    To the OP, thanks for writing an informative post.

    I had an open neutral situation back when I was living with my parents. Every time the wash machine would change cycles, the TV would turn off and the lights in the living room would get very bright. It was really strange. Turns out the neutral was loose at the service drop connection. Com Ed had it fixed within a couple hours of reporting it.
     
  7. J85K

    J85K Ham Member QRZ Page


    Hello Dereck,

    1) Noted; but I was not deliberately taking you out of context, but merely underscoring a substantial issue that can effect our on the air audio. Looking forward to the additional installments on this topic.

    2) With reference to the above captioned, I take it that they shut off the water supply. Do they physically disconnect the line? They would need gloves to avoid being shocked at that juncture. Reason being, that the water itself is a conductor throughout the mains supply. Do I have it correct?

    Thanks and regards,

    Kumar_J85K
     
  8. K8MHZ

    K8MHZ Ham Member QRZ Page

    Tom,

    Haven't we been through this before? Glen is correct, ALL electrode systems MUST be bonded together. There is a reason the NFPA requires it. A good one, too.
     
  9. K8MHZ

    K8MHZ Ham Member QRZ Page

    They most certainly do. Start at NEC Article 810, Part III, labeled "Amateur Transmitting and Receiving Stations - Antenna Systems" Make sure you follow all the references to other articles.
     
  10. KD0CAC

    KD0CAC Ham Member QRZ Page

    I got called to a friends house , just after he bought it because the furnace was not working , winter and near 0*F .
    Also nothing else in the house was working , I put my multi-meter on the feed coming into the main breaker panel on either leg of the 120 and to ground bar in panel , I got varying volts of about 60 .
    So went out to look at the entrance to house to see if I could see a break in the neutral , as I had the owner call the power company .
    I told the service guy what I had found , and he argued with me saying it was the owners issue , he was figuring it was in the house , this went on for 15-20 minutes before he gave in and started doing testing at the rain-head mast , then out to the pole .
    What he ended up finding was that the neutral , which serves double duty , caring the wait of the 3 lines had broken off at the pole , a tree branch had pulled from the tie at pole .
    Now waiting for more on the thread hear :)
     
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