safe grounding

[David, K3TUE]

In my effort to put together my antenna system I have been reading about ground systems as well.  OMFG, what I nightmare this is turning out to be.  The more I learn, the more I am concerned (perhaps unnecessarily).

My house was made around 1950.  All of the original wiring appears to be 2 conductor in corrugated metal shield (I think I have heard it referred to as M-class (for metal), good for garages and other non-enclosed walls).  All of the grounds to the outlets seem to be using this as the safety ground conductor (all outlets test fine with a 3-prong plug testor), but I am not sure that modern wiring standards consider this sufficient for a safety ground conoductor.

I am planning on using 2.2M resistors as static bleeders on my antenna radiators, so I need a ground for this.  I was originally planning on sinking a ground rod and running some black insulated #6 stranded copper from it to the shack (since without close inspection it looks like RG-6 cable, which is good because I don't own the building and, well, you know HOA's and all those damn rules).  I was planning on running the ground wire up the outside wall to the window and tying it inside to the ground strip I have on the desk connected to the outlet safety ground.  But now I am reminded that all grounds should be tied together, which I don't believe is covered by what I was planning on doing.  It is possible to run a ground wire from this new ground bar through a hole in the foundation under the house and up to the ground bar in the breaker box (I doubt there is a the ground bar under each house to tie it to directly), but that just increases the visibilty of the wholoe thing and the odds that someone will raise a stink.  I understand the importance of tying all of tghe grounds together to make a common potential and not have different ground loop potentials.

I guess my question is, is it sufficient to tie this outside ground connection to the safety ground bus in my shack (which is tied to the system through the wiring) or do I have to tie it to the ground feed point for the whole house?  Or should I just forget about safe radio operation until sometime in the distant future when I live in a house instead of a condo and I don't have to worry about a damned HOA?

[David, K3TUE]

As a followup, is it acceptable to sink a ground rod completely underground?

[David, K3TUE]

And now I think the actualy service entry ground is at the other end of the (multiple unit) building 240ft away connected to a copper water pipe.  If this is the case, would it still be OK to run the shack ground to tie in to my circuit breaker ground bus?

[Bacon, WA3WDR]

I am familiar with that steel-wrapped cable as "BX" cable, but today it is called "armored cable" or armor-clad cable, or AC (as opposed to BX), and it has been improved over the older designs.  In the BX that I saw, there was a bare ground conductor inside, along with the insulated hot and common lines.  This has been good wherever I have seen it.  I often worry about a nail going into the wall and penetrating the plastic "Romex" cable that is normally used today.  Romex is generally used, but I think that armored cable is a bit safer because of the strong grounded metal shell around the wires within.

In my parent's old home (1920s construction on Long Island), the BX had some kind of cloth-rubber insulation, and I knew not to bend it around very much when replacing switches and outets.  More modern armored cable that uses plastic insulated wire is pretty good, I think, but heavy, and expensive, I'm sure, and especially expensive with a war going on.

Here's a link to info about this type of power wire:
http://www.seatekco.com/bx.htm

And here's some good info:
http://www.codecheck.com/wiring_history.htm#bx

I found that ground rods have a hundred ohms or more of resistance to actual ground.  So they help, but only so much.  Some English hams found that they got better antenna efficiency at LF if they kept the water pipes and power mains grounds separate from their antenna grounds.  But for safety I would think that it would be better to tie all grounds together - water pipes, power grounds, and any ground rods too.  I imagine a general ground, it may not be a real good ground, but it's good locally.  If lightning strikes, I think I'd rather have the power system ground tied to the ground rod(s) and the water pipes in the house so that the potential between them is not so high.  If the whole ground swings 10KV, at least I'm not between high voltage points, but I'm along one conductor, and there's not much potential between things around me.  It would be like being a bird perched on a high voltage distribution line.  The ground rods will tend to make the nearby ground area more like the rest of the ground system, which I think would be a good thing.  But one ground rod is just... one ground rod.  The more, the merrier.

Also, not all single-family houses are HOA-free.  And HOAs can be handy when a neighbor starts overcrowding their house.  But yes, a bad HOA can be a nightmare.

[W1RKW]

Dave,
I don't know if you've seen this or not http://www.polyphaser.com/ppc_ptd_home.aspx  but if not there's a wealth of grounding info here that might help you out.

BW

[W3SLK]

David asked:

As a followup, is it acceptable to sink a ground rod completely underground?

I just finished a course on NEC 2005 two weeks ago. In cases where a ground rod could not be pounded in securely, ie. shale/slate earth, during new construction it is perfectly acceptable to 'throw' the ground rod in the excavated hole, say for your foundation, and cover it back up with the wire running out on the earth. What was highly recommended that if you are pouring concrete, tack the groundwire to your rebar. The claim is concrete provides good grounding..

Bacon said:

I'd rather have the power system ground tied to the ground rod(s) and the water pipes in the house so that the potential between them is not so high.

And that's the way to go. To go putting different sub-feeds on separate grounds is an invitation for trouble. Ground loops have a way of making life miserable when it comes to RF or troubleshooting any strange problem in an electronic device and lightning. When I ran my sub-panel for my shack, I ran tri-plex, without the benefit of a ground. Now I find out after attending this NEC course that I have to run a ground from my service feed panel to my sub. The way I can get around this is to tack from the SE ground to my copper water line then tap off of the water line to the sub-panel, and tie my 'shack ground' to the sub-panel. Thereby putting everything at the same potential and avoiding ground loops.

[David, K3TUE]

If that cold water pipe ground cheat is acceptable, can I just connect the cable to the ground rod to it and then use the water pipe as the tap for my shack ground?  I have a cold water pipe for the bathroom behind a service panel in my shack.

[w3jn]

THe NEC says that all auxilliary grounds (for antennas or whatnot) must be bonded together at the service entrance ground stake.  That means if you drive an extra ground rod or use the cold water pipes for an RF ground, you gotta bond that to the service entrance ground.

The reason for this is safety.  The service entrance ground is the ground reference for the building/facility.  Because of the resistance between the service entrance ground and other grounds used, there will most likely be a voltage differential between the two.  There are many failure modes where this could be deadly.  And connecting your ham rig to building cold water pipes that may or may not be bonded to the service entrance ground is putting everyone's life in the building on the line.  DO NOT DO THIS UNLESS YOU **KNOW** THAT THE PIPES ARE BONDED TO THE SERVICE ENTRANCE GROUND!!!

[W3SLK]

Ditto what you said John.

[k4kyv]

To go putting different sub-feeds on separate grounds is an invitation for trouble. Ground loops have a way of making life miserable when it comes to RF or troubleshooting any strange problem in an electronic device and lightning. When I ran my sub-panel for my shack, I ran tri-plex, without the benefit of a ground. Now I find out after attending this NEC course that I have to run a ground from my service feed panel to my sub. The way I can get around this is to tack from the SE ground to my copper water line then tap off of the water line to the sub-panel, and tie my 'shack ground' to the sub-panel. Thereby putting everything at the same potential and avoiding ground loops.

I use one main grounding point, at the meter entrance,  for the a.c. power system.  The a.c. neutral wire is treated exactly the same as a hot wire throughout the house and shack.  All other ground points are bonded to the main entrance ground with #4 bare copper, buried below the surface of the soil. 

I checked mine recently, and there was about 0.15 volt a.c. potential between the neutral and ground in my shack.  Shorting them together with a clip lead raised the hum level in my receiver's external audio amp as well as the TX audio system.  I could actually see small sparks when I touched the grounded clip lead to the neutral wire.

Not sure what the NEC would say about it, but I sometimes use a small radial ground system where it is not convenient to drive a rod.  The only safety problem I could see with this would be during dry weather when the soil is dehydrated down several inches.  Just to make sure, whenever I can, I drive a ground rod and then add several radials at least 10-15 feet long.  I believe the radials give better lightning protection, since the steep wavefront of a lightning pulse makes it act more like r.f. than a simple a.c. or d.c. electrical discharge.

One of the mods I installed in the Gates broadcast transmitter was to isolate the a.c. neutral from the transmitter cabinet, and ground the cabinet to the shack's ground system.  The factory simply bonded the neutral wire to the metal cabinet.  As I recall, this is actually a violation of the code, although it may be permitted with short (about 6') ground leads.

[David, K3TUE]

So to be safe and sure, it looks like I should limit myself to the following:
1) only transmit into a dummy load and
2) do not install a shack ground rod but rely on the safety ground and hope for the best in stray RF
3) only transmit into an antenna in clear and dry weather and disconnect the antenna completely whenever I am not transmitting
4) install and use a shack ground only when I can bind it to the service ground entrance at my breaker box

[w3jn]

That's a bit extreme.  Any so-called "rf ground" with a run over about 10 feet is going to be highly reactive and relatively ineffective anyway.  Try running it without a ground and see what happens.  The ground wiring in the building will probably act as a fairly effective counterpoise anyway.

Hams love to violate the NEC with their grounds.  It's one thing to create a safety hazard in your own house.  Its entirely another to create a potentially deadly situation in a condo you share with many other innocent and ignorant (of the situation you may have created) people.

[David, K3TUE]

That's a bit extreme.

I was just trying to convey frustration with my situation, not anyone here.  Everyone has been very helpful, especially by reenforcing the fact that the rules are there to ensure the safety of persons and property.

Any so-called "rf ground" with a run over about 10 feet is going to be highly reactive and relatively ineffective anyway.  Try running it without a ground and see what happens.  The ground wiring in the building will probably act as a fairly effective counterpoise anyway.

That is what I was hoping.

Hams love to violate the NEC with their grounds.  It's one thing to create a safety hazard in your own house.  Its entirely another to create a potentially deadly situation in a condo you share with many other innocent and ignorant (of the situation you may have created) people.

I agree, and this is what I am trying to avoid.

[David, K3TUE]

I have a followup, but it's probably best put in another thread.

[WA1GFZ]

My building inspector told me the breaker panel ground bus should be the single point ground not the meter or the rods. I have 500 feet of #8 around the footings down the sewer trench and some on the surface. He had me bond my radio ground to the copper water main then run a ground to the breaker panel ground bus. I used #4 solid (200 amp service. required ground conductor.) Lightning hits a lead in concrete the stuff will explode. Two different ground systems is begging for a large offset voltage. Say you have 1 ohm between systems and you take a 5000 amp long pulse. 5KV offset will blow everything in its path.

[David, K3TUE]

Thank you everyone.  I am convinced.  I am using the outlet safety ground for now.  At some point in the future I may run a dedicated #4 ground from my shack to the circuit breaker ground bus.  I'll be disconnecting my antenna every night after transmit.

[KB2WIG]

pulling da plug isnt a bad idea eather...... you can try a 1/4 length wire to your transmitter gnd lug to give you a cheep RF gnd at a particular frequency.. dont conect the end to nuthin, just lay it running away from the x mitter (tape the end with lectrical tape)


also, some jurisdictions want to see the connection to a driven ground; others let you 'bury everything......  can't hurt to ask...   

The I3E emerald book has cool stuff in it...             klc

[WA1GFZ]

My Dad just had his meter socket replaced and the guy did the two required ground rods. After it was inspected they let my Dad bury the tops of the rods. I left mine above the surface so I could keep an eye on them. I plan to put a spark gap on the antenna feeders and connect to the rods. My feeders will enter the building a few feet away from the service entrance to avoid loops. The antenna tuner will be close to the single point ground.
If it was my choice I would made the meter socket the single point ground and keep the lightning current out of the building but I don't write the NEC just do a fair amount of testing and see the effects.

[WB3JOK]

Can the grounding experts please give me some pointers about my shack?
I'm in rural Mo. in the middle of 121 acres, and there is no zoning/inspection/permits whatsoever. Which explains a lot of the wiring around here 

Recently the power company upgraded my drop and meter socket from 100 to 200A ampacity which is what it should have had all along. Anyway there is now a main breaker/disconnect out in the yard on the pole just below the meter, which is about 50' from each of the buildings.  The shack and garage used to be fed from a 60A breaker in the house breaker panel to ugly dangling daisy-chained overhead wires. They are now buried directly from each building to the pole.

There are three sets of lugs provided at the pole-mounted disconnect. One has the 4/0 service entrance conductors to the house; another feeds the detached garage/workshop (to a separately boxed 60A main breaker I just installed, which now feeds the existing breaker panel); and the third runs to the shack building, also to a new separate 60A main breaker, feeding the shack "load center" panel. Hopefully that's a clear enough description?

So, where should I have ground rods, bonding screws in the panels, etc? I get lost trying to decide at which panel to bond the ground and neutral, if any, or where to install another ground rod. Right now there is only the power company-supplied rod at the meter pole, and I have a separate rod at the shack for antenna/RF ground that I haven't connected to anything yet. Any help appreciated.

thanks
Charles
WB3JOK/0

[w3jn]

Where is the service entrance ground?  That's where you need to be running a wire from your station ground.

There is probably one for each building, as the prospects of touching both buildings simultaneously is pretty low.  Usually the ground is right at the entrance to the building, and is bonded to the breaker panel.

Just because your county doesn't have strict building codes doesn't mean you don't have to comply with the NEC for insurance purposes.

[WA1GFZ]

All neutrals should be isolated from safety grounds until you get to the main breaked where thay are connected so you don't have ground loops. Add all the grounds you want but run them back to the main ground.  In Ct. we need 2 8 foot rods at least 5 feet apart for 200 amp service. I've added the water main and 500 feet of #8 so far bonded with #4 solid back to the main saftey ground bus. More to come.

[WB3JOK]

Where is the service entrance ground?  That's where you need to be running a wire from your station ground.

The house has three conductors running to it from the pole - two hots, one neutral. There is a rod at the bottom of the pole. No separate ground wire connecting the pole and the house.

Do you mean, run the station ground to the house ground, or to the meter pole ground? I think to the pole makes the most sense, as the power is fed from there too.

There is probably one for each building, as the prospects of touching both buildings simultaneously is pretty low.  Usually the ground is right at the entrance to the building, and is bonded to the breaker panel.

"Probably" and "usually" are the operative words here... as I said, there are a large number of firetraps out here. Somewhere I have pics of the old wiring - you would be appalled.

Just because your county doesn't have strict building codes doesn't mean you don't have to comply with the NEC for insurance purposes.

That's yet another reason I am doing it right, since our house is paid off!
The shacks that pass for housing in the rural Ozark counties probably aren't compliant in many ways.

So if I'm interpreting this correctly, I should have a ground rod at each of these physically separate locations: the pole (already installed), the house, the garage, and the shack, and each rod will be bonded to the respective building's breaker panel ground.

All neutrals should be isolated from safety grounds until you get to the main breaked where thay are connected so you don't have ground loops. Add all the grounds you want but run them back to the main ground.

Which main breaker, the disconnect on the meter pole that turns off everything, or the one in each building?So the "Bonding Screw" (in each panel, that connects the neutral bus bar and the safety ground), should not be installed in any of the panels including the house?

Do I also need to run a heavy conductor from each building's ground rod back to the pole rod?

I never realized how confusing this grounding stuff was, until I started thinking about it 
thanks
-Charles

[KB2WIG]

 With  residential  wiring, USALLY, the service entrance is the breaker box (or fuse box). This is where you want to tie your grounds to. This bonding screw on this box is used. The outbuildings complicate your 'code' requirements. There are requirements specific to these buildings.

As I understand your set up, I would treat the 'home' electrical box as the service entrance and run my grounds to it...along with two driven ground rods.. and use the bonding screw on this box... since you have a driven ground at your station, bond your station ground back to the 'entrance'..   

If you have any questions, its best to get an expert out to your location and have him/her eyeball it... the hard part is finding a qualified person; not the guy who buys some tools and and calls themselves a lectrition....

There are some good texts on the Code written but the good ones aren't cheep..... but, neither is your life.....      klc 

[k4kyv]

Several years ago we had a licensed electrician install a new circuit breaker box.  He used a name brand (Square D), and the electrical inspector came out afterwards and left his stamp of approval.

Everything worked ok for 2 or 3 years, until one day I turned on the transmitter, running 1 kw off a 110 v. line, and as soon as I put it into transmit mode, the lights lit up like flashbulbs.  I quickly turned everything off before any damage was done to the house or any equipment.  I checked out the breaker box and found the trouble.  The common bus for the neutral inside the breaker box was divided into two sections, and the only thing bonding the two heavy copper sections together was the rivets that attached them to the steel enclosure!!!  Those rivets had loosened, and corrosion had set up around them, so every circuit whose neutral was connected to that half of the bus bar was intermittently losing neutral.  In effect, the lights and everything connected to the outlets were all in series across 220v.  Before the transmitter was turned on, they happened to pretty much balance out, so that everything was getting approximately normal voltage.  But as soon as I hit the transmit switch, the side of the line feeding the transmitter acted like a dead short, and while the transmitter lost nearly all its voltage, everything on the other side of neutral was getting almost the full 220V!

Since the box and installation were already several years old, I just decided to fix it myself.  Each bus bar still had about a half dozen empty slots for additional neutral wires, so I got some #10 and filled up those unused slots with jumpers running between the two bus bars, and made sure each bridge was connected good and tight.  That solved the problem, and that repaired breaker box has remained in use for over 20 years, with no problems.

[WB3JOK]

I've done some searching online. What I really need is a copy of the NEC Article 250. Somewhere in my piles of boxes is a copy of Grounding and Bonding, too, but I can't find it. 

I found the answer to my outbuilding questions:
http://www.mikeholt.com/code_forum/showthread.php?t=57182 and also
http://www.mikeholt.com/mojonewsarchive/GB-HTML/HTML/Grounding-versus-Bonding-Part-5-of-12~20050304.php

Since there is no conducting path between the buildings, I can bond the neutral and ground at each outbuilding's main breaker panel (as if it were a service entrance) and I don't need to dig up the wires to add a grounding conductor. However, each building does require its own ground rod.

-Charles