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Electrical Ground Question
Again Billy, If this is a secondary panel - that is, if it's deriving power from the same source that supplies other buildings and/or power panels - that new ground bar (electrode) needs to be bonded back to whatever's being used as the common ground. This is typically the ground electrode system associated with the service entrance (electric meter). Not doing so creates unequal ground potential, which in turn still leaves you vulnerable to ground loops, static, et cetera. For electronic equipment, that translates into noise - and electronics don't work their best in noisy electrical environments.
And further to what BA said; if you get the electrician to come back out to do the electrode, he should know enough to bond the new one back to the common ground electrode as part of the job.
//greg//
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Electrical Ground Question
Greg, these aren't sub panels. There is a 200 amp main service disconnect right under the electric meter. There's two sets of 3 wires going to each panel in tow different buildings. Below is an email from a friend of mine. This guy knows his shit and deals with high dollar electronics every day.
Billy,
Hey yes...it certainly has been a long time! Where you been! Last I heard you were having problems with your computer and e-mail system. Hope those problems got resolved. Hope everything is going well for you.
Okay now, understanding that you've made a serious investment in equipment to run your houses...then hired someone who claimed to be a trained professional to install this expensive equipment...and understanding that the equipment must be installed properly or it may get destroyed by lightening, power line transients, or any number of other power system anomolies...I would begin by doing the following, and in the same order:
1. Dig a shallow hole about 6' by 3' by 3 feet deep
2. Shoot "electrician" who installed your equipment
3. Dump body in aforementioned hole
4. Lime liberally and then cover with dirt
5. Go back in a couple of days and smooth over the depression from the body shrinking
Now that we have the "electrician" taken care of and out of the way we can get down to correcting what he did.
I assume he ran 220/240 volt AC power to your houses. This would be one leg, another leg, and a neutral line...L1, L2, and N on drawings or diagrams. This being the case your neutral line goes to ground, but only at the distribution transformer. This is as it should be. Don't mess with this.
Leave the neutral and ground bus bars separated.
I don't remember if your houses have concrete or dirt floors in the control equipment rooms. If they're dirt, cool. If they're concrete, I would plan on drilling a hole through it and then filling that in when we're done.
Do you know how far down your water table is? We need to get a ground rod down a couple of feet below the top level of the water table when it's at its lowest. Sometimes this requires an 8 foot rod, sometimes longer. I believe they come in 8, 10, 12, and 16 foot lengths. Let's hope the 8 footer will do and this is the shortest ground rod I would use.
I don't like steel ground rods even if they do meet code. I like solid copper or copper clad rods. Some supply houses will try to sell you a copper plated rod as a clad rod, they're lying to you. Plating is only several micro inches thick, millionths of an inch. A copper "clad" rod will have about a 1/32 to 1/16 inch thick layer of copper around the rod from end to end. If your dirt isn't too bad to dig in and you can use it, I would use solid copper when ever possible.
You need one rod for each control panel.
I would install the rod as close as possible to the control panel. Right below it would be great.
After you're done with this run a cable from the ground bus on the panel to your rod, clamp, and you're good to go. Ground cable - I like to use a braid type cable rather than a solid wire like the power company uses. Solid wire is okay for just a safety wire and low frequency AC, 60 Hz as with line power. One of the more serious issues you have to deal with is lightening, which is a very short duration, high energy content pulse. A ground cable for this is much better when there are many, many more strands of wire in the cable...the more the better. Without getting into the technical details and physics of why, this just presents a much lower impedance (which is a spiffy name for the AC resistance of a conductor) to high frequency energy...lightening. Copper braid isn't cheap, but do we want to protect thousands of dollars worth of controllers with a 10 dollar piece of wire? This is 1/2 inch copper braid. I would use 2 lengths, run in parallel, to ground my panel.
Hope this helps. Let me know if I can be of any further help Billy.
REB
ollar control computer?
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Electrical Ground Question
Oklahoma code notwithstanding, Reb has described to you the way I'd have done it. Following his advice does not require the services of a licensed electrician, because nothing he told you to do breaks the meter seal. At least that's how it works around here. Sounds like a reasonable do-it-yourself fix. Only thing I would add- as before - is to bond all individual electrodes (ground rods) together (and to the common ground) to equalize ground potential.
Curious though - why didn't your electrical inspector catch this?
//greg//
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Electrical Ground Question
why didn't your electrical inspector catch this?
Because the electrician and the inspector are the same person and both are idiots. He just happens to work for the company that put all the new equipment in. He's actually a decent electrician but is lazy as hell. I believe the only reason they keep him is he knows how to work on the controllers.
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Electrical Ground Question
In normal house wiring, the neutral is bonded to the box where the main disconnect is located and a ground conductor runs from the neutral bar to the ground rods. (as in 2 ground rods, 10' apart.) The neutral and ground never come in conatact again. However, when a sub-panel is power in a different building, you can run a three-wire curcuit and bond the nuetral in the sub-panel and run a ground conductor from the neutal bar to ground rods driven at the building where the sub=panel is located. BTW: Never use smaler than #6 copper for a gound conductor. Number * is legal for a 100 amp service, but it requires mechanical protection (conduit), where as #6 does not require protection.
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I personally think he should come out and check it out. Make any repairs at no charge to you. I never tell a custermer how to fix something I did.
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