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Old 10-01-2007, 11:18 AM   #1
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Ground reference


Hi;
I have an old home (80 yrs) which had a new panel box installed around 1998.
There is only one ground rod outside the meter.
I would like to add at least one more to bring the system up to current code.

Code states that at least two rods are required, unless a resistance of 25 ohms or less can be proven. My question is: 25 ohms to what?
What is the reference point?
Logic would dictate that the ref point would be the center wire on the POCO line on the street, but that isn't something I can get access to.

Next question:
If I add the new ground rod(s), I understand that I need to use one continuous wire. Currently, the wire coming from the panel ends at the only ground rod outside. So this means that I will have to replace this wire from the panel.
That's not really a problem, but I just wanted to confirm it before I do.

Thanks

FW

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Old 10-01-2007, 11:41 AM   #2
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Ground reference


You may have a ground wire connected to your water lines if they are metallic and in contact with the earth for 10 foot or more. This would be the primary and the rod would be secondary.

The wire from the first rod to the second rod can be a jumper wire. It does not have to be one piece from the panel. If you drive a second rod it should be no closer than 6 foot from the first rod.

The 25 ohms is measured to ground and requires a specialized meter to test. It is easier to just drive the 2nd rod.

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Old 10-01-2007, 03:02 PM   #3
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Ground reference


Are you doing this for an inspection? If not, I wouldn't go to the trouble. Ground rods only come into play during lightning events and high voltage surges on the power grid. If the first rod is installed correctly, than a second provides no additional benefit. All your ground fault protection comes from that center wire you mentioned in your post.
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Old 10-01-2007, 05:01 PM   #4
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Ground reference


What Andy said!

Many folks think rods have something to do with fault protection. They do NOT.
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Old 10-01-2007, 07:20 PM   #5
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I was of the impression that the code says water line is not allowed to be a primary ground.
All of our water lines are copper and brass, but I have to check if there is a jumper around the meter.
Should also be one around the water heater.

I am mainly concerned about grounding to protect my expensive computer equipment, especially during a lightning strike.

For now, I don't expect an inspection. The main panel was installed 9 years ago, and I assume it was inspected at that time.

While on the subject of grounding, the other day while mapping circuits in the house, I discovered that when Sears installed the new washer about a year ago, the installer used a pigtail adapter on the 3-wire plug, and did not bother to connect the ground tab!
The only reason he used the adapter is that the dryer (gas) is plugged into one receptacle and both the washer and dryer plugs are right angle facing down, so one could not be plugged into the top receptacle with the other in the bottom one. The adapter raised the washer's plug above the dryer's, allowing it to be plugged in.

I could have lived with the installation temporarily if he had used the ground tab properly, but without it, we had an ungrounded washer for almost a year.
Good thing the washer is bran-new.
I was not living in the house at the time (it is my parent's house), so I didn't realize what had been done.

My solution for now was to use a heavy (air conditioner, 12AWG) short extension cord for the dryer. The extension cord happens to have an angle plug that goes the other way, so it works in the upper receptacle.
I plan on replacing the receptacle shortly. If I can't get anything that will accept two plugs angled in the same direction, I will install two duplexes in one 4" box. As a matter of fact, the box is already 4", so all I have to do is replace/add the receptacles and a new plate.

FW
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Old 10-02-2007, 05:49 AM   #6
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Ground reference


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Originally Posted by fw2007 View Post
I was of the impression that the code says water line is not allowed to be a primary ground.
All of our water lines are copper and brass, but I have to check if there is a jumper around the meter.
It is the opposite. If the water line coming into the house is metallic, and it is in contact with the earth for at least 10', the this MUST be your primary electrode. In this case any rod(s) are supplemental, and also required.



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Should also be one around the water heater.
No, this is not expressly required. The bond between cold and hot is made through many shower and sink valves, boilers, etc.




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I am mainly concerned about grounding to protect my expensive computer equipment, especially during a lightning strike.
Another rod might help. Probably not. There is NO way to tell. Lightning is more vicious then most folks can imagine.

A GOOD TVSS (whole house surge suppressor) would be a much better investment.
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Old 10-02-2007, 07:45 AM   #7
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Ground reference


Thanks Speedy;
I have read many horror stories about lightning. Being an Amateur Radio operator, I have always had to deal with grounding.
It's scary when you have a "lightning rod" (my antenna) connected to an expensive piece of radio equipment.
That is why I got into the practice of completely disconnecting the radio from the antenna while not in use during lightning season.

Even with good surge protection at my computers, I disconnect them from the mains when we have a severe storm.

FW
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Old 10-07-2007, 07:41 AM   #8
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Ground reference


Quote:
For now, I don't expect an inspection. The main panel was installed 9 years ago, and I assume it was inspected at that time

Is there a sticker on the panel saying it was inspected?

You could also check with your local building dept. / electrical dept to see if it was inspected - but if it wasn't you might open a can of worms...
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Old 10-08-2007, 01:08 PM   #9
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Ground reference


You do not need another grounding rod (electrode). NOTHING can stop a direct lightening strike. They do make some surge suppressors for your incoming power. Google ( lightning suppressors). But I know they will not protect from a direct strike. Maybe a strike from some distance away.

Get good suppression strips with built in breaker and plug all expensive equipment into them. No garranty!!!!!!

If a lightning strike were to hit your service directly, you will be shopping for new equipment, and possibly a new home.

I read some where than a lightening bolt has enough energy to light all of New York city.
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Old 10-08-2007, 03:36 PM   #10
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Ground reference


Quote:
Originally Posted by fw2007 View Post
Thanks Speedy;
I have read many horror stories about lightning. Being an Amateur Radio operator, I have always had to deal with grounding.
It's scary when you have a "lightning rod" (my antenna) connected to an expensive piece of radio equipment.
That is why I got into the practice of completely disconnecting the radio from the antenna while not in use during lightning season.

Even with good surge protection at my computers, I disconnect them from the mains when we have a severe storm.

FW
Good call. Be sure to disconnect EVERYTHING. Some folks think just unplugging equipment is enough. They forget things like CATV, phone, grounds, etc., are ALL susceptible to lightning.That little phone line connected to the back of the computer can do some real damage.

BTW- I just passed my Tech test this summer.
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Old 10-10-2007, 02:18 PM   #11
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Ground reference


Good call. Be sure to disconnect EVERYTHING. Some folks think just unplugging equipment is enough. They forget things like CATV, phone, grounds, etc., are ALL susceptible to lightning.That little phone line connected to the back of the computer can do some real damage.

BTW- I just passed my Tech test this summer.

Roger that! A lot of people totally forget the surge protectors on the CATV and phone line. Should have one on any Ethernet lines as well. Lightning can induce heavy currents into UTP.

Congrats on the Tech ticket. No more code, right?
I had been hearing that all code (radio, not NEC) was going to be dropped!
I don't read up as I should, so I still don't know if it has<g>
I only operate 2m/70cm now, and only occasionally at that.
What a waste of an Advanced ticket<g>

FW
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Old 10-10-2007, 08:01 PM   #12
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Congrats on the Tech ticket. No more code, right?
I had been hearing that all code (radio, not NEC) was going to be dropped!
I don't read up as I should, so I still don't know if it has<g>
I only operate 2m/70cm now, and only occasionally at that.
What a waste of an Advanced ticket<g>
Me to, obviously without my General. I was thinking of getting a 6m rig. I hear there is quite a bit of activity around here.
I mostly sandbag but do get on once in a while.

Nope, no code anymore. That really did persuade me into getting my ticket. I have been into radios for quite a while but never serious enough to take the test. The last couple of years I started to get more and more into it so once the code was dropped I figured what is stopping me.
I know I would get seriously flamed on some Ham boards for this attitude, especially from the purists, but I always thought CW was a completely outdated and useless form of communication. It really has been for about what, 80 years or so?
For anyone wanting to go there voluntarily I say great. I am actually in awe of some of those guys. 20WPM??? Incredible! I will give credit to anyone who can learn another whole language, which is basically what CW is.

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