View Full Version : improperly grounded panel?
Bob in Maine
06-30-2008, 07:13 PM
This is probably a pretty basic question, but I'm not proud.
My old house built in the 1920s has an updated 200 amp breaker panel. Some circuits are still wired with the original flexible metallic conduit containing two fabric covered wires. Other circuits (kitchen, bathroom, and garage) have been replaced with three wire ROMEX®.
The only ground I see for the panel box is a braided wire running from the bottom of the panel to a clamp on the water entrance pipe about three feet away from the panel.
Is this an appropriate ground? All of the ROMEX® circuits and most of the circuits with metallic conduit read as grounded when I check them with a tester.
07-01-2008, 04:17 AM
As confusing as it seems, a ground rod, or a water pipe bond/ground, has NOTHING to do with the third round hole in a receptacle. NOR does it have to do with the bare wire run in the wiring with the circuits.
The safety ground in your home, the one that "grounds" that center hole, comes from the neutral to ground bond in the main panel. That's IT.
To answer your question, NO that is not enough. A supplemental ground rod is also required along with your water pipe grounding electrode.
This may come right off the same wire as the water pipe though. Check that.
07-01-2008, 12:41 PM
You can remove the ground wire totally and that tester will still show the ground ok on the outlet. It just verifies the connection from ground back to the neutral in the main box.
Around here the electrical inspectors require two ground rods placed 6 ft. apart and a separate large ground wire run from one of these rods (which are connected together) to the panel.
Then for the cold water pipe ground, water meters can sometimes have rubber grommets and a jumper is installed around the meter to continue the ground connection past the meter. And water heaters can have "dielectric couplings" and a ground jumper is placed on the pipes above the water heater flexible pipes to pass the ground from the cold water pipe to the hot water pipe. (If you have plastic pipe, forget about it!)
Turn off the main power if disconnecting / connecting ground wires (just to be safe). Sometimes there can be an appliance "leaking to ground" and you could get a zap.
Bob in Maine
07-07-2008, 07:30 PM
Ok, I re-checked the grounding situation, and the only wire that looks like the ground is a a single, bare copper, twisted wire, about 1/4" in diameter that leaves the bottom of the panel and clamps to the water line about 3 ft away.
Is this an "Oh my God, I've got to call an electrician right away!" sort of problem, or a "Well, it's been like this for years, and it'll probably be ok for many more years," type of problem?
Again, the house was built in the late 1920s and seems to have been partially re-wired about six years ago. I can't find a copper grounding rod anywhere around the perimeter of the foundation.
07-07-2008, 08:09 PM
If that pipe is metal and goes out underground you are likely FINE.
Earlier codes did not require the additional ground rod along with a water pipe ground. No matter, ground rods do VERY little any way.
07-08-2008, 06:29 AM
As far as electrical safety goes, so long as you have *one* good ground, you are OK!
BUT... Keep in mind that there are all sorts of different situations the electrical code needs to cover. Like...
Someone has just a cold water pipe ground, they get a leak and replace their metal pipe with plastic. Then they no longer have a ground!
Or the ground wire is run down the wall along the house. Someone comes along with a lawn mower and hits and breaks the ground wire, then they no longer have a ground!
For these reasons, it is a good idea when installing or upgrading an electrical panel to have two separate grounds. One a cold water pipe ground and the other a separate ground wire going to two ground rods placed 6 ft. apart. Then if one wire gets cut or plastic is installed to replace the water pipe, you still have *one* good ground left.
So it is kind of a double back-up system to be sure there will always be at least one good ground (for people who do not understand these things).
In your case you understand you need a ground, so just be sure you always have that ground.
07-08-2008, 06:47 AM
You can't have too many grounds. You can, however, misundertand what a ground actually is.
I built a building in Upstate NY for the local sewerage authority. All the buildings on the "campus" were on piles deep into the marl deposits. Mine had 33 steel H piles, all about 260' long. My Dad was the electrical engineer for the project, had about 45 years experience back then, and used one of the piles to ground the main panel.
The local building inspector made us put in a 5/8" x 10' ground rod.
07-08-2008, 07:02 AM
Sort of an opposite situation I saw once... There was a satellite/microwave relay station on a mountain top and not much dirt up there, mostly rock. They had big problems with lightning and poor grounding due to the rock.
So they installed about 5 ground rods and put in two 50 gallon drums. Then filled the drums with salt water and ran drip lines to the ground rod areas. This would keep the rocky ground moist and conductive providing a better ground. (Someone would have to cart water up there every so often.)