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I have posted the proposal from the code making panel several different times so this one more time won’t matter that much.
5-236 Log #2432 NEC-P05 Final Action: Reject
(250.104(A)(1))
__________________________________________________ __________
Submitter: Robert P. McGann, City of Cambridge
Recommendation: Revise text to read as follows:
Metal water piping system(s) that is likely to be energized , installed in or attached to a building or structure shall be bonded.
Substantiation: With much expanded use of plastic water piping system(s) isolating section of metal piping systems. This type of installation leaves contractors and inspectors what is required to be bonded.
Panel Meeting Action: Reject
Panel Statement: The requirements of 250.104(A) apply to complete metallic water piping systems. Where there is no complete metallic water piping system, then the requirements of 250.104(B) would apply for those portions of isolated metal water piping system likely to become energized.
Number Eligible to Vote: 15
Ballot Results: Affirmative: 15
Notice the comment about it being a complete metal water pipe system. If there is not continuity from one end to the other then the system is not a complete metal system therefore the bonding requirements for the equipment grounding conductor installed with the branch circuit is all that is required.
As for reading the resistance between the earth connection and some point on the equipment grounding conductors is nothing short of silly.
The equipment grounding conductor is required to be bonded to the neutral conductor of the service so a complete path back to the source is established for fault current to follow.
The earth plays absolutely no role in the function of the circuit. There is no current trying to enter earth.
We connect to earth for four reasons and these four reasons only. It is not to make the fuse blow or to open a breaker of any kind. It is not to allow fault current to have somewhere to go either.
250.4 (A) Grounded Systems.
(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will (1) limit the voltage imposed by lightning, (2) line surges, (3) or unintentional contact with higher-voltage lines and (4) that will stabilize the voltage to earth during normal operation.
Also read the last sentence in 250.4(A)(5)
(5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be considered as an effective ground-fault current path.
Forget anything anyone has ever told you about the earth connection and don’t listen to anyone who tries to sell you on the idea of current flowing into the ground.
You are supposed to get a voltage reading from the hot to any metal anywhere that is bonded to the service and also to the white or bare conductor in the circuit.
Last edited by jwelectric; 02-03-2010 at 12:56 PM.
Well you were shocked because the pipes were not bonded to ground. Something to think about...
Also it is not "ohms law", rather an "ohm meter". A "continuity meter" is next best.
How to use either...
(here used to test fuses)
http://www.dinosaurelectronics.com/Test_Fuse.htm
Last edited by Billy_Bob; 02-03-2010 at 05:03 PM.
Would you mind taking a few minutes and explaining how connecting anything to ground will stop someone from being shocked.Originally Posted by Billy_Bob
jwelectric, what would you say the cause was and the fix should be?
The cause of what?
Are you saying that your water was energized due to the reading on the meter?
Were you getting shocked?
If you were being shocked, what else were you touching when you felt the current?
I felt current when I was washing my hands on several occasions when the vanity light switch was on. I later discovered that I only felt the current when I was using hot/warm water, which is the pipe that the box was touching. I didn't feel it if only the cold water was on. I also do not recall getting "zapped" when using that sink prior to adding PEX to supply that bath. AFAIK, nothing electrical changed with that circuit. It is entirely possible, however, that the copper pipe shifted slightly when I reconnected the water and made contact with the electrical box.
I don't think I was touching anything else. I do not recall if I had shoes on or not. This is a basement bath, carpet/pad on slab
In addition to adding the bonding jumpers around the PEX as recommended, be sure to add a bonding jumper from the metal hot water pipes to the metal cold water pipes. This is usually done at the hot water heater on the pipe side of the water heater fittings/flexible lines.
Hot water heaters have "dielectric unions" and other parts which prevent a contiguous electrical connection from the cold water pipes to the hot water pipes. So this is why it is necessary to install a bonding jumper.
Lets go back a second to all the piping being copper. Lets say there is a high resistance short inside the box. Its a high resistance short so the breaker doesn't trip but there is power flowing from hot to ground. Ok, now you cut out part of the copper pipe and replace it with pex effectively defeating the bonding of the copper pipe at the panel. Now when you use the water you get a shock. You discover that the box is touching the copper pipe, you move it and then no more shocks.
One or more of the following is therefore true. 1) The box is not grounded. If it was you would have still had a path back to the panel so you would have not been shocked. 2)The ground wire has a break in it or is not connected someplace so essentially the box is not grounded. 3) When measuring the voltage between the white wire (neutral) and the ground wire the voltage is not 0. 4 When measuring voltage between hot and neutral and then hot and ground you get different readings. They should be around 120V, but its more important that the readings are the same.
-rick
I have a jumper at the water heater which is also near the water service entrance. Its a gas water heater, btw.
Good! (Safer)
FYI "dielectric unions" are used on gas or electric water heaters. Here is a bit on that...
http://www.hammerzone.com/archives/p...n_de/intro.htm
I connected an outlet to that wire and used a 3 wire plug in tester which didn't show anything as being wrong. No open ground, etc. I used a multimeter to measure hot to neutral and hot to ground and got the same reading. Neutral to ground shows 0.
You keep bring up dielectric unions, but I dont see how they apply in my case. I have yet to see a dielectric union for copper/pex and I don't see where it would be applicable for the water heater either
So far as this discussion, it's not important if you have those unions or not, I'm just trying to point out that sometimes one section of pipe will be electrically isolated from another section of pipe. Sometimes not.
Here is a water meter which might not be electrically conductive (fittings?) and they installed a bonding jumper to be sure of a contiguous electrical connection...
Here they are installing a bonding jumper between the hot and cold water pipes above a traditional water heater tank...
Here there are several different pipes and they have electrically bonded them all together...
Bimmer
Forget all this hog wash about bonding the pipes in your home. Read the Panel statement from the proposal above and you will see that those charged with writing the NEC seems to think all this bonding around this and that is nothing more than hog wash also.
The only place that bonding of a water pipe is important is if you have 10 feet or more in contact with earth which would make it a grounding electrode. I have already covered what the purpose of an electrode is so I won’t rehash that.
In order for current to flow there must be a complete path from the source back to the source just as in any flashlight. Current leaves the battery goes through the conductor of the flashlight through the bulb back to the battery.
If you were feeling a shock from the water there would have had to been a complete path from the transformer supplying your home back to the transformer.
If the metal box was properly bonded to the equipment grounding conductor then any and all current would have had a path back to the source which would have opened the overcurrent device.
If the box was not properly bonded and there was a problem with the light fixture then it is possible that current was entering the water pipe through the box and through your body down to the concrete back on the grounding electrode conductor and completing the path to the source. When you removed the fixture and box you cleared the fault.
When reinstalling the fixture check that the equipment grounding is connected to any and all metal and check the fixture for any failure. Corrosion of the interior of the light could be your problem
JW - go read the WA State post on the Pro forum.
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