Every thing sounds good to me
So the meter pole is 200' away, and 2 hots and a neutral run to the 100 amp house modern panel.
At the house panel there is a ufer ground in the slab and a driven ground rod.
What are the dangers or level of danger in this installation?
Pretty expensive job to add the ground back to the meter pole.
Everything works and checks out at this house.
Every thing sounds good to me
What is a ufer ground?
I hope the sparkies can confirm this....I don't think the service is grounded at the pole. Two hots and the neutral come off the transformer. You Ground the neutral at the house.
Yer good to go.
Remember, you only link the neutral to the ground once. There is no need to bond the meter case to the service panel case.
The grounding at the house is correct. The grounding at the meter case is adequate.
Around here there are different standards in how the utilities and municipalities ground or not the transformers up on the pole.
SoCalEdison does not ground its transformers, it relies on the ground at the various service panels that it feeds. Burbank Water and Power has a dedicated ground for all their pole mounted transformers. I like that approach better, and once did come across evidence of the ground at one home caring all the current to ground that the transformer was trying to dump.
You COULD ground the case of the meter socket, but you don't need to.
The utility companies use the earth as their ground fault path or in other words they use earth for the same purpose as we use the equipment grounding conductor.
With the utilities having such a high voltage this voltage can push fault current through earth.
The codes that govern the installation of grounding electrodes for us mandates that we have a ground potential of 25 ohms but the codes that govern the utilities mandate no more than 10 ohms although most utilities will try for a lot less.
Remember Ohmís Law, E=I*E. With the voltages of our systems the most we will be able to deliver to earth would be 120 volts and at 25 ohms of resistance the most current that we would ever be able to push through earth would be 4.8 amps.
In most cases across America the primary on the transformers supplying our homes the voltage will be 7200 volts and this would be able to a push 288 amps through earth at the same 25 ohms of earth resistance. Most drop out fuses on the primary of the transformers supplying our home will less than 15 amps. This would equate to over 100,000 watts and a lot less than what any residential service would ever draw. At my home the drop out fuse is 5 amps (I was present when it was replaced last time) which would equate to 65,000 watts as my primary is at 13,000 volts and a lot more wattage than I would ever draw.
Here, all service drops must have a driven ground rod. So in this case there is a ground up at the meter pole which has just a100a breaker to the house and a gfci. I understand all panels after that should have the neutrals and grounds seperated and not bonded to the box.
The conduit coming out of the panel (ridged galvenized) that ran under ground to a sub panel in an out building was HOT (almost enough to raise a blister) at the nipple that tied it to the panel case.
I take that to mean that the path to ground here was going thru that conduit, rather then the driven ground that was a few feet away.
I installed an additional driven ground and the problem went away. At least, nothing was hot enough to burn me.
So some current was traveling to ground, it seems to me.
In section 250.4(A)(1) we are told why we connect to earth. There are four reasons and four reasons only. Neither one of these four reasons is to let current run to earth.
250.4 General Requirements for Grounding and Bonding.
The following general requirements identify what grounding and bonding of electrical systems are required to accomplish. The prescriptive methods contained in Article 250 shall be followed to comply with the performance requirements of this section.
(A) Grounded Systems.
(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.
Section 250.4 provides the performance requirements for grounding and bonding of electrical systems and equipment. Performance-based requirements provide an overall objective without stating the specifics for accomplishing that objective. The first paragraph of 250.4 indicates that the performance objectives stated in 250.4(A) for grounded systems and in 250.4(B) for ungrounded systems are accomplished by complying with the prescriptive requirements found in the rest of Article 250.
The requirements of 250.4 do not provide a specific rule for the sizing or connection of grounding conductors; rather, it states overall performance considerations for grounding conductors and applies to both grounded and ungrounded systems.
Without more information I cannot tell you why that extra rod caused the heat to go away but I can promise it wasn’t because the earth ate it.
Edited to add;
My brain is like the joints of my body, when I first get up in the mornings it takes a while before they start working properly.
When you touched that pipe if it was current flowing on the pipe that made it feel warm then you would have felt more than warm, you would have felt the current also. This is enough to say that it wasn’t current that was causing the pipe to feel warm.
During the heat of summer I have picked up pipe that I wanted to turn loose of in a hurry that hadn’t been installed yet. Could this have been the problem?
Last edited by jwelectric; 08-21-2012 at 05:03 AM.
And it never gets that sort of hot up there, it is at 5000 ft, this was early spring, and shady.
Could it be that there was a poor link on the neutral between the main and the transformer, and the unbalanced current was finding a path to the transformer thru the ground?
Even if it is up the ground rod and then neutral of another panel?
In the event of a lost neutral on a 240 volt single phase panel the system will become a 240 volt series circuit and there would be little to no load at all on the Grounding Electrode Conductor (GEC) or the grounded neutral conductor.
If there was a loose connection on the neutral then there would be heat on the conductor not the pipe containing the conductors.
The GEC is in parallel with the neutral conductor but the path of the parallel has the resistance of earth in its path which will limit the amount of current it will carry. The parallel path will have a total series resistance that will limit the voltage. The most I have ever seen in the 44 plus years in the trade was around 3 volts and at an amperage that my clamp-on meter would not read.
For the sake of this discussion letís say that there was current on the rigid pipe and you drove another rod. All you would have done is give the current another path to travel and would not have solved any problem with the system. Those poor old folks are still paying for current they are not using. The heat is now divided between the two paths but it would still be present.
We know that if the rigid pipe is continuous from the panel to the panel that it will have a lower resistance than what the path through earth is so I canít see how adding a rod would relieve the heat if it was coming from current flow.
I was surprised to find that the nipple was hot at the main panel. It was only hot for an inch or so. There was clearly some resistance there.
Hey, I'm just thinking. The sub panel was falling apart, and I replaced it as well, and gave it its own ground.....which the original sub panel did not have.
Possibly the flaw was cleared up when I replaced the old panel with a nice fresh square D?
At least the whole system is well grounded now.