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Our inspectors are going to enforce new rules about grounding and bonding. It strikes me as wrong because we are moving back 40 years to when I started in this trade. The problem only applies to buildings with a metal water supply and metal internal piping – most buildings that might need a service upgrade.

40 years ago, (when I started) the neutral was grounded to the nearest cold water line and the meter was jumpered to maintain the ground if the water meter was removed. City employees were reportedly getting shocks when they changed water meters.

When plastic water lines became popular so a plumber might replace a section of copper line with plastic, we grounded to the street side of the water meter and bonded the inside copper lines.

Now, we are to ground the neutral at the top of the mast. The ground wire runs to the meter socket where the socket is bonded, and continues to ground rods or a ground plate. My understanding of this type of ground is that it will have a resistance of more than 10 ohms, and a lot higher when the ground is frozen.

From the meter socket, the panel is bonded. The closest cold water line is bonded to the panel. So, the neutral is electrically connected to the water line, but we now call it a bond.

The jumper across the water meter is to be removed.

My issue is that I have a metal water meter. I isolated it and it clearly has 0 ohm resistance across the meter. Removing the jumper doesn't stop electricity from flowing through the meter.

In the future, if we lose an overhead neutral from the poco, the return path will be through the water line, through the meter and through the incoming water line which is bonded to neutral in the neighbor's house. If a plumber cuts a line, or a city employee removes a meter, they will break the new return circuit. I don't think being in parallel with a 10 ohm ground rod is going to save them.

What do you think?

I don't see where much really changed except they don't trust water pipes as being a grounding electrode anymore. I agree back in the old days with solid metal water systems the water pipe was the current path when the neutral opened so breaking that pipe circuit might always present a danger.
These days the Ufer (concrete encased electrode) is rapidly becoming the "go to" grounding electrode and it is part of the footer inspection in Florida, to insure it will be "present".

The water line is still a parallel path to the transformer through the neighbor's house. the only thing that changed is that they renamed the "ground" wire as "bond" wire. If the overhead neutral is lost, the water meter becomes the return path. That problem was solved before I started in the trade in 75 and now we unsolved it.

Lets put it another way. Cut the overheat neutral and take the water meter out without a jumper. Does the guy working on the meter get a shock?

We aren't installing Ufer grounds. Where did that come from?

Does anyone know the resistance of two ground rods?

twh:

"We aren't installing Ufer grounds. Where did that come from?"

I guess that is a difference between Canada (CEC) and the USA (NEC)

We require a Ufer to be installed on new construction, additions with new footings, etc. Both resi and commercial. The metal water line is becoming a thing of the past.

Yes, we still jump out water meters that have metal supply visible within the structure. It could be plastic out to the street, but who knows.

One POCO does not allow the ground conductor to enter the meter pan, another does. It gets interesting when some ECs work in an area that they are not familiar with.

On the funny side, I occasionally come upon the hot/cold bond at a water heater that has PEX piping. Waste of two pipe clamps and a length of wire.

Here is a sketch of two buildings grounded and bonded to our new rules, with the fault path if a poco neutral is broken.

I am not sure what changed. The service can be grounded anywhere from the service point to the bus bar in the service disconnect enclosure. It is grounded (or bonded) pretty much like it always was. The only reason we distinguish between grounds and bonds is to describe the intent of the connections. The electrons don't know the difference. You have always been using the water utility as your best connection to the utility neutral. We just can't say that. It is like saying my swimming pool is my best grounding electrode. (I don't have utility water)
It doesn't sound right to say that but it is still a fact.

Greg, it isn't the point where neutral is grounded that is the issue. It doesn't matter. Don't get stuck on that. I just show it on the drawing to be exactly accurate.

The point is that if the poco neutral is lost, the system keeps working because there is a neutral connection through the water meters. Then, if the plumber cuts the line, he is cutting the neutral connection.

OK, I see your points with the sketch and your comment above.

Yes, if the metal water line is cut, the return path is broken, if the utility neutral is 'lost'.

There have been lost utility neutrals, both OH & UG, that sometimes create havoc, and sometimes go unnoticed for some time, all dependent on the earth ground system integrity.

We collectively have to accept that the 'water piping' as an earth ground is becoming a thing of the past with the proliferation of non-metallic water supply piping. IMHO, that is one of the main reasons to install the Ufer system.

I have had a few calls over the years of techs from the water utility getting 'shocks' when changing out water meters. The utility held a safety meeting, and requires their meter techs to look for the NEC required jumper first, and if one is not present advise the owner.
They also have 'temp jumpers' for safety. Yes, we still have 'aged' homes that lack the jumpers on the water meters, and the water heater units.

The metal utility water line has always been a neutral path, whether the PoCo neutral is connected or not. Remember current doesn't take the path of least resistance, it takes all paths. The copper water pipe may end up having more circular mils and lower resistance than the 1350 aluminum conductor. Back in the olden days the whole water system was a grounded conductor. This is nothing new. What is new is that water pipe is probably plastic now. That will certainly be true soon if the original was lead.

I'm about a month away from changing the service in my own home. I'm going to insert a section of plastic waterline next to the meter to isolate it.

I'm in Canada and our dirt is frozen for several months out of each year. To me, that means our ground plates will be in ice instead of dirt which probably means a really high resistance. Because our ground, or in the winter, crappy-ground, is in parallel with the poco earth return, we might get a tingle voltage between ground and cement basement floor. I won't be able to measure that because all my neighbors are using the water line as ground. My understanding is that our poco target resistance for their grounding is 5 ohms. Does anyone have any experience with this? (without a Ufer ground, of course)

When I moved into this house it was far more than just tingle voltage between the EGCs and the floor. The first thing I did on day one was connected the cooktop to a cold water pipe and that fixed the problem temporarily. Later I figured out the "ground" I was using was actually the cast iron drain pipe from the stainless kitchen sink, connected continuously by metal to the earth under the slab. (Chrome over brass tailpiece and trap, copper drain pipe)
Shortly after that I drove new rods and connected new copper from the panel to them. As time went on my GES was improved. Now I think I may be the ground for the neighbors too. I have a couple of amps on the PoCo neutral with my main breaker off. There is so much stray current going around it is hard to figure out what is going on. All of the grounding leads coming down the poles carry current, all the way up my street. The worst is almost 3 amps.



I suspect that will be true anywhere that has wye distribution tho. (a whole street, ~20 transformers, fed from a single phase) All of that unbalanced current is going wherever there is a path and a 2ga neutral on the poles is not carrying all of it. I really do not think there has been nearly enough analysis of where stray current comes from and where it goes. It has been blamed for pin holing pipes here and a number of other less noticeable issues.

Greg, if you have current on the ground with the main off, you might be the return path for your neighbors or you might be the earth return for the transformers. Do you have a pool with a lot of grounding?

Yes I think that is exactly what is happening. As I said I may be the ground electrode for the neighborhood. I am the only one within a quarter mile with an in ground concrete pool and that has to be the best Ufer ground around. The poles depend on a single strand of #6 copper, stapled to the bottom of the pole and most people just have a rod or two. When I was building my pool and deck, everything was bonded and it gets tied back to the service ground via a bunch of copper EGCs. I also accidentally exposed the rebar in my garage footer doing something else and I tied that in too. Every time something becomes "available" it gets used. I now have rods at the satellite dish and also at the HVAC condenser at the far end of the house, tied into the system.
The up side of all of this is in spite of a thunderstorm about 150 days a year, I have not lost a thing.

As soon as you have a neutral/ground connection anywhere and bonded water pipes the pipes can and will become a return path. The whole stray current issue is the main reason why some distribution network operators in Europe prefer TT systems where the building grounding conductors are only connected to rods/UFER but not to the neutral. The neutral is only earthed at the transformer. The downside of TT is obviously the considerably higher impedance, requiring additional earth leakage protection (i.e. an RCD for all circuits).

Re: impedance of rods: that totally depends on local conditions but 5 Ohms is pretty low. Very low for rods in fact. When ours was newly installed it measured at slightly over 8 Ohms and I'd say we've got decent conditions here (mostly clay). By OVE standards, up to 100 Ohms are considered acceptable.

That was the thinking when the NEC stopped regrounding the neutral beyond the service disconnect. They were trying to avoid neutral current in grounding conductors. They started with "no parallel paths, then they just stopped allowing 3 wire feeders to additional buildings altogether.

When I went to school, they taught that, if a neutral and ground were both taken to a barn, they must be tied together and ground rods installed. The instructor said it is known that there is a parallel path but it is better than what can happen if they aren't tied together.

This is what can happen if they are not tied together:

You can lose the ground connection and never know because everything still works. Then, if there is a fault from hot to ground, the breaker might not trip.

With a water bowl frame tied to hot and the cattle standing in their wet poop, they will be electrocuted.

If the animals don't get it, a farmer or electrician might turn the power off to a piece of equipment but when they open it up, there is voltage between neutral and ground.

Why are we going back to a proven failure?

I assume you mean the "grounding" connection (the egc going back to the service disconnect in a 4 wire feeder) but if you have a 3 wire feeder that becomes a lot worse than in a 4 wire feeder because it is an open neutral condition along with all of the issues of a lost EGC added on. I suppose the lesson is make sure you don't have a fault in the neutral or the grounding conductor. It is not going to end well.

An open neutral is repaired immediately because the equipment quits working. An open ground remains until someone gets a shock, or something dies. The old way, that we are returning to, wasn't better.

Wouldn't a better solution be to take an insulated neutral and and ground, both of the same size and connect them together at the out-building? Then, we would have half the chance of any fault and it would never be an open ground that couldn't be detected.

Ground fault protection isn't a good solution because some equipment won't work with GFI protection. VFDs for example.

While you are providing redundancy when you reground the neutral, you are also putting neutral current on the grounding conductor. I could argue either way but 250.6 and 310.4 gets in the way of the redundancy argument.

Greg, when I say the rules are dangerous, you say the rules prevent solving the problem. They didn't prevent solving the problem, here, when the rule was that Neutral and Ground were to be connected together in buildings housing livestock.

Our rules were changed because they were dangerous. Now, we are to go back to dangerous because we don't want current on a ground wire.

You have current on your ground wire. What about the rule?

We have a special thing going on. We went back to connecting the ground to the nearest water line to the panel and we prevented current on the ground wire by renaming it as a "bonding conductor". I'm appalled, but rules are rules.