ECN Forum Forums General Topics of the Trade General Discussion Area Amps on the water line

Don,

We're back on the "Single Point Grounding" subject again ( I think ) which I'm in favor of.

But, the problem with trying to combine a single point grounding system with the existing (nationwide) SERVICE system would be the same if a insulator was inserted in the incoming water line.

What happens when a person bridges that insulator, beit on a normally operating multiple premises service with, say 50% grounded conductor amperes is returning on the metal water line or on a system where a fault of some high value, say 10,000 amperes?

With-out a complete revamp of old services ( or in this thread, adding water line insulators on old systems as well).
I JUST DON'T SEE THAT EVER HAPPENING.

Glenn

Glenn,
The parallel path for the grounded conductor current creates excessive EMF. As we learn more about the health effects of EMF, I think we will see code rules designed to limit the EMF. I think that this will be the driving issue, and not the safety of the plumbers, but the result will be the same. Also code rules are not retroactive, so any change would only apply to new installations. There would be no requirement to make changes to existing installations.
In many areas the water pipe parallel path is disappearing. All of the water utilities in this area are using nonmetallic distribution mains. This prevents the direct parallel path back to the transformer. This may begin to cause the TV cable utilities problems, as their system also provides a parallel path for the grounded conductor current. Here again this parallel path for grounded conductor current is required by the NEC.
Don

[This message has been edited by resqcapt19 (edited 07-16-2002).]

Don,

Your point about the health effects of EMF driving changes in GEC practice, IMHO, is excellent. It is only a matter of time until the wave of litigation starts moving towards the crest (litigation for compensation for documented health effects).

Your comment about the cable company adds a whole new meaning to the ideas in "open neutral." A residential coax cable feed shield, depending upon how complete it is, will have a conductor gauge equivalent between #16 and #12!

Steve T,

Consider this image of a residential configuration. Three houses on three seperate adjacent lots, one power transformer and a common metal water pipe system.



It doesn't matter much what is going on in houses #1 & #2, one could shut off the service disconnect and remove the meter from the socket and there is still going to be neutral current.

This current flows when the house farther away from the transformer is unbalanced. The more the unbalance in #3, the more the current in #1 & #2.

This is from an ECN thread from last November titled New Service or Subfeed . This is not the only source of the current that might be found on the water service of your potential(?) client. The power company's distribution grid, depending on its configuration, may also cause measurable currents.

Al

[This message has been edited by ElectricAL (edited 07-17-2002).]

Joe and Don
I have seen suggestions to insulating the water lines before, leaving the 10 foot section intact and at that point inserting and insulating coupling to isolate the waterline from the rest of the system.
Also another problem with these waterlines is what has come to be known as a "Shorted Neutral" to the water line. This has to do with magnetic fields but it does happen and the return current winds up on the waterline.
These suggestions as I stated above, also stated that alot of plumbers carry jumper cables to jump the sevtion of pipe they are getting ready to cut. I havent seen this but suppose its possible.
My question is this, now that I have finally become aware of this, where does the current go execpt to another house and use its neutral to get back to the source. On one street I recently worked there were 16 houses on one transformer, I believe the transrormer was a 69kva type leaving about 25 amps per house and the tri-plex went everywhere I measured about 400 feet of triplex and during one of the hottest days the voltage drop was significant, since all these homes had some sort of A/C. The waterline current in the particular home I was working in was almost 10 amps. It seems to me that the utilitys have got to do a better job monitoring there systems and their terminations.
-Mark

Here's the information that is available at the reference link that I provided above:

Effects of Electrical Grounding on Pipe Integrity and Shock Hazard
Prepared by Steven J. Duranceau, Boyle Engineering Corporation and Melvin J. Schiff and Graham E.C. Bell, M.J. Schiff & Associates, Inc.

June 1996

AWWA Research Foundation Order Number: 90702

BACKGROUND
The practice of using water pipe as all or part of the grounding electrode system of buildings has been commonplace for more than 80 years. The practice was predicated on the assumptions that grounding of alternating current (AC) had little or no effect, compared to direct current (DC), on the corrosion behavior of buried metals; that current would only flow during off-normal conditions; and that there were no safety implications for water utility employees.

Some modern electronics (variable speed motors, televisions, computers, etc.) produce DC on the water service piping. Increases in corrosion rates due to stray DC are well documented. Further, when electrical transformers serve multiple buildings and customers, water services and distribution piping can act as parallel neutral return paths for AC from building electrical systems to the transformers. The alternating current can also increase the rate of corrosion of distribution and service piping. The increased corrosion leads to increased operating costs, as well as possible water quality issues for the water industry.

The presence of electrical currents on water services and mains results in random shock incidents for water utility employees and contractors during routine operations. The severity of these shock incidents ranges from mild tingling sensations to burns to numbness in the extremities. Most such incidents go unreported due to lack of a reporting protocol, poor record keeping, "macho" crew attitudes, and so forth.

This report presents the results of the study in terms of the shock hazard for utility employees and reduced service life of the mains due to possible external corrosion caused by current flow.

CONCLUSIONS

1. Shock incidents, minor and serious, occur frequently in the water utility industry.

2. Minor shock incidents occur at a much higher rate.

3. Shock incidents occur despite the efforts of utilities to provide their employees with equipment, training, and procedures for avoidance of shock hazards.

4. Electrical insulation of water services is effective in reducing the number of shock incidents.

5. Alternating currents cause corrosion and the rate of corrosion is much less than that of DC.

6. Electrical currents on water pipes change the corrosion state of buried metal piping.

7. Relatively high amounts (greater than 1 amp-AC) of alternating current were found on more than fifty percent of the water services tested during this investigation.

8. Electrically resistive, but not insulating, connections in metal piping systems are common and have an effect on grounding currents, which in turn affect pipe integrity.

9. Electrical insulators can affect water quality in terms of metal release.

RECOMMENDATIONS
1. The water utility industry should formally and directly approach the electric power distribution utility industry and the National Electric Code (NEC) committee of the National Fire Protection Association and declare their intent to electrically insulate exterior water services.

2. If a utility decides to install electrical insulation in an existing water service, the utility should coordinate with the power company and inform the building owner of the impending changes.

3. Water utilities should implement safety procedures consistent with state, local and federal requirements for protecting their employees from shock hazards inherent with water service piping which is bonded to the electric power system.

4. The NEC should be changed to require adequate grounding of a structure without considering the presence of underground water pipe.

5. Elevated lead and copper concentrations may be related to high levels of AC/DC current.

FUTURE RESEARCH

The decision to insulate water services is not simply a technical decision based on this or other reports. The question involves local, state, and federal agencies, including the U.S. Environmental Protection Agency and Occupational Safety and Health Administration, as well as consideration of indemnification and litigation risk. The legal and political implications are beyond the scope of this work and have not been addressed in depth by any previous study.

The water utility industry should conduct a study to determine the specific legal liability of electrical insulation of water services. The study should include potential litigation exposure from employees and customers, as well as from contractors and subcontractors who perform work for utilities and customers.

The brief tests of the effects of insulators on water quality which were found in this study for copper release should be extended to other pipe materials, lead in particular, and profiled for other water sources and treatment. Field verification and laboratory investigation of the effects should be pursued.

Touch read, radio, and remote meter reading systems rely on the measurement of a voltage signal to register water consumption and calculate the customer's bill. As far as can be determined, the possible effect of grounding currents and voltages on meter system accuracy has not been investigated.



[This message has been edited by Joe Tedesco (edited 07-17-2002).]

I figured this question would spark a lot of conversation about the subject, which I know has been talked about before. Trying to explain to people all the different variables involved is difficult when they are not electrically adept. Especially home inspectors who pick up bits and pieces of information and then misapply it in their jobs, or are just trying to avoid a lawsuit so make a mention of the situation just so they can say they put the info in their report.
I am going to print this thread and give it to them. I will let them know that these are just different peoples opinions and not necessarily fact so you good people don't get hit with a lawsuit. I, as a village inspector have tort immunity and can't be sued. but that's another subject.

Thanks all!!

Don,

We are on the same page on this issue as well as 99.99% of the time on most other issues.

I know the Code is not retroactive.

How many years will/would it take to have the parallel path(s) of the service grounded conductor eliminated with out some type of law. Never in my opinion.

Glenn