Well Casing Grounding

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Re: Well Casing Grounding

The specific problem occurred at a loaction where the service to several houses along a street where served by transformers located on poles along the back line of the properties. Each house has a pool. In many cases, the pools are only 5 linear feet from the utility poles themselves. This created a very low impedance path for normal current to flow as the pool bonding grid was effectively earthed and connected to the equipment grounding conductor for the pool equipment. More than 50% of the normal operating current would be present at metal parts of the pool structure.

I consider a good percentage as more than is necessary, meaning, it can be effectievely reduced.

Using a well casing as a GEC will not provide as low enough impedance path to allow the operation of the OCD, even if coonected with a #4 and directly to the main bonding location. You don't want fault current to use the GEC system, you want it to use the service grounded conductor. My example above would and could carry fault current as well as normal operational current, and that in my opinion is bad design.
 
Re: Well Casing Grounding

Brian If the neutral that runs from these transformers to the houses have a good connection this would be the path of almost all the neutral return current. And what would be left would not be much. The resistance of any electrode (including a deep well casing) with Earth would be high enough that almost all the neutral current would still flow back to the transformer via the main neutral. Now when there is a bad connection in the neutral path then it will try to take another route. and if one of these transformers lost the primary neutral then even more current would flow through the houses EG system. That would include the EGC bonding the pool pump that will also tie in the equal potential bonding at the pool causing a differential voltage and step touch potential at the pool.
With what your saying there would have to be a very large voltage drop in the neutral to have a high enough voltage deferential between the house service and the power pole. and if this was the case there would be a very bad dimming and brightening of the lights in the house for this to occur, and every house that don't have a water grounding electrode would have this touch potential at every ground rod. :eek: Unless it was a primary neutral problem. Also it was found that running an electrode deeper does not lower the impedance enough to make it worth while. There's a chart at a web site somewhere that shows this. as there are other more cost effective grounding methods.
It just don't add up. :confused:
 
Re: Well Casing Grounding

Bryan,
More than 50% of the normal operating current would be present at metal parts of the pool structure.
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That number seems excessive to me. In areas where there is a common under ground metal water piping system and a common utility transformer, I've never seen more than 25% of the grounded conductor current on the water piping system when the service neutral is in good repair. I would think that the impedance of the metal under ground water piping system would be far less than any mumber of grounding electrode systems. I think that there was more to the pool problem then the required bonding to the building electrical system...maybe as Wayne suggested a primary neutral problem.
By providing a low impedance path, normal current will flow, possibly enough to cause step potentials around the well itself.
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Doesn't this same problem occur at all grounding electrodes? Isn't the "step potential" reduced as the impedance of the grounding electrode goes down?
Don
 
Re: Well Casing Grounding

Hello Wayne,

I agree with everything you are saying. What I don't understand is why everyone finds it so important to obtain the low imepedance possible for the grounding electrode system? Some people say it is for safety, some say it helps to reduce stray voltages, others are convinced this will help with the operation of the serivce/feeder OCD. I see no evidence of any of this.

I have seen homes with an extensive, low impedance grounding electrode system get hit by lightning and receive severe damage to the electrical system. I have also seen homes with a single point ground rod system take a direct strike and not have one circuit effected.

My point? Grounding Electrode Systems seem to create more problems than the solve. I asked several months ago if two houses could share a single electrode system. No one could find a code violation. Communities using common underground water pipes experience more problems than those that have isolated systems.

Your point of an open neutral condition is significant. I have seen and heard of cases where an open neutral condition went unoticed for months due to the grounding electrode system being common between two separate services.

So please someone, explain to me the benefit of running a #4 conductor to a well casing and bonding it to the service grounded conductor verses bonding it to the pump EGC and using another means as the GEC?
 
Re: Well Casing Grounding

If the equipment grounding conductor for the well pump motor was bonded to the well casing, this thread wouldn't have started. That is not the case (at least not in my area).

In fact the well driller did not want the well casing grounded.

I still believe the well casing should be grounded.
 
Re: Well Casing Grounding

I had a problem with the well man running the wire and am curious as to just who hooked up the wires.Some one with a license to do electrical needs involved in this install.Who takes the liability if that wire is not deep enough?
The grounding issue should fall on the electrical contractor.I would suggest a meeting with the AHJ and perhaps print this intire thread.Then if anything bad happens there is a record of it being called to there attention.I vote with you that at min. it needs bonded to the pump.Would rather see a #4 back to panel,it can't hurt.
 
Re: Well Casing Grounding

Bryan,
Communities using common underground water pipes experience more problems than those that have isolated systems.
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Do you have any documentation for this statement?
Don
 
Re: Well Casing Grounding

No, just information from articles I have read and review of Florida Power and Light documentation. FPL receives over 100 calls a day concerning power quality, power loss, and various power problems. One of the listed issues is common grounding electrode systems. Many of the complaints and/or concerns were reported by water utility organizations, well and irrigation companies, pool installers, and electrical contractors.
 
Re: Well Casing Grounding

Bryan,
What types of complaints are being recieved that point to the common grounding electrode systems as a problem. Also many utilities use a MGN system which makes almost all grounding electrode systems common to each other both on the primary and secondary of the service transformers.
Don
 
Re: Well Casing Grounding

I guess you guys can tell that I am new to this forum. I am not new to grounding and bonding. I am a retired electrical contractor.

I have 40 years of installing electrical systems in residential, commercial and industrial properties.

I have taught the NEC at the community college for years
I have taught residential wiring at the community college.
I have taught NEC upgrading to the union inside wiremen.

I have seen many times what lightning has done to electrical equipment as well to structures. I don't pretend to understand lightning entirely, however, I know that rural areas here in Michigan's upper peninsula have much more trouble with lightning damage than the small cities with community water systems. By much more, I mean by a factor of 50 to 1.

I don't have a current code book.(That is why I asked my question) I cannot do any contracting without sacrificing my pensions.

I started this thread with a question: "Does the well casing have a code requirement to be grounded.

The consensus is no. The AHJ cannot demand that it is to be grounded.

In this area, the well digger selects and installs the well, the pump motor, piping and wiring to the premises. He installs the holding tank, pressure switch and associated fittings. The electrical contractor installs the branch circuit and local disconnect. Note: In my area, the pipe and wiring are installed 5-6 ft deep.

My daughter got her electrical permit as a homeowner.

I explained the hazard with a pump motors wiring shorted against the well casing causing electrical shocks to be felt on an adjacent property pool ladder. Isn't this cause for alarm?

I have heard of electricians bonding well casings by drilling a hole in the casing and installing a bolt and nut to connect the gound wire. Surface water fell into the well casing through the hole drilled and contaminated the well.

Well I've rattled on long enough :D Thanks for listening to me.

Regards,

Derwith
 
Re: Well Casing Grounding

Why not simply use 250.90

250.90 General.
Bonding shall be provided where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed.
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If it is common for well pumps or the wire dropping down to them to fault to the well casing wouldn't that code section fit?

Just my opinion, Bob

[ September 09, 2004, 05:57 PM: Message edited by: iwire ]
 
Re: Well Casing Grounding

I have never seen the wires to a submersible pump in conduit.

It is very difficult to roll conduit up when retrieving the pump. :D
 
Re: Well Casing Grounding

Let me refrase that a bit.
What i an wondering is if that 4 inch steel casing since it has wires be called conduit ?
I think you know where i am hedding.
 
Re: Well Casing Grounding

What does 250.90 say? Remember I have no code book. If is says all metal raceways must be grounded, the 6"well casing contains wires but is it a raceway?
 
Re: Well Casing Grounding

250.90 General.
Bonding shall be provided where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed.
Click to expand...
 
Re: Well Casing Grounding

The well driller will say that he securely attaches the wires to the water pipe in the center of the well so that the wires are not "likely" to cause a fault.
 
Re: Well Casing Grounding

Derwith,
I explained the hazard with a pump motors wiring shorted against the well casing causing electrical shocks to be felt on an adjacent property pool ladder. Isn't this cause for alarm?
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As Bryan pointed out in the second post, the NEC requires the metal well casing to be bonded to the pump circuit EGC to prevent such an accident.
250.112 ...
(M) Metal Well Casings. Where a submersible pump is used in a metal well casing, the well casing shall be bonded to the pump circuit equipment grounding conductor.
Click to expand...
Don

[ September 09, 2004, 09:41 PM: Message edited by: don_resqcapt19 ]
 
Re: Well Casing Grounding

Thank you Don. My guns are now loaded and the inspector will be contacted in the morning.
 
Re: Well Casing Grounding

Most submersible pumps are wired with submersible pump cable, a flat 4 conductor ribbon cable with outer jacket, and is UL listed. The cable is strapped to the drop pipe, typically with 2" wide scotch 50 tape, or for large installations, 1/2" wide ss banding straps. If the well is fairly straight, there will be little abrasion of the drop cable
 
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