UFR Question?

[Cavie]

I'm gonna give all you smarta$$$s out there a chance to have some fun at my expence. The question is about pool bonding. If we bond all the metal within 5' of a inground pool and then run it the the pump housing, Haven't we just createdated one big gigantic UFR Ground??? With a # 12 bond wire? A short needs to go to ground, it goes to the panel, looks for a placd to go, finds very dry sandy soil in Florida in the wintertime, very high resistance, It looks at the pool ground wire and sees a #12 ground to the pump motor. then it sees a #8 bare conductor buried 10 feet undergorund and attached to a lot of steel. In a sence, we have a #12 attached to a #8 to a lot of steel. Did I mention that in some parts of Florida galvinized ground rods have a way of desolving into the soil in a number of years. Let the flames begin.

 

[roger]

Cavie, bonding a pool has nothing to do with a "short" or "any" fault condition, it is simply to keep everything equal. With a properly bonded pool, we could go ahead and attach an ungrounded conductor of say 120v to the bonding system, actually energizing everything to 120v and be safe.

Roger

 

[roger]

By the way, I hope my answer qualifies me as a smarta$$, and if so, I guess I can assume I did good.

Roger

 

[Cavie]

Nope you don't quailify. Then will come.

 

[don_resqcapt19]

Cavie,

A short needs to go to ground, ...

WHY????

 

[Cavie]

OK, I'll play, change that to "IF" a short goes to ground. Why do people change the subject and avoid the question????

I asked this question cause an electrican ran the bond wire from the pool steel and cage up to the Pool panel ground and then down to the pool pump bond lug.. I told him to remove it from the ground bar in the panel. He said, " Didn't I just hook it to the Main ground bar in the Main panel via the #12 equipment ground on the pool pump??

 

[winnie]

While you might think of the pool with all of its bonded metal as a sort of 'concrete encased electrode' for the building, connected with an 'undersized' EGC, the rest of your question doesn't make much sense.

You seem to suggest that in the event of a short circuit, electricity will be trying to find a path to the ground electrode. This is a _false_ understanding of how electricity operates.

Electric current always follows a closed path. This path goes from the source of supply, through conductors and the load, and back to the _source_. _Ground_ has nothing to do with this closed path.

In the event of a short circuit, a conductive path is established which bypasses most of the load, and excessive current flows. Again, this has nothing to do with the ground. The excessive current will flow in the service conductors feeding the home.

Where 'ground' enters the picture is that we intentionally connect the electrical system neutral to the earth via grounding electrodes. Because of this, the earth _may_ become a path back to the source. If you are standing on wet soil and touch an energized conductor, you get a shock because the electric current flows from the source, through the conductor, through you, then through the soil, to the grounding electrode, and back to the source. Not to the Earth, but back to the _source_.

Because we have grounding electrodes at the home and at the transformer, the earth will form a parallel path for the neutral. However the resistance of this parallel path is many orders of magnitude greater than the resistance of the neutral conductor. In the event of a short circuit in the home, most of the current will flow via the neutral conductor, with only slight current flow through the earth.

Significant ground current can enter the picture if the ground itself is part of the source of electric current. This is not the case with the electrical power supplied to the home, but can be the case when lightning current gets added to the mix.

In the event of a fault that causes significant current to flow into the earth via the various home grounding electrodes, it is possible that the pool will be the best grounding electrode, and that this could overload the EGC between the pool and the home. This could be caused by a primary to secondary fault at the transformer feeding the home, or could be caused by a lightning strike on the home electrical system. In either of these cases, the damage to the #12 EGC is the least of ones worries.

-Jon

 

[Jim W in Tampa]

I'm gonna give all you smarta$$$s out there a chance to have some fun at my expence. The question is about pool bonding. If we bond all the metal within 5' of a inground pool and then run it the the pump housing, Haven't we just createdated one big gigantic UFR Ground??? With a # 12 bond wire? A short needs to go to ground, it goes to the panel, looks for a placd to go, finds very dry sandy soil in Florida in the wintertime, very high resistance, It looks at the pool ground wire and sees a #12 ground to the pump motor. then it sees a #8 bare conductor buried 10 feet undergorund and attached to a lot of steel. In a sence, we have a #12 attached to a #8 to a lot of steel. Did I mention that in some parts of Florida galvinized ground rods have a way of desolving into the soil in a number of years. Let the flames begin.

So far your short has had 20 20 vision so it should be able to see all this steel is a pool full of water and people.LOL

On the serious side there is a hazard if the neutral to poco opens.Normally shorts (fault current) is cleared by opening a breaker (not fed pacific) because of over current thru the ground wire back to the neutral.Yes if this happens and it can then you have a shock hazard.You also now have an unbalanced 120/240 volt system that will begin to burn out all the higher amperage 120 volt loads (frig,pumps,coffee makers,etc.).While your point is valid i dont know of a cure.Like it or not to meet 680 this is the way pools need to be wired.What is it that you would suggest ?

 

[e57]

Listen Jerkie, yup its one big ufer. Now lemmie talk to youy boss! Does this qualify? smarta$$$s

I'll agree with Rogers first post if it doesn't....
And it doesn't really qualify as a system electrode, unless it was specificaly constructed to do so. IMO

 

[Cavie]

e57 you quilify

e57 you quilify

Thank you Jim. I don't have a suggestion. Just food for thought. I do what the book says and don't really care if it is right or wrong. My boss said " Here is the code. If it's in here inforce it"

 

[Bill W]

I believe the #8 gets bonded to the underground steel and then returns to panel on the ground that supplies the power in question. Personally I think I would add the #8 to the panel as well...I suppose I should check the book before I throw suggestions out.

 

[bphgravity]

Fault current is a very short duration event, or at least should be. In the event of a ground fault in the premise wiring, much more current will flow via the main bond jumper to the service grounded conductor and back to the source, thus opening the protective device in a relatively instant time frame.

So this issue is not so concerning. What may be concerning is the amount of normally operating current that can and will flow over the pool parts as it serves as a return source of normally operating current because of its electrode characteristics.

I feel the interconnection of the equipotential grid to the premise grounding system is hazardous. Current bonding and grounding requirements at pools and pool equipment mandates this interconnection.

 

[Cavie]

We also mixed them with the bonding of the Wet nitch thru the light transformer.

 

[LarryFine]

And it doesn't really qualify as a system electrode, unless it was specificaly constructed to do so. IMO

In the abstract, I wouldn't agree with that statement. A building's rebar-reinforced foundation certainly qualifies as a GE, and isn't costructed for that purpose.

 

[e57]

In the abstract, I wouldn't agree with that statement. A building's rebar-reinforced foundation certainly qualifies as a GE, and isn't costructed for that purpose.

Not all rebar or foundations meet the criteria.... Recently had a bulding that had a membrane liner for the whole foundation, no portion of it could be considered an electrode. Had to put in rods under the foundation, and have them sealed as a penetration of the membrane.

(3) Concrete-Encased Electrode. An electrode encased by at least 50 mm (2 in.) of concrete, located within and near the bottom of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 6.0 m (20 ft) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (? in.) in diameter, or consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 4 AWG. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means.

 

[Jim W in Tampa]

Fault current is a very short duration event, or at least should be. In the event of a ground fault in the premise wiring, much more current will flow via the main bond jumper to the service grounded conductor and back to the source, thus opening the protective device in a relatively instant time frame.

So this issue is not so concerning. What may be concerning is the amount of normally operating current that can and will flow over the pool parts as it serves as a return source of normally operating current because of its electrode characteristics.

I feel the interconnection of the equipotential grid to the premise grounding system is hazardous. Current bonding and grounding requirements at pools and pool equipment mandates this interconnection.

We both are in FL and know that our ground rods in sand are not great for a ground system.Our pools offer far more contact with the earth than the rods ever could.In the event of a fault electric does not read code books.It looks for the better ground and sees the pool or a well steel casing.In the event of a lost neutral it will try to use it as the return to the poco.This was covered in one of mike holts tapes i bought 10 years ago and the lost neutral was shocking the pool users.

 

[bphgravity]

"The Code is not structured to protect against abnormal conditions such as open neutrals that may develop." - CMP 5

You’re preaching to the choir Jim...