Grounding/Bonding - CEE

[NMCB13]

In the North Eastern States when you install a service for a residental dwelling with city water, you install a ground
rod with the coccect sized ground wire to the meter pan. Next you install a properly sized grounding conductor to
the water meter (street side) and shunt it to the house side and terminate at the neutral bus in the panelboard.
Therefore, you have a complete (low resistance) reference palne to ground.

Now here in Florida the EC is required to install a Ufer/Concrete Encased Electrode and terminate in the meter
pan, Ok. Next the copper piping (generally) at the hot water heater a grounding conductor in installed and a
connection is made to the copper piping. The other end is connected to the panel, Ok.

Now what happens if all the plumbing system in all non-mettalic (except for the hose bibs and facuets)? Now you
are solely relaying on the Ufer/Concrete Encased Electrode as the sole point for the grounding plane. As I metioned
in an earlier post, the footer is installed with a plastic vapor barrier between the footer and earth. Thus reducing the
surface area to acheive a low resistence to ground, as required by the NEC.

To my understanding (and I am not an engineeer) the grounding resistance is made up of the type of
electrode used, contact resistance between the electrode and the resistance of the soil. I have also read the
IEEE 4.2.3 and appears to me that the more surface area the better chances to acheive a low resistance to ground
would be. So now that a plastic vapor barrier in installed between the footer and the Ufer/CEE, how would this affect the grounding system? To me this would reduce the total surface area that is in contact with the earth. Now that the plumbers are using non-metallic piping systems how (if any) deos this affect theoveral grounding system?

At this point I think that an independant test should be preformed on the CEE to determine what the resistance is,
and that it is in compliance with the NEC.

Would love to hear everbody's comments.

...We accept the norm as a standard and run with it without question, but when we alter from the norm we still
don't question it ..... we just accept it.

"Can Do'

 

[raider1]

If the footing is not in direct contact with the earth then it does not qualify as a grounding electrode as laid out in 250.52(A)(3).

A vapor barrier installed to separate the footing from the earth would render the footing not in direct contact with the earth.

Chris

 

[Cavie]

If the footing is not in direct contact with the earth then it does not qualify as a grounding electrode as laid out in 250.52(A)(3).

A vapor barrier installed to separate the footing from the earth would render the footing not in direct contact with the earth

Chris

The vapor barrier does not go all the way up the outside of the footer therefore exposing the concrete to the earth all around the perimeter. Welcome to Florida.

 

[kwired]

The vapor barrier does not go all the way up the outside of the footer therefore exposing the concrete to the earth all around the perimeter. Welcome to Florida.

What purpose does a vapor barrier serve in a footing anyway, especially if only on bottom but not sides?

 

[GoldDigger]

What purpose does a vapor barrier serve in a footing anyway, especially if only on bottom but not sides?

1. It keeps the concrete from drying before it is fully cured if poured on dry soil.
2. It keeps a high ground water table from wicking up through the concrete and causing problems inside. More important for basements or land with poor drainage. (Hello Florida!)

 

[kwired]

1. It keeps the concrete from drying before it is fully cured if poured on dry soil.
2. It keeps a high ground water table from wicking up through the concrete and causing problems inside. More important for basements or land with poor drainage. (Hello Florida!)

Keeping from drying too fast I can understand, keeping high water out makes no sense if barrier is on bottom only.

 

[GoldDigger]

Keeping from drying too fast I can understand, keeping high water out makes no sense if barrier is on bottom only.

You can put a drain tile feeding to a low area or to a pumped sump around the outside or inside edge of the footing wall (where there is no barrier.) But that will not necessarily prevent water from welling up in the middle of the slab. Depends on soil conditions, etc.
You could probably put a drain tile grid under the whole slab instead, but that would cost more.

 

[kwired]

You can put a drain tile feeding to a low area or to a pumped sump around the outside or inside edge of the footing wall (where there is no barrier.) But that will not necessarily prevent water from welling up in the middle of the slab. Depends on soil conditions, etc.
You could probably put a drain tile grid under the whole slab instead, but that would cost more.

We are not talking about slabs, we are talking about footings.

 

[GoldDigger]

We are not talking about slabs, we are talking about footings.

In which case it does not make nearly as much sense to put a vapor barrier under it but not all the way to the surface. Point taken.
In the case of slab construction, the vapor barrier under the slab might, for convenience, be extended under the footing at the perimeter of the slab. But for free-standing footings, I do not see the point either, except for letting the concrete dry slowly.