Thread: electrical bonding to earth with Post tension

Home built in 2008 with Post tension and of course PEX, could not find a Earth Bond and a few other Electrical items. Buyer requested repairs, seller is a Investor with a Electrical Contractor on his payroll and tells the buyers Agent that the home has PEX and does not need Bonding to Earth, his reasoning "the piping is plastic".

I told my customer that all homes required a Bond to Earth and explained why. After I went through my copy of the Home Reference Book, my Building Code and Code check, couldn't find a exception, Who out there know of a exclusion in the Residential Building Codes for PEX and or Post tension.

Thanks, be safe and profitable Nick

Phoenix Home Inspector, Arizona Commercial Inspections, AZ Property Inspectors, HUD, FHA, VA Alati’s Inspection Service LLC

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According to the NEC the structure requires a grounding electrode system (GES). All electrodes present at the house are required to be connected to the GES. If there are no electrodes present (such as a 10' buried metallic water pipe or a concrete encased electrode) then one must be installed. At the minimum the house should have 2 ground rods if no other electrodes exist.

III. Grounding Electrode System and Grounding Electrode Conductor
250.50 Grounding Electrode System.
All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.

It sounds like someone is confusing grounding of the electrical service with bonding of the plumbing pipes.

In modern construction, the grounding conductor is often embedded in the foundation (Ufer) and hidden inside a wall cavity. You can only see it where it enters the panel containing the main disconnect.

Originally Posted by nick alati

Home built in 2008 with Post tension and of course PEX, could not find a Earth Bond and a few other Electrical items. Buyer requested repairs, seller is a Investor with a Electrical Contractor on his payroll and tells the buyers Agent that the home has PEX and does not need Bonding to Earth, his reasoning "the piping is plastic".

Electrical contractor is correct - no bonding to plastic piping is required, besides, what you would be bonding to ... plastic? ... and for what purpose?

I told my customer that all homes required a Bond to Earth and explained why. After I went through my copy of the Home Reference Book, my Building Code and Code check, couldn't find a exception, Who out there know of a exclusion in the Residential Building Codes for PEX and or Post tension.

You are incorrect, and the problem is likely that you are looking up the wrong thing - you are looking for an 'exception' to the bonding when you should be looking up the bonding requirement for interior water piping:
- From the NEC (bold and underlining is mine)
- - 250.104 Bonding of Piping Systems and Exposed Structural Steel.
- - - (A) Metal Water Piping. The metal water piping system shall be bonded as required in (A)(1), (A)(2), or (A)(3) of this section. The bonding jumper(s) shall be installed in accordance with 250.64(A), (B), and (E). The points of attachment of the bonding jumper(s) shall be accessible.

Post tensioned cables are not 'concrete encased electrodes' as they are not encased in concrete - they are encased in a sleeve which allows the cables to be pulled under pressure.

Pre-tensioned pre-cast cables might be able to be classified as 'concrete encased electrodes', except that all of the pre-tensioned pre-cast panels and slabs I have seen are not 'in direct contact with earth':
- (3) Concrete-Encased Electrode. An electrode encased by at least 50 mm (2 in.) of concrete, located horizontally near the bottom or vertically, and within that portion 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 (½ 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. Where multiple concrete-encased electrodes are present at a building or structure, it shall be permissible to bond only one into the grounding electrode system.

There may be some installations where the pre-tensioned concrete can serve as a concrete encased electrode, I've just never been on jobs which used them that way.

Jerry, please expound on the requirement for a GEC in a home electrical system (please ignore the way the OP stated his question.)

Originally Posted by nick alati

Home built in 2008 with Post tension and of course PEX, could not find a Earth Bond and a few other Electrical items.

Are we to assume that you meant you could not find a connection to any grounding electrodes at the service disconnect?

PEX or no PEX, either way the house requires a grounding electrode system.

Originally Posted by Robert Meier

According to the NEC the structure requires a grounding electrode system (GES). All electrodes present at the house are required to be connected to the GES. If there are no electrodes present (such as a 10' buried metallic water pipe or a concrete encased electrode) then one must be installed. At the minimum the house should have 2 ground rods if no other electrodes exist.

Thanks All!

Your support is Appreciated

Nick

Originally Posted by Jim Luttrall

Jerry, please expound on the requirement for a GEC in a home electrical system (please ignore the way the OP stated his question.)

Jim,

Not sure just what you mean to expound on what part of them, but if there is steel in a footing or foundation, at least 20 feet of steel reinforcing (there are other options listed in the code reference above), and the steel is encased in at least 2 inches of concrete all around it (steel reinforcing is required to have 3 inches of concrete cover between the steel and earth), and if the concrete is in direct contact with earth (such as is the case for footings and foundations), then the concrete encased electrode is required to be used.

Never mind Jerry, others covered it. I was just trying to steer the conversation toward the Grounding electrode requirements as opposed to bonding.

I agree with the conclusions mentioned, wanted to add, as someone who has worked in the electrical industry for a while, I have never heard the phrase "bond to earth". Ground yes.
Perhaps misunderstandings occurred, but if this is in the United States, and a utility has hooked up electrical power, than the above information about proper "Grounding" must take place