250.53(C) Bonding Jumper.

Relying on the rebar to interconnect the water pipe to the service as in the image is a code violation.
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Relying on the rebar to interconnect the water pipe to the service as in the image is a code violation.

Code Change Summary: Revised code language on the use of rebar in grounding electrode systems.

For many code cycles NEC® 250.52(A)(3) has permitted 20 or more feet of ½ inch or larger rebar encased in at least 2 inches of concrete and located horizontally within a concrete footing that is in direct contact with the earth to serve as a grounding electrode.

Some have felt that if the rebar can be a grounding electrode then why can’t it also serve as a conductor to interconnect other electrodes that are present. The problem is that rebar has never been evaluated to be equivalent in size to wire type conductors.

On larger installations where rebar emerges from the footing and is stubbed up in a wall for example, if the rebar is being used as the conductor to interconnect other electrodes such as metallic water pipe to structural steel or to interconnect the grounding electrode conductor for multiple services as permitted in 250.58, this interconnection could require 3/0 AWG copper or 250 kcmil aluminum. The ½ inch rebar has not been evaluated to be equal in size to specific size copper or aluminum conductors.

In the 2020 NEC® this has been cleared up by adding a sentence to 250.53(C) stating that rebar cannot be used as a conductor to interconnect other electrodes of a grounding electrode system.

Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2020 NEC® edition of NFPA 70.

2017 Code Language:

250.53(C) Bonding Jumper. The bonding jumper(s) used to connect the grounding electrodes together to form the grounding electrode system shall be installed in accordance with 250.64(A), (B), and (E), shall be sized in accordance with 250.66, and shall be connected in the manner specified in 250.70.

2020 Code Language:

250.53(C) Bonding Jumper. The bonding jumper(s) used to connect the grounding electrodes together to form the grounding electrode system shall be installed in accordance with 250.64(A), (B), and (E), shall be sized in accordance with 250.66, and shall be connected in the manner specified in 250.70. Rebar shall not be used as a conductor to interconnect the electrodes of grounding electrode systems.

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250.53(C) Bonding Jumper.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Based on the 2020 NEC, which of the following is true?

A: Rebar can be used as a conductor to interconnect the electrodes of grounding electrode systems.
B: Rebar shall not be used as a conductor to interconnect the electrodes of grounding electrode systems.
C: Rebar cannot be used as a grounding electrode under any circumstance.
D: Rebar is not permitted to be stubbed up out of the slab.
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