Question

Question: Our local utility has a requirement for electricians to install a copper conductor from their meter can directly to a ground rod and sized per 250.66. The copper conductor should be installed so that it does not enter the service disconnect enclosure even if the service disconnect enclosure is mounted below the meter can as well on a temp pole for a site trailer. I understand that the grounding electrode connection can be made from the meter can enclosure per 250.24, but it requires this to terminate where the grounded service conductor is connected at the service disconnect.How are electricians installing their GEC at the grounded conductor in the meter can enclosure but also at the service disconnect?Since the bond is happening in the meter can, is the service disconnect still required to be bonded?If bonding still needs to occur at the service disconnect, is it acceptable to have a bond in the meter can, with the copper conductor (GEC) routed directly to the ground rod (instead of going to the SE disconnect) Then, would it be acceptable to install only the grounded and ungrounded conductors from the meter can to the service disconnect, bond the grounded and ungrounded conductors at this point, and run a new copper conductor sized according to 250.66 to a separate ground rod? Note that our utility grounds their neutral conductor at the transformer.Our utility has provided an illustration and I prefer to have everything at the service disconnect but need to comply with the utilities requirement as well. In the illustration, it shows only the ungrounded and grounded conductors going from the meter can to the SE disconnect with a bonding jumper to bond the neutral and equipment grounds together. However, it doesn't show another copper conductor in the SE disconnect to a separate ground rod which I don't believe fully complies with 250.24.

Answer 1

Okay, this is a common situation with utility companies having specific requirements that sometimes seem to contradict the NEC (National Electrical Code) at first glance. Let's break down the problem and how to approach it.

Understanding the Utility's Requirement

The utility's requirement likely stems from several reasons: Control of Grounding

They want a direct and robust path to earth at the meter to help manage fault currents and system stability on their side of the service point. They want the grounding electrode system tied to their equipment.

Isolation from Customer Wiring

They want to minimize the influence of customer wiring issues on their system. A direct ground connection helps isolate them.

Liability

Potentially, they are looking to reduce liability.

The NEC's Requirements and Common Practices

Here's a summary of the relevant NEC sections you mentioned: 250.24 (Grounding Service-Supplied Alternating-Current Systems)

This section allows grounding at the meter enclosure if the grounded conductor is connected to the grounding electrode conductor at the service disconnect. This is often done, but not universally required.

250.66 (Size of Alternating-Current Grounding Electrode Conductor)

Dictates the size of the grounding electrode conductor based on the size of the service entrance conductors.

Analyzing Your Situation and Possible Solutions

Here's a breakdown of the questions and possible solutions, considering the utility's specific requirements:1. How are electricians installing their GEC at the grounded conductor in the meter can enclosure but also at the service disconnect? Answer

You are essentially being asked to provide two grounding electrode connections to the grounded conductor: one at the meter can and one at the service disconnect. This is not inherently wrong, but it needs to be done correctly to avoid creating parallel neutral paths or other undesirable conditions.2.

Since the bond is happening in the meter can, is the service disconnect still required to be bonded? Answer

Yes. The service disconnect must still be bonded. The requirement for bonding the neutral and equipment grounding conductors together within the service disconnect enclosure (typically through the main bonding jumper) remains. This bonding is critical for fault clearing within the customer's electrical system.3. If bonding still needs to occur at the service disconnect, is it acceptable to have a bond in the meter can, with the copper conductor (GEC) routed directly to the ground rod (instead of going to the SE disconnect) Then, would it be acceptable to install only the grounded and ungrounded conductors from the meter can to the service disconnect, bond the grounded and ungrounded conductors at this point, and run a new copper conductor sized according to 250.66 to a separate ground rod? Note that our utility grounds their neutral conductor at the transformer. Answer

This is the most likely compliant solution, and aligns with what the utility likely intends, if interpreted correctly. Here's the breakdown of why this approach works: Meter Can

The utility's requirement is met. You have a GEC (sized per 250.66) running directly from the meter can to a ground rod, providing that connection to earth on the supply side of the service point. The utility is happy.

Service Disconnect

You run only the ungrounded conductors (hot wires) and the grounded conductor (neutral) from the meter can to the service disconnect.

Bonding at the Service Disconnect

You install the main bonding jumper within the service disconnect, connecting the neutral bus to the enclosure. This is essential for creating a low-impedance fault current path.

Service Disconnect GEC

You run another GEC (sized per 250.66) from the neutral bus in the service disconnect to a separate ground rod (or to the same grounding electrode system as the meter can).

Diagram of the Recommended Solution

Utility Transformer (Grounds Neutral)Service Drop/Lateral|+---------------------+|   Meter Can         |+---------------------+|   Grounded (Neutral)  |---(GEC, 250.66)---> Ground Rod (UTILITY GROUND)|   Ungrounded (Hot)    |---(Conductors)--->|                     |+---------------------+
 Ungrounded, Grounded Conductors|+---------------------+| Service Disconnect  |+---------------------+|   Ungrounded (Hot)    Grounded (Neutral)  |---(Bonding Jumper to Enclosure)--->Equipment Ground|   Grounding Electrode  |---(GEC, 250.66)---> Ground Rod (CUSTOMER GROUND)+---------------------+
 Customer's Load|

Important Considerations and Cautions Ground Rod Placement

Ideally, the two ground rods (one for the meter can and one for the service disconnect) should be at least 6 feet apart to minimize interaction between their grounding zones.

Ground Rod Resistance

It is generally not required to test the ground rod resistance. However, having very high resistance is not good and should be addressed.

Utility Coordination

Crucially, discuss this solution with the utility inspector before you implement it. Show them this diagram and explain your interpretation of their requirements and how it complies with the NEC. Get their written approval, if possible. Miscommunication can lead to costly rework. Local Amendments

Check for any local amendments to the NEC that might affect grounding requirements. Your municipality or jurisdiction may have stricter rules.

Safety

Grounding and bonding are critical for safety. Double-check all connections and ensure they are secure and properly torqued.

Parallel Neutral Paths

Avoid creating unintentional parallel neutral paths. This can occur if the utility's and your grounds are too close together, or if other metal structures (e.g., metal water pipes) create unintended connections to ground. The recommended design above avoids this.

Why the Utility's Illustration Might Be Incomplete

The utility's illustration might be simplified for clarity, focusing only on their grounding requirements at the meter. It's likely they assume the electrician understands the separate bonding and grounding requirements at the service disconnect. They may see it as outside their scope of responsibility.

In summary, the solution of providing a direct GEC from the meter can to a ground rod for the utility's purposes, and then separately bonding and grounding at the service disconnect according to the NEC is likely the best approach. However, communication with the utility inspector is paramount to ensure everyone is on the same page and to avoid code violations. Flag for review

Answer 2

Okay, this is a common situation with utility companies having specific requirements that sometimes seem to contradict the NEC (National Electrical Code) at first glance. Let's break down the problem and how to approach it.

Understanding the Utility's Requirement

The utility's requirement likely stems from several reasons: Control of Grounding

They want a direct and robust path to earth at the meter to help manage fault currents and system stability on their side of the service point. They want the grounding electrode system tied to their equipment.

Isolation from Customer Wiring

They want to minimize the influence of customer wiring issues on their system. A direct ground connection helps isolate them.

Liability

Potentially, they are looking to reduce liability.

The NEC's Requirements and Common Practices

Here's a summary of the relevant NEC sections you mentioned: 250.24 (Grounding Service-Supplied Alternating-Current Systems)

This section allows grounding at the meter enclosure if the grounded conductor is connected to the grounding electrode conductor at the service disconnect. This is often done, but not universally required.

250.66 (Size of Alternating-Current Grounding Electrode Conductor)

Dictates the size of the grounding electrode conductor based on the size of the service entrance conductors.

Analyzing Your Situation and Possible Solutions

Here's a breakdown of the questions and possible solutions, considering the utility's specific requirements:1. How are electricians installing their GEC at the grounded conductor in the meter can enclosure but also at the service disconnect? Answer

You are essentially being asked to provide two grounding electrode connections to the grounded conductor: one at the meter can and one at the service disconnect. This is not inherently wrong, but it needs to be done correctly to avoid creating parallel neutral paths or other undesirable conditions.2.

Since the bond is happening in the meter can, is the service disconnect still required to be bonded? Answer

Yes. The service disconnect must still be bonded. The requirement for bonding the neutral and equipment grounding conductors together within the service disconnect enclosure (typically through the main bonding jumper) remains. This bonding is critical for fault clearing within the customer's electrical system.3. If bonding still needs to occur at the service disconnect, is it acceptable to have a bond in the meter can, with the copper conductor (GEC) routed directly to the ground rod (instead of going to the SE disconnect) Then, would it be acceptable to install only the grounded and ungrounded conductors from the meter can to the service disconnect, bond the grounded and ungrounded conductors at this point, and run a new copper conductor sized according to 250.66 to a separate ground rod? Note that our utility grounds their neutral conductor at the transformer. Answer

This is the most likely compliant solution, and aligns with what the utility likely intends, if interpreted correctly. Here's the breakdown of why this approach works: Meter Can

The utility's requirement is met. You have a GEC (sized per 250.66) running directly from the meter can to a ground rod, providing that connection to earth on the supply side of the service point. The utility is happy.

Service Disconnect

You run only the ungrounded conductors (hot wires) and the grounded conductor (neutral) from the meter can to the service disconnect.

Bonding at the Service Disconnect

You install the main bonding jumper within the service disconnect, connecting the neutral bus to the enclosure. This is essential for creating a low-impedance fault current path.

Service Disconnect GEC

You run another GEC (sized per 250.66) from the neutral bus in the service disconnect to a separate ground rod (or to the same grounding electrode system as the meter can).

Diagram of the Recommended Solution

Topic: GEC in Meter Can