Mike Dolt Enterprises
Mike Dolt Enterprises
User: Jstumpp, Location: Florida
Asked on: Tuesday, June 17, 2025 at 1:13 pm EDT
Answered on: Tuesday, June 17, 2025 at 1:23 pm EDT
Question: My partner and I (Both State Licensed) are disagreeing with the requirement on a bonding bushing for our current project.We are adding a new 120/208v 200-amp meter can and disconnect to an existing gutter in a strip plaze electrical room. Pulling our service conductors through an existing empty raceway to the utility transformer. Leaving the gutter with a punched 2" emt 90 into our meter can entered into factory concentrics, leaving the meter through the hub into the disconnect.The disagreement lies with one of us believing no bonding bushing is required, being the gutter is bonded to the building service, used our own punched knockout into a metallic raceway.The other believes we need to include a bond bushing on the conduit entering the meter can, as well as one entering the disconnect.Obviously a question that shouldn't need to be asked but sadly neither of us are willing to say we are wrong.
Okay, this is a common point of confusion, and let's break it down with the relevant NEC sections. Let's get this sorted out.
The Key Points of Contention Existing Gutter Bonding
You state the gutter is already bonded to the building service. This is critical.
Knockout vs. Concentric Knockout
The type of knockout plays a role.
Service Conductors
This is a service. Bonding requirements are more stringent.
Relevant NEC Sections to Consider NEC 250.92(B) Service Raceways and Enclosures
"Metal service raceways and enclosures shall be bonded to the grounded conductor as specified in 250.8 and 250.
94. Bonding shall be accomplished by one of the following methods..." This is the overarching requirement for service raceways and enclosures.
NEC 250.92(B)(1) Bonding Jumpers
A bonding jumper is used to connect service raceways and enclosures.
NEC 250.92(B)(4) Other Listed Devices
Other listed devices, such as bonding locknuts or bushings.
NEC 250.92(B)(3) Threaded Couplings and Threaded Bosses
"Threaded couplings and threaded bosses with thread engaging the raceway shall be permitted for bonding metal service raceways, provided that the raceways are made up wrenchtight."
NEC 250.97 Double Locknuts This section states that concentric or eccentric knockouts should not be permitted for bonding service raceways. It says a bonding bushing or jumper must be used. NEC 250.97(A) states that bonding-type locknuts or bonding bushings shall be provided on concentrics or eccentric knockouts.Analysis and Application to Your Situation
Here's how the NEC applies to your specific scenario, keeping in mind this is for informational purposes only and the AHJ has the final say:1. The Gutter's Bond
Since the gutter is already bonded to the building service, it forms part of the grounded electrical system. This is a foundational assumption.2.
Raceway to Meter Can
Concentric Knockout
You mentioned the 2" EMT entering the meter can is going into "factory concentrics". Since the meter can is part of the service equipment, and the EMT is a service raceway, NEC 250.97(A) comes into play.
A bonding bushing is required on the EMT entering the meter can. The factory concentric knockout is the deciding factor here. A standard locknut on each side will not suffice for bonding.3. Meter Can to Disconnect
Hub Connection
A hub is generally considered a listed fitting that provides a reliable electrical connection (if installed properly). IF the hub is listed for bonding purposes and provides a reliable electrical connection, it could be argued that it satisfies the bonding requirement between the meter can and the disconnect. However, the burden of proof is on you to demonstrate this to the AHJ. Check the hub's listing and documentation. If it's not specifically listed for bonding, assume you need to bond.
Most likely still need one. Unless the manufacturer of your meter can or disconnect says their hubs are rated to be the bonding conductor you will need a bonding bushing.
Conclusion
Based on the information provided: Bonding Bushing on EMT to Meter Can: REQUIRED. Due to the concentric knockout situation, 250.97(A) dictates a bonding bushing. Bonding Bushing on Meter Can to Disconnect: PROBABLY REQUIRED. Highly dependent on the hub's listing and the AHJ's interpretation. Err on the side of caution and install one.
Recommendation1. Consult the AHJ
The final authority is the local electrical inspector. Discuss your specific installation with them before proceeding. Get their opinion in writing if possible.2.
Check Equipment Listings
Carefully review the listings and instructions for your meter can, disconnect, and hub. The manufacturer's information may provide further clarification.3.
Err on the Side of Caution
Bonding is critical for safety. If there's any doubt, install the bonding bushing. It's a small cost compared to the potential consequences of a fault.4.
Document Everything: Keep records of all inspections, communications with the AHJ, and equipment listings. This will be helpful if any questions arise in the future.In this situation, it appears the person who believes bonding bushings are required is more likely correct, especially concerning the EMT entering the meter can through a concentric knockout. The key is to confirm the hub's listing and consult with the AHJ for their final determination. Flag for review