Mike Dolt Enterprises
Mike Dolt Enterprises
User: malachi constant, Location: Minneapolis
Asked on: Sunday, February 16, 2025 at 7:06 pm EST
Answered on: Thursday, March 6, 2025 at 8:45 am EST
Question: I have always understood panels (breaker panel, distribution panel, switchboards, etc) that are rated "service entrance" to have two things different: a main bonding jumper and a UL sticker. However I have a situation that has me scratching my head.I am the engineer and designed a service to a new building with a service-entrance rated distribution panel (with a main breaker) located inside the building. The contractor called up to say we need to add a disconnect outside...because otherwise they can't safely shut off power to the building without calling the utility company. But isn't that what the main disconnect is for, I ask? Yes, they say, but if we shut it off we still have to put on a moon suit to work on the panel since it has live feeders coming into it.In review of the shops (screensnip attached, with identifying information removed) I see there is no listing anywhere of the equipment as service entrance rated. I see that the main breaker (1000A I believe) is nestled up in with the other distribution breakers - it appears to receive power into the breaker, and the breaker then feeds the bussing. I don't have a very responsive contact with this manufacturer so ran it past another manufacturer. My question being, weirdness aside of how the panel fed, do I need to start designing services with the disconnect in its own enclosure/section? This manufacturer stated that service entrance equipment has a barrier that physically separates the lugs from the rest of the panel, making it safe to work in "cold" once the switch has been turned off and bus has been confirmed as cold.Where to begin in sorting this out...1) Does service entrance rated mean that main lugs should include a physical barrier?2) Service entrance rating aside - are service panels generally constructed with that kind of a physical barrier?3) Does such a physical barrier allow for service panels to be worked on as if they were cold, even with hot utility conductors terminated within?4) If not...how does one design something like this, with safety in mind? How does this work IRL? When an electrician needs to add a new breaker in a service panel, are they usually calling the utility company? Usually working as if it was hot, wearing proper PPE (though many panels will not have level of PPE listed)? Does one usually find a physical barrier separating the utility conductors, that allows you to work as if it was cold?Then - almost an aside but actually the hot item right now - the electrician is adamant we need a disconnect outside. The panel does not appear to have a service entrance rating but does have a main breaker. Does the proposed exterior disconnect need to be service rated? Does it need to be fused, or is this now acting only as a safety switch so it can be non-fused? If the disconnect is not fused or service rated, the can the electrician bond the neutral and ground within the "service" panel that is already ordered?I need to engage the manufacturer and the electrician to get on the same page here, but am hoping the community here can clarify my thinking a bit first. Thanks!
Okay, this is a common point of confusion and a very important one to clarify. Let's break it down systematically
Understanding "Service Entrance"
A service entrance is the point where the utility's power conductors connect to your building's electrical system. Everything downstream of that point is technically distribution. However, for practical purposes, a "service entrance rated" panel (or equipment) means it's suitable to be located at the service entrance point and to perform the functions required there.1. Does service entrance rated mean that main lugs should include a physical barrier? Generally, no, specifically it depends on the standard used by the manufacturer. A barrier is not an inherent requirement of all service entrance ratings. While some manufacturers design their service entrance rated equipment with barriers to provide a degree of safety, it's not a universal standard. The NEC doesn't mandate physical barriers, but it does require guarding or isolation of live parts, which can be achieved in different ways. Note: Some standards may require barriers, which brings up the importance of the UL listing.2. Service entrance rating aside - are service panels generally constructed with that kind of a physical barrier? No. Most standard distribution panels do not have physical barriers separating the main lugs from the rest of the panel components. This is especially true for larger panels with high amperage main breakers integrated into the breaker section.3. Does such a physical barrier allow for service panels to be worked on as if they were cold, even with hot utility conductors terminated within? Absolutely not! This is a dangerous misconception. Even with a physical barrier, the utility conductors remain hot until the utility de-energizes them. The barrier may offer some protection, but never treat it as a guarantee of safety. Always assume the incoming conductors are live and follow proper safety procedures, including verifying absence of voltage. A barrier does not make it safe to work on a panel as if it were cold, even if the main breaker is open. Always, always verify absence of voltage on all parts before working.4. If not...how does one design something like this, with safety in mind? How does this work IRL? Safety First
Safety starts with the design.
External Disconnect
An external disconnect is becoming increasingly common, for exactly the reason your electrician stated. It provides a readily accessible, safe way to de-energize the entire building, without requiring utility involvement in many cases.
Proper PPE
Electricians always work with energized panels using appropriate Personal Protective Equipment (PPE). The level of PPE required is determined by an arc flash risk assessment (as required by NFPA 70E). This assessment considers voltage, fault current, and working distance to determine the potential arc flash hazard and the necessary PPE.
Lockout/Tagout (LOTO)
Proper LOTO procedures are essential. Verify de-energization before working.
Documentation
Provide clear, up-to-date single-line diagrams and panel schedules.
How it works in real life
Adding a breaker in a service panel can be done live (energized) if it is deemed safe to do so per arc flash hazard analysis and if proper PPE is used per NFPA 70E. If not, the entire panel needs to be shut down. Some jurisdictions require utility involvement for service disconnects regardless. It depends on company policy as well as the task to be performed. In some instances the utility company is called to de-energize the service. In some instances, the company would permit a shut-down with PPE. Electricians almost always work on electrical equipment with PPE. It is possible to work with energized equipment in a safe way with the proper controls, and the most current version of NFPA 70E has information to aid in this.
The Electrician's Concerns & Your Specific Situation
Your electrician's concerns are valid. They are thinking about safety and code compliance. A readily accessible external disconnect makes maintenance and emergency situations far safer.
Addressing Your Specific Questions
Exterior Disconnect
Service Rated? Yes, the exterior disconnect must be service entrance rated. This is because it's now part of the service entrance. It must be suitable for interrupting the available fault current and meet all applicable requirements for service equipment. Fused or Non-Fused? This is a design decision. Fused
Provides overcurrent protection at the service entrance. This is generally recommended.
Non-Fused (Disconnect Switch)
Acts only as a switch to de-energize the building. The overcurrent protection relies on the main breaker in your distribution panel. If you go this route, ensure the disconnect switch is rated for the full available fault current.
Bonding the Neutral & Ground
If you use a non-fused disconnect and the distribution panel is not service entrance rated (as it appears from the shops), then the neutral and ground MUST be bonded at the disconnect. The service equipment (the disconnect) is where the neutral is bonded to ground.
Here's what you need to do
Manufacturer Verification
Contact the panel manufacturer directly. Request the following: Confirmation of whether the panel is listed (not just rated) as service entrance equipment. Documentation (UL listing information, etc.) to support this claim. Clarification on whether the main breaker compartment is designed with a barrier.2.
Review Shop Drawings
Closely examine the shop drawings. Look for the UL listing mark and the specific UL standard to which it's listed. Service entrance equipment typically has a specific listing (e.g., UL 67 for panelboards).3.
Engage the Electrician
Have a thorough discussion with the electrician to understand their concerns and requirements.4.
Revise the Design (Potentially)
If the panel is not listed as service entrance equipment, you must add a service entrance rated disconnect outside. Even if the panel is listed as service entrance equipment, strongly consider adding the external disconnect for safety and ease of maintenance. This is becoming best practice.5.
Overcurrent Protection
Decide whether the external disconnect will be fused or non-fused, and size accordingly.
Key Takeaways
Service entrance rating is critical. It ensures the equipment is suitable for the service entrance environment. Safety is paramount. An external disconnect significantly improves safety for electricians and other personnel. Communicate clearly with the manufacturer and electrician. Ensure everyone is on the same page and understands the requirements. When in doubt, err on the side of caution and add the external disconnect.
By following these steps, you can ensure a safe and code-compliant electrical service for your building. Remember to consult with a qualified electrical engineer and electrician to finalize the design. Flag for review