Load Center vs Panelboard: The Engineer’s Selection Guide (With NEC Requirements)

What did you miss? And more importantly, how do you choose between a load center and a panelboard so this never happens again?

The answer isn’t in the voltage rating or the price difference. It’s buried in NEC Article 408, UL 67 listing requirements, and a handful of selection criteria that most spec sheets conveniently ignore. Let’s fix that.

Load Center vs Panelboard: The Legal Truth

Here’s what your electrical distributor won’t tell you: according to NEC Article 408 és UL Standard 67, there is no difference between a “load center” and a “panelboard.”

Both terms refer to the same thing—a distribution assembly with buses and overcurrent protective devices designed to be placed in a cabinet or enclosure. The NEC uses only one word: panelboard. UL 67 (the standard that governs testing and listing) uses the same single term. “Load center” is marketing terminology that emerged in North America to describe smaller, lower-cost panelboards sold primarily for residential applications.

So if they’re legally identical, why does the distinction matter? Because the physical construction differences és UL listing variations create real-world performance gaps that can kill your installation—sometimes literally.

The UL 67 Listing Trap Most Engineers Miss

Here’s where it gets technical, and where installations fail inspection.

UL 67 allows two types of panelboard listings:

1. “Panelboard” (panel only, no enclosure)
2. “Enclosed Panelboard” (panel + enclosure tested as complete assembly)

This difference matters because of short-circuit current ratings. When a panelboard is listed without a specific enclosure—just the bare panel—UL gives it a default short-circuit current rating of 10,000 amperes (10kA) maximum. That’s it. Doesn’t matter if the breakers inside are rated for 65kA or 100kA interrupting capacity. The assembly caps out at 10kA.

This is “The 10kA Default Trap.”

If your building’s available fault current at the panel location exceeds 10,000A (common in commercial buildings close to the utility transformer), and you installed a “Panelboard”-only listing? Code violation. NEC 110.9 requires that all equipment have an interrupting rating at least equal to the maximum available fault current.

Enclosed panelboards—the ones tested with their specific cabinets—can be listed for much higher short-circuit ratings (22kA, 42kA, 65kA, or more) because the entire assembly was tested as a system. Load centers, being smaller residential-focused units, are typically listed as enclosed panelboards but rarely exceed 22kA ratings.

Pro-Tip #1: Before specifying any panelboard or load center, verify the UL listing type. Look for “Enclosed Panelboard” on the label if you need ratings above 10kA, and always calculate available fault current per NEC 110.24(A)—it’s required in all but one- and two-family dwellings anyway.

Beyond the Spec Sheet: 6 Real Selection Criteria

Forget the comparison tables that just list voltage and amperage. Here are the technical factors that actually determine whether your installation passes inspection and serves the building for its design life.

1. Breaker Mounting: The Bolt-On Difference

Load centers use plug-in breakers exclusively. You snap them onto the bus—quick, easy, cheap. Panelboards offer both plug-in and bolt-on breakers.

Why does this matter? Vibration, back-feeding, and connection integrity.

Plug-in breakers work fine in quiet residential basements. Move that panel to an industrial plant with compressors shaking the building, or deploy it for solar back-feed? Problems. NEC 408.36(D) directly addresses this risk: “Plug-in-type overcurrent protection devices…that are backfed…shall be secured in place by an additional fastener that requires other than a pull to release the device.”

We’ve seen installations where back-fed solar breakers weren’t properly secured—just friction-held with the standard plug-in clips. First inspection? Red tag. The breaker could literally be pulled off the bus while energized, exposing live 240V gyűjtősínek.

Bolt-on breakers eliminate this risk. The breaker bolts directly to the bus with mechanical fasteners. The connection can’t vibrate loose, can’t be accidentally pulled free, and provides superior current-carrying capacity for high-amperage circuits. This is why panelboards—especially those rated above 225A—increasingly use bolt-on construction.

Pro-Tip #2: For any back-fed application (solar, generator, energy storage), verify NEC 408.36(D) compliance. If using plug-in breakers, the “additional fastener” usually means a specific hold-down kit from the manufacturer. If the inspector doesn’t see it, you’re getting tagged.

2. Voltage & Phase: The Three-Phase Dividing Line

This is the clearest hard stop between load centers and panelboards.

Load centers: Maximum 240 volts, single-phase only.

Panelboards: Up to 600 volts (or higher with special designs), single-phase or three-phase.

If your load calculation includes any three-phase equipment—commercial HVAC, machine tools, large motors, data center PDUs—the load center option just disappeared. You need a panelboard. There’s no way around it.

Even in single-phase applications, voltage matters. A 208Y/120V commercial building (common in multi-tenant spaces supplied from a three-phase utility service) requires a panelboard, not a 120/240V load center. They’re electrically incompatible.

3. Ampacity Ceiling: Where Load Centers Stop

Load centers max out at 400 amperes. Most are 200A or less.

Panelboards scale from 100A to 1,200A (with switchboards taking over above that).

Here’s the trap: that 400A load center rating is the bus rating, not your usable capacity. NEC 215.2(A) requires feeder ampacity to be “not less than the noncontinuous load plus 125 percent of the continuous load.” NEC 408.36 requires the overcurrent protective device protecting the panelboard to not exceed the panelboard’s rating.

So if you’ve got a 300A continuous load (common in commercial buildings with 24/7 lighting and HVAC), your minimum calculation is:

300A × 125% = 375A minimum feeder/breaker size

Your 400A load center’s main breaker would need to be 375A or 400A. But here’s the problem: if you use a 400A main breaker on a 400A bus, you’ve consumed your entire rating just protecting the continuous load properly. Add bármilyen non-continuous load, and you’re over-capacity.

The correct solution? Specify a panelboard with a 600A or 800A bus rating. Then you have room for both the 375-400A main breaker és future growth.

This feeds directly into our next concept…

4. Expandability: The 2-Year Full Problem

Load centers have fixed capacity. The number of spaces is what you buy—typically 12, 20, 24, 30, or 40 spaces. Once it’s full, it’s full. Your only option is a subpanel or complete replacement.

Panelboards are modular. Many commercial panelboards can be expanded with additional sections, or designed from the start with space for future breakers.

Here’s the scenario we see constantly: A small commercial building starts with a 200A, 30-space load center. Looks reasonable—10 circuits for lighting, 8 for outlets, 5 for HVAC, 3 for miscellaneous equipment. That’s 26 circuits, leaving 4 spaces for future expansion. Great, right?

Year 2: Tenant wants to add a server closet (2 dedicated circuits), upgraded HVAC (3 circuits), and EV charging station (1 circuit). That’s 6 new circuits. You only have 4 spaces left.

Year 3: Different tenant moves in, needs commercial kitchen equipment (5 circuits), upgraded lighting with dimmer panels (4 circuits).

Game over. The 2-Year Full Problem strikes again.

Now you’re pricing out a complete panel replacement ($3,500 for materials), plus installation labor (8-12 hours at $125-150/hr = $1,000-1,800), plus coordinating a shutdown window with all tenants, plus permit and inspection fees, plus the cost of disappointing a tenant who has to wait for electrical capacity.

Total cost of the “budget-friendly” load center decision: $5,000-7,000 in replacement costs within 3 years, versus spending an extra $800-1,200 upfront for a properly sized panelboard with expansion capacity.

Pro-Tip #3: The 125% Growth Rule (not in NEC, but battle-tested): Calculate your initial circuit count, multiply by 1.25, and spec that many spaces minimum. For commercial applications with expected tenant turnover, use 1.5× initial circuit count. Yes, you’ll have empty spaces initially. That’s the point.

5. Short-Circuit Rating Reality Check

We covered the 10kA default trap earlier, but let’s get specific about why it matters.

NEC 110.24(A) requires all industrial and commercial installations (not one- and two-family dwellings) to have the maximum available fault current calculated and permanently marked on the service equipment and distribution panelboards. The date of calculation must be included.

Your inspector will check three things:

1. Is the fault current marked on the equipment? (If not, tag #1)
2. Does the panelboard’s short-circuit rating exceed the marked available fault current? (If not, tag #2)
3. Do all the breakers inside have interrupting ratings at least equal to the available fault current? (If not, tag #3)

Load centers, with their typical 10kA or 22kA ratings, fail this test in many commercial buildings. A 3,000A service located 50 feet from a 1,500 kVA transformer can easily have 35-50kA available fault current at distribution panels. Your 22kA load center just became a code violation.

Panelboards spec’d for commercial use typically carry 42kA, 65kA, or 100kA short-circuit ratings—matched to the building’s actual fault current levels.

6. Environment & Application: NEMA Ratings and Special Conditions

Load centers: NEMA Type 1 (indoor, dry locations) with occasional Type 3R (outdoor, weatherproof) options.

Panelboards: Available in all NEMA types including Type 3R, 4, 4X, 12 (industrial), and hazardous location ratings (Class I Div 1/2, Class II, etc.).

If your application involves:

• Outdoor installation → You need NEMA 3R minimum
• Washdown areas/food processing → NEMA 4X (stainless)
• Dusty industrial → NEMA 12
• Chemical/petrochemical → Hazardous location rated panelboard

Load centers aren’t manufactured for these conditions. Panelboards are.

Also, NEC 408.43 prohibits installing panelboards in “face-up or face-down” position (horizontal with front facing up/down). They must be vertical or horizontal with the front facing a wall. This applies to both load centers and panelboards equally—we mention it because it’s a common violation when space is tight and installers get creative with mounting angles.

Pro-Tip #4: Always verify the NEMA rating matches the installation location before procurement. We’ve seen non-weatherproof load centers installed outdoors because “it’s under an overhang.” That overhang doesn’t stop wind-driven rain or condensation. The inspector won’t care about your overhang.

How to Size for Compliance (And Avoid the Red Tag)

Here’s the systematic approach that passes inspection the first time.

Step 1: Calculate Your True Load (125% Rule Applied Correctly)

Most engineers know about the 125% multiplier for continuous loads when sizing conductors (NEC 210.19, 215.2). What they miss is that this same multiplier affects panelboard selection through the interconnection between NEC 215.3 and 408.36.

NEC 215.2(A)(1) states: “Feeder conductor ampacity…shall not be less than the noncontinuous load plus 125 percent of the continuous load.”

NEC 408.36 states: “Each panelboard shall be protected by an overcurrent protective device…The rating shall not be greater than that of the panelboard.”

Here’s how they connect: Your feeder conductors are sized at 125% of continuous loads. Those conductors must be protected by an OCPD (main breaker). That OCPD cannot exceed the panelboard’s rating. Therefore, your panelboard bus must accommodate the 125%-adjusted load, not just the actual connected load.

Continuous load is defined in NEC Article 100: “A load where the maximum current is expected to continue for three hours or more.” This includes:

• Lighting in commercial buildings (operates all day)
• HVAC systems in continuously occupied spaces
• Hűtőberendezések
• EV charging (NEC 625.42 explicitly requires continuous load treatment)
• Server/data loads

The calculation:

Let’s say you have:

• Continuous loads: 180A (lighting + HVAC)
• Non-continuous loads: 85A (receptacles, occasional equipment)

Minimum feeder/panelboard calculation:

• (180A × 125%) + (85A × 100%) = 225A + 85A = 310A minimum

You need a panelboard with at least a 350A or 400A rating (next standard size up per NEC 240.6). A 200A load center fails this requirement before you even talk about future expansion.

Exception: If you’re using 100%-rated overcurrent protective devices (rare, expensive, explicitly listed for continuous duty at full rating), you can size at 100% of continuous loads. But check NEC 210.19(A)(1) Exception and 215.2(A)(1) Exception No. 1—this requires the entire assembly (panel + breaker) to be listed for 100% operation. Your average load center isn’t.

Pro-Tip #5: For commercial kitchens, assume all cooking equipment is continuous. Even if the restaurant isn’t open 24/7, NEC load calculations for commercial cooking treat it as continuous load per Table 220.56. This catches a lot of designers off-guard when their 200A kitchen panel calculation comes back at 260A minimum after the 125% multiplier.

Step 2: Determine Available Fault Current

NEC 110.9: “Equipment intended to interrupt current at fault levels shall have an interrupting rating at least equal to the maximum available short-circuit current available at its point of application.”

NEC 110.24(A): “Maximum available fault current…shall be field marked on…service equipment…at buildings or structures supplied by feeders or branch circuits.” (Exceptions for one- and two-family dwellings.)

You must calculate this. It’s not optional for commercial/industrial work.

How to get the number:

1. Ask the utility: Most utilities will provide available fault current data for the service point. Expect 5-10 business days for the request.
2. Calculate from transformer data: If you have access to the transformer nameplate (kVA rating, impedance %), you can calculate fault current using:Fault Current (A) = (Transformer kVA × 1000) / (√3 × Voltage × %Z/100)Example: 500 kVA transformer, 480V, 3.5% impedance:

   Fault current = (500,000) / (1.732 × 480 × 0.035) = 17,182A at transformer secondary

   This decreases with distance due to conductor impedance, but at the first distribution panel, assume 80-90% of this value.

3. Use fault current calculators: IEEE and several manufacturers offer calculation tools.

Once you have this number, compare it to your panelboard’s short-circuit rating. If the panelboard’s rating is less than the available fault current, you have three options:

• Option A: Specify a higher-rated panelboard (42kA, 65kA, etc.)
• Option B: Use series-rated protection per NEC 240.86 (requires specific tested combinations)
• Option C: Add current-limiting devices upstream

For most installations, Option A is simplest and most reliable.

Remember “The 10kA Default Trap”: If your panelboard is only listed as “Panelboard” (not “Enclosed Panelboard”), and your available fault current is above 10kA, you’re in violation of NEC 110.9. The installation will fail inspection.

Step 3: Plan for Growth (The Expansion Tax Calculator)

This is where load centers die—not from technical inadequacy today, but from zero flexibility tomorrow.

The Expansion Tax is the total cost of replacing undersized equipment, calculated as:

Expansion Tax = (Replacement Cost + Installation Labor + Downtime Cost + Permit Fees) ÷ Years Until Replacement

Real-world example:

Forgatókönyv: 3,000 sq ft commercial office building, initial load calculation: 180A

Option A: 200A Load Center

• Equipment cost: $450
• Installation: $600
• Total initial: $1,050

Idővonal:

• Year 0: 26 circuits installed, 4 spaces remaining (30-space panel)
• Year 2: Tenant improvements require 8 new circuits—panel full + 4 circuits short
• Year 2 costs: Replace with 400A panelboard ($2,200) + labor ($1,500) + downtime during business hours (lost productivity ~$2,000) + permit ($180) = $5,880

Total 5-year cost: $1,050 + $5,880 = $6,930

Expansion Tax: $5,880 ÷ 2 years = $2,940/year penalty

Option B: 400A Panelboard with 42 Spaces

• Equipment cost: $1,850
• Installation: $950
• Total initial: $2,800

Idővonal:

• Year 0: 26 circuits installed, 16 spaces available
• Year 2: Add 8 circuits (now 34 circuits, 8 spaces still available)
• Year 5: Add 6 more circuits (now 40 circuits, 2 spaces available)
• Year 5 costs: $0

Total 5-year cost: $2,800

Expansion Tax: $0/year

The decision: Pay $1,750 more upfront to save $4,130 over 5 years. That’s a 2.4× ROI on the initial investment, not counting the avoided headaches of coordinating replacement during occupied operations.

Pro-Tip #6: The Circuit Density Test

Calculate: Square Footage ÷ Number of Circuits

• If result is < 100 sq ft/circuit → High likelihood of future additions. Spec 150% of initial circuit count.
• If result is 100-150 sq ft/circuit → Moderate growth expected. Spec 125% of initial circuit count.
• If result is > 150 sq ft/circuit → Low density, stable application. Spec 110% of initial circuit count (still need some buffer).

For the 3,000 sq ft office with 26 circuits: 3,000 ÷ 26 = 115 sq ft/circuit → Falls in moderate growth category → Spec 33 spaces minimum (26 × 1.25), which means a 42-space panel is appropriate.

Step 4: Check Voltage & Phase Requirements

This is the simplest step, but it’s binary—get it wrong and nothing else matters.

Single-phase applications:

• Residential: 120/240V (split-phase)
• Light commercial fed from single-phase utility: 120/240V
• Commercial building on three-phase utility with single-phase panel: 120/208V (derived from Wye system)

→ Load centers work here, if all other criteria are met (capacity, fault current, etc.)

Three-phase applications:

• 208Y/120V (common commercial)
• 480Y/277V (industrial, large commercial)
• 600Y/347V (Canadian, some industrial)
• 240V Delta high-leg (older commercial, being phased out)

→ Panelboard required. No exceptions.

How to identify: Look at the utility service entrance. Count conductors:

• 3 conductors (2 hot + neutral) = Single-phase
• 4 conductors (3 hot + neutral) = Three-phase Wye
• 3 conductors (3 hot, no neutral) = Three-phase Delta

If you see four or three conductors at the service, and you’re distributing to commercial loads, you’re in panelboard territory.

Warning about high-leg Delta systems: NEC 408.3(F) requires special marking: “Caution ___ Phase Has ___ Volts to Ground.” (Example: “Caution B Phase Has 208V to Ground” for a 240V Delta system.) These systems are falling out of favor but still exist in older buildings. If you’re working with high-leg Delta, verify your panelboard is rated for it, and ensure the high-leg conductor terminates on the correct phase per NEC 408.3(E).

Step 5: Verify Breaker Típuskövetelmények

Beyond just plug-in vs bolt-on, there are specific NEC requirements:

NEC 408.36(D) – Back-Fed Devices:

“Plug-in-type overcurrent protection devices…that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device.”

Translation: If you’re using a plug-in breaker to feed power into the panel bus (solar interconnection, generator back-feed, alternate power source), the standard friction clips aren’t enough. You need a hold-down screw, bracket, or other mechanical fastener.

Why: A back-fed breaker has line voltage on the breaker’s load terminals, which are exposed when you remove the breaker from the bus. Without an additional fastener, someone could accidentally pull the breaker out while it’s live—instant arc flash hazard.

Inspectors check this. Have the hold-down kit installed before the inspection.

Breakers Marked “Line” and “Load”:

NEC 110.3(B) requires installation per manufacturer’s listing and labeling. If a breaker is marked with “Line” and “Load” designations, you cannot back-feed it. Period. It’s not listed for reverse current flow.

Solution: Use breakers specifically rated for back-feed applications, or use bolt-on breakers which are generally bidirectional.

Step 6: Environment & Code-Specific Requirements

Final checks before procurement:

NEC 408.43 – Position:

“Panelboards shall not be installed in the face-up or face-down position.”

Panels must be vertical or horizontal with the cover facing a vertical surface (wall). This prevents debris accumulation and liquid ingress into the bus compartment. We’ve seen installations where panels were mounted horizontally on the ceiling with the cover facing down—creative use of space, but flagged immediately.

NEC 408.4 – Circuit Directory:

“Every circuit and circuit modification shall be legibly identified as to its clear, evident, and specific purpose or use.”

“In other than one- and two-family dwellings, the identification shall include sufficient detail to allow each circuit to be distinguished from all others.”

Vague labeling like “Lights,” “Receptacles,” “Misc” won’t pass commercial inspection. You need specifics: “North Office Lighting Zones 1-3,” “Server Room Dedicated Outlets,” “HVAC Unit 2 – Roof.”

Best practice: Use a professional label maker or pre-printed directory inserts. Handwritten directories are technically acceptable but reflect poorly on the installation quality.

Hazardous Location Requirements:

If your panelboard is in a Class I, II, or III hazardous location (chemical plants, grain handling, spray booths, etc.), standard load centers and general-purpose panelboards are not suitable. You need:

• Class I Div 1: Explosion-proof or purged/pressurized panelboard per NEC 501.6
• Class I Div 2: General-purpose in some cases, explosion-proof in others per NEC 501.115
• Class II (dust): Dust-ignitionproof enclosures per NEC 502.115

These are specialized panelboards, not available in load center configurations.

Environmental NEMA Ratings:

Match the NEMA type to the environment:

• 1. típus: Indoor, dry locations (general purpose)
• Type 3R: Outdoor, rain-resistant
• 4. típus: Watertight (not submersible)
• 4X típus: Watertight, corrosion-resistant (stainless steel or fiberglass)
• 12. típus: Industrial, dust/drip resistant

Your spec sheet should explicitly call out the required NEMA type. Don’t assume “indoor” means Type 1 if the location is a commercial kitchen with steam or a warehouse with overhead door exposure to weather.

When to Choose Which: The Quick Reference

Decision Matrix:

Case Study 1: When a Load Center is the Right Choice

Project: 1,800 sq ft residential garage/workshop addition

Loads:

• Lighting: 12A (continuous)
• Receptacles (general purpose): 30A (non-continuous)
• 240V Air compressor: 20A (non-continuous)
• 240V Welder: 30A (intermittent, high inrush)

Számítás:

• Continuous: 12A × 125% = 15A
• Non-continuous: 30 + 20 + 30 = 80A
• Total: 15 + 80 = 95A

Selection: 100A load center, 20-space, plug-in breakers

• Available fault current at location: 6.5kA (verified with utility)
• Load center rated 22kA (enclosed panelboard listing)
• Cost: $285 equipment + $450 installation = $735 total

Result: Perfectly appropriate application. Fixed residential use, low fault current, simple single-phase 120/240V, no expansion anticipated (workshop is end-state design). The load center saves $600-800 versus a commercial panelboard with no performance compromise.

Case Study 2: The Expansion Tax in Action

Project: 2,400 sq ft commercial retail space in strip mall

Initial Loads (Year 0):

• Lighting: 45A (continuous – LED throughout)
• Receptacles: 40A (non-continuous)
• HVAC (RTU): 28A (continuous)
• Sign: 8A (continuous)

Initial Calculation:

• Continuous: (45 + 28 + 8) × 125% = 101.25A
• Non-continuous: 40A
• Total: 141.25A → 150A minimum

Actual Choice: 200A load center, 30-space

• Equipment: $520
• Installation: $680
• Total: $1,200

Kezdeti értékelés: “Perfect! We have 150A calculated, 200A panel, and only using 22 of 30 spaces. Plenty of room.”

Year 2: First tenant improvement

New tenant wants to install:

• Commercial espresso machine (dedicated 20A circuit)
• Under-counter refrigeration (2× 20A circuits)
• Additional task lighting (3× 15A circuits)
• POS system dedicated circuit (20A)

New circuits needed: 7

Probléma: 22 circuits + 7 = 29 circuits. Only 30 spaces in panel. Barely fits.

Year 3: Second tenant improvement

Tenant expands into adjacent suite (lease growth), needs:

• Extended lighting zones (4 circuits)
• Additional receptacles (3 circuits)
• Second HVAC unit for expanded space (1 circuit)
• Kitchen equipment (3 circuits)

New circuits needed: 11

Probléma: 29 + 11 = 40 circuits. Panel maxed out 10 spaces ago.

“The Expansion Tax” Comes Due:

• New 400A panelboard, 42-space: $2,100
• Removal of old panel + installation: $1,800 labor
• After-hours work (can’t shut down retail during business): +$600 premium
• Permit/inspection: $195
• Coordination/project management: 8 hours @ $95/hr = $760

Total replacement cost: $5,455

Total 3-Year Cost: $1,200 (original) + $5,455 (replacement) = $6,655

What should have been specified initially: 400A panelboard, 42-space

Cost if specified correctly:

• Equipment: $1,650
• Installation: $950
• Total: $2,600

The Expansion Tax: $6,655 – $2,600 = $4,055 penalty for choosing the “budget option”

Annual cost: $4,055 ÷ 3 years = $1,352/year in wasted money

Lesson: For any commercial application with potential tenant improvements or occupancy changes, assume growth will happen faster than the owner expects. “The 2-Year Full Problem” is real, and “The Expansion Tax” is painful.

From Red Tag to Code Compliance

The inspector who red-tagged that $15,000 installation wasn’t being difficult. He was enforcing NEC 110.9, 408.36, and 110.24—the same code sections that keep buildings from becoming fire hazards and equipment from exploding under fault conditions.

The difference between a failed inspection and a first-time pass comes down to understanding that “load center vs panelboard” isn’t just a price comparison. It’s a system selection decision involving six critical factors: load calculation with 125% continuous multiplier, available fault current determination, growth planning, voltage/phase requirements, breaker type specifications, and environmental compliance.

Here’s your systematic checklist:

1. Calculate true load per NEC 215.2 (continuous × 125% + non-continuous × 100%)
2. Verify available fault current and match to equipment short-circuit rating (watch for “The 10kA Default Trap”)
3. Plan for growth using circuit density analysis (prevent “The 2-Year Full Problem”)
4. Confirm single-phase vs three-phase requirements (hard stop for load centers at three-phase)
5. Specify correct breaker mounting (bolt-on for back-feed per NEC 408.36(D))
6. Match NEMA rating to environment and verify NEC 408.43 position requirements

Get these right, and your installation passes inspection, serves the building’s design life, and avoids “The Expansion Tax.”

One final note: NEC 2023 introduced new requirements for replacement panelboards in Section 408.9. If you’re retrofitting existing installations, you now have specific rules about field evaluation requirements when available fault current exceeds 10kA and you’re not using an enclosed panelboard listing. The days of casually swapping panels into old cabinets are over—field evaluation by a qualified body is now required in many cases. Factor this into your replacement project costs.

Ready to spec the right distribution equipment the first time? VIOX Electric manufactures NEC-compliant panelboards and load centers with complete UL 67 listings, available fault current ratings from 10kA to 100kA, and technical support to verify code compliance before procurement. Contact our application engineering team for load calculation review and panel selection guidance—because passing inspection shouldn’t be a gamble.