NEC 90.8: Wiring Planning (Or: Think Ahead So Future-You Doesn't Want to Punch Present-You)

The Plain-Language Breakdown

Look, we've all been there. You're six months into a new job when the customer calls: "Hey, we need to add thirty more circuits." You head to that panel you installed, pop the cover, and... it's packed tighter than a festival porta-potty. Every space is full, there's no room in the pipes, and the nearest place to add anything is forty feet away through concrete.

That's what 90.8 is trying to save you from.

This section isn't a hard rule with enforceable penalties—it's more like your crusty old foreman giving you advice: "Kid, leave yourself some wiggle room, or you'll be the one crawling through the ceiling adding circuits later."

Part (A): Future Expansion and Convenience

Translation: Don't be cheap. Size those raceways like the customer might actually grow their business. Leave spare conduits stubbed in. Put panels where people can actually reach them without a ladder, a prayer, and thirty minutes of moving stored junk.

The wisdom here:

Spare raceway space = When you pull four wires through 3/4" EMT that could hold six, future-you (or some poor apprentice) can add circuits without tearing walls apart
Spare raceways = Stub in an extra conduit or two to mechanical rooms, data centers, wherever. Costs peanuts now; worth gold later
Accessible distribution centers = Don't stick the panel behind the water heater in a janitor's closet where nobody can get to it without Olympic-level contortion skills

Real talk: The NEC isn't requiring this—it's recommending it. But if you ignore it, you're just setting yourself (or the next guy) up for a nightmare retrofit. And karma's real, brother.

Part (B): Number of Circuits in Enclosures

Translation: Don't cram forty circuits into a space that should have twenty. When (not if) something goes wrong, you want the smoke show contained to a manageable disaster, not a catastrophic meltdown that takes out half the building.

Why this matters: When you get a dead short or ground fault in an enclosure that's overstuffed like a Thanksgiving turkey, the heat and arc-flash potential multiplies. It's like the difference between one firecracker and a whole brick of them—the more concentrated the energy, the bigger the BOOM.

By limiting circuits per enclosure (as required in other Code sections—hello 408.36, 408.54), you're practicing electrical compartmentalization. It's the same reason ships have watertight doors. One problem shouldn't sink the whole operation.

Key Takeaways (The Stuff You Actually Need to Remember)

✅ 90.8(A) is advisory, not mandatory – Think of it as "strongly suggested adulting"

✅ Leave spare capacity – Minimum 25% raceway fill is required elsewhere; this says think bigger picture for future growth

✅ Accessibility is king – Put panels and distribution equipment where people can actually work on it safely (Code does require working space per 110.26—this is the philosophical "why")

✅ Don't overload enclosures – Other articles will give you the actual limits, but understand the safety reason: limit potential damage from faults

✅ This is about fire prevention and future-proofing – Two things every electrical inspector and business owner cares deeply about

Real-World Jobsite Scenarios

Scenario 1: The Retail Remodel Nightmare

You wire up a new clothing store. Owner goes cheap, insists on minimal panel with zero spares and maxed-out conduits. Eighteen months later, they want to add a bunch of LED displays and security cameras. Now you're surface-mounting wiremold everywhere because there's nowhere to pull new circuits. The place looks like hell, your change order is huge, and the owner's mad at YOU even though they made the original call.

The lesson: Show them 90.8(A) during the planning phase. "Hey, for $800 more now, we can avoid a $5,000 headache later."

Scenario 2: The Overloaded Gutter

You're troubleshooting a tripped breaker in a big wireway feeding multiple panels. When you pull off the cover, there are THIRTY circuits jammed in there like electrical spaghetti. You find the fault—melted insulation from one circuit has damaged four others. Now what was a simple breaker replacement becomes rewiring six circuits because somebody ignored the concept behind 90.8(B).

The lesson: More circuits = more potential for cascading failure. Spread it out.

Scenario 3: The Panel Behind the Shelving Unit

There's a 200A main panel in a warehouse, installed perfectly to Code... fifteen years ago. Now it's behind twelve feet of heavy shelving loaded with inventory. Building's for sale, and the inspector fails it because you can't maintain 36" of working clearance (110.26). Guess who gets called to relocate a 200A service? (Hint: it ain't cheap.)

The lesson: 90.8(A) says put it somewhere accessible. Future owners will thank you.

What to Study (Exam-Focused Content)

Here's the deal: 90.8 rarely shows up directly on licensing exams because it's advisory, not enforceable. BUT understanding it helps you nail related questions.

For Apprentice/Journeyman Exams:

Know that Article 90 is introductory/explanatory, not rules (90.5(C) tells you that mandatory rules use "shall")
Understand raceway fill requirements (Chapter 9, Table 1) – this is where 90.8(A) philosophy becomes actual Code
Panel and enclosure access requirements (110.26) – the enforceable cousin of 90.8(A)'s accessibility suggestion

For Master/Contractor Exams:

System design philosophy questions – they might ask "Why does the NEC recommend spare capacity?" (Answer: safety, convenience, future expansion)
Working space requirements (110.26) and how poor planning violates them
Cost-benefit of following advisory sections – masters are expected to understand project planning, not just wire-pulling

Cross-References to Actually Study:

90.5 – How to identify mandatory vs. advisory language
110.26 – Working space around electrical equipment (ENFORCEABLE)
Chapter 9, Table 1 – Raceway fill percentages (ENFORCEABLE)
408.36 – Overcurrent device arrangement in panelboards
408.54 – Maximum number of overcurrent devices in panelboards

Pro tip for test-taking: If an exam question asks about "planning" or "future expansion," they're probably testing whether you know the difference between advisory (90.8) and mandatory requirements. Read carefully.

The Bottom Line

Section 90.8 is your grandpa's advice: "Measure twice, cut once, and for the love of God, don't paint yourself into a corner."

It won't get you failed on an inspection because it's not enforceable. But ignoring it WILL make you (or whoever comes after you) miserable when renovation time comes.

Be the electrician who thinks three moves ahead. Your future self will buy you a beer. 🍺

Now get out there and leave some damn spare spaces in that panel.