What a Texas candidate needs to know about NEC 110.26 before test day

Ten questions, one section

Our bank holds 500 items, 140 of them in wiring methods and installations. Ten of those 140 put a question directly on the space around equipment. An eleventh reaches it through the stationary battery article, which asks for guarded live parts, working space and a disconnect together. A twelfth uses 110.26 as a wrong answer to a wire bending space question, where 312.9 holds the answer in the 2026 edition.

That is a heavier concentration than any other single section in the area, and it happens for a reason an item writer will recognize. The section holds six separate requirements, most people can quote one, and four options fit on a page with no arithmetic in them, which makes a subject where the confident answer is incomplete cheap to write and expensive to sit.

One more item, over in the administration area of the bank, asks where the general rules live that apply to an installation whatever the equipment is. Working space is named in the stem as an example, and the answer is Article 110. Candidates lose time hunting through the equipment article for a rule that was never equipment specific, and that's the habit this page exists to break. The opposite habit pays on disconnecting means, where the equipment does name the article.

Six answers in one section

Before you look for a number, name which of the six the stem wants. They are separate requirements with separate logic, an installation satisfies all of them or it fails, and generous width buys back nothing on short depth.

The parent text sets the purpose: working space, and the access to and egress from it, is provided and maintained about all electrical equipment so it can be operated and maintained safely. The dimensions in 110.26(A) attach to equipment likely to require examination, adjustment, servicing or maintenance while energized, and that qualifier does real work. A stem describing the equipment carefully is often telling you whether the dimensions apply.

Where the depth is measured from

Distances run from the live parts where they're exposed, and from the enclosure front or the opening where they're enclosed, under 110.26(A)(1). On a dead front panelboard that means the front of the can, and measuring from the bus gives away the depth of the enclosure.

The figure itself sits in Table 110.26(A)(1), indexed by nominal voltage to ground one way and by one of three conditions the other. Look it up in your own book. Our bank item offers voltage alone and records it as half the answer, the half people remember, which is how the table catches anybody working from memory.

The conditions are decided by what sits on the far side of the space, and they are prose:

• Condition 1. Exposed live parts on one side and nothing live or grounded on the other, or exposed live parts on both sides where insulating material guards them effectively.
• Condition 2. Exposed live parts on one side and grounded parts on the other, with concrete, brick and tile walls counting as grounded parts.
• Condition 3. Exposed live parts on both sides with no effective guarding between them.

Read the guarding clause in Condition 1 twice. Live parts on both sides can still be Condition 1 where an insulating barrier is in place, and an item mentioning a barrier is testing that. Two permissions sit alongside it: 110.26(A)(1)(c) allows Condition 2 clearance between dead front assemblies across an aisle in an existing building, on written procedures and qualified people, and 110.26(A)(1)(a) asks for 30 inches of horizontal space where rear access reaches nonelectrical parts.

The two dimensions nobody looks up

Width is the width of the equipment or 30 inches, whichever is greater, measured across the face under 110.26(A)(2). Equipment doors and hinged panels open at least 90 degrees. Our bank item offers 30 inches in every case, the equipment width alone, and 36 inches from the face, the last of which borrows a figure belonging to a different dimension.

Height is clear space from the grade, floor or platform up to 6.5 feet or the height of the equipment, whichever is greater, under 110.26(A)(3). A duct run at 6 feet across the front of a panel breaks a dimension almost nobody checks. The wrong answers here are the ceiling of the room and a flat seven feet, and the ceiling option is the dedicated space rule wearing the wrong label.

Two further subsections are worth knowing. 110.26(A)(4) sets separate terms where access is limited, such as equipment above a suspended ceiling. 110.26(A)(5) handles lower voltage equipment sharing a vault, room or enclosure with exposed parts operating above 1000 volts ac or 1500 volts dc, separated off by a partition, fence or screen. Equipment at 4160 volts is answered from the part of Article 110 written for over 1000 volts, and one bank item exists because candidates carry the low voltage conditions upstairs.

Two ratings decide the way out

Two ampere thresholds live in 110.26(C) and they do completely different jobs.

Large equipment gets an entrance to and egress from the working space at each end, at least 24 inches wide and 6.5 feet high, under 110.26(C)(2). It is defined two ways: equipment rated 1200 amperes or more that is also over 6 feet wide, or a set of service disconnects, or building or structure feeder disconnects, whose combined rating reaches 1200 amperes and whose combined width runs over 6 feet.

That second limb catches people, because no single enclosure in the lineup has to be 1200 amperes. Six 400 ampere service disconnects side by side are added together for rating and for width, and the group lands inside the rule while every piece of it looks small. On the first limb both halves hold or the rule stays out, so a 1200 ampere motor control center 5 feet wide sits outside it. Two exceptions bring it back to one entrance, one on unobstructed egress and one on doubling the depth.

The space above is different

110.26(E) reserves a different volume for a different reason, and mixing the two up is the most productive mistake here. The dedicated space is the footprint of the equipment, its own width and its own depth, running from the floor to 6 feet above the equipment or to the structural ceiling, whichever is lower.

Working space sits in front of the equipment so a person can stand there. Dedicated space is the column the equipment sits in, and it exists so that somebody else's pipe stays off your gear. Piping, ducts, leak protection apparatus and other equipment foreign to the electrical installation are kept out of that zone. Above the zone the answer flips: foreign systems are allowed where protection is installed against condensation, leaks and breaks, and sprinkler protection for the room is allowed. A suspended ceiling with removable panels is allowed inside the dedicated space itself, the clue that a dropped ceiling falls short of the structural ceiling the 6 feet measures to.

Our bank item puts a water line across the ceiling above a panelboard and offers working space depth, working space height measured down from the ceiling, and nothing regulated above a panel. A mechanical room stem often plants one problem in front of the gear and one above it, so read for both before you commit.

What this costs after inspection

110.26(B) keeps the working space clear of storage, and two of our bank items are written about exactly that because it's the most common real world violation in the code. A space clear at inspection stops being clear the week somebody needs a home for a ladder. The wrong answers record the excuses: material that is easily moved, material below waist height, an unfinished space, and the idea that passing inspection once settles it.

The requirement runs continuously, so the cost lands on whoever owns the building on the day it gets looked at again. Say so at handover, in the same breath as the panel schedule.

Cities in Texas keep the power to require inspections and to adopt local amendments to the code, under Tex. Occ. Code 1305.201(a) and (c), and subsection (d) requires electrical work inside the city limits to follow all applicable local ordinances. The governing text in a given city is the state adopted edition plus that city's amendments, so two jobs twenty miles apart can be held to different books in the same week.

What to do before test day

Put one tab where Table 110.26(A)(1) starts and a second on 110.26(E). The second earns more, because the dedicated space is the rule people go looking for and take four minutes to find. PSI accepts only tabs the publisher of the code book manufactured or provided, so buy them with the book and mark it before the session, since writing in it during the session is refused.

Then work four steps in order:

1. Decide whether the dimensions apply at all, since they attach to equipment likely to be examined, adjusted, serviced or maintained while energized.
2. Name which of the six answers the stem wants.
3. For depth, settle the condition before you open the table, since the table is entered by condition and by voltage together.
4. Check the stem for a second violation before you commit, because these items usually carry one loud problem and one quiet one, and the quiet one is often above the equipment.

Two short subsections round it off. 110.26(D) requires those indoor working spaces to be lit and bars control of all the luminaires by automatic means inside the space, so an occupancy sensor as the only control fails and a reachable wall switch passes. 110.26(F) treats a locked electrical room as accessible to qualified persons, so a stem mentioning one is usually describing something lawful. The enclosure type question about the same panel is a separate lookup, and the worked dimensions sit in the question set.

Questions people ask

What decides the depth of working space?

Two things together: the nominal voltage to ground, and what sits on the opposite side of the space. Table 110.26(A)(1) is entered by both, so an answer built on voltage alone is half the rule and it's the half most people remember. The opposite side is described by three conditions in prose, turning on whether the far side is clear, grounded, or carrying exposed live parts of its own, with an allowance where insulating material guards live parts on both sides effectively. Settle the condition before you open the table.

Is working space width measured from the breaker?

It is measured across the face of the equipment, and 110.26(A)(2) asks for the width of the equipment or 30 inches, whichever is greater. So a narrow panel takes the 30 inch figure as a floor and a wide switchboard takes its own width. The space is centered on nothing in particular, which is why an item that describes one breaker in the middle of a lineup is steering you toward a wrong answer. Equipment doors and hinged panels also have to open at least 90 degrees.

Can two panels share the same working space?

Yes, where the full required space is present for each of them. 110.26 is written as room for a person to stand, work and get clear, and it states depth, width and height for each piece of equipment without assigning a piece of floor exclusively to one panel. Two panelboards on walls meeting at the corner of a small electrical room can overlap legitimately. What the section declines to tolerate is anything taking the space away when it is needed, which is why storage is the common violation and an overlap is ordinary.

What triggers a second entrance to the working space?

Ampere rating and physical width together, under 110.26(C)(2). Equipment rated 1200 amperes or more that is also over 6 feet wide needs an entrance at each end of the working space, at least 24 inches wide and 6.5 feet high. A group of service disconnecting means, or building or structure feeder disconnects, counts on combined rating and combined width, so six 400 ampere disconnects side by side can land inside the rule. Voltage appears nowhere in this trigger, and reaching for it is a habit carried over from the depth rule.

Is a water line above a panelboard a violation?

It is a dedicated space problem under 110.26(E), which is a separate subsection from the working space in front of the gear. The dedicated space is the width and depth of the equipment running from the floor to 6 feet above it or to the structural ceiling, whichever is lower, and piping, ducts, leak protection apparatus and other foreign equipment stay out of that volume. Above it, foreign systems are permitted where protection is installed against condensation, leaks and breaks, and sprinkler protection for the room is allowed inside.

Do these rules apply to equipment at 4160 volts?

The familiar working space section is written for 1000 volts nominal and below. A separate part of Article 110 picks up above that with larger clearances and its own rules on entrances, locked rooms and signage. Carrying the low voltage depth conditions into a medium voltage room understates the space by a wide margin, which is why one of our bank items is built on exactly that error. Article 490 covers the equipment itself and leaves the installation clearances where they are, so naming it alone answers a different question.