110.13 - MOUNTING AND COOLING: Because "Good Enough" Isn't Good Enough

The Straight Talk Translation

Alright, listen up. This section is basically telling you two things your grandma could've told you: Don't hang heavy stuff with bubble gum, and don't suffocate your equipment.

Part (A): Mounting - No Wooden Plugs, Sparky!

Your equipment needs to be firmly secured to whatever surface you're mounting it on. And here's the kicker that trips up the old-timers: NO WOODEN PLUGS driven into masonry, concrete, plaster, or anything similar.

I don't care if your uncle did it that way in 1987. I don't care if "it's still holding." Wood shrinks, rots, gets eaten by bugs, and generally stops giving a damn after a few years. That panel you hung with wooden plugs? It's gonna be hanging by its conduit when the homeowner's trying to reset a breaker during the Super Bowl. Guess who's getting that call?

Use proper anchors: Tapcons, wedge anchors, expansion anchors, toggle bolts—anything designed for the job. Your truck has a whole bin of them. Use 'em.

Part (B): Cooling - Let It Breathe, for Crying Out Loud!

Electrical equipment gets hot. Shocking, I know. And most of it is designed to cool itself using this fancy technology called "air." Revolutionary stuff.

Natural circulation and convection cooling means heat rises and cool air comes in from below. It's not magic—it's thermodynamics. But it only works if you don't:

Jam equipment right up against walls
Stack equipment so tight a gnat couldn't squeeze through
Block ventilation openings because "it looks cleaner that way"

Floor-mounted equipment needs clearance on top so rising hot air can escape. Wall-mounted stuff needs space around it. Equipment with vent holes? Those holes aren't decorative—don't block them.

You wouldn't park your truck in the garage with the engine running and close the door, right? Same concept. Let. It. Breathe.

Key Takeaways (The Stuff That Actually Matters)

Secure equipment FIRMLY to the mounting surface—no shortcuts, no "temporary" installations that last 10 years
WOODEN PLUGS ARE PROHIBITED for mounting in masonry, concrete, plaster, or similar materials (this is a hard NO in the Code)
Proper anchors only: Use Tapcons, expansion anchors, toggle bolts, or other approved fastening methods
Air-cooled equipment needs airflow over exposed surfaces—don't block it with walls or adjacent equipment
Floor-mounted equipment needs clearance on top for heat dissipation (hot air rises, remember 8th grade science?)
Ventilation openings must remain unobstructed—if it's got louvers, grilles, or vent holes, they need free air circulation
This applies to ALL equipment: panels, transformers, motor controllers, VFDs, switchgear—if it makes heat, it needs to breathe

Real-World Jobsite Scenarios (Tales from the Trenches)

Scenario 1: The Closet Panel

You're on a residential remodel, and the designer wants the electrical panel in a closet "to keep it hidden." Sure, sounds great for aesthetics. You install it, close clearances per 110.26, all good, right?

Wrong.

The homeowner immediately hangs winter coats all around it, blocks the top, and stacks boxes underneath. Six months later, breakers are nuisance tripping because the panel's cooking itself. The neutral bar is so hot you could fry an egg on it.

The lesson? 110.13(B) working together with 110.26. Just because you have working clearance doesn't mean the equipment can cool properly. Talk to the customer. Explain why that closet location is a bad idea. Or at least document it in writing so when you get the callback, you can show them you warned them.

Scenario 2: The Stacked Drives

Commercial job. You've got three VFDs to install, and the engineer's specs show them stacked tight—6 inches apart—because wall space is limited. You follow the plans, pass inspection, job done.

Fast forward three months: all three drives are alarming for overtemp, and the factory tech voids the warranty because the installation "doesn't meet minimum cooling requirements." The engineer's drawings didn't account for 110.13(B), and now you're back on site doing rework on your dime.

The lesson? The manufacturer's installation manual works WITH the Code, not instead of it. If the drives say they need 12 inches of clearance and the plans show 6, you stop and ask questions before you start drilling. Get it in writing, or you're the one eating the labor later.

Scenario 3: The "Temporary" Wooden Plug Panel

Old-school guy on the crew mounts a subpanel using wooden plugs in a concrete block wall. "I've done it this way for 30 years, never had a problem." You're the apprentice, you keep your mouth shut.

Two years later, the wooden plugs have dried out and shrunk. The panel's listing forward. The conduits are holding it up, and they're getting stressed. One good yank on that panel door and the whole thing's coming off the wall—live.

The lesson? Just because nobody died YET doesn't mean it's Code compliant or safe. 110.13(A) exists because wood is organic material that changes over time. Use the right anchor, every time. Your 30 years of "never had a problem" means you've been lucky for 30 years, not that you were right.

Scenario 4: The Transformer in the Corner

You're installing a 75 kVA transformer in a utility room. The drawings show it in the corner—perfect, out of the way, lots of working clearance in front per 110.26.

But the corner location means the back and one side are tight against walls. The transformer relies on natural convection—heat rises from the fins and cooling surfaces. With two sides blocked, the heat just builds up. The transformer runs 20-30 degrees hotter than rated, insulation life is cut in half, and you're replacing it in 10 years instead of 30.

The lesson? Read 110.13(B) AND the manufacturer's installation requirements. Just because it fits and meets working space doesn't mean it'll cool properly. That transformer might need 24 inches on all sides for air circulation. Find out BEFORE you set it.

What to Study (Your Exam Cheat Sheet)

If you're taking your Journeyman or Master exam, here's what the test writers love about 110.13:

Most Likely to Appear:

The wooden plug prohibition - They LOVE this one. Expect a question like: "Which of the following is permitted for mounting a panelboard to a concrete wall?" The wrong answers will include "wooden plugs" or "wood blocks." Don't fall for it.
Cooling clearance requirements - Scenario questions about equipment mounted too close to walls or other equipment, asking you to identify the Code violation. Know that air-cooled equipment needs airflow.
Floor-mounted equipment - Questions about clearance above floor-mounted gear for heat dissipation. Remember: heat rises, so clearance on TOP is critical.

How They'll Try to Trick You:

"The wooden plugs have been in place for 15 years with no problems" - Doesn't matter. Still prohibited.
"Working clearance per 110.26 is maintained" - Great, but that doesn't address 110.13(B) cooling requirements. Two different things.
"The equipment is listed for the application" - Listing assumes proper mounting and cooling. If you're not meeting 110.13, the listing doesn't save you.
Pictures showing equipment crammed in tight spaces - Look for blocked ventilation openings, equipment tight against walls, or no clearance above floor-mounted gear.

Code Book Navigation:

110.13 is in Article 110, Part I - General installation requirements that apply to EVERYTHING
It's early in the book (Chapter 1), which means it's fundamental—it applies unless specifically modified elsewhere
Cross-reference with 110.26 (working space) and manufacturer's instructions for complete picture

Memory Hook:

"Mount it RIGHT, let it BREATHE, and NO WOOD in the CONCRETE"

That's 110.13 in nine words. Mount properly (firm anchors, no wood), cooling (air circulation), and the big prohibition (no wooden plugs in masonry).

The Bottom Line

110.13 is one of those Code sections that seems obvious until you see it violated on half the jobsites you walk into. Proper mounting and cooling aren't "nice to haves"—they're Code requirements that directly affect safety and equipment life.

Use the right anchors. Give your equipment room to breathe. And for the love of all that's holy, stop using wooden plugs in concrete just because "that's how we've always done it."

Your inspector will thank you. The equipment will last longer. And you won't be the guy getting the callback when the panel falls off the wall.

Now get back to work. Those Tapcons aren't gonna drill themselves.

Remember: The Code is the MINIMUM. Manufacturer's instructions might require MORE clearance or stricter mounting. When in doubt, do both—and do it right the first time.