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By Matt Lohens, P.E., MHL Consulting PLLC. Last reviewed: October 2026 Short answer: A short-circuit study finds the maximum fault current at every point in your electrical system and checks that each breaker, fuse and switchboard can safely interrupt or withstand it. A coordination study sets protective devices so that only the device closest to a fault opens, instead of tripping a main and shutting down the whole facility. Together with an arc flash study they form a comple

By Matt Lohens, P.E., MHL Consulting PLLC. Last reviewed: October 2026 Short answer: An arc flash study (also called an incident energy analysis) calculates how much thermal energy a worker could be exposed to at each piece of electrical equipment during a fault. The results drive equipment labels and PPE choices. NFPA 70E requires the study to be reviewed at least every 5 years and updated whenever the electrical system changes. MHL Consulting performs and stamps these studi

By Matt Lohens, P.E., MHL Consulting PLLC. Last reviewed: October 2026 Short answer: A power control system (PCS) is a listed system that monitors electrical current and limits it so the total load never exceeds the rating of a service, feeder or busbar. The NEC now lets designers account for that limit instead of the full connected load, which can let you add EV chargers, heat pumps, electric cooking or batteries to an existing service without upgrading it. A licensed PE can

By Matt Lohens, P.E., MHL Consulting PLLC. Last reviewed: October 2026 Short answer: Often yes. Many commercial and industrial buildings can add new equipment, such as lab equipment, production lines, chillers, UPS systems or tenant build-outs, without upgrading the electrical service. A licensed PE verifies what the existing switchboard and feeders can actually carry, calculates the real load using measured demand and noncoincident-load methods, and documents that the new eq

The panel says 200A" is not a load calc. I hear a version of that sentence on almost every panel upgrade job that comes back red-lined, and it's the single most common reason a load calculation permit package gets rejected. Here's what a plan checker is actually looking for, why the nameplate rating doesn't cut it, and how to get the load calc right the first time. Why Load Calcs Get Red-Lined A load calculation isn't a summary of what equipment is installed. It's a demand ca

Actual MHL Single Line Example If you've ever had a permit package sent back by the AHJ, you know the pain: the job is scheduled, the materials are on order, and now you're stuck waiting on corrections that could've been caught before you submitted. Most rejections come down to the same few issues. Here's what I see repeatedly as a PE reviewing these packages — and what contractors can do to avoid the back-and-forth. What the AHJ Actually Wants to See Plan checkers aren't try

If you're pulling a 200A or 400A service upgrade and keep getting red-lined at plan check, the problem usually isn't your installation — it's the drawing package. AHJs have gotten more specific about what PE-stamped submittals need to include, and a one-page riser with a load calc thrown in isn't cutting it anymore. Here's what a complete panel upgrade permit package looks like and why each piece matters. Why PE Drawings Get Red-Lined on Service Upgrades Most rejection notes

If you've ever had a permit application bounce back from the AHJ with a correction notice, you already know how costly electrical plan review can be — not because the fee is high, but because the delay is. A rejected set of drawings can push a project schedule back by weeks, trigger GC penalties, and create friction with clients who expect permits to be a contractor's problem to solve, not theirs. This guide breaks down how electrical plan review works, what reviewers are act

Short answer: yes. If you're installing a Level 2 or DC fast charger, you need a permit. Full stop. The only gray area is a 120V Level 1 outlet pulling off an existing circuit — and even then, if the outlet is new, you're probably pulling a permit. Here's what you actually need to know before you schedule the rough-in. Level 2 and DCFC Always Require a Permit A Level 2 charger (240V, typically 30–80A) is a new electrical circuit. Any new circuit means a permit. That's NEC 210

You won the bid. You've got the materials specced. Your crew is ready. But the building department wants engineered electrical drawings before they'll issue the permit, and now your timeline is on hold. If you're an electrical contractor dealing with commercial permit drawings for the first time, or if you've been through the process before and gotten burned with corrections that added weeks to your schedule, this post is for you. I'm going to walk through what AHJs actually

If you've started bidding commercial EV charger installations, you already know the permit process can be a moving target. Requirements vary by jurisdiction, utilities move slowly, and one missing document can stall a job for weeks. This guide walks you through exactly what a commercial EV charger permit package needs to contain, where contractors most commonly get rejected, and how to move through the process efficiently — whether you're in California, Texas, Colorado, Nevad

Why Your PE Keeps Flagging the 1.25 Factor (And Why the Meter Reading Doesn't Settle It) If you've done electrical work on facilities with large continuous loads, you've probably had this conversation: "The breaker is rated for 800 amps. We measured the feeder at 330 amps. Why is the engineer telling me I'm overloaded?" It comes up constantly, especially on indoor cultivation, data centers, and commercial lighting projects. And I get it. From a contractor's perspective, the m

Published by MHL Consulting | mhlconsulting.co If you've ever waited weeks for a permit only to get a correction letter back from the building department, you're not alone. Across the country, it is remarkably common for electrical permit packages to require at least one round of revisions before approval. Some jurisdictions openly acknowledge that applications "rarely meet all code requirements in the first round of reviews." But here's the thing — the reasons drawings get s

Why we built a simple, defensible method for a TBB M12 LiFePO₄ project—and who else needs it The client problem (common in the wild) Our...

When it comes to choosing an interconnection point for your PV system, it may be tempting to connect to the nearest electrical...

As more consumers adopt electric vehicles (EVs), the demand for charging infrastructure is growing. As a business owner, investing in EV...

As the popularity of electric vehicles continues to grow, the demand for charging stations is also increasing. In an effort to encourage...

In today's world, electricity is a vital component of our daily lives. From powering our homes to keeping our businesses running, it's...

The National Electric Code (NEC) is a comprehensive set of guidelines and standards for electrical installations in the United States. It...

If you are involved in electrical systems design and installation, then you are well aware of the importance of compliance with the...