Southwire FAQ: Which Multimeter to Buy, Voltage Drop, and Answers From a Working Electrician

I'm an electrical contractor in northwest Georgia, and I've spent the last eight years running calls that have to be done yesterday — a failed feeder at a restaurant on a Friday afternoon, a tenant moving in overnight, an inspector coming back at 7 a.m. Last year alone, my crew and I turned around 47 rush orders, and this year is shaping up the same way.

Because Southwire's headquarters is less than an hour from my shop (and because most of the wire we pull says SOUTHWIRE on the jacket), I get the same questions over and over. These are the ones I actually answer — on job sites, in hardware-store aisles, and in this article.

1. Is Southwire actually a good brand, or do people just buy it because it's everywhere?

Both, honestly. Southwire is one of the largest wire and cable manufacturers in North America, so it's on a lot of job sites for a simple reason: it's available, it's consistent, and the specs are printed right on the jacket. That consistency matters more than people think. A conductor that's a half-gauge off, or insulation that fights you through conduit, will burn labor hours fast.

I started out doing small side jobs out of a Honda Civic — $200 orders, one roll of wire at a time. Nobody treated me differently because the ticket was small. The THHN showed up with the same labeling, the same packaging, and the same documentation I still rely on today when we're ordering $15,000 worth of spools. Bottom line: for commodity cable, Southwire is the benchmark. That doesn't mean it's the cheapest, or always the right call for a specialty run. But you're not paying for an empty name.

2. What's the difference between THHN, Romex, and UF-B cable?

Quick version, because I've explained this in a hardware store with the clock running:

• THHN — a single insulated conductor that runs through conduit or raceway. The workhorse for commercial and exposed industrial runs.
• Romex (NM-B) — a sheathed cable with two or more conductors inside. For indoor, dry locations like stud bays and attics.
• UF-B — the direct-burial version, with a solid, moisture-resistant jacket. No conduit required underground.

The mistake I see on rush jobs is people grabbing the closest roll of Southwire because "it's all copper, how different can it be?" Fairly different. Romex isn't rated for wet or underground locations. UF-B is stiff, a pain to strip, and doesn't suit every indoor install. And THHN without conduit is unprotected. In an emergency, the wrong one doesn't just fail inspection — it costs you a second truck trip and, more often than not, an all-nighter.

3. What is voltage drop, and when should I actually worry about it?

Voltage drop is the loss of electrical pressure in the wire as current flows through it. Every conductor has resistance, and resistance turns current into heat and wasted voltage. The longer the run and the smaller the wire, the bigger the drop.

NEC 210.19(A)(1), informational note: branch circuit voltage drop should be no more than 3%, and combined feeder plus branch no more than 5%.

That note is guidance, not a hard code requirement in most jurisdictions, but inspectors treat it like a rule — and so do I. A 120-volt, 15-amp circuit on 100 feet of 12 AWG copper loses about 5% at the far end. Lights look dim, motors run hot, chargers act weird. The fix is usually easy — step up to 10 AWG or shorten the run — but you have to catch it before the walls close. It took me six years and a couple of frustrating callbacks to understand that voltage drop isn't an "is there power?" question; it's a "how good is the power?" question. My experience is mostly residential and light commercial in the Southeast. If you're doing industrial 480V work, the principles are the same, but the math and the margin for error get far less forgiving.

4. Which multimeter should I buy — the Southwire 21050T or the Fluke 117?

This is the one I get most from apprentices: they're standing in an aisle staring at a $30 Southwire and a $140 Fluke, both reading volts. Here's how I think about it.

The Southwire 21050T is a compact entry-level digital multimeter: AC/DC voltage, resistance, continuity — basically everything you need for most residential and light commercial checks. I've seen it priced anywhere from $25 to $40 depending on the seller (as of early 2025). For that money, it's a no-brainer as a first meter, or a beater bag meter that won't break your heart if it grows legs on a job site.

The Fluke 117 is a different category: auto-ranging, true RMS, non-contact voltage detection, CAT III 600-volt rating. It's the electrician's meter. The VoltAlert feature alone has saved me from touching a wire that was still live more times than I care to count.

I went back and forth between a cheap meter and the 117 for two weeks when I rebuilt my go bag. On paper, both read volts. But my gut said spend the extra $100 on the tool I'd trust at 9 p.m. on a ladder. Then again, if you're only working on dead circuits and basic checks, the 21050T is honestly plenty. No one should convince you that spending more than a job requires is a virtue.

5. What is a CAT rating, and why should I care when buying a multimeter?

CAT ratings come from UL 61010-1, the safety standard for electrical test equipment. They tell you how much transient overvoltage a meter can survive — not steady voltage, but the spikes that show up during faults and lightning strikes.

A CAT II meter is designed for outlets and appliance circuits on the load side of a panel. A CAT III meter is for distribution panel work. CAT IV is for utility entrances. Here's the ugly part: if a meter is overrated on the sticker but underbuilt inside, a surge can arc across the internal clearances. And you're the one holding it. So I always check the rating before I recommend any budget meter to anyone.

As for the 21050T specifically — I'm not 100% sure of its exact rating without the spec sheet in front of me; I believe this class is CAT II, but don't hold me to that. It's fine for day-one apprentice checks. Just don't bring it to a main breaker panel and assume it owes you protection, because it doesn't.

6. Southwire interview questions — wait, aren't you here to pick a multimeter?

If you typed "Southwire interview questions" into Google, I promise I'm not hiding anything. I've hired electricians for my own crew, and I have friends who've gone through Southwire's hiring process, so here's the honest version.

Southwire interview questions lean heavily on behavioral and safety themes. Expect things like "tell me about a time you had to meet a tight deadline" or "describe a time you stopped work because something wasn't safe." They're a manufacturer with their own training programs, so they're not expecting you to recite ampacity tables from memory. They are listening for whether you think methodically, whether you follow through, and whether you take safety seriously.

My advice: use a real job site story. The time you had to diagnose a fault before an inspector arrived. The Friday-night call where the wrong cable would've meant another week of shutdown. Those stories show how you handle pressure — which, in my experience, is the real screen. And if you've actually used their products, say so. It's a small world, and the people interviewing you will appreciate that you know the difference between UF-B and Romex without looking it up.

7. What Southwire resource actually saves you in a real emergency?

The voltage drop calculator, no contest. It's free on their website and in the app, and it settles arguments in about four seconds.

Here's a real story. In March 2024, a client called at 2 p.m. — a restaurant's walk-in cooler was down, and the equipment rep wanted a 240-volt circuit run 140 feet to a new condenser before the Friday health inspection. Normal turnaround for that run was about two days. We had five hours. Standing in the parking lot, I punched the numbers into Southwire's voltage drop calculator: 37 amps at 240 volts over 140 feet. It came back with 10 AWG copper as the minimum to stay under 3% — which, thankfully, we already had on the truck.

The run went in that evening. The inspector signed off the next morning. The client's alternative was a $4,000 cooler repair and a red sticker on the door. The calculator didn't do the physical work, of course — that was the crew, and a lot of coffee. But it turned a potential disaster into a manageable Tuesday. And you don't even need to be a Southwire customer to use it, which says something.