Mike PleziaInside service technician, Clark Associates · Commercial Equipment, HVAC, and Refrigeration professional

Clamp One Wire, Trust the Nameplate #hvac #multimeter #tradetips

26 Aug 2026 · 2 min

Watch on YouTube

1:35

In this instructional video, the speaker provides practical trade advice on using a clamp meter to measure electrical current safely and accurately. He first explains the symbols on a clamp meter—an "A" with a wavy line indicates AC amperage, and a jaw icon shows that the measurement is taken via the clamp’s magnetic sensor. He then emphasizes the essential rule of clamping around a single live conductor only; clamping around both hot and neutral wires causes their magnetic fields to cancel, yielding a false near‑zero reading. After obtaining a correct current reading, the speaker advises comparing it to the equipment’s nameplate ratings. He distinguishes between RLA (Rated Load Amps) for compressors and FLA (Full Load Amps) for motors, fans, and pumps. Readings at or below these values indicate normal operation, while readings approaching or exceeding them signal potential problems such as overcharge, high head pressure, or mechanical issues. The video concludes by encouraging viewers to share this knowledge with others.

Chapters

Hey, are you new to the trades? Here's something you may not know about measuring current with a clamp meter. On a clamp meter, you'll see an A with a wavy line. That's AC amps. And you'll see a little jaw icon. That tells you this measurement happens through the clamp. Here's why we clamp instead of breaking into the wire. Clamping reads the magnetic field around a live conductor, No cutting, no disconnecting. Just open the jaw and close it around the wire. But there's a rule you cannot break: clamp around one wire. Just one. Clamp around 2 conductors, hot and neutral together, and the magnetic fields cancel out. You'll get a false reading, close to zero, even with the unit running. Now, once you've got a clean reading, what do you compare it to? The nameplate. You'll see 2 terms out there: RLA and FLA. RLA is rated load amps; that's for compressors. FLA is full load amps; that's for motors, fans, pumps. Take your reading and compare it to the nameplate. Running close to or above that number? That's a red flag. Overcharge, high head pressure, a mechanical problem. Running steady, at or below nameplate? That's healthy. Simple as that. Now that you know, you can help someone else know.