Voltage

What is voltage? Simply put, voltage is “potential.” It is what gives the current in a circuit the potential to flow. But keep in mind, the term “potential” has a few meanings.

For “potential” to exist, there needs to be a reference point. For instance, when I tell you my meter reads 120 Volts AC (“VAC”), I am referring to 120 VAC when testing to Neutral, which is 0 VAC. To drive this point home, consider this: You have two meter leads. If you put one on a live 120 VAC line and wave the other one in the air … your meter will read 0 VAC, even though your line voltage is present. But, when you put your other lead on a known 0 VAC source – such as neutral or a metal surface – your meter will then present you with that 120 VAC measurement. This is voltage potential.

And even going a step further, as you will learn later on, if you put both meters on the same 120 VAC line, your meter will read 0 VAC. This is because there is no potential difference between the 120 VAC at one point in the line, and the 120 VAC a foot down the line. We’ll explore the importance of understanding this in our diagnostic approach in later modules.

But for now, voltage is “potential.” In other words, “What potential does one line have with regard to another?”

Let’s consider electric dryers and ovens, for instance. 240 VAC. What is 240 VAC? How do we get it? Is it one line charged with 240 VAC? No, not really.

When we dive into the 240 VAC realm, we are expanding on “potential” – and to understand this expansion, we need to know what “phases” are.

Phases

Most appliances and household applications work on single phase, 120 VAC, 60Hz electricity. What this means is, regarding neutral, we have a 120 volt sine wave that flip-flops 60 times per second – hence, the 60Hz. When the sine wave is in the upward position, we have 120 VAC with regard to Neutral. A split second later, that sine wave is -120 VAC, which still reads as 120 VAC, since we are comparing it to Neutral. This happens so fast, multimeters read it at 120.

This might be a bit tough to grasp, so we’ll have a video to explain it a bit more in depth with visuals. However, the important thing to understand is that electrons get excited and they do their thing when they have a distance to jump. As we’ll see shortly, electrons are negatively charged little buggers who are always looking for a more positive experience. When our sine wave dips to -120 VAC and drags the electrons along with it, the 0 VAC neutral looks pretty awesome to those electrons, so they blast their way to the neutral. During this trek, what happens to the sine wave? It inverts and becomes +120 VAC. So, the electrons, having reached the 0 VAC from -120 VAC now see a +120 VAC. Where do you think they’re headed?

Electrons

Electrons are the force that get our loads into motion. Electrons make up current, which is also called amps. Amps (current) are the aggregate of electrons passing a given point at any given point. Knowing the exact amount of electrons passing a given point that constitute a single amp isn’t an essential bit of knowledge to retain, but in essence, the more electrons, the more amps.

Ohms Ω

And on the topic of amperage, we would be a sad bunch of repair technicians if we didn’t understand what keeps those amps in check. And believe me when I say I’ve spoken with techs who don’t know what ohms are, and they don’t know what setting to put their meter on. Since you’re taking this course, I assume you don’t plan on being one of those techs.

Ohms (Ω), or resistance, is the restrictive force in a circuit. If you connect a 120 VAC line directly to Neutral, those electrons have an unfettered path and will create an unpleasant scene. While we’re going to dive into it deeper later on, with no resistance, our current will do what it can to reach infinity. Before that happens, we’ll typically see a breaker trip or a transformer on the pole outside become a fireworks display.

The key to remember with appliances in particular is that our loads (such as a heating element or a drain pump) are in essence resistive devices placed in a circuit to prevent amps from going too far on their journey to infinity.

When a load has resistance, we can measure that using the Ohms setting on our multimeter. The multimeter that we sent you is auto-ranging, so that means you don’t have to set the proper ohms scale. I have seen many tech misdiagnose a load as “Open” because they unwittingly had it on the wrong scale.

Power (Watts)

I’m gonna shoot you straight on this one. In my appliance repair journey, I have not found much use for wattage. Now, don’t get me wrong, I am not saying this is irrelevant – it is! What I am saying is, I’m not going to dive too deep into it.

Power, or wattage, is the … power output of a load.

Why I say I don’t find much use with this is because other than using it to find the amp draw on a circuit (say, an oven bake element), I have rarely ever said to myself, “Let me measure the wattage” – except on inverter compressors. 

Now, saying that, I will say it’s still important to understand what it is and what role it plays.

Summary

See? We just breezed right through that. Don’t think to yourself, “that’s weak.” I know it is. But having undergone multiple in-person and online trainings, I have found that most of what they taught me about electricity before talking appliance went right over my head, and I felt like I was relearning what I was taught when they went to the actual appliance and said, “We went over this in the basic electricity course.”

The goal of this course’s structure is to teach you what you need to know on a case by case basis as it applies to the appliance you’re working on, but there are some basics that we need to cover before we jump right in.