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HVAC School - For Techs, By Techs

Dec 1, 2016

In this episode, Bryan and Nathan have a banter-filled conversation about electrical components that confuse techs. If you are looking for a serious educational episode, we suggest you look elsewhere.

Low-voltage circuits may confuse the new technician because the "common" terminology is far too common in the circuit. (See how confusing it sounds in everyday use? We don't have to say "common this," "common that," but we do.)

Single-phase power can also be confounding for technicians. One phase of line voltage comes in, and it gets split when it enters the circuit. That is why we also call single-phase power "split-phase" power.

Another perhaps surprising area of confusion is normally open (NO) and normally closed (NC) switches. Water metaphors could potentially contribute to the confusion, as shutting off the faucet seems analogous to "closing" a circuit, but it actually has the same effect as "opening" a switch. As instructors, we need to clarify that "open" and "closed" are different from doors, faucets, etc. "Open" means that there is no path, and "closed" means that there is a path. "Normally" merely indicates the state of the switches when nothing is happening.

Sometimes, transformers can be difficult to understand. A transformer is an inductive load that alters voltage and "steps it down" to a secondary voltage. Loads are what "do something" in a circuit, like a light bulb or motor. Inductive loads are magnetic (motors and transformers), and resistive loads create heat (light bulbs and toasters). Inductive and resistive loads are perfect subjects for PG-13+ metaphors, as Nathan demonstrates.

Join Nathan and Bryan on a vulgar learning adventure of bad metaphors as they discuss:

  • Relays
  • Sequencers
  • Inductive loads
  • Resistive loads
  • Blower/heat interlock
  • Transformers
  • Contactors


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