Open and Closed Case


I know I'm gonna get some eye-rolling here, but it needs to be said.

When we teach electricity to new techs, we use a lot of “water” metaphors. We talk about volts like PSI, amps like flow, and watts like GPM (speaking of GPM in HVAC, check out our article on hydronics HERE). Even the word “flow” gives us a vision of water moving.

When we talk switches and circuits, we say “open” to mean no path/no flow and “closed” to mean a path or flow.

That's the opposite of water.

With water, we “open” the tap when we want flow, and we close it to stop the flow.

With a switch, we “close” when we make a circuit, and we “open” when we break a circuit.

Someone pointed out to me that describing an “open” switch or circuit like a drawbridge may be better. Cars (electrons) can move when the bridge is closed and cannot move when the bridge is open.

It struck me that this water metaphor may be one reason newbies struggle to grasp relays.

Or maybe I'm just overthinking it.

—Bryan

Related Tech Tips

The Troubleshooting Mindset
This article was written by Senior Refrigeration tech Jeremy Smith. Big thanks to Jeremy for his contributions to HVAC School and the tech community. Having spent many years in the trade and many years reading posts from techs on forums and social media, a big issue that I see is that troubleshooting is something of […]
Read more
Keys to Success - Find a Mentor
When I started in the field, I was a 17-year-old helper with one year of tech school under my belt. In other words, I knew nothing. As I've mentioned before, a few experienced techs took me under their wings at different stages, but the most influential was a guy named Dave Barefoot. For whatever reason, […]
Read more
What Makes an Autotransformer Different?
The definition of a transformer is a device that changes the voltages in an alternating current circuit. You may have heard of an autotransformer or a buck-boost transformer, and these terms are usually used for the same type of device; they just highlight different aspects. A transformer does not need to be a buck-boost to […]
Read more

7 responses to “Open and Closed Case”

  1. Never thought about it that way, I too was taught basic electrical that way!

  2. Good point Bryan. I’m sure that does confuse some techs. When it is fully explained and white boarded, most will get it.

    • They get it eventually. I just realized that the way I was explaining may have been making it more difficult than it needed to be.

  3. Nah you ain’t overthinking it. That’s small basic information that confused me the first time talked I was talked to about switches until it was explained to me.
    Something small but very helpful to know.

  4. The new breed of tech who goes to school for this should take an electronics course so they can learn gate logic and circuit logic. Especially if they want the big money of commercial/industrial work in the era of green tech.

    I don’t agree with the water metaphor. Real service techs need to learn what a circuit is. If they can’t get it then there is always install.

    • Hmmm. We have a trade that already has a shortage of techs. I wish everyone had an “engineers mind” but we also need to be practical about it.

      • We have a trade where half to most mechanical problems are caused by techs who learn by blowing something up. That needs to change.

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

loading

To continue you need to agree to our terms.

The HVAC School site, podcast and daily tech tips
Made possible by Generous support from