Lockout/Tagout Basics
DISCLAIMER: HVAC School is NOT an official OSHA safety training resource! Although we provide safety tips in good faith, our website is not a substitute for safety training from an authorized OSHA training source.   Locking out and tagging equipment is one of the most basic safety procedures in general industry and maintenance work, especially […]
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Crankcase Heaters and Single Pole Contactors
We keep 2 pole 40 amp 24v coil contactors on all of our vans. They are versatile, reliable and you can replace most residential A/C contactors with them. There are a few things to watch for though, especially when you have a crankcase heater. Many brands power the crankcase heater constantly and shut it on […]
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Short Circuits
The term “short” has become a meaningless phrase in common culture to mean “anything that is wrong with an electrical device”. A short circuit is a particular fault that can mean one of two things in technical lingo. Any two circuits that are connecting in an undesigned manner. This would be the case if a […]
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An Electric Heat Mistake
I started working as a tech when I was 17 years old, fresh out of tech school. My first winter out on my own I went to a service call in an older part of Orlando, a part of town I had never worked on before. It was an especially cold winter that year, and […]
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Isolation Diagnosis
There are many great diagnostic tools available to the service technician today, but I shaven't found a tool as versatile than the simple isolation diagnosis. There are many ways this concept can be applied but let's start with some examples so you get what I mean. Low Voltage Short Circuit Isolation Diagnosis You arrive on […]
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The Unexpected Result of Series Circuits
We do this exercise when I teach electrical basics where we sit down and connect a 10 watt bulb to a power supply and through a switch. A SUPER SIMPLE circuit, the kind you might have learned about in high school science class. But then I grab another 10 watt bulb and tell them to […]
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Strip Control Wires Properly
Erich Vinson is a tech from Colorado and one of the most entertaining people I interact with online. He wrote this quick tech tip on stripping back the outer jacket properly on control wires and it happens to also be something I preach. Thanks Erich. In the first picture (above), you can see what happens when […]
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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 […]
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Grounding and Bonding Myths
Grounding is an area of many myths and legends in both the electrical and HVAC fields. This is a short article, and we will briefly cover only a few common myths. For a more detailed explanation, I advise subscribing to Mike Holt's YouTube Channel HERE. Myth – Current Goes to Ground Actually, current (electrons) will […]
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