Theory and troubleshooting using short modules packed with images to make learning quick and easy.
Lessons on individual HVAC components and how each part works. For students and working technicians identifying parts and their function.
The side facing outside furnace / the side facing inside of the furnace Flame rollout switches are mounted around your burners. They exist to sense when/if the flame were ever to pose a risk to the homeowner. These are usually bimetal switches that warp when heated to break the heat cycle when they sense a…
Above images are two of the more common high limits found in residential and lite commercial furnaces Overhead view with the supply air plenum removed so you can see into the furnace A high-limit switch is a bi-metal snap disc switch that warps when heated to break a heat cycle and used to protect the…
Thermocouple A thermocouple is a type of flame safety that prevents the gas valve from dispensing the gas into the burners without the presence of a flame. These are found mostly in older standard pilot appliances including (mostly older) furnaces, water heaters, and unit heaters. A typical thermocouple will produce upwards of about 30 millivolts.…
There are two types of capacitors you'll encounter in HVAC field. We have the run capacitor and the start capacitor. Both are measured in microfarads which you will see labeled as uf, µF, or mfd. Capacitors are used only in single-phase motors. You will not see a capacitor in a three-phase unit. Run Capacitor Max…
The potential relay is used in all capacitor start/capacitor run motors. They're also used in capacitor start/induction run motors. However, it's rare to see that style of a motor in residential and lite commercial in our industry. The potential relay may also be called a start relay. Without it, the start capacitor could explode or…
Relay We’ll be using the most common type of relay in residential service, a 24v relay. A relay is an electronically operated switch that opens and closes using an electromagnet. The electromagnet is a coil of wire that when powered acts as a magnet to close/open a switch. The above image has two banks of…
A switch opens and closes to allow the flow of electric current or to stop it. There are many types of switches including, but not limited to manual switch you would have to turn on an off, switches reacting to pressure, heat, or to water or air. Switches are designed to be either normally open…