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.
A field guide to avoiding premature valve condemnation and mastering the 4-way mechanism. The reversing valve is the heart of a heat pump's ability to provide year-round comfort. It is the component responsible for seasonal switching, physically redirecting refrigerant flow to turn an air conditioner into a heater. For many technicians, however, the reversing valve…
You'll run into these terminals commonly on older standing pilot furnaces. TH/TR is a common connection, but that doesn't explain much in itself. We'll overview which each of these terminals is intended for: TH – The 24v hot leg from the thermostat on a call for heat (R+W closing on the thermostat) to the gas…
The thermostat is the command center for an HVAC system. The thermostat is what will switch the equipment on and off. Most people are familiar with the thermostat on the wall for their heating and cooling, but they're in almost everything from water heaters to freezers and kitchen equipment. Modern thermostats sense temperature using a…
Improper condensate trapping can cause a lot of property damage. It's necessary that a drain line is installed correctly to avoid damage to a residence or business. Evaporators coils are installed to allow a blower to either push or pull air across the coil. The pressure, either positive or negative applied across the coil is…
Thermistors are used to sense/measure temperature. You will find them in ductless splits to detect evaporator coil or condenser temperature, temperature measuring devices such as a digital thermostat, ambient air temperature, PTC start relay, and supply or return air temperature. The name thermistor is a combination of "thermal" and "resistor." A thermistor changes electrical resistance…
The plastic orifice shown in the image above is a snubber. Sometimes the appliance will experience sudden pressure changes such as wind against the exhaust or the burners igniting. The snubber is designed to only allow a designed amount of pressure to be pulled against the switch at one time. The insert should not be…
Two different fan center controls Fan center controls generally are found in older standard furnaces. These are added to separate the heating side from the air conditioning side and added while air conditioning is installed. Newer furnaces have everything controlled via the control board. Older atmospheric furnace fans are controlled by temperature and a temperature-controlled…
The igniter is what's going to ignite the gas in the combustion chamber. Two of the most common igniters are the silicon carbide and silicon nitride. Silicon Carbide Silicon carbide is among the older of the hot surface igniters. They come in different styles, and most of them run off 120v. They are very fragile…
Inshot Burners There are many different kinds of burners. We're mainly going to focus on the inshot type burner as seen above. The inshot burners are in most modern furnaces. A combustion blower is used to pull the flames through the burner tubes into the heat exchanger. Burners are used to prepare the air:gas mixture…
Furnace control boards can be very intimidating for newer technicians without much experience working with them. They'll typically have many wires running to/from them, flashy lights, bulky built-in relays, resistors, and capacitors. It all looks very confusing, but it's really not. Ignition control boards Ignition control boards are typical in older systems. They control the…