Theory and troubleshooting using short modules packed with images to make learning quick and easy.
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Air conditioners and walk-in coolers do not create cold. They remove heat from an area where you do not want it and dump it somewhere where it does not matter. To move that heat, the system circulates refrigerant through a closed loop of copper tubing. By changing the pressure of the refrigerant, the system forces…
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…
Mastering the Vitals of the Refrigeration Cycle If you want to know what is actually happening inside a refrigeration system, you have to look past the pressures. Gauges are a great start, but they only tell half the story. To truly diagnose a system, you need to understand the relationship between temperature and pressure. Superheat…
Air Combustion air: Air required to complete combustion (primary air and secondary air)Ambient air: This is the air that surrounds usDilution air: The ambient air admitted to the draft hood, draft diverter, or draft regulator. It's used to cool the venting system and vent the flue gasesExcess air: The portion of the combustion air supplied…
Take any chance you have to skip connecting refrigerant gauges to a system. Each time you attach your gauges, you remove a small amount of refrigerant from the system through your hoses. The longer the hoses, the more charge that's lost. After a few times of doing this, you might end up chasing a leak…
Supply Air Sheet metal box connected directly to the supply outlet of the HVAC appliance that directs the heated or cooled air to the ductwork. Return Air Most units have multiple, or at least one return duct in the house moving conditioned room air to the HVAC unit. When air is forced through the supply…
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 following sequence is for the Rinnai tankless water heater. If you can learn this sequence, you will have a good understanding across the board for all brands out there as they all follow a similar sequence of operation. Step 1. Upon a call for hot water, the water flow sensor will sense water flow…
The following is an example of a 90%+ furnace. Things may differ slightly from manufacturer to manufacturer, but they’ll all be pretty close, and theory will remain the same. Furnaces equipped with a control board are continually checking to confirm rollout switches and the high-limit switch are all closed. It also sends 80V - 110V…
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…