Theory and troubleshooting using short modules packed with images to make learning quick and easy.
Lessons on electrical theory, circuits, components, and meter readings. For students and working technicians troubleshooting electrical faults.
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 flame sensor exists to prove a flame across the burners. Without this flame sensor, there’s a risk of releasing gas without flame and risking an explosion upon ignition. The flame sensor is positioned on the opposite end of the burners from the igniter to ensure all burners ignite correctly. Upon a call for heat,…
When passing an alternating current through a coil of wire, like a transformer or a solenoid valve, the expanding and collapsing magnetic field created by the alternating current induces a back-voltage (back EMF) in the coil which goes against the supply voltage. All coils of wire will have this. If you have two sets of…
Solenoids operate on the principle of electromagnetism. With current moving through a conductor, a magnetic field forms around the conductor. A single straight conductor by itself will not generate a strong magnetic field, but if the conductor is wound into a tight coil, it will produce a strong magnetic field. Each loop of the coil…
A GFCI is not the same as a breaker or fuse. It exists to protect people whereas a fuse or breaker exists to protect the conductors in your house. A GFCI works on the principle that the current moving through a circuit should be the same at all points of the circuit. The GFIC monitors…
Fuses A fuse is designed to break current flow in the circuit when there's excessive current flowing through a circuit. A fuse contains a strip of metal, which when exposed to higher current than designed for will melt/break before any damage can be done to the wires in the circuit. Example: A circuit with #14…
Circuit breakers and fuses will protect against both overloaded circuits as well as overcurrent in a circuit. It's important to know the difference between both. Overload An overload in a circuit is when there's an increase of current (amperage) above the rating for the circuit. If the circuit is allowed to draw the excess current,…
So let’s quickly recap the representations for voltage, resistance, and amperage in the Ohm’s Law triangle: E = Voltage (electromagnetic force) I = Current (amps) R = Resistance For a given resistance, the current is directly proportional to voltage. That said, if you increase the voltage in a circuit with a fixed resistance, the current…
A parallel circuit allows for more than one path for current to flow. We have the same two loads from the series circuit below, but we have two paths now for electrons to flow. Each pathway for current to flow is called a branch. 2 loads in series Vs. 2 loads in a parallel circuit…
series noun a number of things, events, or people of a similar kind or related coming one after another. So given the above definition, a series circuit is when there’s only a single path for current to flow. Any break in the wiring or a faulty load will stop current throughout the entire series circuit.…