Category: HVAC Components

Thermocouple and thermopile

Thermocouple and thermopile

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. To give you an understanding of how small of a voltage that is, 1,000 millivolts is 1 volt. continue reading...

Potential relay

Potential relay

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 destroy the windings in the motor within seconds. Using a start capacitor with a potential relay is known as a hard start kit. continue reading...

Relay and contactors

Relay and contactors

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 power for the 24v electromagnet coil seen with each horizontal line. Only one set of terminals needs to be powered. In most cases, you’ll only ever use one set.

Terminal 1 of this relay is the common terminal. It’s “common” to terminal 2 and 3. Terminal 1 will be our terminal that will pass on power to and/or complete the circuit between terminal 2 or 3 when 24v is applied to the electromagnet. continue reading...

Switches

Switches

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 (NO) or normally closed (NC). They will either make or break a circuit. continue reading...