Hvac School - For Techs, By Techs

In this short podcast episode, Bryan dives into NTC, PTC, and thermocouples. NTC and PTC are two types of thermistors, and all three tools are used to sense temperature. Thermistors are resistors that change their resistance based on a change in temperature. They must be powered, and the resistance changes the amperage. You can test a thermistor with an ohmmeter at a fixed temperature. The best temperature for testing is the thermistor's rated temperature, typically 77 degrees Fahrenheit.  NTC thermistors are negative temperature coefficient thermistors; as the temperature decreases, the resistance increases, and vice versa. Temperature and resistance are inversely proportional. PTC thermistors are positive temperature coefficient thermistors, and the temperature and resistance are directly proportional. These types of thermistors are usually quite accurate, and they are common in thermostats. PTCs are common in certain types of hard start kits, in which they help take the start capacitor or start winding out