Potential relays are commonly found on many smaller, single-phase, capacitor-start, capacitor-run motors in the HVACR industry. Their function is to assist in starting the electric motor. Potential relays are sometimes referred to as voltage relays because they rely on the back-electromotive-force (BEMF) or voltage, which is generated by the motor for their operation.
Even though some manufacturers are incorporating solid state relays with their equipment, the potential relay is still probably the most popular small horsepower motor starting relay because of its ease of operation and troubleshooting. Because of the popularity and abundance of potential relays in the HVACR service field today, it is of utmost importance for service technicians to understand not only how this starting relay operates but also how to troubleshoot the components that make up the relay.