What is a dry contact and no volt contact in the context of electrical engineering?

Answer 1

A "dry" contact is a contact that is not initially connected to a voltage source. It could be stand-alone, such as a pressure switch mounted on a boiler. Or, if the contact is mounted as part of an electrical unit that has a power source, then the "dry" contact has no pre-wired electrical connection to that power source. For example, a magnetic motor starter may have an extra contact that is not connected to the control circuit that starts and stops the motor. However, when the motor starts, the "dry" contact changes state, because the mechanical action of the starter moves the contact. This "dry" contact could then be wired to devices/circuits that are separate/remote from the motor starter circuits. I do not recognize the term "no volt contact" but I suspect that it is the same thing. A specific type of dry contact in the USA is a "form C" contact which is a three wire contact: Normally Open(NO), Normally Closed (NC), and a Common (C).