A device in a heat pump that reverses the flow of refrigerant as the system is switched from cooling to heating. Also called a reversing valve or four-way valve.
Swivel
Connection that allows the connected parts to rotate freely so that they do not become twisted together.
Swivel wrench
Swivel wrenches, or saltus wrenches, combine socket and open end wrenches at either end of the tool for versatility and easier access.
Symbol
Mark designating a specific item and representing that item.
Symbol schedule
Legend that defines the symbols on a construction drawing, with their meanings.
Symmetrical
Something that is evenly proportioned with each side having similar characteristics.
Synchronous
Occurring together, simultaneous.
Synchronous generator
An electrical generator that runs at a constant speed and draws its excitation from a power source external or independent of the load or transmission network it is supplying.
Synchronous inverter
An electrical inverter that inverts direct current electricity to alternating current electricity, and that uses another alternating current source, such as an electric power transmission and distribution network (grid), for voltage and frequency reference to provide power in phase and at the same frequency as the external power source.
Synchronous motor
A type of motor designed to operate precisely at the synchronous speed with no slip in the full-load speeds (rpm).
