High-pressure switches are used on many refrigeration systems. They are designed to shut down a compressor if the system’s high pressure rises above an unsafe level, not allowing the compressor to restart until the pressure returns to a safe level. High-pressure switches are available with either an automatic or manual reset.
An automatic reset will automatically restart the compressor when the pressure falls to a safe value. A manual-reset high-pressure switch needs to have an operator manually press a reset button in order to restart the compressor. They are also available with either an adjustable cut-out setting that could be adjusted by a technician, or fixed settings, which cannot be adjusted by a technician.