Varmstart

Varmstart is a term used in Swedish, Norwegian, and Danish technical literature to denote starting a system while it is already at an elevated or at least non-ambient temperature. The phrase is equivalent to the English term “warm start” and is commonly contrasted with “cold start,” which describes starting from a cold or ambient-temperature state, and in some contexts with “hot start,” which refers to starting from a very hot or fully heated state.

In automotive and mechanical engineering, varmstart describes starting an engine or machine after it has reached operating temperature. Starting from a warm state generally reduces wear and improves efficiency compared with a cold start, where brittle lubricants and thermal expansion can cause greater stress. In this context the concept is used to optimize procedures, fuel usage, and emissions during restart after normal operation, minor stops, or warm restarts.

In information technology and computing, varmstart is used to refer to a warm reboot or warm boot—restarting a computer without a full power-down, allowing stored state in memory to be retained. This is typically faster than a cold boot, but may not clear all transient faults. The term may appear in Scandinavian manuals and documentation to distinguish reboot routines from complete power cycles.

In process engineering and industrial controls, varmstart can describe restarting equipment after it has cooled only partially, or after a short shutdown where the system remains warm. The exact definition and procedures vary by industry and organization.

See also: cold start, hot start, warm reboot.