Panel fit and derating
The Siemens 5SQ2170-2YA03 is a 1-pole SENTRON miniature circuit breaker with C-curve tripping, rated 3 A at 30 °C and 240 VAC. EN 60898 certifies the breaker for overcurrent protection in household and similar installations. For industrial feeder panels with higher prospective fault current, check the upstream SCCR coordination. Temperature derating is published: at 40 °C the continuous rating drops to 2.78 A, at 50 °C to 2.61 A, and at 60 °C to 2.4 A.
The C-curve (tripping characteristic class C) means the magnetic trip fires between 5× and 10× In — so for a 3 A breaker, instantaneous trip starts between 15 A and 30 A. If the load is purely resistive with no inrush, a B-curve would give tighter protection; for high-inrush welders or drives, a D-curve would avoid nuisance trips. This C-curve is the general-purpose middle ground. Degree of pollution 3 and overvoltage category 3 mean the breaker is rated for the conductive environment inside a typical industrial panel — not for clean-room or sealed electronics cabinets. Pollution degree 3 permits occasional condensation and temporary conductivity; overvoltage category 3 covers fixed-installation equipment with transient overvoltages up to 4 kV at 240 VAC.
Installation note
Installation depth is 55 mm, which is the standard SENTRON 5SQ footprint. It occupies one 18 mm modular-width unit on the DIN rail. The single-pole design switches only the line conductor — neutral conductor switching is not provided (the product component field confirms no neutral switching). For single-phase circuits where the neutral must be switched, pair this with a compatible neutral-switching module or specify a 2-pole variant.