What this 4-pole D-curve 63 A MCB does for your panel
The 4 MW (72 mm) width on DIN rail matches the standard 4-module footprint; any mounting position is acceptable, so it fits tight enclosures without derating.
D-curve and 63 A — why that matters for motor and transformer circuits
A D-curve MCB holds through the 10–20× In magnetic trip zone, which means it passes the starting surge of a 63 A-rated motor or a 63 A-rated transformer without clearing. The 63 A continuous rating at 400 V AC gives roughly 43 kW of three-phase motor load (at 0.85 PF) before the thermal element begins to move. For an ammonia compressor or a cold-store condenser fan group, that D-curve is the difference between a clean start and a nuisance trip every time the contactor pulls in. If your panel feeds a transformer with higher SCCR, you will need upstream current-limiting fuses or a higher-rated MCCB to keep the 5SL6463-8CC within its rated short-circuit capacity.
Lifecycle and sourcing — active, not a phase-out part
The SENTRON 5SL6 series is Siemens' standard MCB family for residential and infrastructure duty. The 5SL6463-8CC is the 4-pole, 63 A, D-curve variant with 6 kA breaking capacity. No official successor has been announced, and no phase-out date is on record.
Mounting and wiring — what fits and what does not
The 72 mm width occupies four 18 mm module spaces. Terminal screws accept solid or stranded copper from 0.75 mm² up to 25 mm²; tighten to 2.5–3 N·m.
Environmental limits — cold-store and freezer considerations
That covers most refrigerated spaces down to -25 °C ambient; below that, the thermal trip element may shift and the breaker could nuisance-trip or fail to trip on overload. In a -30 °C freezer room, locate the MCB in a heated panel enclosure or use a cold-rated supplementary protector. Maximum operating humidity is periodically 55 °C with 95% relative humidity — typical for unheated electrical rooms in cold stores where condensation forms on the panel door. The IP20 enclosure does not prevent internal condensation; a panel heater or breather drain is recommended.