What this 1-pole MCCB carries — and where it fits
The Siemens SENTRON 3VA4120-5ED54-0AA0 is a 1-pole molded-case circuit breaker (MCCB) in the system-protection version, rated 20 A continuous at 40 °C with a TM210 thermal-magnetic release (LI characteristic — long-time and instantaneous protection). Its interrupting capacity is 85 kA at 120 V AC, 35 kA at 277 V AC, and 18 kA at 347 V AC — numbers that govern where it can be placed in a distribution panel without cascading upstream. The 85 kA at 120 V is the headline figure; the 18 kA at 347 V is the one that matters for 347/600 V wye systems common in Canadian and some US commercial installations. The 75.1 mm depth and 50.8 mm width mean this breaker fits the standard 1-pole footprint in a SENTRON distribution panelboard — no extra gutter space needed for the line-side lugs.
Thermal derating — real-world current at panel ambient
The 20 A rating holds at 40 °C and 45 °C. At 50 °C it derates to 19 A, at 60 °C to 18 A, and at 70 °C to 17 A. If the panel ambient runs above 40 °C — common in enclosed switchgear or near heat sources — size the load circuit at the derated figure, not the nameplate 20 A. Maximum power loss is 2.8 W, low enough that ganging multiple 1-pole breakers side-by-side doesn't drive a significant temperature rise in the enclosure.
Panel integration notes
IP40 on the front — protected against tools and wires larger than 1 mm, but not sealed against washdown. Suitable for indoor panel mounting, not for wet or outdoor locations without an additional enclosure. No trip indicator, no undervoltage release, no communication function, no motor drive option. This is a plain thermal-magnetic breaker for straightforward branch-circuit protection — no auxiliary signaling or remote trip capability built in. UL file MEAB covers the UL listing for the US market. Operating temperature range is -25 °C to 70 °C; storage range -40 °C to 80 °C.