40 A MCCB with ETU350 — what the ratings mean for your panel
The Siemens 3VA2040-7HN42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for 40 A continuous current across the full ambient range from 40 °C to 70 °C — no derating needed up to that ceiling. That's unusual for a thermal-magnetic breaker; the ETU350 electronic trip unit holds the rating flat through the temperature band, so you don't lose headroom on a hot switchgear lineup. Four poles give you full switching and protection on three-phase plus neutral. The interrupting ratings climb to 330 kA at 240 VAC and stay above 240 kA through 440 VAC, dropping to 187 kA at 500 V and 3 kA at 690 V — that's a high-fault package for a 40 A frame, sized for industrial mains where available fault current is substantial. Designed for line protection, not motor or feeder selective coordination out of the box — the ETU350 is an electronic release with adjustable overload and short-circuit settings, but this variant ships without communication, undervoltage release, or ground-fault monitoring. If you need those, this isn't the trim.
Panel fit — dimensions and IP rating
Footprint is 140 mm wide by 181 mm tall by 86 mm deep — a standard 4-pole MCCB envelope that drops into most SENTRON 3VA switchboard and panelboard layouts without re-drilling gland plates. Front protection is IP40, so it's fine for enclosed distribution boards but not for washdown zones. Maximum power dissipation is 1.2 W at rated load — negligible for thermal budgeting inside a sealed enclosure, but worth noting if you're packing multiple breakers into a small stainless cabinet.