What this MCCB carries and where it fits
The Siemens SENTRON 3VA2340-5JQ32-0DH0 is a 3-pole molded case circuit breaker rated 400 A at 40 °C with an adjustable thermal-magnetic trip range of 600 A minimum to 4 000 A maximum — meaning you set the pickup to match the feeder or branch load, not the other way around. Its interrupting capacity hits 187 kA at 240 V, drops to 121 kA at 415 V and 440 V, then 75.6 kA at 500 V, and 7.5 kA at 690 V — so the SCCR you need for the fault-current study determines which voltage column you read. Designed for line protection, it includes an undervoltage release and a communication function for remote monitoring or trip-signal integration into a BMS or PLC.
Thermal derating — the real current rating changes with panel temperature
At 40 °C, 45 °C, and 50 °C the breaker holds 400 A continuous. At 55 °C it derates to 375 A, at 60 °C to 350 A, at 65 °C to 325 A, and at 70 °C to 300 A — so a panel running hot near the top of the enclosure loses 25 % of the rated current. Mounting in a sealed, high-ambient cabinet means you size the breaker for the derated value, not the nameplate 400 A. The 98.5 W max power loss contributes to the internal heat rise — account for it in the thermal budget.
Auxiliary and alarm switching — what the HQ suffix means
The breaker ships with 2 auxiliary switches plus 1 trip alarm switch (HQ designation) — so you get a separate contact for remote status (open/closed) and a dedicated alarm contact that changes state only on a trip event, not on manual opening. The basic switch variant is 3VA2340-5JQ32-0AA0 — if you see that code, it is the same frame and trip but without the aux/alarm block. The -0DH0 suffix adds the HQ aux block and the undervoltage release.