Siemens SENTRON 3VA1120-4EF36-0HA0 — 20 A MCCB with TM240 release
The Siemens SENTRON 3VA1120-4EF36-0HA0 is a 3-pole molded case circuit breaker (MCCB) rated for 20 A continuous current, with a TM240 thermal-magnetic overcurrent release. It is designed for line protection in distribution panels where the load current stays within 20 A and the available fault current at the panelboard can reach 121 kA at 240 V. The breaking capacity varies with system voltage: 121 kA at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at 690 V. For a 480 V delta service, the 52.5 kA rating at 440 V is the closest published figure — the actual SCCR at 480 V will be lower, so verify coordination with the upstream device. The rated insulation voltage is 800 V. Thermal derating is minimal up to 50 °C (full 20 A), then drops to 19.2 A at 55 °C, 18.8 A at 60 °C, 18.4 A at 65 °C, and 18 A at 70 °C. If the panel ambient runs above 50 °C, the continuous current must be reduced per these values — the breaker does not trip early; it just carries less before the bimetal element reaches its calibrated curve.
Physical fit and panel integration
Dimensions: 130 mm high, 76.2 mm wide, 70 mm deep. The 76.2 mm width is a standard 3-pole footprint. Front IP40 protection means the breaker is protected against tools and wires >1 mm, but not against water ingress — install inside a panel with a door. No auxiliary contact or communication module is fitted; the auxiliary trip is a shunt trip (STL) with order code 3VA9688-0BL30, which must be ordered separately if remote tripping is required.
Key ratings and what they mean for the buyer
The TM240 overcurrent release is a thermal-magnetic design: the thermal element handles overload protection (time-delayed, inverse-time curve), and the magnetic element handles short-circuit protection (instantaneous). The '240' designation indicates the magnetic trip threshold is 240 A (12x the 20 A rating), so the breaker will hold through motor inrush up to that level before the magnetic coil pulls in. No undervoltage release, no phase-failure detection, and no ground-fault monitoring are built in. If any of those functions are needed for the application, an external relay or a different 3VA variant with those options must be specified. The shunt trip (STL) is the only auxiliary release fitted — it allows remote tripping by applying a control voltage to the 3VA9688-0BL30 accessory. Latching endurance is 15,000 operations under no-load conditions.