What it is and what it does
The Siemens 3VA1020-4ED32-0BH0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in distribution panels. It's a 3-pole unit rated at 20 A continuous, with a rated insulation voltage of 800 V. The 20 A rating holds steady from 40 °C through 55 °C, then derates slightly to 19 A at 60 °C and above — useful to know if this breaker lands in a warm cabinet or near other heat sources. Breaking capacity is the headline here: 121 kA at 240 V AC, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at both 500 V and 690 V. That 121 kA figure at 240 V means it handles high-fault scenarios typical on the secondary side of large step-down transformers — useful for service-entrance or main-switchboard positions where available fault current is high. It ships with an undervoltage release (UVR) and a complement of auxiliary switches: two auxiliary switches plus one trip alarm switch (HQ). The undervoltage release will trip the breaker if control voltage drops below a threshold — standard for applications where you need loss-of-voltage protection on a motor feeder or safety circuit.
Panel fit and integration
Dimensions are 130 mm high, 76.2 mm wide, and 70 mm deep — a compact footprint for a 3-pole MCCB with this breaking capacity. The 76.2 mm width (3 inches) matches the standard SENTRON 3VA1 form factor, so it slots into a panel alongside other 3VA breakers without odd spacing. Maximum power loss is 14.5 W. In a dense panel, that heat adds up — factor it into your thermal budget, especially if the breaker is enclosed or adjacent to temperature-sensitive electronics. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The storage minimum matters if the breaker sits in an unheated warehouse before installation — it's rated to survive cold storage without damage.