MCCB for high-fault panels — what the ratings mean
The Siemens 3VA1120-5EF36-0BH0 is a SENTRON molded case circuit breaker (MCCB) with three poles, rated 20 A continuous at 40 °C and carrying a 187 kA interrupting capacity at 240 V — that is the short-circuit current it can safely clear without welding contacts or venting arc gas into the enclosure. At 415 V the breaking capacity is 121 kA; at 440 V it is 75.6 kA; at 500 V and 690 V it holds at 17 kA. The 800 V rated insulation voltage means the internal creepage and clearance are designed for 800 V systems, so the breaker can be applied in 480/277 V or 600 V panels with margin. This version includes an undervoltage release (UVR) — when control voltage drops below the dropout threshold the breaker trips, which is standard for emergency-stop or undervoltage-protection schemes. It also ships with two auxiliary switches plus one trip alarm switch (HQ type), so you get status feedback for the main contacts and the trip event without adding external relays.
Thermal derating and power loss
The breaker holds its full 20 A rating from 40 °C up to 55 °C; at 60 °C it derates to 19 A, and at 70 °C it stays at 19 A. That is a shallow derating curve, so in a warm panel the part still delivers close to nameplate. Maximum power loss is 14.5 W — useful to know when calculating enclosure heat rise.
Mechanical fit and panel integration
Dimensions are 76.2 mm wide (3 in), 130 mm tall (5.12 in), and 70 mm deep (2.76 in). The 3-pole footprint matches standard SENTRON 3VA panel cutouts and bus-bar centers. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C, so it can sit in an unheated warehouse before installation.