What it is and what it does
The Siemens SIRIUS 3RB2036-1UB0-ZX95 is a solid-state overload relay for three-phase motor protection. It monitors current in the main circuit and trips on overload according to Class 10E — meaning it will disconnect within 10 seconds at 7.2× the set current, a standard speed for general-purpose motor starting. It mounts directly onto a contactor (contactor mounting), saving DIN-rail space in the panel. The 55 mm width and 92 mm height keep the footprint compact for a 3-pole device.
Key ratings and what they mean for fit
Trip Class 10E is the headline rating: it defines the thermal memory curve for motor starting. A Class 10E relay is a good fit for standard induction motors that start unloaded or with low-inertia loads — pumps, fans, compressors. It's not intended for high-inertia starts that need a longer trip class like 20 or 30. The auxiliary contacts are rated for switching: 2 A at 24 V, 4 A at 120 V, 3 A at 230 V. That covers typical PLC input or contactor coil signals. The 6 kV surge voltage rating and 2 kV burst immunity (IEC 61000-4-4, severity 3) mean it will hold up in industrial electrical environments without nuisance trips from transients. Terminals accept solid wire from 0.5 to 4 mm² (2x 0.5 to 2.5 mm²) and stranded up to 35 mm² (1x). That covers most motor power wiring up to about 15 kW depending on the contactor match. The screw-type terminals are standard for panel wiring.
Where it's used
This overload relay is designed for motor control centers and individual motor starters in industrial automation. The ATEX Ex II (2) GD certification means it can be used in Zone 22 (dust) and Zone 2 (gas) areas when paired with an appropriate enclosure — common in food processing, chemical plants, and grain handling where explosive atmospheres are a risk. The 100 % relative humidity rating and -25 to +60 °C operating range suit it for washdown areas and outdoor cabinets, provided the enclosure keeps direct spray off the terminals.
Integration notes
Mounting position is any orientation, which simplifies panel layout. The 109 mm depth is the dimension from the contactor face to the back of the relay — check clearance against the back panel or enclosure wall, especially in shallow cabinets. The solid-state design means no bimetals to age, so trip accuracy stays consistent over time. No power dissipation per pole (0.02 W) means negligible heat contribution inside the enclosure.