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Siemens 5SY8340-8BB08 — 3-Pole MCB (DIN Rail)

Siemens 5SY8340-8BB08 SENTRON MCB, 3P, D Curve, 25kA @ 400V

MPN5SY8340-8BB08
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Siemens SENTRON 5SY8340-8BB08, miniature circuit breaker, 3-pole, D tripping characteristic, 25 kA breaking capacity at 400 V AC per IEC 60947-2, magnetic-only trip, 3 modular width units.

Sourced new & surplus through independent channelsAuthenticity-screened · ESD-safe packingListing updated Aug 2026

Specifications

5SY8340-8BB08 — Identification
ParameterValue
Brand nameSENTRON
Number of poles3
Pole configuration3P
Suitability for operationMechanical engineering / industry
5SY8340-8BB08 — Protection
ParameterValue
Tripping characteristic (curve)D
Breaking capacity per IEC 60947-225 kA
Overvoltage categoryIII
IP protection classIP20, with connected conductors
Pollution degree3
5SY8340-8BB08 — Electrical
ParameterValue
Rated voltage (AC, multi-phase)440 V
Voltage type (AC/DC)AC
Supply frequency range50/60 Hz
Power loss per pole at rated current (AC, hot)3 W
Mechanical service life (operating cycles, typ.)10 000
Neutral conductor switchingNo
Rated voltage (AC, single-phase)440 V
5SY8340-8BB08 — Mechanical
ParameterValue
Modular width units3
Mounting positionany
Width54 mm
Height90 mm
Depth76 mm
Installation depth70 mm
Terminal tightening torque, max.75 °C
Terminal tightening torque, min.-40 °C
Combined terminal, topYes
Combined terminal, bottomYes
Fastening methodQuick assembly system
SealableYes
Accepts supplementary devicesYes
5SY8340-8BB08 — Environmental
ParameterValue
Halogen-freeYes
Silicone-freeYes
Influence of surrounding temperaturemax. 95% to 55°C, max. 55% to 70°C, max. 35% to 75°C
Vibration resistance (IEC 60068-2-6)±1mm at 5 to 25Hz; 50m/s² at 25 to 150Hz

Product details

The magnetic-only trip (no thermal bimetal) means it reacts solely to short-circuit currents, not overloads, so it's paired with a separate overload relay or motor-protective device. IP20 with connected conductors — standard for panelboard use, not for wet environments.

The 25 kA rating at 400 V AC (IEC 60947-2) is the headline number. For UL 1077 / CSA C22.2 No. 235 applications, the rating drops to 5 kA — a common derating when moving from IEC to North American supplementary protector standards. If your panel SCCR calculation depends on this device, the 5 kA figure is the binding limit for UL-listed assemblies. That's higher than a B or C curve, so it won't nuisance-trip on motor start or capacitor bank inrush. But it also means the let-through energy (I²t) is higher during a fault — verify downstream cable and device withstand if coordinating with a smaller branch.

Panel integration

Sealable design allows lockout/tagout provisions.

Environmental and electrical margins

Humidity derating applies above 55 °C: max 95% RH up to 55 °C, then 55% RH to 70 °C, then 35% RH to 75 °C. Vibration resistance per IEC 60068-2-6: ±1 mm at 5–25 Hz, 50 m/s² at 25–150 Hz — survives normal machine vibration but not continuous high-frequency shaker tables. For a 3-pole breaker that's 9 W total — negligible for thermal budgeting in most panels, but worth summing if you have dozens of breakers in a sealed enclosure.

Frequently asked questions

What is the breaking capacity of the 5SY8340-8BB08?

25 kA at 400 V AC per IEC 60947-2, and 5 kA per UL 1077 / CSA C22.2 No. 235.

Where can I buy the 5SY8340-8BB08?

Sourced and quoted to order against an RFQ through independent distribution. Availability and current pricing confirmed at quote time.

What does the D tripping characteristic mean for this MCB?

The D curve trips magnetically at 10–20 times rated current, making it suitable for loads with high inrush like motors and transformers. It is a magnetic-only trip — no thermal overload element — so it must be paired with a separate overload protection device.

Will the 5SY8340-8BB08 fit in a panel designed for a 5SY4310-7CV?

Both are 3-module-width SENTRON MCBs on the same DIN-rail footprint, so the mechanical fit is identical. The key difference is the 5SY8340-8BB08 is a D-curve magnetic-only breaker with 25 kA breaking capacity, while the 5SY4310-7CV is a different rating/curve — verify the trip characteristic and interrupting rating match your circuit requirements before substituting.

MPN
5SY8340-8BB08