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Siemens BQD370 three-pole bolt-on breaker, grey toggle, compact industrial housing

SIEMENS

SIEMENS BQD370 70A 3 Pole 480V AC Circuit Breaker

SKU CH-QE58-FR1NT

Protects three-phase circuits up to 480V AC with a 70A bolt-on breaker rated for 14kA interrupting capacity

  • 70 A three-pole protection for 480 V AC three-phase circuits
  • 14 kA interrupting rating at 480 V AC handles high fault currents
  • Bolt-on mounting fits Siemens P1 panelboards directly
  • Compact 4.5 in frame saves panel space
  • Rated for continuous operation up to 104 °F

Application fit

The SIEMENS BQD370 is a 70A three-pole miniature circuit breaker rated for 480V AC. It is designed for bolt-on installation in Siemens P1 panelboards where a standard toggle actuator and 14kA interrupting rating at 480V AC are required. The 100A frame size suits loads that stay within the 70A trip setting. It is not for DC circuits, panels outside the P1 series, or applications needing a higher AIR rating than 14kA at 480V AC.

Thermal and power behaviour

The breaker carries 70 amps continuously at up to 104 degrees Fahrenheit ambient without nuisance tripping. Power dissipation appears as heat across the lug terminals during normal operation; no active cooling or fan is involved. The toggle actuator provides a clear mechanical indication of status. There is no acoustic noise from the device itself under load.

Deciding specification

The single figure that determines fit is the 14kA maximum AIR rating at 480V AC. If the available fault current at the panelboard exceeds this value, the breaker cannot be applied safely regardless of its ampere rating or frame size.

Highlights

  • 70 A three-pole protection for 480 V AC three-phase circuits
  • 14 kA interrupting rating at 480 V AC handles high fault currents
  • Bolt-on mounting fits Siemens P1 panelboards directly
  • Compact 4.5 in frame saves panel space
  • Rated for continuous operation up to 104 °F

Specifications

BrandSIEMENS

Questions about this item

How do I bolt the BQD370 into a Siemens P1 panelboard, and what step do installers often miss?

Mount the 4.5 in long breaker onto the P1 bus using the bolt-on lugs; the step often missed is torquing the lug bolts to the panelboard manufacturer's specified value so the 70 A connection stays secure at 480V AC.

What maintenance or replacement will the BQD370 need after years of service?

Periodically inspect the toggle actuator and bolt-on terminals for overheating or corrosion; replace the breaker if it trips near its 14 kA interrupting limit or shows contact wear, as no user-serviceable parts exist inside.

What is the first limit the BQD370 hits under sustained heavy load?

The 104 °F maximum operating temperature is reached before the 70 A thermal trip curves activate, so sustained loads near 70 A in a warm enclosure will cause nuisance tripping first.

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