Siemens KMB3B800 Molded Case Circuit Breaker
- 800A
- 3 Pole
- Bolt-On
Quantity
Siemens KMB3B800 - 800A 3 Pole Molded Case Circuit Breaker
Re-Certified
Quantity
Description
Designed to handle demanding loads, the Siemens KMB3B800 is a 3-pole, 800A MCCB. It features an interchangeable thermal-magnetic trip unit for reliable fault protection. This bolt-on unit integrates into Siemens P5 panelboards, SB switchboards, and MCCs. For infrastructure updates, this legacy breaker is replaced by the RD63B800 (kit required). Operating on 600VAC systems, it provides a 30kAIC rating at 480V. Load lugs are omitted and must be acquired independently.Specifications
| Brand | Siemens |
|---|---|
| Part Number | KMB3B800-R |
| Series | KMB |
| Amperage | 800A |
| Poles | 3 |
| Mounting Style | Bolt-On |
| Voltage | 240VAC, 480VAC, 600VAC |
| Phase | 3 |
| AIC Rating | 42kA @ 240VAC, 30kA @ 480VAC, 22kA @ 600VAC |
| Frame Type | KMB |
|---|---|
| Terminal Type | Lugs |
| For Use With | Siemens SB Switchboards, P5 Panelboards, Motor Control Centers |
| Wire Gauge | 3 Cables: 250-500 kcmil (Cu/Al) OR 2 Cables: 500-750 kcmil (Cu/Al) |
| Max Wire | 750 kcmil |
| Min Wire | 250 kcmil |
| Trip Technology | Thermal Magnetic |
|---|---|
| Trip Function Code | LI |
| Trip Function | Long-Time, Instantaneous |
| Trip Adjustability | Fixed Thermal, Adjustable Magnetic |
| Available Options | Shunt Trip, Auxiliary Switch, Undervoltage Release, Alarm Switch, Lug Kits |
|---|---|
| Accessories | Lugs Not Included |
| Standards | UL 489, CSA C22.2 No. 5 |
| Approval | CSA, UL |
| Temp Rating | 40C |
| Construction Features | Interchangeable Trip Unit |
Product FAQs
9 answersWhat panelboards and switchboards accept the KMB3B800?
The KMB3B800 is designed for use in Siemens SB switchboards, P5 panelboards, and compatible motor control centers. It requires the appropriate bolt-on mounting hardware for these enclosures.
What are the accepted wire sizes and configurations for the KMB3B800 lugs?
The standard lugs for this breaker accept either three cables ranging from 250 to 500 kcmil or two cables ranging from 500 to 750 kcmil per phase. Both copper and aluminum conductors are supported.
How does the trip unit operate on the KMB3B800?
This breaker features a thermal magnetic trip unit. It provides fixed thermal protection for long-time overloads and an adjustable magnetic trip setting for instantaneous short-circuit protection.
Is the KMB3B800 a current production breaker?
The KMB frame is part of the Siemens legacy molded case circuit breaker family. It is typically sourced as a direct replacement for existing installations rather than for new panel construction.
Can this breaker be DIN rail mounted?
No, the KMB3B800 is strictly a bolt-on circuit breaker. It is not compatible with DIN rail or plug-in mounting systems.
What is the maximum fault current this breaker can interrupt at 480V?
When applied in a 480V AC system, it can safely interrupt up to 30kA of fault current. For systems with higher available fault current, a current-limiting fuse or a breaker with a higher AIC rating is required.
What frame size category does the KMB3B800 fall under?
This breaker is classified under the Siemens M-Frame group. It shares physical dimensions and mounting footprints with other KMB frame breakers.
How do the interrupting ratings scale with voltage on the KMB3B800?
The KMB3B800 provides a maximum short-circuit interrupting rating of 42kAIC when used on 240V AC systems. This rating decreases to 30kAIC at 480V and 22kAIC at 600V.
What does the "LI" trip function code mean on the KMB3B800?
The "LI" designation indicates that the breaker provides Long-Time (L) and Instantaneous (I) protection. The long-time function protects against sustained overloads, while the instantaneous function trips immediately during a short circuit.
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