Eaton Magnum SB insulated-case power circuit breaker
Manufacturer: Eaton
Eaton Magnum SB insulated-case breakers for UL 891 switchboards, the Magnum family's economy frame
This model is part of SecondWatt’s switchgear research catalogue. Specifications and price observations are included where supported by sources. Equipment availability and commercial terms require confirmation.
Eaton Magnum SB dossier: insulated-case breakers 200-6,000 A for UL 891 switchboards, priced observations from 14,500 USD, listing distinctions, inspection.
Magnum SB is a breaker, not a switchgear line: Eaton frames it as the insulated-case power circuit breaker built for the performance and economics of UL 891 switchboards (such as Pow-R-Line C), while Magnum DS carries the top ANSI ratings for UL 1558 switchgear. Frames run narrow (800-2,000 A), standard (800-3,200 A), and double-standard (3,200-6,300 A) for 200-6,000 A overall at up to 635 V AC, with interrupting capability to 150 kA on current-limiting designs, fixed or drawout, and Digitrip RMS trip units; a documented SBS608 rates 800 A at 100 kA (480 V), 100%-rated.
The concept continues into the Power Defense SB naming under the PXR electronics generation, per Eaton's combined Magnum PXR / Power Defense SB technical guide, keeping the installed base serviceable.
Priced supply is thinner than Magnum DS: an SBS608 new at 14,500 USD and an SBSC20 2,000 A new-open-box at 17,500 USD, with SBSC30 3,000 A units in dealer stock quote-only. Two public price points are too few to state a market range.
Why it matters
SB is the economy tier of the Magnum family, and its listing split (switchboard-duty insulated-case versus switchgear-duty UL 1066) is one of the most common used-breaker purchasing errors. Knowing the distinction, with live price anchors, prevents expensive misfits.
Who buys it
Owners of Pow-R-Line-class UL 891 switchboards with SB mains buy spares and replacements; contractors restoring boards buy tested units. The UL 891-versus-UL 1066 listing distinction decides fit, and buyers cross-shopping DS frames must check cassette compatibility rather than assume family interchange.
Role in the data center
Main and tie breakers in UL 891 distribution switchboards such as Pow-R-Line C, feeding mechanical and house loads rather than the critical bus. It is the economy alternative to a full UL 1558 switchgear main, which is why it turns up in support-space boards and back-of-house distribution rather than in the UPS lineup.
Key specifications
| Frame tiers | 800-2,000 / 800-3,200 / 3,200-6,300 A |
|---|---|
| Overall range | 200-6,000 A |
| Voltage ceiling | 635 V AC |
| Interrupting ceiling | 150 kA (current-limiting) |
| SBS608 example | 800 A, 600 V, 100 kA @480 V, 100%-rated |
| Application standard | UL 891 switchboards |
| Observed SBS608 new | 14,500 USD |
| Observed SBSC20 open-box | 17,500 USD OBO |
| PXR-era continuation | Power Defense SB (guide PA013006EN) |
| Trip units | Digitrip RMS (LSI plus metering) |
Technical summary
Type: insulated-case power circuit breaker for UL 891 switchboards. Frames: narrow 800-2,000 A; standard 800-3,200 A; double 3,200-6,300 A. Overall range: 200-6,000 A at up to 635 V AC. Interrupting: to 150 kA (current-limiting designs); SBS608 = 100 kA @480 V. Builds: fixed or drawout; 3P/4P. Trip units: Digitrip RMS (LSI + metering); PXR-era continuation as Power Defense SB. Rating basis: 100%-rated designs documented. Companion: Magnum DS carries UL 1558 switchgear duty.
Major variations
Three frame tiers, narrow at 800-2,000 A, standard at 800-3,200 A and double-standard at 3,200-6,300 A, in fixed or drawout construction, 3-pole or 4-pole, with Digitrip 520 and RMS trip generations and the Power Defense SB continuation under the PXR electronics generation. Listing note for buyers: Eaton positions SB against UL 891 switchboard economics while some dealer literature cites a UL 1066 listing, so the label on each individual unit decides what it can legally be installed in.
Configurations and options
Three frame tiers set the envelope, narrow at 800-2,000 A, standard at 800-3,200 A and double-standard at 3,200-6,300 A, covering 200-6,000 A overall to 635 V AC. Within a tier the order variables that move price are interrupting rating, up to 150 kA on current-limiting designs, fixed or drawout construction, 3-pole or 4-pole, and the Digitrip RMS trip-unit level with its metering content. Whether a unit is 100%-rated is a separate nameplate item that changes what it can be applied to. A documented example: an SBS608 is 800 A, 600 V, 100 kA at 480 V and 100%-rated.
Compatibility and dependencies
Eaton positions Magnum SB against the performance and economics of UL 891 switchboards such as Pow-R-Line C, while Magnum DS carries the top ANSI ratings for UL 1558 switchgear, and dealer literature has also described SB units as UL 1066 listed. The listing marked on the individual unit decides which board it can legally be installed in, so it has to be read rather than inferred. Drawout units need their own cassette, and an SB will not seat in a Magnum DS cell. Interrupting rating must be coordinated with the available fault current at the board rather than taken from the frame's ceiling. Acceptance work uses Eaton O&M manual IB2C12063H03 and Digitrip secondary injection.
Pricing and availability
Comparable secondary-market band: 14500–17500 $ per breaker. Trend: rising Two dated observations exist for this frame family, both logged 2026-08-18: an SBS608 800 A drawout, new, at 14,500 USD from a stocking outlet, and an SBSC20 2,000 A new-open-box at 17,500 USD with a test report and a one-year warranty. Larger SBSC30 3,000 A dealer stock is quoted rather than priced. Electrical Trader's 2026-04-01 review puts circuit breakers up 47% since 2021 at category level, and the 32-41 week switchboard queues recorded by the VAWN lead time index on 2026-08-13 are what keep in-stock frames trading near new-channel levels. Lead time, new: Switchboard class 32-41 weeks; breakers via distribution. Lead time, used or refurbished: 1-4 weeks (dealer stock). Warranty, used: 1-year typical from reconditioning dealers.
Lifecycle and maintenance
LV power circuit breakers serve 30-40 years on 3-5 year maintenance cycles per ANSI/NETA MTS and NFPA 70B, with mechanism lubrication and injection testing the critical items. A deep reconditioning ecosystem (Relectric, NAS, Bay Power, Bullock) tests to NETA specifications and warrants units for 1 year. OEM trip-unit retrofit programs (Eaton PXR, ABB EntelliGuard R, Siemens 3WA retrofit) extend installed platforms past electronics obsolescence, which sustains used-breaker values.
Thermal and emissions profile
Switchgear produces no combustion emissions; the regulatory profile is electrical safety and materials. NFPA 70B became a standard in its 2023 edition, making maintenance programs mandatory rather than recommended, and arc-flash rules (NFPA 70E) govern work practices. LV air-insulated gear carries no F-gas exposure, and construction standards (UL 891, UL 1558, IEEE C37.20.1) plus arc-resistant options under IEEE C37.20.7 define the safety envelope buyers should verify.
Common failure points
- Mechanism springs and lubrication — Slow trips, trip-free on close, failure to latch on aged units
- Trip unit electronics — Nuisance trips or no-trip from aged or obsolete electronics
- Contacts and arc chutes — Overheating and interruption failure from eroded contacts or cracked chutes
- Secondary wiring — Control faults from damaged secondary disconnects and aux switches
- Provenance and counterfeits — Counterfeit or mis-labeled breakers fail catastrophically under fault
- Cassette and racking wear — Misalignment and cluster contact damage on worn cradles
Inspection checklist
Mechanism: exercise open/close 10+ cycles; verify the charge/close/trip sequence completes and the mechanism latches on every close; treat any failure to latch on close as a finding and check it against the OEM acceptance procedure. Trip curve: primary injection test; NETA field data shows 22% of LV power breakers off their published curves. Secondary injection: verify all 4 protection functions (LSIG) against settings; record as-found/as-left values. Contact resistance: micro-ohm test each pole; investigate readings above 1.5x sister poles. Insulation resistance: megger at 1,000 V per ANSI/NETA MTS acceptance tables. Contact wear: inspect arcing contacts and wear indicators against the OEM replacement limit. Arc chutes: remove and inspect for cracks, erosion, and metal splatter; replace damaged chutes. Lubrication: verify mechanism grease condition; dried lubricant is the leading slow-trip cause on 20+ year units. Racking: exercise draw-out mechanism through connect/test/disconnect; verify shutter operation.
Procurement channels
Breaker Outlet sells new units at published prices, NAS carries priced open-box stock plus quote-only SBSC30 3,000 A frames, and the wider Magnum dealer network holds the rest. Acceptance work is supported by Eaton's O&M manual IB2C12063H03 and the Digitrip secondary-injection test ecosystem, both of which a buyer should have in hand before a unit is energized.
Regional notes
A North American product for 600 V class, 60 Hz switchboards, applied under UL 891 and UL 1066 practice with no IEC equivalent to import, since an IEC 60947-2 breaker is not a substitute. The concept continues into the PXR electronics generation under Power Defense SB naming, documented in Eaton's combined technical guide PA013006EN, so a North American buyer replacing a Digitrip-era unit is choosing between used SB stock and a current-generation successor rather than a like-for-like new order.