Eaton Magnum SB insulated-case power circuit breaker
Eaton Magnum SB insulated-case breakers for UL 891 switchboards, the Magnum family's economy frame
Eaton Magnum SB insulated-case power circuit breaker is one of 41 data center switchgear tracked in the SecondWatt catalogue, each with specifications, lead times and indicative secondary-market pricing.
Eaton Magnum SB insulated-case power circuit breaker switchgear — specifications, pricing tiers, and availability on SecondWatt.
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. Documenting the distinction, with live price anchors, prevents expensive misfits and positions the catalog as the buyer's technical ally.
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 feeding mechanical and house loads; the economy alternative to full UL 1558 switchgear mains.
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) |
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
Pricing and availability
Comparable secondary-market band: 14500–17500 $ per breaker. Trend: up 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.
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 charge/close/trip sequence without trip-free behavior 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 Auxiliary wiring — verify secondary disconnects, charging motor voltage (24-125 V options), and aux contacts Trip unit vintage — identify electronics generation; obsolete trip units reprice the breaker toward core value Counterfeit screen — verify serial numbers with the OEM; counterfeit LV breakers documented since the 2007 CPSC recall Ratings match — confirm frame, sensor/rating plug, and interrupting rating (kA at 480 V) against the application Listing match — verify cassette/cradle compatibility and UL 1066 or UL 489 listing matches the switchgear type Records — factory test report, service history, and injection results; missing records reprice toward as-is
Procurement channels
Breaker Outlet (priced new), NAS (priced open-box and quote-only SBSC30 stock), and the Magnum dealer network; O&M manual IB2C12063H03 and the Digitrip test ecosystem support acceptance.