Siemens NXAIR air-insulated switchgear family
Manufacturer: Siemens
Siemens NXAIR metal-clad switchgear family, from 17.5 kV at 50 kA to the 36 kV NXAIR H, inherently SF6-free
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.
Siemens NXAIR dossier: air-insulated metal-clad family from 17.5 kV at 50 kA to 36 kV NXAIR H, Siemens AG ownership, spares channels, inspection.
NXAIR is Siemens AG Smart Infrastructure's air-insulated, metal-clad, withdrawable vacuum-breaker MV switchgear family, and it is commonly undersold twice: attribution (Siemens AG, not Siemens Energy) and range ('to 17.5 kV' describes only the base family). The lineup runs NXAIR to 17.5 kV at up to 4,000 A and 40 kA, NXAIR 50 kA at 17.5 kV/4,000 A/50 kA, NXAIR M at 24 kV/25 kA, NXAIR C at 24 kV/2,000 A/25 kA, and NXAIR H at 36 kV, 2,900 A, 31.5 kA.
Construction is natural air with vacuum interrupters, inherently SF6-free, with IEC 62271-200 type-tested internal arc containment and options for IEC 61869 low-power instrument transformers and digital condition monitoring. It is an IEC line; Siemens serves the ANSI market with separate US switchgear.
Why it matters
NXAIR is Siemens' volume answer to UniGear and PIX, and its air-plus-vacuum construction makes it F-gas-proof without a 'blue' variant, an underappreciated procurement angle as SF6 rules tighten. The 50 kA tier covers dense-fault urban networks that most AIS families cannot serve.
Who buys it
IEC-market utilities, industrials, and campus projects specify NXAIR across its five variants; US exposure arrives via imported process skids and IEC-spec colocation builds. Used demand centers on withdrawable breakers and panel spares for installed lineups.
Role in the data center
Primary MV distribution for IEC-market campuses, with the 50 kA tier serving high-fault-density urban interconnects.
Key specifications
| Base family | 17.5 kV / 4,000 A / 40 kA |
|---|---|
| 50 kA tier | 17.5 kV / 4,000 A / 50 kA |
| NXAIR M | 24 kV / to 25 kA |
| NXAIR C | 24 kV / 2,000 A / 25 kA |
| NXAIR H | 36 kV / 2,900 A / 31.5 kA |
| Insulation | air + vacuum (SF6-free) |
| Arc containment | IEC 62271-200 type-tested |
| Digital options | IEC 61869 LPIT, condition monitoring |
| Manufacturer | Siemens AG Smart Infrastructure |
Technical summary
NXAIR: to 17.5 kV / 4,000 A / 40 kA NXAIR 50 kA: 17.5 kV / 4,000 A / 50 kA NXAIR M: 24 kV / up to 25 kA NXAIR C: 24 kV / 2,000 A / 25 kA NXAIR H: 36 kV / 2,900 A / 31.5 kA Insulation: natural air + vacuum interrupters (SF6-free by construction) Arc containment: IEC 62271-200 type-tested (IAC) Digital options: IEC 61869 LPIT sensors, condition monitoring Construction: withdrawable vacuum breakers, metal-clad panels Owner: Siemens AG Smart Infrastructure
Major variations
Five variants by voltage/fault tier (base, 50 kA, M, C, H) plus NXAirS for specific markets; the legacy NXAIR P high-rating variant is retired from the current lineup.
Configurations and options
Five variants, and the variant is the specification: NXAIR to 17.5 kV at 4,000 A and 40 kA, NXAIR 50 kA at 17.5 kV, 4,000 A and 50 kA, NXAIR M at 24 kV to 25 kA, NXAIR C at 24 kV, 2,000 A and 25 kA, and NXAIR H at 36 kV, 2,900 A and 31.5 kA, with NXAirS built for particular markets. Within a variant the order items that move price are panel duty, breaker rating, relay package, and whether IEC 61869 low-power instrument transformers and condition monitoring are fitted in place of conventional instrument transformers. The legacy NXAIR P high-rating variant is absent from the current lineup, its position taken by NXAIR 50 kA.
Compatibility and dependencies
Insulation is natural air with vacuum interrupters, so the design is SF6-free by construction and carries no gas obligations, but it needs the air clearances that come with that: panel dimensions and the internal arc exhaust path are what the IEC 62271-200 type-tested arc containment depends on, and the room has to reproduce them. Withdrawable breakers are matched to their cassettes by variant and rating. The 50 kA tier exists for dense urban interconnects where the network fault contribution exceeds what the base family withstands, so bus rating and short-time withstand have to be matched to the actual fault level rather than to the family name. Low-power instrument transformers to IEC 61869 require relays that accept sensor inputs rather than 1 A or 5 A CT secondaries.
Pricing and availability
Trend: up Lead time, new: 52-80 weeks (metal-clad class). Lead time, used or refurbished: Quote-only overseas resellers; no US channel. Warranty, used: 1-year typical from reconditioning dealers.
Lifecycle and maintenance
Metal-clad MV switchgear routinely serves 40+ years: vacuum interrupters rated for 10,000-30,000 operations far outlast the mechanical duty standby service imposes, so lineup life is governed by insulation condition and relay/controls vintage. Breakers recondition readily and trade as units, while lineups modernize in place with digital relays and retrofit breakers. ANSI/NETA MTS acceptance testing at purchase plus PD surveys in service are the condition gates.
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
- Vacuum interrupters — Loss of vacuum ends interrupting capability with no external sign
- Insulation tracking and PD — Partial discharge across dusty or damp insulation progressing to flashover
- Racking and interlocks — Damaged racking screws and defeated interlocks from forced operation
- Protection relays — Obsolete or drifted relays mis-operate under fault
- Instrument transformers — CT/VT failures disable metering and protection inputs
- Space heater failure — Condensation-driven tracking in unheated outdoor or humid gear
Inspection checklist
Vacuum integrity — hipot test each interrupter per OEM procedure (e.g., 36 kV test on 15 kV class) Insulation resistance — megger bus and breakers at 2,500-5,000 V; compare to ANSI/NETA MTS tables Contact resistance — micro-ohm each pole; investigate imbalance beyond 50% between phases Partial discharge — ultrasonic and TEV survey; investigate any reading 6 dB above baseline Contact erosion — measure vacuum interrupter erosion marks against the OEM wear allowance Racking mechanism — cycle connect/test/disconnect positions 3 times each; verify interlocks and shutters Mechanism timing — verify open/close times; closing beyond 5 cycles flags mechanism trouble Bus insulation — inspect epoxy and boots for tracking or corona; clean and torque joints Instrument transformers — verify CT/VT ratios, insulation, and fusing Protection relays — test to calibration cycle; electromechanical relays need 1-2 year intervals Arc rating — confirm arc-resistant construction class (IEEE C37.20.7 Type 2B) matches the installation Heaters — verify space heaters work; condensation drives tracking failures in unheated gear Nameplate — confirm voltage class, BIL (60-150 kV by class), and interrupting rating against the application Standards — verify IEEE C37.20.2 construction and UL/CSA labels; run ANSI/NETA MTS acceptance tests Records — factory test report, maintenance history, and operation counts; missing history reprices as-is
Procurement channels
Siemens channels for new; overseas resellers (quote-only) for the installed base; Surplus Record's Siemens and MV-vacuum categories are the long-shot monitors.
Regional notes
An IEC line; Siemens serves the ANSI market with separate US switchgear products, so an NXAIR panel is not a North American specification and a 50 Hz lineup is not usable on a 60 Hz project without significant engineering. The owner is Siemens AG, Smart Infrastructure; Siemens Energy AG has been a separate listed company since the September 2020 spin-off and has never sold this line. Because the design is air-insulated and SF6-free, it is unaffected by the EU F-gas cutoffs reshaping the gas-insulated part of the category.