CHINT NU5-I+II 15-275 Surge Protective Device

Model Definition: NU5-I+II = Type T1+T2 combined SPD; 15 = Iimp 15kA (10/350μs); 275 = Uc=275V

✅ Core Parameters

Standards: GB/T 18802.11, IEC 61643-11

Test Class: Class I+II (T1+T2). Applied as primary lightning protection and secondary voltage limiting for main incoming cabinets

Maximum Continuous Operating Voltage Uc: 275V AC (for 230V single-phase systems)

Impulse Current Iimp (10/350μs): 15 kA

Nominal Discharge Current In (8/20μs): 25 kA

Maximum Discharge Current Imax (8/20μs): 50 kA

Voltage Protection Level Up: 1.5 kV

Mounting: Standard TH35-7.5 DIN rail

Construction: Pluggable module. Base remains in place; only replace the failed module

Status Indication: Visual window (Green = Normal, Red = Fault); Remote alarm contact optional

Ambient Temperature: -35℃ ~ +70℃

Certifications: CQC, CE, CB, RoHS

Available Poles: 1P / 2P / 1P+N / 3P / 4P / 3P+N

✅ Wiring & Accessories

Conductor cross-section: 2.5～25 mm², tightening torque 2～3 N·m

Required back-up protection: NSCB5-I+II dedicated SPD back-up protector (ordinary MCBs are not recommended)

Protection Modes: L-PE, L-N, N-PE

✅ Application Scenarios

Main incoming distribution cabinets of buildings, boundary of lightning protection zone LPZ0→LPZ1. Used for simultaneous discharge of direct lightning current (10/350 waveform) and induced surge (8/20 waveform). Widely used for 230V single-phase and 400V three-phase TN-S systems.

✅ Same Series Comparison

NU5-I+II 12.5-275: Iimp=12.5kA

NU5-I+II 15-275: Iimp=15kA (this model)

NU5-I+II 25-275: Iimp=25kA

✅ Equivalent Alternatives

CHINT upgraded replacement: NXU-I+II series;

Other brand equivalents: Delixi DXH01-FS, Schneider iPRD1 15r, ABB OVR T1+2 15-275, etc.

Application Scenarios for CHINT NU5-I+II 15-275

Positioning: T1+T2 combined SPD, Uc=275V, suitable for 230V single-phase / 400V three-phase TN-S distribution. Installed at LPZ0→LPZ1 lightning boundary on main incoming cabinet to discharge direct lightning energy and induced surge in one unit.

✅ Building Applications (Most Common)

1. Main incoming distribution panel of buildings (at main equipotential bonding point): High-rise buildings, commercial complexes, office buildings, hotels, hospitals, schools. Eliminates the need for separate Type T1 SPD and saves cabinet space.
2. Class II & Class III lightning protection buildings that require Type T1 SPD at power inlet per codes; preferred in high lightning density areas.
3. Main distribution boxes of residential compounds and incoming cabinets in power distribution rooms.

✅ Industrial Applications

1. Main power incoming cabinets and general power cabinets of factories; for systems with downstream PLCs, VFDs, servo drives, instruments, DCS and other low-voltage automatic control equipment requiring surge protection at source.
2. Outdoor independent control rooms, pump houses, fan rooms, sewage treatment station power incoming cabinets.
3. Low-voltage outgoing cabinets of box-type transformers (TN-S system).

✅ New Energy Applications

1. Grid-tie cabinets of residential and small commercial PV systems (AC side 230/400V). PV sites are vulnerable to surges induced by nearby lightning strikes.
2. AC inlet side of small energy storage systems.

✅ Other Applications

1. Main incoming feed of monitoring rooms and computer rooms (Note: This SPD can be installed upstream of UPS; additional T2/T3 SPD shall be fitted downstream of UPS output for graded protection).
2. Outdoor base stations, centralized street light distribution boxes, weather stations, remote field monitoring equipment power inlet.
3. Power supply cabinets for fire alarm hosts and fire pumps (fire distribution lightning protection).

✅ System Compatibility

Suitable for: TN-S (preferred), TN-C-S, 230V single-phase, 400V three-phase AC 50Hz

Uc=275V, NOT suitable for TT systems or grids with elevated line-to-earth voltage (TT systems generally select 385V versions)

Not for DC circuits

⚠️ Not Recommended Applications

1. Sub-distribution cabinets inside LPZ1 zone (NU5-II Type T2 SPD is normally used here; I+II models cost more)
2. Terminal sockets and equipment side (use T3 fine protection)
3. 10kV high voltage side, DC side of PV arrays, inverter DC terminals
4. Grids with sustained overvoltage or severe neutral drift (switch to Uc=385V variant)

✅ Key Installation Notes

NSCB5-I+II dedicated SPD back-up protector is mandatory. Ordinary miniature circuit breakers shall not be used as back-up protection. Equipotential bonding is recommended and earth resistance shall meet lightning protection requirements of the project.

Graded Lightning Protection Scheme for CHINT SPD (Matching NU5-I+II 15-275)

Applicable System: AC230/400V 50Hz TN-S / TN-C-S, Class II / III lightning protection buildings, industrial automation rooms, data rooms, PV AC side; Lightning Zones LPZ0→LPZ1→LPZ2→LPZ3

Principle: Stepwise voltage limiting & energy coordination. Front-end T1+T2 diverts heavy lightning current; downstream T2/T3 further suppress residual voltage to withstandable levels for sensitive electronics.

Full Graded Configuration List

Pole Selection Guide:

Single-phase circuit: 1P+N

Three-phase TN-S: 3P+N (preferred)

TN-C-S: Convert to 3P+N at main inlet before branch distribution

Two Simplified Versions

Scheme A: Full Standard Scheme (Preferred for Computer Rooms, Automation, DCS, Inspection Acceptance)

Main Inlet: NU5-I+II 15-275 → Sub-distribution: NU5-II 40-275 → Low-voltage cabinet: NU5-II 20-275 → Equipment terminal: NU5-III

✅ Advantages: Good energy coordination, surge energy attenuated stage by stage, highest safety for precision equipment, easy to pass lightning inspection

✅ Suitable for: Projects equipped with PLC, VFD, instruments, UPS, servers and fire alarm systems

Scheme B: Economy Simplified Scheme (Ordinary Office Buildings, Residential Districts, General Lighting & Power)

Main Inlet: NU5-I+II 15-275 → Sub-distribution: NU5-II 40-275

No separate T3 at terminals; add T3 only for critical equipment as required

✅ Suitable for: Systems dominated by lighting and power loads with few low-voltage devices, cost control

⚠️ Critical Coordination Rules (Key for Acceptance)

1. Cable Length Requirement for SPD Energy Coordination

Cable length between T1+T2 (NU5-I+II) and next-stage T2 SPD ≥5m; Decoupler must be fitted if less than 5m. Otherwise front SPD may not operate and downstream SPD will fail first.

Recommended ≥5m between T2 and T3; decoupler is also required if insufficient.

2. Earthing & Wiring

SPD earthing conductor: short, straight and thick, ≥16mm² copper recommended, avoid looping and sharp bends

PE terminal of all SPDs connect to same equipotential bar, daisy-chain earthing is forbidden

3. Precondition for Uc=275V

Stable grid voltage with minimal neutral drift. For TT systems or grids with high voltage, upgrade the whole set to Uc=385V series (NU5-I+II 15-385)

4. No Mixing of Back-up Protectors

NSCB5-I+II must be used for I+II SPD instead of ordinary MCB; NSCB5-II for T2 SPD. Otherwise, SPD fire hazard cannot be reliably isolated.

📌 Application Example (Three-phase TN-S Automation Workshop)

Transformer low-voltage incoming cabinet: 3P+N NU5-I+II 15-275 + NSCB5-I+II

→ Workshop power sub-cabinet: 3P+N NU5-II 40-275 + NSCB5-II

→ PLC control cabinet inlet: 1P+N NU5-II 20-275 + NSCB5-II

→ VFD control power & sensor power supply: NU5-III

Supplementary: Signal Surge Protection (Often Overlooked)

After power surge protection, separate signal SPDs are required for Ethernet, RS485, 4-20mA analog signals. All SPDs share the same equipotential bonding; otherwise surge may damage modules through signal lines.

CHINT Low-voltage Power SPD Full Model List (Common Engineering Models by Series)

Naming Note: Suffix F = with remote alarm contact; Poles: 1P / 1P+N / 2P / 3P / 3P+N / 4P; Uc options 275V / 385V

1. NU5 Series (Mainstream established series; NU5-I+II 15-275 belongs here)

NU5-I+II (T1+T2 combined, main inlet primary lightning protection)

NU5-I+II 12.5-275 (Iimp=12.5kA)

NU5-I+II 15-275 (Iimp=15kA, this model)

NU5-I+II 25-275 (Iimp=25kA)

NU5-I+II 12.5-385

NU5-I+II 15-385

NU5-I+II 25-385

Remote alarm variant: NU5-I+II-F xxx-xxx

NU5-II (T2 secondary, sub-distribution cabinet)

NU5-II 20-275 / 20-385

NU5-II 40-275 / 40-385

NU5-II 65-275 / 65-385

NU5-II 80-275 / 80-385

NU5-II 100-275 / 100-385

NU5-II 120-275 / 120-385

Remote alarm variant: NU5-II-F

NU5-III (T3 fine protection, equipment terminal)

NU5-III 10-275

NU5-III 10-385

1. NXU Series (New upgraded series to replace NU5, compact size, improved performance)

NXU-I+II (T1+T2 combined)

NXU-I+II 12.5-275

NXU-I+II 25-275

NXU-I+II 12.5-385

NXU-I+II 25-385

NXU-I+II 50-275/385

Remote alarm variant: NXU-I+II-F

NXU-II (T2 secondary)

NXU-II 20, 40, 65, 80, 100, 120, 160-275 / 385

Remote alarm variant: NXU-II-F

NXU-III (T3 terminal)

NXU-III 10-275 / 385

III. NU6 Series (Economical T2, widely used in real estate & civil projects)

NU6-ⅡG (T2, G = pluggable modular, remote alarm optional)

NU6-IIG 40, 65, 80, 100-275 / 385 / 440

Remote alarm variant: NU6-IIGF

NU6-III (T3 terminal, socket / weak current box)

NU6-III 10-275

1. Other Low-volume Power SPDs

NU210-40: Non-pluggable economical T2

NUH-40B: Legacy stock model, phased out

1. Matching SCB Back-up Protectors (Must match SPD type, cross-type use forbidden)

NSCB5 (For NU5 series)

NSCB5-I+II: Exclusively for NU5-I+II T1+T2

NSCB5-II: Exclusively for NU5-II T2

-Current ratings: 20A, 40A, 65A, 100A, 120A; Poles 1P/2P/3P/4P

NXSCB (For new NXU series)

NXSCB-I+II: Back-up for NXU-I+II

NXSCB-II: Back-up for NXU-II

1. Signal Surge Protectors (For automation: RS485 / Ethernet / Analog)

NVS-RJ45: Ethernet surge protection (CCTV, switches)

NVS-485: RS485 bus surge protection (instruments, PLC)

NVS-AI: 4-20mA analog signal surge protection

NVS-BNC: Coaxial video surge protection

✅ Quick Selection Guide

1. Main inlet LPZ0→LPZ1: NU5-I+II / NXU-I+II
2. Floor / workshop sub-panel LPZ1→LPZ2: NU5-II / NXU-II / NU6-IIG
3. Inside PLC & UPS cabinet: NU5-II 20kA class
4. VFD, camera, sensor terminal: NU5-III / NXU-III
5. Back-up rule: NSCB5-I+II only for I+II SPD; NSCB5-II for T2 SPD

⚠️ Discontinued Model Note

Legacy NU1, NU2, NU3, NU4, Ex9UE series are discontinued. New projects are recommended to adopt NU5 or NXU series.