Spark gap SPD vs MOV SPD is not a simple “better or worse” comparison. A spark gap uses voltage-switching behaviour. An MOV uses voltage-limiting behaviour. This guide explains how those structures affect Type 1, Type 1+2, N-PE and 3+1 selection for engineering procurement and OEM approval.
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A spark-gap-based SPD remains electrically isolated during normal operation and switches into a low-impedance discharge path when its sparkover condition is reached.
Un MOV-based SPD progressively lowers its resistance as voltage rises, diverting surge current while limiting the voltage across the protected circuit.
Spark gaps are widely used for Type 1 lightning-current and N-PE duties. MOVs dominate Type 2 protection and are also used in tested Type 1+2 designs. Type 1 is a complete-device test classification, not a component name.
Procurement rule: compare Iimp, Uc, Up, protection modes, follow-current behaviour, Isccr, backup protection and the exact certified model.
Spark Gap SPD vs MOV SPD
The table describes common engineering behaviour. Actual performance depends on the complete SPD construction, ratings and test results.
| Punto di confronto | Spark-gap-based SPD | MOV-based SPD | Procurement implication |
|---|---|---|---|
| Basic behaviour | Commutazione di tensione | Limitazione di tensione | Review the complete voltage-time behaviour and declared Up. |
| Stato normale | Very high impedance with an open gap | High impedance; leakage depends on the design and operating voltage | Check leakage-current and insulation requirements where they matter. |
| Uso tipico | Type 1, high lightning-current duty, N-PE modules | Type 2 and many compact Type 1+2 designs | Do not infer the test class from the component alone. |
| Key Type 1 rating | Iimp, Up, sparkover behaviour and follow-current performance | Iimp, Uc, Up, TOV and thermal-disconnection performance | Match ratings to the installation and certificate. |
| Seguire la corrente | May occur in some designs; modern products may limit, extinguish or avoid it | No arc-based line follow current | For spark gaps, verify Ifi or the manufacturer’s no-follow-current claim. |
| Thermal concern | Arc chamber, electrode condition and interruption behaviour | TOV, cumulative stress, overheating and disconnection | Review safety tests and internal disconnector design. |
| Maintenance format | Available as fixed or pluggable construction | Commonly pluggable with visual and remote status options | Confirm replacement-module compatibility and indication. |
| N-PE application | Widely used for N-PE total-current paths in 1+1 and 3+1 systems | May be used in other certified architectures | Verify the actual N-PE technology and Iimp/Itotal. |
| Approval rule | Do not approve merely because it is a spark gap | Do not reject merely because it is MOV-based | Approve the complete SPD model and documented system fit. |
What is a spark-gap-based SPD?
A spark gap uses electrodes separated by a controlled insulating space. Under normal voltage, the path remains open.
When the dynamic sparkover condition is reached, the gap ionises and forms an arc path that diverts surge current. After the surge, the SPD must return to its non-conducting state.
Power-frequency spark gaps may use air, gas, carbon, graphite, encapsulated, triggered or multi-gap constructions. These designs should not be treated as technically identical.
- High lightning-current capability can be achieved.
- Normal-operation electrical isolation is possible.
- Follow-current behaviour is a key system-availability issue.
- Dynamic sparkover and residual-voltage behaviour must be verified.
What is an MOV-based SPD?
An MOV is a metal oxide varistor with a strongly nonlinear voltage-current characteristic.
As voltage rises, its resistance falls. The MOV then diverts surge current and limits the voltage across the protected circuit.
MOVs support compact DIN-rail products, pluggable cartridges, status indication and remote contacts. The complete SPD must still manage TOV, heat and short-circuit failure conditions.
- Low voltage-limiting performance can be achieved.
- Compact and pluggable designs are common.
- Uc selection and TOV behaviour are critical.
- Thermal disconnection is part of the safety design.[7]
Does a Type 1 SPD have to use a spark gap?
No. Spark gaps are common in Type 1 lightning-current arresters, but Type 1 is a test classification for the complete SPD or declared protection mode.
A Type 1 device is associated with lightning impulse-current duty using the 10/350 μs waveform and the declared Iimp. A spark gap does not prove Type 1 compliance by itself. A tested MOV-based device is not automatically excluded from Type 1 or Type 1+2 classification.[3][4]
Why spark gaps are frequently selected for Type 1 duty
The benefit comes from the engineered complete product, not the word “spark gap” on a catalogue page.
Scarica di corrente da fulmine
Type 1 SPDs may be installed where partial lightning current must be handled. Spark-gap constructions are widely engineered for this high-energy duty.
Electrical separation
An open gap can provide very high impedance during normal operation. This is especially relevant for certain N-PE paths and leakage-sensitive applications.
Wave-shaping behaviour
After ignition, a well-designed spark gap can create a low-impedance discharge path. Dynamic sparkover, arc voltage and system coordination remain important.
Avoid a false hierarchy: “spark gap = premium” and “MOV = low-end” is not a valid engineering rule. Phoenix Contact publicly offers spark-gap, varistor-based and coordinated spark-gap-plus-varistor Type 1+2 structures, showing that multiple architectures can satisfy different project needs.[4]
Why spark gaps are widely used for N-PE protection in 3+1 systems
For a TT 3+1 arrangement, the N-PE path is not an afterthought. It can carry the combined discharge current from the phase-to-neutral protection paths.
In a typical three-phase 3+1 arrangement, three protection paths operate between L1-N, L2-N and L3-N. A separate protection path operates between N and PE.
Spark-gap-based N-PE modules are widely used because they remain electrically separated during normal operation and provide a defined high-current discharge path during a surge.
DEHN specifies spark-gap-based Type 1 N-PE arresters for 3+1 and 1+1 circuits between neutral and protective earth, including products intended for TT systems.[5][6]
Importante: “3+1” describes a circuit arrangement. It does not guarantee that every supplier uses the same internal component technology, Iimp distribution or certificate wiring diagram.
Verify the N-PE path separately
- System earthing arrangement
- N-PE Uc
- N-PE Up
- N-PE Iimp or Itotal
- 1+1 or 3+1 circuit diagram
- Protection-mode marking
- Protezione di emergenza
- Exact certificate model
Follow current is one of the most important spark-gap procurement checks
It connects the SPD’s internal structure to the actual short-circuit conditions and upstream protective device at the installation point.
The gap fires
The surge raises the voltage above the dynamic sparkover level. The gap ionises and forms an arc path.
The surge ends
The power system may continue feeding current through the low arc voltage. This is line follow current.
The SPD must recover
The design must limit, extinguish or prevent this current without creating unacceptable upstream tripping or damage.
What the buyer should request
- Ifi or equivalent follow-current performance data
- Prospective short-circuit current at the installation point
- Permitted upstream fuse or circuit breaker
- Backup-protection and selectivity requirements
- Short-circuit current rating of the complete SPD arrangement
Do not generalise all spark gaps
Traditional and modern designs can behave differently. Phoenix Contact documents triggered spark-gap products designed to operate without line follow current, while the Schneider Electrical Installation Guide defines Ifi as a spark-gap-related characteristic that must be considered against the prospective short-circuit current.[3][8]
Why “response time” alone cannot select a Type 1 SPD
A component-level nanosecond figure does not describe the installed voltage stress seen by downstream equipment.
Actual protective performance also depends on
- Dynamic sparkover voltage
- MOV voltage-current characteristic
- Impulse amplitude and waveform
- Declared and measured Up
- Internal and external inductance
- Connection conductor length
- Protection modes and downstream coordination
Procurement rule: Do not approve a Type 1 SPD because a supplier claims a faster response time. Compare the complete device’s certified ratings, voltage-time behaviour, installation conditions and backup-protection requirements.
Leakage current, TOV and ageing require different checks
MOV-based designs
Verify Uc margin, TOV withstand, thermal stability, leakage-current behaviour, thermal disconnection and end-of-life indication. Sustained abnormal overvoltage can overheat an MOV if the protection design is inadequate.[7]
Spark-gap designs
Verify dynamic sparkover, arc containment, follow-current performance, impulse endurance and recovery after discharge. Do not assume unlimited service life.
Hybrid designs
Verify that coordination is part of the tested product or manufacturer-approved system. Do not create an unverified hybrid by combining arbitrary modules.
Which structure should a B2B buyer evaluate?
The table is a starting point for specification review, not a universal product prescription.
Lightning-current switching or N-PE isolation is central to the project
Focus on complete-device performance rather than assuming every spark gap provides the same result.
- The installation is at a Type 1 lightning-current boundary.
- A TT 1+1 or 3+1 N-PE discharge path must be verified.
- Normal-state electrical separation is important.
- Follow current, Ifi and upstream protection can be checked.
Compact Type 1+2 voltage limiting and pluggable maintenance are priorities
The complete model must still pass the required Type 1 and Type 2 tests.
- Panel width and replaceable modules matter.
- Low declared Up is needed for coordinated protection.
- Uc, TOV and thermal-disconnection data are available.
- Certificate and short-circuit ratings match the project.
The project needs lightning-current handling and lower residual voltage in one system
Hybrid does not mean that arbitrary modules can be assembled together.
- The combination is tested or approved by the manufacturer.
- The protection modes and internal coordination are documented.
- N-PE technology is identified separately.
- Installation and backup-protection rules are clear.
| Applicazione | Structure to evaluate | Primary engineering checks |
|---|---|---|
| Building with external LPS | Certified Type 1 or Type 1+2, spark gap, MOV or approved hybrid | Required Iimp, Up, LPZ position, protection modes and certificate scope |
| Main industrial switchboard | High-duty Type 1 or coordinated Type 1+2 | Iimp, Isccr, follow current, fuse coordination and availability |
| TT-system main board | 1+1 or 3+1 arrangement with verified N-PE module | N-PE Iimp/Itotal, Uc, Up, system diagram and certificate |
| Compact OEM panel | Compact combined Type 1+2 | Width, heat, terminals, replacement format and documentation |
| High fault-current location | SPD with documented short-circuit and backup-protection performance | Prospective fault current, Isccr, Ifi where relevant and upstream device |
| Apparecchiature sensibili a valle | Coordinated Type 1/Type 2 or verified combined SPD | Up, connection length, residual-voltage behaviour and insulation coordination |
| Importer or distributor stock range | Limited, clearly differentiated standard models | Regional grid systems, Uc options, certificates, accessories and replacement modules |
Type 1 SPD verification workflow
Move from system definition to document matching and sample approval. Do not begin with housing colour, logo or a headline kA number.
1. System data
- Nominal and maximum system voltage
- TN-C, TN-S, TT or IT arrangement
- Single-phase or three-phase
- External LPS and installation position
- Prospective short-circuit current
- Upstream protective device
2. SPD specification
- Type 1 or Type 1+2
- Iimp per protection mode
- Uc e Up
- N-PE Iimp or Itotal
- Follow-current performance
- Isccr and backup protection
3. Verification documents
- Exact model number
- IEC or EN certificate
- CB report when required
- Datasheet and wiring diagram
- Product marking and label sample
- Sample approval record
Approval gate: The datasheet, certificate, test report, product marking, wiring diagram and physical sample should identify the same product configuration. Any mismatch should be clarified before project approval or bulk production.
How LEEYEE turns this guide into a verifiable B2B decision
Technical content should connect to real product data, testing capability and certificate scope. Internal checks support engineering review, but they do not replace independent certification.
Available engineering and production checks
LEEYEE publicly documents the following test and inspection capabilities for SPD development, production verification and buyer review.[9]
Used to review component electrical behaviour before it is accepted into the finished SPD production process.
Used to evaluate declared impulse-current performance under the applicable waveform and test arrangement.
Used to observe behaviour under sustained abnormal voltage and thermal stress conditions.
Used to review SPD response under a combined voltage and current surge test environment.
LEEYEE LY1-12.5/1(S)+1 Type 1+2 SPD
This example shows why buyers must distinguish a power spark-gap structure from an MOV + GDT hybrid product.
Common buying mistakes
Type 1 means spark gap
Type 1 is verified by the complete device’s test classification and declared Iimp—not the component label.
MOV Type 1 is automatically inferior
A tested MOV-based Type 1+2 may fit the application. Compare the complete ratings and system requirements.
Imax is treated as Iimp
Imax is normally associated with an 8/20 μs waveform. Iimp is the Type 1 lightning impulse-current parameter.
Response time decides everything
Up, waveform, wiring inductance, sparkover and system coordination are more useful than one nanosecond claim.
The N-PE path is ignored
In TT 3+1 systems, the N-PE path may have different technology and total-current duty from L-N modules.
Follow current is not checked
A spark-gap SPD must suit the prospective short-circuit conditions and upstream protective device.
A product photo proves compliance
Only matched model data, certificates, reports, markings and samples support approval.
Uc is selected by nominal voltage only
Uc must also suit the earthing arrangement, voltage tolerance and TOV conditions.
Need help confirming a Type 1 SPD specification?
Send the system voltage, earthing arrangement, required Iimp and certificate requirement. LEEYEE can help compare the protection structure, ratings and exact model scope before sample approval or OEM quotation.
Spark gap SPD vs MOV SPD FAQ
Is a spark gap better than an MOV for a Type 1 SPD?
Not in every application. Spark gaps are widely used for high lightning-current and N-PE duties. MOVs provide voltage-limiting behaviour and can be used in tested Type 1+2 products. Select the complete SPD according to the system, ratings and documentation.
Can an MOV-based SPD pass Type 1 requirements?
Yes. The manufacturer must demonstrate that the complete SPD or declared protection mode meets the applicable Type 1 test requirements and ratings. Phoenix Contact publicly lists varistor-based Type 1+2 products, which confirms that Type 1+2 is not limited to spark-gap architecture.[4]
Why is a spark gap often used between N and PE?
It can provide electrical separation during normal operation and a high-current discharge path during a surge. Spark-gap-based N-PE arresters are widely used in 1+1 and 3+1 circuits, especially for TT applications.[5]
Does every spark gap produce line follow current?
No. Follow-current behaviour depends on the design. Some products specify an extinguishing capability, while modern triggered designs may be engineered to operate without line follow current. Verify the exact model data.
Does a spark-gap SPD have zero voltage protection level?
No. The installed voltage stress includes dynamic sparkover, arc voltage, internal inductance and connection effects. Use the declared and tested Up of the complete device.
Does Type 1+2 always contain both a spark gap and an MOV?
No. Type 1+2 means the complete device fulfils the declared Type 1 and Type 2 requirements. The internal architecture may be spark-gap-based, MOV-based or a coordinated combination.
What should an OEM buyer verify first?
Start with system voltage, earthing arrangement, protection modes, installation position, required Iimp, Uc, Up, short-circuit conditions and certificate requirements. Discuss branding and packaging only after the technical configuration is confirmed.
Should a 100 kA headline be used to compare Type 1 SPDs?
No. Determine whether the value is Iimp, Itotal, In or Imax; identify the waveform and protection mode; and verify whether it applies per pole, per path or to the complete assembly.
Riferimenti
Technical statements were reviewed against current IEC pages, primary manufacturer engineering resources and clearly identified LEEYEE first-party product and testing information.
Reviewed by the LEEYEE Technical Team. Last updated July 23, 2026.
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- IEC 61643-11:2025 — Low-voltage surge protective devices connected to AC low-voltage power systems: requirements and test methods.
- IEC 61643-01:2024 — Low-voltage surge protective devices: general requirements and test methods.
- Schneider Electric Electrical Installation Guide — The Surge Protection Device (SPD), including Iimp, Up and Ifi explanations.
- Phoenix Contact — Type 1+2 surge protection, including spark-gap, varistor-based and coordinated hybrid product structures.
- DEHN — N-PE lightning current arresters for 1+1 and 3+1 circuits.
- DEHN — DEHNgap spark-gap-based total-current arrester for TT-system 1+1 and 3+1 configurations.
- Littelfuse — Thermally protected MOV information covering sustained abnormal overvoltage and overheating protection.
- Phoenix Contact — Spark-gap technology, residual-voltage behaviour and no-line-follow-current designs.
- LEEYEE — documented SPD production and verification equipment, including MOV/GDT testing, lightning impulse, thermal stability and combination-wave testing.
- LEEYEE LY1-12.5/1(S)+1 — Type 1+2, L-N/N-PE product data with declared MOV + GDT protection elements and impulse-current ratings.
- LEEYEE Certificates — selected LY1-12.5 and LY1-7 Type 1+2 certificate scope and model-verification guidance.
Standards and product portfolios change. Confirm the edition, certificate status, national adoption and exact manufacturer model required by the project before approval.
