FR331 fire resistant cables are 300/500 V silicone-insulated, LSZH-sheathed cables designed to maintain circuit integrity for 90 minutes under IEC 60331-21 fire-test conditions. Choose an overall-screened OS construction where electromagnetic interference is a concern, or an unscreened UN construction for fixed circuits where screening is not required. Core count and conductor size must match the circuit load and approved system design.
The series covers screened and unscreened constructions, 2-core and 3-core options, and nominal conductor sizes from 1.0 mm² to 2.5 mm². The three models below represent the main selection paths; confirm the exact construction, test documentation and delivered cable data for the model specified in your project.
FR331-UN-0225
A 300/500 V, 2-core unscreened cable with stranded bare-copper conductors, silicone insulation and a red LSZH sheath. Consider it for fixed critical circuits where an overall screen is not required. The published outer diameter is 7.6 ± 0.2 mm.
View Product Details →FR331-OS-0210
A compact 300/500 V, 2-core construction with an aluminum-foil overall screen and tinned-copper drain wire. Consider it where the cable route is exposed to electromagnetic interference. The published outer diameter is 5.8 ± 0.2 mm.
View Product Details →FR331-OS-0325
A 300/500 V, 3-core screened option for circuits that need an additional conductor and overall foil screening. It uses silicone insulation, a tinned-copper drain wire and an LSZH sheath. The published outer diameter is 8.7 ± 0.2 mm.
View Product Details →Start with the circuit design, then choose screening, core count and conductor size. FE90 describes circuit integrity under a defined fire test; it does not replace load calculations, local code review or approval of the complete installed system.
Choose OS when the route or connected equipment requires an overall aluminum-foil screen and drain wire for interference control. Choose UN when the approved design does not require screening. Screening must be terminated and earthed as specified by the system designer.
Select 1.0, 1.5 or 2.5 mm² only after checking current demand, run length, voltage drop, protective-device coordination and the equipment manufacturer's limits. A larger cross-section is not automatically the correct choice for every circuit.
Match the number of insulated conductors to the approved circuit arrangement. The FR331-OS-0325 provides three 2.5 mm² conductors, while the other representative models shown here use two conductors.
FE90 means the cable is specified to maintain circuit integrity for 90 minutes under the applicable IEC 60331-21 fire-test conditions. It is a test classification, not a promise that every installed circuit will operate for 90 minutes under all real fire conditions.
Use screening, core count and conductor cross-section to make the first shortlist. All three representative models are rated 300/500 V and use silicone insulation with a red LSZH sheath; final approval should be based on the model-specific data sheet and required test reports.
| Model | Construction | Nominal Size | Outer Diameter | First Selection Check |
|---|---|---|---|---|
| FR331-UN-0225 | Unscreened | 2 × 2.5 mm² | 7.6 ± 0.2 mm | Use where the design does not require an overall screen. |
| FR331-OS-0210 | Overall screened | 2 × 1.0 mm² | 5.8 ± 0.2 mm | Compact screened option for 2-core circuits. |
| FR331-OS-0325 | Overall screened | 3 × 2.5 mm² | 8.7 ± 0.2 mm | Screened option where three conductors are required. |
OS adds an overall screen around the insulated conductors; UN does not. Both use stranded bare-copper conductors, silicone insulation and a red LSZH outer sheath, but the selected model's construction drawing should be used for final approval.
The OS construction includes an aluminum-foil overall screen and a tinned-copper drain wire. Confirm the screen termination and earthing method with the system designer.
The UN construction omits the overall screen and drain wire. Use it only where the approved circuit design and installation environment do not require screening.
Fire resistance, flame propagation, smoke density and corrosive-gas emission are separate performance questions. Specify each required test explicitly and request documentation that identifies the exact cable model and test scope.
| Performance Question | Referenced Standard | What It Addresses |
|---|---|---|
| Circuit integrity during fire | IEC 60331-21, FE90 | Electrical continuity for 90 minutes under the stated test conditions. |
| Flame propagation | IEC 60332-1-2 / IEC 60332-3-24 | Flame spread for a single cable or a bunched-cable arrangement. |
| Smoke density | IEC 61034-1/2 | Light transmission through smoke generated during combustion. |
| Halogen and acidity | IEC 60754-1/2 | Halogen-acid gas content and acidity/conductivity of combustion gases. |
FR331 cables fit fixed critical circuits that must remain operational during a specified fire exposure. Suitability depends on the complete system design, installation method, local code and model-specific approval documents.
Use for approved alarm, detection or control circuits when IEC 60331-21 circuit-integrity performance is specified. Check compatibility with the panel, loop design and local fire code.
Consider FR331 for fixed emergency-lighting or exit-sign circuits that require fire survival. Confirm conductor sizing, voltage drop, protective devices and the required cable support method.
Use only when the selected cable model, connected equipment and complete control circuit meet the project specification. Cable fire performance alone does not approve the whole system.
Hospitals, airports, tunnels, data centers and industrial buildings may specify fire-survival circuits. Verify the country-specific standard, CPR or other classification, installation environment and approval scope before ordering.
It is a 300/500 V silicone-insulated, LSZH-sheathed cable family specified for 90-minute circuit integrity under IEC 60331-21 conditions. The range includes screened OS and unscreened UN constructions in multiple conductor sizes and core counts.
FR331-OS has an overall aluminum-foil screen and tinned-copper drain wire; FR331-UN has no overall screen. Choose based on interference-control requirements and the approved circuit design, not on price alone.
No. LSZH describes low-smoke, zero-halogen material behavior, while fire resistance describes circuit integrity during a defined fire test. The project may require separate evidence for IEC 60331, IEC 60332, IEC 61034 and IEC 60754.
Yes, when the exact FR331 model and complete installed circuit satisfy the equipment requirements, project specification and local code. Confirm voltage, current, conductor size, support method and required test classification before approval.
Request the selected model's data sheet, construction drawing, circuit-integrity report, flame-spread and LSZH test evidence where required, certificate scope, sample identification and delivered-batch traceability documents.
You do not need to know every cable term before asking for a quote. Share the circuit and approval requirements below so the exact FR331 model and supporting documents can be matched to your project.
Required construction: FR331-OS screened or FR331-UN unscreened
Core count and nominal conductor cross-section in mm²
Circuit voltage, current, run length and allowable voltage drop
Required circuit-integrity duration and exact fire-test standard
Required flame-spread, smoke-density and halogen/acidity standards
Installation environment, cable support method and minimum bend constraints
Target country, local code, CPR or project-specific approval requirements
Quantity, reel length, packaging, marking and traceability requirements
Certification and compliance references for project review, qualification and purchasing documentation.
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