(B) Fire Rated Cable (Retardant / Resistance Cable)
- Fire is one of the biggest risks in factories, public place and a majority of them occur due to electrical faults.
- The terms Fire Resistant and Fire Retardant (both are commonly referred to as FR) terms are very similar and misused or confusing a lot.
- Both are different in structure, in materials, in Application and react even differently in the event of a fire. If we required one but select other can lead the problem.
(1) Fire Retardant Cables
- Insulating Material of Fire Retardant Cable is chemically treated to Retard or Slowdown ignition or Burning of Fire hence slow down the spreading of fire. It also actually self-extinguishes when exposed to an open flame.
- Flame-retardant Cable is characterized by delaying the spread of flame along the cable so that the fire does not expand.
- Fire-resistant cables and flame-retardant cables are different in structure and materials.
- The basic structure of the flame retardant cable is:
- The insulation layer uses flame retardant.
- The inner sheath and outer sheath are made of flame retardant.
- The tape and filling use of flame retardant material.

Advantage:
- Low Cost compared to Fire Resistance Cable.
- Produce Low Smoke
Disadvantage:
- By Adding Fire Retardant Material / Filler in PVC it decreases insulation property at least 10% compare to normal PVC, however its conductor temperature withstanding capability (during overload) remains only at 70 deg C same as ordinary PVC cables.
Applications:
- Control Wiring of Building
- Fire Alarm Circuit
(2) Fire Resistant cables
- The Fire resistance materials (non-flammable.) are designed to prevent / Resist the spread of fire (self-extinguishing) and will not melt or drip when in close proximity to a flame.
- Because it self-extinguishes once the source of ignition is removed and does not melt or drip. Fire-resistant cables can maintain normal operation for a certain period under flame burning conditions and maintain the Circuit integrity and continue to work for a specified period of time under defined conditions hence improving the chances of escape and survival.
- Because of Fire resistant fabrics are not usually made from 100% flame resistant materials, they will burn, but will do so very, very slowly and are often self-extinguishing.
- A Fire-resistant cable is a cable that can maintain safe operation for a certain period under flame-burning conditions. Fire-resistant wires are widely used in high-rise buildings, subways, underground shopping malls, power stations, and important industrial and mining enterprises related to fire safety and fire rescue. For example, power supply wires and control wires for firefighting facilities.
- Fire-resistant cable is divided into class A and class B.
- Class B: Class B cable can be in 750 ℃ to 800 ℃ flame and rated voltage to withstand burning for at least 90min, and the cable is not broken.
- In the refractory layer to improve the manufacturing process and increase the refractory layer and other methods based on
- Class A: Class A fire rated cable can be 950 ℃ to 1 000 ℃ flame and rated voltage to withstand burning for at least 90min and the cable is not punctured.
- Class A fire-resistant cable fire performance is better than class B.
- Mineral Insulated Cable (MI): mineral insulated cable is a better performance of fire-resistant cables made of copper core, copper sheath, magnesium oxide insulation material processing, referred to as MI (mineral insulated cables) cable.
- MI cable has good fire resistance characteristics and can work for a long time under 250 ℃ high temperature, but also explosion-proof, strong corrosion-resistance, high flow rate, radiation resistance, high mechanical strength, small size, lightweight, long life, and smokeless. However, the price is high. The process is complicated, the construction is difficult in the oil irrigation area, important public buildings, high-temperature places, and other fire-resistant requirements, and the economy can accept the occasion and use fire-resistant cable.

Advantage:
- Produce Low Smoke compared to Fire Retardant Cable.
Disadvantage:
- High Cost compared to Fire Resistance Cable.
- By Adding Fire Retardant Material / Filler in PVC it decrease insulation property at least 10% compare to normal PVC, However its conductor temperature withstanding capability (during overload) remains only at 70 deg C same as ordinary PVC cables.
Applications:
- In Fire Fighting System,
- In Fire Alarm Circuit
(3) FRLS (Fire Retardant Low Smoke)
- To overcome these deficiencies of FR Cable, FRLS Cable was developed.
- FRLS has special flame retardant, low smoke emitting and toxic fumes suppressing properties.
- In FRLS Cable, inner sheath and/or outer sheath is made material of Polyethylene Material having Fire Retardant Properties.
- In the Case of fire, convectional PVC insulated wires give out thick black smoke and toxic fumes of hydrochloric acid gas. This impairs visibility and hampers rescues operations. But in FRLS Cable not only emits very little smoke and toxic gases, but also retards the spreading of fire. It is thus ideal of concealed and conduit wiring in multi-storied high-rise buildings such as hotels, banks, hospitals, factories, commercial complexes and residential apartments, etc

Advantages
- Excellent flame-retardancy
- Low smoke generation
- Low toxic gas emission
(4) FRLSZH/ NHFR / ZHFR (Fire Retardant Low Smoke Halogen Free)
- FRLSZH, Halogen Free Flame Retardant non-toxic smoke house wires for building wiring.
- FRLSZH Wires are recommended especially in a situation where high degree of safety of personnel and equipment are obligatory like Hotels, Theatres, Hospitals, High-rise buildings, Commercial complexes, Centrally A.C. offices, Residential properties etc.
- Owing to its special insulation characteristics the wires continue to provide uninterrupted power supply even during fire – keeping alive fire alarm circuits, exit lights, Lifts & other emergency Circuits.
- As part of sustainable green building technology, to bringing down the use of hazardous PVC from green building. Normal PVC cables will be replaced with Green Cable.

Advantages
- Excellent flame-retardancy
- Halogen Free
- Low smoke generation
- Low toxic gas emission
- Better visibility help easy for people escape
- Environment friendly
- Benefit to environment
- PVC is not only hazardous during the manufacturing process but also potential risk in case of fire. Green Cable is superior performance cable with utmost quality which is replacement for PVC cables.
- Generally used where green environment and higher safety is expected for Human life and valuables
Disadvantages
- Costly Compare to FR and FRLS Cables
Applications:
- Airports
- Centrally A. C. Buildings
- Complexes
- Educational Institutions
- General House wiring
- Green Buildings
- High Raise Building
- Hospitals
- Hotels
- Public Places, Theaters
Flame retardant (FR) or FRLS compounds are not suitable for building wires for the following reasons:-
- FR & FRLS PVC compounds are said to be flame retardant because they have better LOI (Limiting Oxygen Index) and TI (Temperature Index) than ordinary PVC, but, only better LOI & TI does not guarantee better flame retardant properties. LOI & TI are only quality control tests and flame retardant testing is incomplete without finished cable testing as per IEC 332-1 &3.
- Moreover, all the FR and FRLS PVC compounds contain Antimony Trioxide which is a probable carcinogen. When inhaled, ATO can cause irritation of the respiratory track, mouth, nose & stomach. It may also cause the heart to beat irregularly or even stop.
- The use of FR & FRLS PVC compounds does not solve the issues of dense black smoke and HCL acid gas emitting from burning which are the main cause of loss of human lifes during fire accidents.
- All PVC,FR & FRLS compounds also contain phthalate plasticizers. These plasticizers leach out of PVC compound after some time and results in PVC loosing its flexibility and other properties. Moreover most of the phalates presently used have been identified as suspected endocrine disrupters and reproductive toxicants
Difference between Fire Resistant vs. Fire Retardant Cable
- Fire Resistant and Fire Retardant cables are being used increasingly due to their usefulness in the event of fire. However, though they both sound similar, they have vastly different uses and react differently in the event of a fire.
- Heat resistant: It will operate as normal at high temperatures, but may not operate as normal in the event of a fire.
- Fire retardant: It will not operate as normal within fire conditions, but will actively prevent the fire from spreading.
- Fire resistant: It can operate as normal within fire conditions.
- Conclusion:
- In brief, Fire retardant cables are designed to resist the spread of fire into a new area. It would not maintain circuit continuity for Work.
- Fire resistant or fire rated cables are designed to maintain circuit integrity and continue to work, allowing power to be transferred through it under defined for a specified period of time and conditions.
- The distinction between the two is crucial when it comes to maintaining critical circuits required for life safety or for a safe and immediate plant shutdown.
- Fire resistant cables are used in critical electrical circuits, such as safety circuits and life support circuits which are required to function in the case of emergencies.
- Flame retardant cables on the other hand are used in all other circuits so if there’s a fire, they can curb its spread. A flame resistant cable will be passed as per IEC 60331 and are encased in a red outer sheathes. Flame retardant cables behavior under fire is predefined as per passing the IEC 60332 and are encased in a grey or black outer sheathe.
Fire resistant (fire rated) cables |
Continues to operate in the presence of fire, hence their reference as Circuit Integrity cables. |
Flame retardant cables |
Fire performance limited to not propagating fire |
Difference between FR vs PVC vs LSF vs LSHF Cables
- FR Cables:
- Fire resistant and fire retardant cable sheaths are design to resist combustion and limit the propagation of flames.
- Fire Retardant (FR): Designed for use in fire situations where the spread of flames along a cable route needs to be retarded
- Fire Resistant (FR): cables are designed to maintain circuit integrity of those vital emergency services during the fire
- FR is for essential services such as fire alarms, emergency lighting, life safety and firefighting applications.
- These systems have to operate during a fire to detect the fire, alert people and help them evacuate and also help emergency services do their job.
- These circuits need to function fully and retain circuit integrity in the event of fire.
- In case of fire, it does not emit toxic or corrosive gases, thereby protecting public health and avoiding any possible damage to electronic equipment
- LSF, LSHF and PVC Cables
- Low smokes cables have a sheath designed to limit the amount of smoke and toxic halogen gases given off during fire situations
- Low Smoke and Fume (LSF): burns with very little smoke and fumes compared to standard PVC, fumes may contain halogens
- Low Smoke Zero Halogen (LSZH): when burns there is very little smoke and fumes contains no Halogen (compared to standard PVC)
- LSHF and PVC cables are used for non-essential services that do not need to operate in a fire.
- These include all the usual power circuits in buildings for services such as general lighting or kitchen and office appliances like cookers or photocopiers.
- These circuits are not essential for the safety of the public; they can fail in a fire with no increase in danger so they do not need to be fire resistant.
- For public buildings however, all cables need to be low smoke and zero halogen type but in domestic premises and for buried cables they do not, so PVC is acceptable
- Both LSZH and LSF are used to limit smoke, fumes and halogen given off in fire conditions.
- In the event of a fire, both types will emit very low levels of smoke. LSF cable will emit toxic gases while LSZH will limit the emission of these (typically under 0.5% hydrogen chloride emission). In addition to being toxic, hydrogen chloride is corrosive to equipment. The use of LSZH cables protect both people and limit the amount of equipment damage during a fire situation.
Comparison of various cable
Comparison of various cable
|
Feature |
Normal PVC Wire |
Heat Resistant HR PVC |
Fire Retardant FR – PVC |
Fire Retardant Low Smoke FRLS |
Zero Halogen Low Smoke ZHFR |
Insulation Material |
PVC |
PVC |
Special PVC |
Special PVC |
Special Polymer |
Insulation Property |
Normal |
Good |
Good |
Good |
Very Good |
Temperature Rating |
700 C. |
850 C. |
700 C. |
700 C. |
850 C. |
Thermal Stability |
Normal |
Very Good |
Good |
Good |
Very Good |
Flam Retardancy |
Good |
Good |
Very Good |
Very Good |
Excellent |
Safety During Burning |
Average |
Average |
Good |
Good |
Excellent |
Requirement of Oxygen to Catch Fire |
> 21% |
> 21% |
> 30% |
> 30% |
> 35% |
Temperature Required to catch fire ( with 21% oxygen) |
Room Temp. |
Room Temp. |
> 2500 C. |
> 2500 C. |
> 3000 C. |
Visibility during Cable burning |
< 20% |
< 20% |
< 35% |
< 40% |
< 80% |
Release of Halogen Gas during burning |
< 20% |
< 20% |
< 20% |
< 20% |
0% |
Abrasion Resistance during Installation |
Good |
Good |
Good |
Good |
Good |
Comparison various Specification’s of Cable
|
Test |
Function |
Specification |
Values of FRLS Compound |
Values of Halogen Free Compound |
Values of PVC |
Critical Oxygen Index |
To Determine % of Oxygen Required For Supporting Combustion of Insulating Material at room temperature. |
ASTM–D-2863 |
> 29% |
More than 29% |
23% |
Temperature Index |
To determine at What Temperature Normal Oxygen Content of 21% In Air will Support Combustion of Insulating Material |
ASTM–D-2863 |
> 2500 C. |
More than 2500 C. |
1500 C. |
Smoke density Rating (Light Transmission) |
To Determine the visibility ( Light Transmission ) under Fire of Insulating Material |
ASTM-D-2843 |
> 40 % |
More than 80 % |
10-15 % |
Acid Gas Generation |
To ascertain the amount of Hydrochloric Acid Gas Evolved from insulation of Cable Under Fire. |
IEC – 754 – 1 |
< 20 % |
Less than 0.5 % |
45-50 % |
International Standards
Halogen & Smoke Emission, Corrosively & Toxicity Standards
- IEC 60754-1/BS6425-1 – emission of halogen
- IEC 60754-2 – corrosivity , Acid gas emission
- IEC 61034-1/ ASTM E662 – emission of smoke
- ISO4589-2/ BS2863 – oxygen index LOI
- ISO4589-3/ BS2782.1 – temperature index TI
- ASTM – D – 2863- Oxygen index
- ES713 – toxicity index
Flame Retardant Standards
- IEC 60332-1 / BS 4066-1 – flame test on single vertical insulated wires/cables
- IEC 60332-3 / BS 4066-3 – flame test on bunched wires/cables
- UL Standard for Fire Retardant Cable
- NFPA -262 =CMP (Plenum Flame Test/ Steiner Tunnel Test)
- UL1666=CMR (Riser Flame Test)
- UL 1581=CM (Vertical Tray Flame Test)
- UL1581=CMG (Vertical Tray Flame Test)
- UL1581=CMX (Vertical Wire Flame Test)
Fire Resistance Standards
- IEC 60331 – fire resistance test
- BS 6387 / BS 8491: BS 8434/2 – fire resistance test (more stringent than IEC 60331)
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