Fire Resistant Cables – What Do E90, E60, E30 and FE180 Mean?
During a fire, the continued operation of electrical systems can be just as important as the fire resistance of the building itself. In the event of a fire, certain electrical systems must continue to operate to support evacuation and the operation of fire safety systems.
Such installations use fire-resistant or circuit-integrity cables, which are designed to maintain the operation of electrical circuits for a specified period of time during a fire. Depending on the cable and system design, designations such as FE180, E30, E60 or E90 may be specified.
What Is a Fire-Resistant Cable?
A fire-resistant cable is a cable designed to maintain the operation of an electrical circuit for a specified period of time under defined fire conditions.
It is important to understand that the terms “flame-retardant,” “halogen-free,” “fire-resistant” and “E90” do not mean the same thing.
For example, a cable may be flame-retardant and limit the spread of fire, but this does not necessarily mean that it will maintain electrical circuit operation for 90 minutes during a fire.
The IEC 60331 series specifies test methods for cables that are required to maintain circuit integrity during a fire. For example, IEC 60331-1 and IEC 60331-2 cover low-voltage cables tested under fire and mechanical impact conditions.
What Does E90 Mean?
E90 is a designation indicating that an electrical installation system can maintain circuit functional integrity for 90 minutes during a fire.
The E90 classification is associated with DIN 4102-12, which tests not only the cable itself but the complete cable system, including the cable, its supports and the supporting structure.
Therefore, it is important to understand:
E90 is not simply a property of the cable. E90 is a classification of the functional integrity of a cable system in a specific tested configuration.
This means that an E90 cable should be installed using a suitable E90-rated cable support and fixing system, where required by the relevant certification or project design.
E30, E60 and E90 – What Is the Difference?
| Class | Functional integrity period | Meaning |
|---|---|---|
| E30 | 30 minutes | The electrical circuit maintains operation for at least 30 minutes during fire exposure |
| E60 | 60 minutes | The electrical circuit maintains operation for at least 60 minutes |
| E90 | 90 minutes | The electrical circuit maintains operation for at least 90 minutes |
Within the scope of DIN 4102-12, E30, E60 and E90 indicate the period during which the tested cable system must maintain circuit integrity.
Why Are E90 Cables Required?
During a fire, some systems must continue operating even after dangerous temperatures and smoke concentrations have developed inside the building.
Fire-resistant cables and E90 cable systems can be used, for example, for:
- emergency and escape-route lighting;
- fire detection and alarm systems;
- smoke extraction systems;
- fire-fighting pumps;
- sprinkler system control and power circuits;
- power supply for lifts and other safety systems;
- ventilation and smoke extraction equipment;
- other systems that require continuous power during a fire.
The specific E30, E60 or E90 requirement depends on the building, the system and the fire safety design of the project.
What Does FE180 Mean?
Fire-resistant cables may also carry the designation FE180.
FE180 relates to the integrity of the cable insulation under specified fire test conditions. It is not the same as E90.
In simple terms:
FE180 → relates to maintaining cable insulation integrity during a specified fire test.
E90 → relates to the ability of a cable system to maintain electrical circuit functional integrity for 90 minutes under the specified system test conditions.
Therefore, when selecting a cable for a fire-resistant electrical installation, it is not sufficient to look at only one marking. The complete cable specification and installation system must be considered.
E90 Does Not Mean “The Cable Does Not Burn”
It is important to understand that E90 does not mean that the cable will not burn or be damaged during a fire.
The purpose of E90 is to ensure that the electrical circuit maintains its function for a specified period of time during fire exposure.
IEC 60331 test methods include testing cable operation under fire exposure and, in certain tests, mechanical impact conditions.
Why Are Cable Supports Also Important?
This is one of the most important aspects of an E90 cable system.
If the cable itself can withstand fire exposure but its supports or cable tray system collapse during the fire, the electrical circuit may stop operating.
DIN 4102-12 tests the cable system as a whole, including the cables and their supporting structures.
Therefore, an E90 installation must take into account:
- the cable;
- cable trays or ladders;
- cable clips;
- fixings;
- supporting structures;
- installation spacing;
- cable type and cross-section;
- permissible cable load.
It cannot automatically be assumed that any cable marked E90 will form an E90 system when installed with any type of cable tray or support system.
Fire-Resistant, Halogen-Free and Flame-Retardant Cables – What Is the Difference?
These terms are often confused.
| Designation | What does it describe? |
|---|---|
| Flame-retardant | The cable limits the spread of flame under specified test conditions |
| Halogen-free / LSZH | Cable materials are halogen-free and designed to produce low smoke and low corrosive gas emissions according to the relevant tests |
| FE180 | Maintenance of insulation integrity under specified fire test conditions |
| E30 | Cable system maintains functional integrity for 30 minutes |
| E60 | Cable system maintains functional integrity for 60 minutes |
| E90 | Cable system maintains functional integrity for 90 minutes |
Therefore, for example, a halogen-free cable is not automatically an E90 cable, and an E90 cable should not be evaluated solely based on whether it is halogen-free.
How to Choose an E90 Cable?
When selecting a cable for a fire-resistant electrical installation, at least the following should be checked:
- Cable type and construction
- Rated voltage
- Number of cores and conductor cross-section
- FE180 or another insulation integrity classification, if required
- E30/E60/E90 classification
- Compliance with the relevant standard
- Manufacturer's test and certification documentation
- Compatibility with the specific cable support system
- Installation method and fixing distances
It is particularly important to verify whether the E90 classification applies to the specific cable construction and specific installation system that will be used in the project.
E90 Cable Is Not the Only Fire Safety Element
Creating a fire-resistant electrical installation requires more than simply selecting an appropriate cable. The appropriate cable support system and fixings must also be selected, and the manufacturer's specified installation method must be followed.
A correctly designed system helps maintain the power supply to equipment whose operation is essential for human safety and for limiting the consequences of a fire.
In Summary
E90 means that the electrical circuit can maintain functional integrity for 90 minutes during a fire under the conditions of the specific tested cable system.
It is not simply a designation meaning that the cable “does not burn”. E90 is a system classification in which not only the cable but also its supports and supporting structure can be important.
When selecting fire-resistant cables, always check the manufacturer's technical documentation and the requirements of the specific electrical installation.