The purpose of MI cable is to meet the 2-hour fire rating requirement Article 332 of the NEC. It is used for critical fire protection applications. It is available in single or multi-conductor assemblies and most are rated for 600 volts.
NEC Article 332.10 Uses Permitted, are as follows:
- For services, feeders, and branch circuits
- For power, lighting, control, and signal circuits
- In dry, wet, or continuously moist locations
- Indoors or outdoors
- Where exposed or concealed
- Where embedded in plaster, concrete, fill, or other masonry, whether above or below grade
- In hazardous (classified) locations where specifically permitted by other articles in this Code
- Where exposed to oil and gasoline
- Where exposed to corrosive conditions not deteriorating to its sheath
- In underground runs where suitably protected against physical damage and corrosive conditions
- In or attached to cable tray
Informational Note: The “Uses Permitted” is not an all-inclusive list
MI cable can be found in the following facilities:
- High-rise buildings
- Health care facilities
- Historic buildings
- Hazardous locations
MI cable may be used for the following applications:
- Fire pump feeders
- Emergency generator feedersR
- Emergency exhaust fans
- Emergency lighting
- Emergency communications systems
- Exit signs
- Firefighter’s elevators
A complete MI cable takeoff would include the following:
- Cable lengths by number and size of conductors
- Number of termination fittings by cable size and conductors
- Splice kits if necessary
- Firestopping thru fire rated walls
- Hangers – Unistrut trapeze racks or strapping – 6 ft spacing as per NEC, vertical or horizontal supports.
- If installed in cable tray, appropriate straps
Things to remember:
- MI cable manufacturers may require minimum quantities.
- Terminating MI cable requires special tools.
- MI Cable is extremely heavy.
- Most manufacturers will make custom configurations.
- Physical protection is required where cable comes out of a slab.
- If encased in concrete, the cable may need to be wrapped in a protective cover.
Remember, estimating is expensive, poor estimating is costly, but quality estimating is profitable.