Yes, there can be benefits to using EMT conduit in concealed locations for Emergency (EM) circuits over MC cable, particularly regarding fire and physical damage, though the advantages aren't always clear-cut and depend heavily on the specific installation and local codes. Here's a breakdown

Fire Resistance & Protection
Enhanced Fire Containment

EMT, being a rigid metal raceway, offers superior fire containment compared to MC cable. If a fire originates outside the raceway, the EMT provides a robust barrier, delaying the fire's access to the conductors inside. This buys valuable time for the EM system to remain operational. MC cable, while often having a fire-rated jacket, is still less resistant to direct flame impingement and heat penetration.

Fire Stopping

EMT systems, when properly installed with fire-rated fittings and penetrations sealed according to code, contribute to compartmentation. This means that in the event of a fire, the conduit system helps to contain the fire within a specific area, preventing its spread to other parts of the building. MC cable doesn't offer this level of compartmentalization.

Reduced Smoke and Toxic Gas Emission

In a fire, the plastic components of MC cable (jacket, conductor insulation) can produce smoke and toxic gases when burned. EMT systems, especially when installed with low-smoke, zero-halogen (LSZH) conductors, minimize the release of these harmful substances, improving occupant safety.

Physical Protection Superior Mechanical Strength

EMT is significantly more resistant to physical damage than MC cable. It can withstand impacts, crushing forces, and abrasion much better. This is crucial in concealed locations where accidental damage from construction activities, renovations, or even pests is a possibility. MC cable is more susceptible to punctures, cuts, and deformation.

Protection from Rodents and Pests

EMT provides a barrier against rodents and pests that can chew through the jacket and insulation of MC cable, leading to shorts, ground faults, and system failures.

Earthquake/Seismic Resistance

In seismically active areas, a properly installed EMT conduit system provides better support and restraint for the conductors, preventing damage during an earthquake. MC cable, being more flexible, can be more prone to stress and breakage during seismic events.

Other Considerations Grounding Path

EMT, when properly installed with listed fittings, provides a reliable equipment grounding path. This is important for safety and can help reduce electrical noise. While MC cable has a grounding conductor, the EMT system offers a more robust and redundant grounding path.

Future Modifications/Upgrades

EMT conduit offers more flexibility for future modifications or upgrades. You can pull new conductors through the existing conduit without disturbing the building structure. Altering or adding circuits with MC cable typically requires running entirely new cable.

Code Compliance

Local electrical codes (often based on the NEC) may have specific requirements for wiring methods used for emergency systems. Some jurisdictions may favor or even mandate the use of EMT in certain applications.

Disadvantages of EMT Labor Cost

Installing EMT typically requires more labor than installing MC cable. Cutting, bending, and joining conduit takes time and skill.

Material Cost

While the cost of the EMT itself may be lower than MC cable, the cost of the fittings (couplings, connectors, straps, etc.) can add up.

Space Requirements

EMT conduit requires more space than MC cable, especially when bends and fittings are involved. This can be a limiting factor in congested areas.

When MC Cable May Be Preferable Tight Spaces

In areas with extremely limited space or where sharp bends are required, MC cable may be the only practical option.

Existing Structures

In existing buildings where running conduit would be extremely difficult or disruptive, MC cable can be a viable alternative.

Cost Considerations

If cost is a major concern and the code allows it, MC cable may be chosen, especially if the risk of damage is low.

In Summary

EMT generally offers superior* protection against fire and physical damage compared to MC cable in concealed locations, especially for critical systems like emergency circuits. However, the decision to use EMT or MC cable should be based on a careful evaluation of the specific application, local code requirements, the potential for damage, fire resistance needs, cost considerations, and the available space. Consulting with a qualified electrical engineer or contractor is crucial to making the right choice. Flag for review