Liquidtight Flexible Metal Conduit (LFMC)

LFMC is flexible metal conduit wrapped in a sunlight- and liquid-resistant plastic jacket, terminated with sealing fittings. It gives you the flexibility of Greenfield plus a watertight seal, which is why it makes the final connection to rooftop HVAC units, outdoor motors, pumps and any equipment in wet or oily environments.

Like FMC, its ability to act as a ground path is limited by length and fitting listings, so a bonding conductor is commonly run inside. The liquidtight fittings must be the type listed for the conduit to actually maintain the seal — a mismatched connector defeats the whole purpose.

When it applies

Liquidtight flexible metal conduit is your flexible, watertight connection for the last stretch to equipment that moves, vibrates, or sits in wet conditions. Think rooftop condensers, outdoor motors, and washdown areas where you need flex to absorb vibration and a jacket that keeps water out of the raceway.

Common mistakes

• Using non-liquidtight connectors that break the watertight seal at the terminations.
• Running excessively long LFMC where the equipment grounding conductor rules require a separate wire ground.
• Exceeding the allowable length or bend limits for the flexible run.

In the field

On a rooftop unit I use LFMC with proper liquidtight fittings and always pull a separate equipment grounding conductor. The jacket handles the weather while the flex takes the vibration off the connections.