CSLB C-10 Electrical ContractorWiring Methods and MaterialsEasy
A rooftop HVAC condensing unit motor requires a flexible raceway connection that will be exposed to rain and vibration. Which raceway type is best suited for this application?
- AElectrical metallic tubing (EMT)
- BLiquidtight flexible metal conduit (LFMC)
- CFlexible metal conduit (FMC)
- DRigid PVC conduit
Show answer & explanationAnswer & explanation
Correct answer: B. Liquidtight flexible metal conduit (LFMC)
Liquidtight flexible metal conduit (LFMC) is designed with a liquid-tight outer jacket over a flexible metal core, making it suitable for wet, outdoor locations subject to vibration, such as rooftop motor connections.
Why the other options are wrong
- A. EMT is rigid and not suitable for flexible vibration-isolating connections.
- C. Standard FMC lacks a liquidtight jacket and is not rated for wet locations.
- D. Rigid PVC is not flexible and cannot accommodate motor vibration.
Liquidtight Flexible Metal Conduit (LFMC)
LFMC combines a flexible metal core with a liquidtight nonmetallic outer jacket, making it suitable for wet locations and vibrating equipment connections.
- Common for motor and HVAC equipment connections.
- Listed for wet locations with liquidtight jacket.
- Fittings must also be listed for wet locations to maintain rating.
Memory trick: 'Liquidtight loves the rain' — LFMC handles wet, vibrating connections.