CSLB C-10 Electrical ContractorWiring Methods and MaterialsEasy
An electrician is installing a new solar array on a rooftop. The DC wiring from the PV modules to the inverter will be run in conduit exposed to direct sunlight and varying weather conditions. Which type of conduit is generally NOT suitable for outdoor use in this application without additional protection or specific listing?
- ARigid PVC Conduit (PVC)
- BElectrical Metallic Tubing (EMT)
- CIntermediate Metal Conduit (IMC)
- DRigid Metal Conduit (RMC)
Show answer & explanationAnswer & explanation
Correct answer: B. Electrical Metallic Tubing (EMT)
While EMT can be used outdoors, it is generally not suitable for direct exposure to the elements and direct sunlight without specific listing for such use or additional protection, as it is more prone to corrosion and damage compared to RMC, IMC, or PVC. NEC 358.12(1) prohibits EMT where subject to severe physical damage, and 358.10(D) requires it to be protected from corrosion where subject to the elements.
Why the other options are wrong
- A. PVC conduit, when properly listed for sunlight resistance, is widely used outdoors and underground.
- C. IMC is similar to RMC in its suitability for outdoor and harsh environments.
- D. RMC is robust and suitable for outdoor and harsh environments.
Outdoor Conduit Suitability
The suitability of conduit for outdoor exposure depends on its material, construction, and listing, particularly concerning resistance to corrosion, UV degradation, and physical damage.
- RMC/IMC are generally robust for outdoor use
- PVC needs to be sunlight-resistant for exposed outdoor runs
- EMT is less suitable for exposed outdoor conditions without additional protection
Memory trick: Outdoor conduits need to Resist the elements, not just route wires.