Draining Electrical Conduit Systems

Luminaires experiencing water ingress, specifically pendant mount fixtures, can be a frustrating and costly problem.

Conduit is the culprit in such instances and provides the perfect path for water to find its way into the wiring compartment or mounting hood of the fixture. Every effort should be made to drain conduit before it terminates into the fixture. Let’s explore how.  

How does water find its way into conduit systems?

- Rain, sleet, snow and ice are obvious
- Hose-down or spray-down locations
- Condensation forms in raceways exposed to weather or temperature changes
- The threads on both Intermediate Metal Conduit (IMC) and Rigid Metal Conduit (RMC) are tapered (NPT), while the standard couplings that come with each ten-foot length of conduit are straight (NPS)

As a result, moisture accumulates within raceways at low points throughout the installation and in luminaires, enclosures, conduit bodies and fittings. Per the National Electrical Code, raceways are required to be installed so that moisture drains from the raceway through drain holes located at appropriate points throughout the system.

Code Review
Let’s review some specific articles of the 2017 National Electrical Code pertaining to raceway systems and wet locations, as follows:

Article 100 – Definitions
Location, Damp
Locations protected from weather and not subject to saturation with water or other liquids but subject to moderate degrees of moisture.

Location, Wet
Installations underground or in concrete slabs or masonry in direct contact with the earth; in locations subject to saturation with water or other liquids, such as vehicle washing areas; and in unprotected locations exposed to weather.

225.22 Raceways on Exterior Surfaces of Buildings or Other Structures
Raceways on exteriors of buildings or other structures shall be arranged to drain and shall be listed or approved for use in wet locations.

314.15 Damp or Wet Locations
In damp or wet locations, boxes, conduit bodies, outlet box hoods, and fittings shall be placed or equipped so as to prevent moisture from entering or accumulating within the box, conduit body, or fitting. Boxes, conduit bodies, outlet box hoods, and fittings installed in wet locations shall be listed for use in wet locations.

300.9 Raceways in Wet Locations Abovegrade
Where raceways are installed in wet locations abovegrade, the interior of these raceways shall be considered to be a wet location. Insulated conductors and cables installed in raceways in wet locations abovegrade shall comply with 310.10(C).

Drain Solutions

Conduit Outlet Bodies and Boxes Incorporating Drains
Emerson offers a full line of Appleton hazardous and non-hazardous rated Drains to thread into a hub of a Conduit Outlet Body or Conduit Outlet Box (normally a T or X configuration). Every location or facility is unique, so it’s imperative that the drain is located appropriately to be effective.

Sealing Fittings with Drains

In addition, Emerson has a complete line of Appleton Sealing Fittings, for ½” – 4” trade size conduit installed in hazardous locations, that incorporate a drain to keep your conduit systems free of water.

Watertight Pendant Hood
An Appleton Watertight Pendant Hood by Emerson can be installed if water cannot be drained from the conduit system prior to terminating into a pendant mounted fixture. The hood protects against water ingress into the fixture housing by incorporating an IP68 cord grip for the conductors to pass through. The Watertight Pendant Hood can be installed on the Appleton Mercmaster LED Generation 3 Series Luminaires and Appleton Mercmaster LED Low Profile Series Luminaires.