Wet is the Nemesis
Environmental Technology Inc. designs and makes products that mix water and electrical systems. OK, not precisely. ETI controls and sensors help radiant cables transform solid water (snow and ice) to liquid and eventually, depending on the application, either to evaporating water, for safe trafficked surfaces in the winter, or flowing water, in freeze prevention/protection applications for pipes, roofs, and gutters.
As essential and ubiquitous as it is, water (or other moisture) is the nemesis of reliable electrical equipment. Further, any water that infiltrates electrical equipment may be contaminated with minerals, chemicals, even debris. This affects the equipment’s operation or expected optimal performance. Then there are the seaside installations which are exposed to the corrosive and conductive nature of salt water residue. Electrical components which have been exposed to water may be extremely dangerous as well.
At any volume, water can degrade the dielectric integrity—that is, the insulating strength—of conductor jackets, an omen of impending fault conditions. Water can corrode wire splices and terminations, which create high impedance connections resulting in poor continuity or increased insulation temperatures sufficient enough to cause loss of efficacy through damage or breakdown.
Water and Electrical Systems – Prevention Strategies
Along with ETI product instructions for proper installation and operating conditions, consider the following recommendations.
Equipment assembly and systems construction should be so tight that they are impermeable to water. If water is introduced, structural integrity is therefore identifiably compromised. When building to water tightness, consider the following points.
- Watertightness of underground or embedded raceways should be imperative.
- Whenever possible, raceway systems – wiring conduits – should be installed with a slope lower and away from electrical connections. Unavoidable low points should be equipped with drain fittings.
Proper Conduit Required
If a nonmetallic conduit (typically PVC) is used, prime the conduit with a uniform coating of solvent cement around the end of the conduit, about a half inch (1.27 cm) from the opening, as well as around the fitting to which it connects. After inserting a conduit length into the mating coupling of the next coupler/elbow/cap/body, the assembly should be twisted 1/4-turn, dispersing the cement, ensuring a tight fit and sealing the connection. Allow for drying time before proceeding. While not as durable or strong as metal conduit, nonmetallic conduit is perhaps better in wet or underground installations.
Otherwise, the threads of rigid metallic conduit should be coated with a commercially available compound containing colloidal zinc or copper. (Caution: the use of nonconductive construction materials compromises the raceway’s inherent ground continuity and may require the remedial installation of an equipment grounding conductor.) Note: Electrical metallic tubing (EMT) may only be embedded in elevated slabs and should always employ UL Listed concrete-tight fittings.
Junction boxes installed in slabs on grade or outdoors, both in-pavement or direct burial, should be of watertight design with raceway terminations waterproofed. Use the same procedure as that described for conduit couplings above.
An exposed junction box installed outdoors or in damp environments must be rain-tight or weatherproof, consistent with its location. All rigid metallic raceway terminations should employ gasketed rain-tight conduit hubs or sealing locknuts. Nonmetallic raceway terminations may employ: waterproof nonmetallic conduit hubs; nonmetallic box adapters, solvent-cemented into nonmetallic conduit couplings; or nonmetallic conduit terminal adapters in conjunction with sealing locknuts.
The Splice is Right
When splicing conductors in hostile locations, we encourage the use of epoxy-filled, water-resistant wire nuts. After immersing test/sample splices in salt water for weeks, we confidently endorse them.
Or Call ETI
These points, as well as those found in the installation instructions of any ETI product, are general considerations. We encourage you to contact ETI for help with your specific application.