Cable Supports in Vertical Raceways

Emerson has been furnishing O-Z/Gedney Cable Supports to the electrical industry for decades. Cable Supports are installed in vertical raceways in high rise buildings throughout North America. They prevent excessive strain on terminations, panels or other connected devices.

Cable supports are one of the electrical industry’s unsung heroes. When installed, they provide end-users with enhanced safety and lower maintenance.

Cable supports must provide needed support to the heavy cable without damaging the insulation or excessively reducing the amount of insulation over time, so the materials that are used and their engineering are important. Impregnated hardwood or Bakelite wedging plugs are standards. Iron or Canvas Bakelite bodies, combined with sealing compound, are also used for certain applications since it can furnish a weatherproof seal and provide ventilation at the top of the conduit riser. Proper venting can reduce the temperature in a riser by up to 20° F.

Learn more with the O-Z/Gedney Cable Supports Reference Chart.

The National Electric Code (NEC) calls out specific installation methods for long vertical runs. NEC Article 300.19 (Supporting Conductors in Vertical Raceways) states that cable support is needed at the top of a long raceway, with intermediate supports installed at specified lengths according to a formula based on the size of the wire, some as frequently as every 40 feet.

Cable support design is deceptively simple: Essentially, cable support bodies are threaded to conduit or rest on an existing bushing atop any conduit raceway in which non-armored cables pass through. The one-piece or multiple segment wedging plug is inserted into the cable support body. The wedging plug exerts pressure around the cable, providing holding force of that required by code.

There are two basic types of cable supports: the one-piece plug and the multiple segment plug. the one-piece has a single wedging plug with a groove for each wire. It is ideal for all types of non-armored cables 600 Volts or less, plus is considered the easiest to install. In contrast, the multiple segment version has a wedging plug constructed so that each cable is supported between grooves in adjacent segments. This uniform pressure distribution is required by the softer types of insulation frequently used at higher voltages. Some supports line cable grooves with coarse grain grit to improve holding power without damaging the jacket or insulation on the cable. In both cases, either single or multiple segment, it is good practice to space conduits about 1/2" or more further than normal to accommodate the cable support body.