The plenum space is above the office dropped ceiling.
Plenum space is the area in buildings dedicated to air handling, flowing and distribution, such as the space above drop ceiling tiles. Cables placed in plenum spaces must be plenum rated. Defined by Underwriters' Laboratories 910 Safety Standard, plenum rated cables must have an outer jacket constructed of materials that retard the spread of flame and produce little smoke. This plenum rating adds costs to the cable itself, but when you use plenum rated cable you do not need to use conduit. The resulting cost savings offset the added expense of the plenum cable.
Instructions
1. Plan the cable route by identifying the beginning and the end of the proposed route. Identify the entry and exit points of the plenum space.
2. Visually inspect the entire route by opening the drop ceiling panels. Identify obstacles along the proposed route. Common obstacles are firewalls, heating and air-conditioning ducts, electrical conduits, water pipes and sewer pipes. Do not compromise the integrity of a firewall by just punching a hole through it. Avoid laying cables over heating and air-conditioning ducts. Keep cables away from existing electrical conduits to minimize interference. Do not have cables touching hot water pipes. Do not lay cables on top of florescent lighting.
3. Look for existing cables which have been run earlier through the same proposed route. It is possible that some other installer has already overcome any route problems.
4. Make "Home Run" routes from point A to point B with no splices in the plenum cable. Splices are potential trouble spots that could later cause problems. They also might be difficult to find.
5. If at all possible, avoid making turns with cables. If you must make a turn, never just pull the cable around the corner, because that could damage the outer sheath of the cable. Pull enough cable to complete the entire run after the turn and then leave a "Figure 8" loop of cable at the turn location.
6. Lay the cable, or multiple cables, on the floor directly below the which is above the drop ceiling. Do not cut the cables yet, because you will need additional length to compensate for the entry and exit portions of the route.
7. Pull the cables up through an open ceiling tile with one person feeding the cables through the ceiling tile and a second person pulling the cable by opening every second or third ceiling tile along the route. Making this is a two person job will prevent pulling cables across the ceiling tile metal support and damaging the outer sheath of the cable. Make sure to pull enough cable to complete the run after the cables exit the plenum space.
8. Clean up your mess when you have finished the job. The area should look like it did before you arrived.
Tags: ceiling tile, proposed route, drop ceiling, plenum rated, above drop