concrete encased conduit duct bank crossing

Manufacturer’s Instructions) (NFPA 70, NEC 110.3(B)) Pull cable at constant velocity not less than 15 feet per minute and not greater than 50 feet per minute. Use power-assisted cable pulling equipment for long or difficult pull or pulls with several transitions. Manufacturer’s Instructions) (NFPA 70, NEC 110.3(B))Ĭable may be pulled manually for short, easy runs. For large conductors or long pulls, assist reel rotation manually or use a power out reel. Carefully control the rate of cable reel rotation. Ensure cable reels are level to reduce drag. Support cable reels with adequately sized reel jacks and reel axle. Use guides adequately sized for the cable being pulled and for the duct, along with properly sized bell and duct adapters. Provide physical protection of cables, such as flexible cable guides or feed-in tubes, at the entrance of manholes, underground ducts, and conduits. “Avoid abrasion and other damage to cables during installation. (Manufacturer’s Instructions) (NFPA 70, NEC 110.3(B))”

“Use a torque-balance pulling line or an adequately sized swivel joint between pulling line and the cable pulling attachment to prevent cable rotation during pulling operations. Minimum bending radius for all cables with metallic shield is 12 times the diameter of the individually shielded conductors or 7 times the overall diameter, whichever is greater.( IEEE 576, 7.3)Ĭonduit shall be sized in accordance with Table 1 in Chapter 9 of the NEC.

“Avoid sharp bending of the cable at the first pulley in overhead installations by locating the pay-off reel far enough away from the first pulley that the lead-in angle is kept relatively flat. Use adequate lubrication of the proper type to reduce friction in conduit and duct pulls. The percent fill requirement shall not be exceeded. Table 3 (IEEE 576, 5.1) See Attachment.īending radius of cables without metallic shielding or armor: Table 4 (IEEE 576, 7.1) See Attachment.īending radius of cables with metallic armor: Table 5 (IEEE 576, 7.1) See Attachment.Įnsure adequate clearance between duct or conduit diameter and cable diameter. (IEEE 576, 4.1.1)Ĭable sidewall pressure limitation – The ratio of pulling tension out of the bend to the radius of the bend of the cable shall be limited to minimized cable damage. The maximum pulling tension for copper conductor should not exceed 0.008 times circular-mil area. When the calculated pulling tension is close to (or within 10% of) the maximum pulling tension, use tension gauge during pulling. (NFPA 70, NEC 300.18)Ĭonsult the cable manufacturer for cable maximum allowable / recommended pulling tension. The raceway systems shall be installed complete prior to installation of MV power cables. I'm not in the IEEE anymore, but their IAS used to have such stuff.Medium Voltage Cable Installation and Commissioning (Rated 5KV through 35KV) Still, I say this only as an experienced electrician (37 yrs), and can't refer you to any papers or studies to support my recommendations, although I'm sure some exist. If your area has flooding or other factors present even rarely, PVC conduits in particular can float and move enough to damage your 'duct bank', which could nullify any initial savings. A multi layer formation would make compaction of dirt difficult, I'd recommend something similar to 'pea gravel' in the conduit formation with a denser cover layer and, if flotation is possible, at least planks of concrete, no less than 4' thick with some re-bar in the planks.Ĭonsider your soil conditions carefully. I would definitely advise considering possible damage in the area, and would also say that 2' of concrete wouldn't even be worth the pour! I admit this is only my opinion, but 2' wouldn't bear any weight or impact, or prevent any flotation. I've been told, whenever I've asked, that it's simply 'what's been spec'd' but these locations have always been where other utilities were nearby, and heavy industrial conditions and occupancies were present.

Concrete encased conduit duct bank crossing