mounted items such as boxes, cabinets, elbows, or other conduit terminations.
355.46 Bushings. Where a conduit enters a box, fitting, or other enclosure, a bushing or adapter shall be provided to protect the wire from abrasion unless the box, fitting, or enclosure design provides equivalent protection.
FPN: See 300.4(G) for the protection of conductors 4 AWG and larger at bushings.
355.48 Joints. All joints between lengths of conduit, and between conduit and couplings,
fitting, and boxes, shall be made by an approved method.
355.56 Splices and Taps. Splices and taps shall be made in accordance with 300.15.
355.60 Grounding. Where equipment grounding is required, a separate equipment grounding conductor shall be installed in the conduit.
Exception No. 1: As permitted in 250.134(B), Exception No. 2, for dc circuits and 250.134(B), Exception No. 1, for separately run equipment grounding conductors.
Exception No. 2: Where the grounded conductor is used to ground equipment as permitted in 250.142.
III. Construction Specifications
355.100 Construction. RTRC and fittings shall be composed of suitable nonmetallic material that is resistant to moisture and chemical atmospheres. For use aboveground, it shall also be flame retardant, resistant to impact and crushing, resistant to distortion from heat under conditions likely to be encountered in service, and resistant to low temperature and sunlight effects. For use underground, the material shall be acceptably resistant to moisture and corrosive agents and shall be of sufficient strength to withstand abuse, such as by impact and crushing, in handling and
Table 355.44 Expansion Characteristics of Reinforced Thermosetting Resin Conduit (RTRC) Coefficient of Thermal Expansion = 2.7 x 10" 5 mm/mm/°C (1.5 x 10 _s inVin/T)
|
Length Change of Temperature RTRC Conduit Change (°C) (mm/m) |
Length Change of Temperature RTRC Conduit Change (°F) (inVlOO ft) |
Temperature Length Change of RTRC Change (°F) Conduit (inJlOO ft) |
|
5 0.14 10 0.27 15 0.41 20 0.54 25 0.68 |
5 0.09 10 0.18 15 0.27 20 0.36 25 0.45 |
105 1.89 110 1.98 115 2.07 120 2.16 125 2.25 |
|
30 0.81 35 0.95 40 1.08 45 1.22 50 1.35 |
30 0.54 35 0.63 40 0.72 45 0.81 50 0.90 |
130 2.34 135 2.43 140 2.52 145 2.61 150 2.70 |
|
55 1.49 60 1.62 65 1.76 70 1.89 75 2.03 80 2.16 |
55 0.99 60 1.08 65 1.17 70 1.26 75 1.35 80 1.44 |
155 2.79 160 2.88 165 2.97 170 3.06 175 3.15 180 3.24 |
|
85 2.30 90 2.43 95 2.57 100 2.70 |
85 1.53 90 1.62 95 1 . 7 1 100 1.80 |
185 3.33 190 3.42 195 3.51 200 3.60 |
during installation. Where intended for direct burial, without encasement in concrete, the material shall also be capable of withstanding continued loading that is likely to be encountered after installation.
355.120 Marking. Each length of RTRC shall be clearly and durably marked at least every 3 m (10 ft) as required in the first sentence of
110.21. The type of material shall also be
included in the marking unless it is visually
identifiable. For conduit recognized for use aboveground, these markings shall be permanent. For conduit limited to underground use only,