Dear Mr. Electrician: What are the five inch electrical conduit dimensions?
Answer: Five Inch (5″) is the trade size, not the actual dimension of electrical conduit. One hundred twenty nine (129) is the metric designator not the actual dimension in millimeters. NOTE: Some text links below go to applicable products on Amazon. As an Amazon Associate I earn from qualifying purchases.
The dimensions for various types of five inch electrical conduits are below. The information was derived from several sources and should not be considered precise. Dimensions may vary slightly between manufacturers.
Use a 5 1/2″ (140mm) hole saw for five inch conduit fittings.
Click here for my post with more detailed descriptions of various types of electrical conduit and their code references, without dimensions.
5″ Rigid Metal Conduit (RMC) is a heavy weight conduit with a galvanized finish throughout. It has factory threads with a 3/4″ per foot taper, 8 threads per inch NPT. 100′ of 5″ RMC weighs approximately 1400 pounds or 634.9 kilograms.
Five inch RMC has an inside diameter of 5.073″ or 128.85mm. It has an outside diameter of 5.563″ or 141.30mm. The wall thickness is .245″ or 6.20mm. 5″ Rigid requires a 5 1/2″ hole for the conduit and fittings. A tap needs a 5 9/32″ (5.2813″) hole for taper pipe threads.
5″ Rigid Polyvinyl Chloride Conduit (PVC) schedule 40 is a nonmetallic, non-conductive electrical conduit that is good to use indoors and outdoors, or underground.
Five inch PVC 40 has some flexibility with an inside diameter of 5.047″ or 128.1938mm. It has an outside diameter of 5.563″ or 141.3002mm. The wall thickness is .258″ or 6.5532mm. 5″ Schedule 40 weighs 315 pounds per 100 feet (142.88148 kilograms). 5″ PVC requires a 5 1/2″ hole for the conduit fittings. A tap needs a 5 9/32″ (5.2813″) hole. Threads per inch for the fittings is 8 NPT.
5″ Rigid Polyvinyl Chloride Conduit (PVC) schedule 80 is a nonmetallic, non-conductive electrical conduit that is good to use indoors and outdoors, or underground. It has limited flexibility.
Five Inch Schedule 80 PVC has an inside diameter of 4.813″ or 122.2502mm. It has an outside diameter of 5.563″ or 141.3002mm. The wall thickness is .375″ or 9.525mm. 5″ Schedule 80 weighs 428 pounds per 100 feet or 194.137376 kilograms. 5″ PVC requires a 5 1/2″ hole for the conduit fittings. A tap needs a 5 9/32″ (5.2813″) hole. Threads per inch for the fittings is 8 NPT.
5″ Reinforced Thermosetting Resin Conduit (RTRC or Fiberglass) is a nonmetallic conduit that is suitable for many conditions.
Five inch RTRC Fiberglass has an inside diameter of 5.380″ or 136.652mm. Outside diameter is 5.572″ or 141.5288mm. The conduit wall thickness is .096″ or 2.4384mm. 100 feet of five inch MW RTRC weighs 120 pounds or 54.43104 kilograms. It requires a 5 1/2″ hole for the conduit fittings. A tap needs a 5 9/32″ (5.2813″) hole. Threads per inch for the fittings is 8 NPT.
5″ High Density Polyethylene (HDPE) is a non-metallic flexible conduit available in long reel lengths to reduce joints and installation time.
Five inch HDPE has an outside diameter of 5.563″ or 141.3002mm. Type SDR-9 has an inside diameter of 4.253″ or 108.0262mm. 100 feet of 5″ HDPE weighs 416 pounds or 188.694272 kilograms. The wall thickness is .618″ or 15.6972mm.
All five inch conduit and fittings require a five inch and a half inch (5 1/2″ or 140mm) opening into an electrical box. The hole can be made with a hole saw.
A tap for five inch 5″ (129) electrical conduit or conduit fittings requires a 5 9/32″ (5.2813″) hole for taper pipe threads. The threads per inch is 8 National Pipe Thread (NPT).
The standard length for most conduits is ten feet 10′ or 3.048 meters. Twenty foot 20′ (6.096 meters) lengths of metal conduit are available, but not always in stock. PVC conduit is available in ten foot 10′ and in some sizes, twenty foot 20′ lengths. RTRC mostly comes in twenty foot 20′ lengths.
Click Here for my blog post with hole saw sizes for electrical conduit.
See my blog post describing various electrical conduit types.
OTHER SIZE ELECTRICAL CONDUIT DIMENSIONS
For more conduit code details and conduit fill see Chapter 9, Tables 1, 4, 5 and 5A.
See the tables in Informative Annex C in the back of the National Electrical Code (NFPA 70) for the allowable number of wires in each size conduit.