the relationship between the pipe length and the number of electric wires. How many wires #12 can be put in the 1/2 pipe if the pipe length of 300 ft?

Question

the relationship between the pipe length and the number of electric wires. How many wires #12 can be put in the 1/2 pipe if the pipe length of 300 ft?

Answer 1

If you are in North America, the length of the pipe has no bearing on how many wires can go inside. The only restrictions on wire fill in pipes (which are actually called conduits, not pipes, when used for wiring) are on diameter and type of conduit. Also, what types of wire and cable, not just the gauge of the wire, also determines how many are allowed by the National Electrical Code to be installed in a conduit. Wires with certain insulation take up more room in the conduit so fewer are allowed. And some types of conduit are allowed to have more wires than others even if they are the same diameter.



Look at the chart in this link which is wire fill for the 4 most common different types of metal conduit and the most common kind of building wire which is copper THHN. For this kind of wire you are allowed 9 wires for EMT conduit but can put 10 in IMC conduit (heavier wall).



http://www.elliottelectric.com/StaticPages/ElectricalReferences/ElectricalTables/Conduit_Fill_Table.aspx



Different wire types, like SO cable, would have different limits. And it doesn't matter if it is 1 foot of conduit or 1,000' of conduit. Length may affect wire size (you have to use larger wire for longer lengths to avoid voltage drop) but length of the pipe run has no bearing on how many wires are allowed in the conduit.

Answer 2

that is one long run and you would be much happier to run one solid wire to a second electric panel == are you trying for a 220volt connection at the end of the 300feet??? if so the 12 gauge THHN will not be correct === if it is all 110volts in your out shed/shop/garage then a 24 inch deep buried #12 or a #10 [[ 3-part cable ]] will supply a 2nd small panel --- it is confusing to try to wire directly from the home panel and the metal pipe is not for underground .. String out the supply cable [[ leaving plenty to make connections ]] and basically feed one PVC section and glue one section of that PVC pipe run just one section at a time -- schedule 40 PVC is best for this job and even though the thin wall PVC is cheaper you do not want to use that and the purple glue for PVC sets up fast and is waterproof ...... hope this helps and rent a Ditch Witch to cut the trench .... Construction Commercial Rentals for the ditch digger. offset the long wire splice and use high voltage sticky=tar tape ....

Answer 3

The fill tables are set in the NEC. The length of the run is not the issue. The type of the insulation on the wire is one factor. the tables show 4 type TW #12 in a 1/2" conduit. Different insulation means a different fill.