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For a distribution panel rated at 400 amps parallel runs of 3/0 conductors will do the job.
Notes: 1. Where multiple sets of service-entrance conductors are used as permitted in Section 230-40, Exception No. 2, the equivalent size of the largest service-entrance conductor shall be determined by the largest sum of the areas of the corresponding conductors of each set. 2. Where there are no service-entrance conductors, the grounding electrode conductor size shall be determined by the equivalent size of the largest service-entrance conductor required for the load to be served. 1 This table also applies to the derived conductors of separately derived ac systems. 2 See installation restrictions in Section 250-64(a).
DON'T CONNECT A GROUND WIRE TO A COLD WATER PIPE!!! Use ground rods in accordance with local codes. When in doubt, contact a local electrician or the local building and zoning office of your city or county. Connecting a ground wire to your cold water pipe can result in electrolysis that will eat away at you water pipe. ---------------- Metal underground water pipe is the first grounding electrode listed in the NEC. It is still commonly used in residential installations and is used in commercial installations when available. When the water pipe is used as the primary grounding electrode, it must be supplemented with another electrode which is most commonly a ground rod. Generally speaking, a 325 amp service requires 350 kcmil copper conductors for residences or 400 kcmil copper conductors for commercial installations. In either case these require a grounding electrode conductor of 1/0 ("one ought") copper.
A 500 MCM wire with an insulation factor of 90 degrees C is rated at 430. Most 400 amp services will use parallel wires on each leg to feed the circuit. A 3/0 wire with an insulation factor of 75 and 90 degrees C is rated at 200 and 225 amps respectively. The insulation rating of these conductors will be 600 volts.
Need to know what size service is going to be installed at the end of the run.
The size of wire for service entrance conductors for a 400 amp 3 phase service could be 500 MCM copper. This is very large size wire and difficult to bend and shape, to connect to terminals in the main disconnect and distribution panel. This problem is solved by using parallel conductors or on higher ampacities triple conductors. Using parallel conductors the wire size would be three ought (3/0) copper.
250 kcmil in copper and 400 kcmil in aluminum. kcmil = 1000 circular mils.
Based on NEC 250.66- #2 copper or 1/0 aluminum.
For a distribution panel rated at 400 amps parallel runs of 3/0 conductors will do the job.
Notes: 1. Where multiple sets of service-entrance conductors are used as permitted in Section 230-40, Exception No. 2, the equivalent size of the largest service-entrance conductor shall be determined by the largest sum of the areas of the corresponding conductors of each set. 2. Where there are no service-entrance conductors, the grounding electrode conductor size shall be determined by the equivalent size of the largest service-entrance conductor required for the load to be served. 1 This table also applies to the derived conductors of separately derived ac systems. 2 See installation restrictions in Section 250-64(a).
Assuming this falls under the National Electrical Code (NEC) the size for the service ground is based on the conductor size of the Ungrounded (Hot) conductors. For 150A the size of XHHW Copper would be 1/0 for the Hot conductors and #6 AWG copper for the ground. Aluminum would be 3/0 for the Hot conductors and #4 AWG aluminum for the ground.
From the question it is hard to establish whether the service size is 350 amps or the service conductors are 350 MCM in parallel. If the service is 350 amps, the grounding conductor is #3 bare copper wire. Parallel 350 MCM conductors will allow for a 600 amp service. The grounding conductor for a 600 amp service is a #1 bare copper wire.
500
DON'T CONNECT A GROUND WIRE TO A COLD WATER PIPE!!! Use ground rods in accordance with local codes. When in doubt, contact a local electrician or the local building and zoning office of your city or county. Connecting a ground wire to your cold water pipe can result in electrolysis that will eat away at you water pipe. ---------------- Metal underground water pipe is the first grounding electrode listed in the NEC. It is still commonly used in residential installations and is used in commercial installations when available. When the water pipe is used as the primary grounding electrode, it must be supplemented with another electrode which is most commonly a ground rod. Generally speaking, a 325 amp service requires 350 kcmil copper conductors for residences or 400 kcmil copper conductors for commercial installations. In either case these require a grounding electrode conductor of 1/0 ("one ought") copper.
A 500 MCM wire with an insulation factor of 90 degrees C is rated at 430. Most 400 amp services will use parallel wires on each leg to feed the circuit. A 3/0 wire with an insulation factor of 75 and 90 degrees C is rated at 200 and 225 amps respectively. The insulation rating of these conductors will be 600 volts.
4/0 copper phases and neutral
Need to know what size service is going to be installed at the end of the run.