Mike Dolt Enterprises
Mike Dolt Enterprises
User: jmsbrush, Location: Central Florida
Asked on: Thursday, April 14, 2011 at 11:54 am EDT
Answered on: Tuesday, May 14, 2024 at 4:12 am EDT
Question: On a residential installation, I have a little chart on wire size.I was looking in the 2008 handbook and I'm not sure if this is correct.Application: 200 Amp 240V single phase.Lets say that I have a 400 amp meter/panel combo. I'm going to feed a 200 amp panel 50ft away. This will be a underground installation.Below is what is on my chart:4/0 Alu Xlpe/Use1 Alu Xlpe/UseNow looking at table 310.15 (b)(6), I see that 4/0 is correct.But when I look at table 250.122, I see that the equipment ground should be #4.Am I missing something or is my wire chart wrong?
Your wire chart is likely correct.
Service Entrance Conductors
According to Table 310.15(b)(6), 4/0 aluminum conductors are required for a 200 amp, 240V single-phase service entrance. This is for the ungrounded (hot) conductors.
Equipment Grounding Conductor
Table 250.122 provides the following requirements for the equipment grounding conductor (EGC): For a 200 amp service, the EGC must be at least 4 AWG copper or 2 AWG aluminum.
Conclusions
Based on the information provided: The ungrounded (hot) conductors should be 4/0 aluminum.* The equipment grounding conductor (EGC) should be #4 copper or #2 aluminum.
Note:
If the underground installation involves direct burial, it is important to refer to Table 310.15(b)(7) for the appropriate ampacity adjustment factors for aluminum conductors. Flag for review