Adding 100 Amp Subpanel

[cabranch47]

Hi, new member here with a question. I am adding a 100 amp subpanel to my 200 amp main panel. They are next to each other and recessed in wall. I have been getting different answers to my question "What size wire to I need to feed my 100 Amp Subpanel?". I would be using copper wire. Can someone give me a definitive answer.?

 

[James]

@Megawatt will know what the usa cable size required is. i can tell you what would be required in the uk.

 

[Megawatt]

Hi, new member here with a question. I am adding a 100 amp subpanel to my 200 amp main panel. They are next to each other and recessed in wall. I have been getting different answers to my question "What size wire to I need to feed my 100 Amp Subpanel?". I would be using copper wire. Can someone give me a definitive answer.?

My friend you need 3 # 3 copper wire and one # 6 copper for your ground wire

 

[cabranch47]

My friend you need 3 # 3 copper wire and one # 6 copper for your ground wire

Thanks you for your input. I contacted my local electrical supply and they acted like they have never heard of #3 and do not stock it. If I downsize to #4, what size breaker should I use?

 

[Megawatt]

Thanks you for your input. I contacted my local electrical supply and they acted like they have never heard of #3 and do not stock it. If I downsize to #4, what size breaker should I use?

On a single family dwelling you can use # 4 THHN copper for 200 amps. I find it strange that they have never heard of # 3 THHN copper. You can buy that at Home Depot or Lowes. Good luck

Thanks you for your input. I contacted my local electrical supply and they acted like they have never heard of #3 and do not stock it. If I downsize to #4, what size breaker should I use?

use a 100 amp breaker. The code will let you derate wire size on a single family dwelling, knowing that you are never going to pull that many amps

 

[cabranch47]

On a single family dwelling you can use # 4 THHN copper for 200 amps. I find it strange that they have never heard of # 3 THHN copper. You can buy that at Home Depot or Lowes. Good luck

use a 100 amp breaker. The code will let you derate wire size on a single family dwelling, knowing that you are never going to pull that many amps

Great, thanks for your reply. I have a picky inspector and did not want any issues.

 

[Darkwood]

200amp supply is big enough to design full discrimination into it so are you sure you are designing this right, as others point out US and UK regs may differ.