100 amp Sub-Panel wire size

[Hard2bej]

Hey all, I’m running into a few of different answers on this. I need to know what size wire I need to complete the install. It’s a 100 amp sub panel in a detached garage 110’ away (total wire length) fed from a 200 amp main house panel. I have 1 1/4 pvc buried. I need 3 current carrying conductors and the ground. The garage will have a main breaker as the disconnect. I’ve heard #4 cu unless far away then #2 cu, prefer alum as its wayyy cheaper, then I read in the code that you could apply the 83% of rated amps. Can someone point me in the right direction? Also #8 ground? I don’t size conductors much as it’s done for me. Thanks in advance!!

 

[infinity]

You'll need a 100 amp conductor (assuming that the feeder OCPD is 100 amps) which is a minimum of #3 copper or #1 Al. The 83% rule does not apply to this feeder.

Welcome to the Forum.

 

[Ohm2]

Hey all, I’m running into a few of different answers on this. I need to know what size wire I need to complete the install. It’s a 100 amp sub panel in a detached garage 110’ away (total wire length) fed from a 200 amp main house panel. I have 1 1/4 pvc buried. I need 3 current carrying conductors and the ground. The garage will have a main breaker as the disconnect. I’ve heard #4 cu unless far away then #2 cu, prefer alum as its wayyy cheaper, then I read in the code that you could apply the 83% of rated amps. Can someone point me in the right direction? Also #8 ground? I don’t size conductors much as it’s done for me. Thanks in advance!!

I agree with infinity! See T 250.122 to confirm your EGC.

 

[electrofelon]

I would often use #2 AL mobile home feeder, although that would need to be on a 90 amp breaker. If you want the full 100 then you will need #1 like Infinity said. Around here no one is going to stock number one mobile home feeder or four wire urd so it would be individual conductors. I probably would pull a two size reduced neutral.

 

[Elect117]

I would suggest using a online tool for voltage drop just to be safe. 110' away is getting close to the threshold on needing to upsize wire due to voltage drop.

When using the calculator, use your projected load for the current. Not the OCPD. You can do the OCPD but it will probably lead to a higher size than needed.

 

[retirede]

I would suggest using a online tool for voltage drop just to be safe. 110' away is getting close to the threshold on needing to upsize wire due to voltage drop.

When using the calculator, use your projected load for the current. Not the OCPD. You can do the OCPD but it will probably lead to a higher size than needed.

The Southwire calculator shows 2.42% for 110’ of #2 AL cable at 90A.