200 amp 3 phase wire sizing

[Stevenfyeager]

The last time I installed a 200 amp 3 phase 208 v service I used AL 250 size wires ( 4 wires) in a 2 1/2 “ riser. I need to install for another customer. Was I correct in using 2 1/2” instead of two inch ? Also, 4/0 is too small, correct? Is that because of more than three current c. conductors or ampacity ? Thank you from one who doesn’t do commercial work very often.

 

[augie47]

Lots of "what-ifs"
If your conductors are XHHW COMPACT then (4) 250s are allowed in a 2", Non-Compact coductors would require a 2-1/2 (assuming rigid conduit)
4/0 could be compliant IF you can confirm a load less no greater than 180 amps.

 

[Cow]

4/0 AL is good for 180 amps.
250 AL is good for 205 amps.

If you can show your calculated load is less than 180 amps, you can legally go up to the next standard size, a 200 amp breaker. That's code minimum.

Over here, we would use 250 AL in a 2.5-3" depending on which size we felt like using. A 3" weatherhead would probably be a little roomier. Sometimes that helps.

 

[Stevenfyeager]

Lots of "what-ifs"
If your conductors are XHHW COMPACT then (4) 250s are allowed in a 2", Non-Compact coductors would require a 2-1/2 (assuming rigid conduit)
4/0 could be compliant IF you can confirm a load less no greater than 180 amps.

Thank you, but I don't know what "Compact" "non compact " means. I've not heard this. ( I've used XHHW or THWN/THHN.) but not noticed the "compact"

 

[kwired]

Thank you, but I don't know what "Compact" "non compact " means. I've not heard this. ( I've used XHHW or THWN/THHN.) but not noticed the "compact"

Look at the cut end of the conductor, if the strands are round it is not compact. If they are formed so there is nearly no gaps between strands that is compact conductor, and because those gaps are filled with conductor material the overall diameter is a little less yet you have same cross sectional area of material. Almost like having a solid conductor but with more properties similar to a stranded conductor.

 

[LarryFine]

Thank you, but I don't know what "Compact" "non compact " means. I've not heard this. ( I've used XHHW or THWN/THHN.) but not noticed the "compact"

The strands are shaped to minimize space among them:

 

[Stevenfyeager]

The strands are shaped to minimize space among them:

View attachment 2552879

Thank you, I've noticed the different shapes of strands before but never knew why.