Sizing ACSR quadplex

[Galt]

I have always used no. 2 Al for 100 amp and 4-0 for 200 amp these are basically all that is available at supply houses around here. I am talking overhead here acsr. Would this be wrong for anything but residential.

 

[GoldDigger]

I have always used no. 2 Al for 100 amp and 4-0 for 200 amp these are basically all that is available at supply houses around here. I am talking overhead here acsr. Would this be wrong for anything but residential.

A #2 Al conductor in open air cannot carry 100A as a general rule. It can be used for a 100A nominal load only when it carries the entire load of a residential occupancy. Use as a feeder carrying part of the load or any use other than residential does not permit a nominal load of 100A.
4-0 Al, on the other hand, can be used for 200A in general use as long as any applicable derating conditions are met.
(But the voltage drop may be a problem if you go more than ~100'.)
Note that this is all based on the calculated load rather than just the nominal size or breaker rating of the service.

 

[Galt]

They are hanging in air and not terminated on any terminals so what could be derated?

 

[ActionDave]

They are hanging in air and not terminated on any terminals so what could be derated?

#2 AL is only good for 90A on the seventy five degrees C column, and you will have to go on the journey of a lifetime to find a breaker or fuse that is has terminals marked for anything higher, so you are stuck using 90A over current protection for anything other than a resi service, (TABLE 310.15(B) (7)) and that's all there is to it.

4/0 AL has a bit of wiggle room because you are allowed to use it for a 200A resi service (TABLE 310.15(B) (7)) and if your calculated load comes out less than 185A 240.4 lets you round up and use 200A over current protection.

 

[iwire]

A #2 Al conductor in open air cannot carry 100A as a general rule. It can be used for a 100A nominal load only when it carries the entire load of a residential occupancy.

To pick some nits.

We can protect 2AWG AL at 100 amps, we can't load it to 100 amps.

 

[GoldDigger]

#2 AL is only good for 90A on the seventy five degrees C column, and you will have to go on the journey of a lifetime to find a breaker or fuse that is has terminals marked for anything higher,

Actually, if it is used as an overhead service drop and connected to other conductors at the weather-head, you only need to find a split bolt or butt splice rated for 90 degrees.
Some Polaris connectors are rated 90, but perhaps not in that size. Although you probably would not use quadplex for that. Similar feeder configurations exist too.

(to pick a nit right back at you....)

 

[Galt]

thanks guys.there is never a problem finding 3 or 2 copper or 3-0 or 4-0 copper to go down the mast. Why is it so hard to find 1 or 1-0 or 250mcm in tri or quad overhead?

 

[JoeStillman]

If you are talking about the quadplex overhead messenger wire, the free-air ampacity in table 310.15(B)(17) applies. #2 THHW 75° AL in free air is rated at 135 A. Ampacities take a big jump when there is no raceway.

 

[augie47]

If you are talking about the quadplex overhead messenger wire, the free-air ampacity in table 310.15(B)(17) applies. #2 THHW 75° AL in free air is rated at 135 A. Ampacities take a big jump when there is no raceway.

That is a very valid point. Folks get used to looking at 310.15(B)(16) and forget the limitations on that Table.
It is pretty much ignored by inspectors but you might want to keep in mind utility type ACSR (triplex) is not even a NEC recognized conductor and is not listed in any Table.
#2 utilit ASCR is nicknamed "shrimp" an with a XLP insulation has an ampacity of 150 amps (based on 40°)
(see here: http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet34)

When you add all the facts together you can see why most inspectors care less about "triplex" as long as it's in free air.

edit: above info was triplex

#2 quadraplex is Belgin or Mustang and 135 amps see here: http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet35

 

[Smart $]

If you are talking about the quadplex overhead messenger wire, the free-air ampacity in table 310.15(B)(17) applies. #2 THHW 75° AL in free air is rated at 135 A. Ampacities take a big jump when there is no raceway.

That is a very valid point. Folks get used to looking at 310.15(B)(16) and forget the limitations on that Table.
It is pretty much ignored by inspectors but you might want to keep in mind utility type ACSR (triplex) is not even a NEC recognized conductor and is not listed in any Table.
#2 utilit ASCR is nicknamed "shrimp" an with a XLP insulation has an ampacity of 150 amps (based on 40°)
(see here: http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet34)

When you add all the facts together you can see why most inspectors care less about "triplex" as long as it's in free air.

edit: above info was triplex

#2 quadraplex is Belgin or Mustang and 135 amps see here: http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet35

Then again, it's max attainable circuit ampacity when under NEC purvue is still going to be regulated by Table 310.15(B)(16) because of 110.14(C) limitations.

 

[Galt]

thanks guys I love this site.