service lateral

[kasimms]

I have an existing overhead service with parallel 3 inch risers with 4 - 500 KCMIL thhn stranded copper conductors with rack mounted ct's at weatherheads . Just inside building is service gutter with two 400 amp 480 volt 3 phase disconnects tapping parallel service. Customer wants to replace overhead with underground lateral. I was planning to set ct can on backside of gutter running 2 - 3 inch pvc conduits underground and up transformer pole on stand off brackets.
1. Is the existing installation legally sized for 800 amp service taking into consideration the 75 degree / 90 degree ampacity ratings and for termination rating.??

2. Considering I will be using schedule 80 pvc for vertical runs is the conduit fill legal for 4- 500 kcmil ?

 

[Rich Elec.]

You state that you are planning to run 2-3" pvc conduits, but then you ask if the conduit is capable of holding the wire.

Were you making a guess?

Check Annex C in your code book.

 

[Dennis Alwon]

Given that the 500mcm is rated 380amp then parralelled 500mcm is worth 760amps. Since the next higher breaker size is 800amps then art. 240.4(B) may be applied as long as the load is not larger than 760amps.

 

[Dennis Alwon]

Chapter 9 Table 4 states that PVC schedule 80 is 2.577 sq. in with over 2 wires 40%.

Table 5 500mcm thhn is .7073 sq. in

You can do the math.:grin: