When to use parallel runs.

Status
Not open for further replies.
Hello All:

I am designing a retrofit for distribution system and am currently selecting the cable sizes for the schedule.
I do not have a code question but would like your input as electricians/engineers.

What size of cables do you generally start specifying parallel runs?

Context:
-I have a need for a cable run with a rating of 250A
-My options are
1) 3 Phase + Neutral of 250 kcmil (75°C) in a conduit (255A rated)
2) 2 Parallel runs of 1 AWG (75°C) for each 3 Phase + Neutral in two conduits (260A rated)

What is the wire size cutoff that you find too hard to pull 4 conductors in commercial situations?

Cheers!
 

luckylerado

Senior Member
Parallel conductors must be 1/0 or larger. 310.10(H)(1). Depending on the length 250s are not terribly difficult to pull in a properly sized conduit.


Edit. Sorry, I just noticed you are North of the Border. IDK how it works in Canada
 

310 BLAZE IT

Senior Member
Location
NJ
You see ampacity diminishing returns after 750kcmil and pulling becomes difficult to impossible depending on the existence of bends after 500kcmil

Cannot paralell les than 1/0 like said above
 

iwire

Moderator
Staff member
Location
Massachusetts
You see ampacity diminishing returns after 750kcmil and pulling becomes difficult to impossible depending on the existence of bends after 500kcmil

Cannot paralell les than 1/0 like said above

If we are talking copper I would put it about 500 kcmil before I parrelel.
 
Hello All:

I am designing a retrofit for distribution system and am currently selecting the cable sizes for the schedule.
I do not have a code question but would like your input as electricians/engineers.

What size of cables do you generally start specifying parallel runs?

Context:
-I have a need for a cable run with a rating of 250A
-My options are
1) 3 Phase + Neutral of 250 kcmil (75°C) in a conduit (255A rated)
2) 2 Parallel runs of 1 AWG (75°C) for each 3 Phase + Neutral in two conduits (260A rated)

What is the wire size cutoff that you find too hard to pull 4 conductors in commercial situations?

Cheers!

Without getting into the copper aluminum debate, with the type of work I do, I am nearly always the decider on the type and size of wire and I use aluminum so my answer is based on that. For copper I may be inclined to go parallel sooner. Probably around/over 500 is when I would think about parallel. Multiples of 500 are good for 1200 amp services. For 600 amps, you could use 3 250's or 2 500's, but with 600 amp equipment you often find you only get 2 lugs per phase.
 
Status
Not open for further replies.
Top