Conductor size
#1
12-17-15, 11:22 PM
Conductor size
Good day,
Sorry for asking but I was wondering what if the ampacity exceeds the ampacities on the table on the code. For example, if the computed ampacity is 900 A, what conductor size should I use?
This was not related to the chiller I post previously. I just wonder what if I got this large amount of ampacity.
Thank you to those who will answer.
Sorry for asking but I was wondering what if the ampacity exceeds the ampacities on the table on the code. For example, if the computed ampacity is 900 A, what conductor size should I use?
This was not related to the chiller I post previously. I just wonder what if I got this large amount of ampacity.
Thank you to those who will answer.
#2
12-17-15, 11:41 PM
Group Moderator
You're talking about a large service. You can get wire up to 1000mcm (about 600A) but you can't work with it. Anything over 500mcm is a bear to work with.
It depends on things like distance, pull points, elbows. It's what size can you pull comfortably.
You could run two parallel 600mcm (450A) but that requires massive conduit....two 4" conduits.
You could run three parallel 300mcm (300A) in three 3" conduits.
It depends on things like distance, pull points, elbows. It's what size can you pull comfortably.
You could run two parallel 600mcm (450A) but that requires massive conduit....two 4" conduits.
You could run three parallel 300mcm (300A) in three 3" conduits.
#3
12-18-15, 08:21 AM
Generally anything that size will require an engineered design with stamped plans from an electrical engineer. The plans will spec out wire, conduits, panels, etc.
#5
12-18-15, 09:37 PM
Group Moderator
#8
12-22-15, 05:47 PM
Group Moderator
They don't make 900A wire.
So basically you would need to make two 450A runs. Two conduits next to each other with three wires plus ground in each pipe. Phase A, B, C and ground in each conduit.
However.... even that wire is too big to work with so you could run three conduits.
That would be three conduits with each one having three phases and and a ground.
You would use 300A wiring in each conduit.
Conduit 1 (300A) + conduit 2 (300A) + conduit 3 (300A) = 900A
Running three parallel sets of feeders requires special lugs as now each phase will be 3 wires.
So basically you would need to make two 450A runs. Two conduits next to each other with three wires plus ground in each pipe. Phase A, B, C and ground in each conduit.
However.... even that wire is too big to work with so you could run three conduits.
That would be three conduits with each one having three phases and and a ground.
You would use 300A wiring in each conduit.
Conduit 1 (300A) + conduit 2 (300A) + conduit 3 (300A) = 900A
Running three parallel sets of feeders requires special lugs as now each phase will be 3 wires.
#9
12-23-15, 06:55 AM
I'll add on one additional point that each parallel run needs to be as identical as possible in terms of length, route, materials, etc. Even small variations in one path can cause significant overloads on some of the conductors.
#10
12-23-15, 06:19 PM
Member
As I recall, the ground wire with each set of paralleled conductors must be sized to the overcurrent device and not by the conductors it is run with. In other words, the ground must be full sized in each of the conduits. This could substantially increase the conduit size and would be a good case for using a conduit ground only.
