2500 amp service conductors and raceway

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dennisdamenace

New member
I am trying to figure what I need to supply a peice of equipment for 2500 amps. I need to know what size wire and conduits I need. It will be 480 volt 3 phase. Also what size transformer I will need and the size of wire and conduit to feed a 4000 amp switchboard. Been racking my brain on these. Thank you so much for your help.
 

augie47

Moderator
Staff member
Location
Tennessee
The actual load is key here.
There are numerous answers depending on variables.
Your basic tool is, of course 310.16. If you have an actual 2500 amp load, then the sum of your conductors must meet that value {(7) 500s =2650 etc)}, but if your load is less, you might be able to use appropriate conductors {(7) 350s=2450}

As for transformer sizing... again the actual load is of prime importance, also, is it a customer transformer or POCO (POCO often allows for more overloading than customer owned)
 
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kwired

Electron manager
Location
NE Nebraska
I don't mean to be rude but it sounds like more than you can handle based on what you asked, or at least how you asked.

How do you know you need 2500 amps? That comes first, sizing conductors whether 250 amps or 2500 amps is a similar task. Overcurrent protection rules are a little different for 2500 than they are for 250.

We are here to help if you have a question on how to do something but are not here to design this for you.
 

tkb

Senior Member
Location
MA
I would consider feeder buss if this is an above ground installation.
There is outdoor feeder buss available.
It will cost more than pipe and wire, but the installation labor would be less.
 

Smart $

Esteemed Member
Location
Ohio
We can make some general assumptions here, since we don't have enough details, as mentioned in earlier posts... it will help guide you.

First assumption, you want available power to the 4000A switchboard to be 4000A non-continuous or 3200A continuous, with an additional assumption the switchboard has no 100% rated gear. As such you are looking at parallel feeder sets, as Gus mentioned, or feeder bus (aka bus duct, busway) mentioned by tkb, sized for 4000A.

Your xfmr will need be rated at a minimum of 4kA ? 480V x 1.732 = 3.33MVA. If there is high inductive loading (high hp motors) that can start simultaneously, you may need to upsize to handle their inrush current.
 

BJ Conner

Senior Member
Location
97006
I am trying to figure what I need to supply a peice of equipment for 2500 amps. I need to know what size wire and conduits I need. It will be 480 volt 3 phase. Also what size transformer I will need and the size of wire and conduit to feed a 4000 amp switchboard. Been racking my brain on these. Thank you so much for your help.
You really need an engineer. As noted above seems like some people try to get free engineering here. I don't scab on electricans but there seems to be a lot of contractors who kind of do or want free engineering.
Remember- "Nothing cost as much as cheap ( or bad or free) engineering"
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I am trying to figure what I need to supply a peice of equipment for 2500 amps. I need to know what size wire and conduits I need. It will be 480 volt 3 phase.
Depends a lot on what you really need. Where did the 2500A number come from? Is that the rating of something, or a calculated load?

Also what size transformer I will need and the size of wire and conduit to feed a 4000 amp switchboard. Been racking my brain on these. Thank you so much for your help.
Is this part of the same system? The answer in general is that the minimum size of the transformer and feeder to the switchboard are based on the calculated load.

I also suspect this is something you might want to get some engineering help on. Stuff like this can have some non-obvious issues that can bite you in the backside.

Something to consider if you can make it work in your situation is that sometimes it is more cost effective to supply multiple smaller units than one large unit to cover the entire load.
 
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