wire sizing

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dshelley

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the contractor on a job where I work is running 2 sets parelled 4-0 3phase 480 v
runs to a 500 amp breaker, then he has paralled two sets of 3-0 copper 3 phase 480 v runs to a softstart controlling a 335 hp motor will this work ?
 
must be the same guy using the welding cable :D
Unsure what type of voltage motoe you are delaing with, if it's a 480 volt 3 phase motor then:
will it work ? probably, just like the welding cable will work.
does it meet NEC ? probably not... but more info would be in order.

ass-u-ming a 335 hp (this time you stated HP) motor would have a FLA of about 400 amps requiring 500 amp comductors. Parrell 3/0s in seperate conduits under normal ambient would be 400 amps.
 
augie47 said:
must be the same guy using the welding cable :D
Unsure what type of voltage motoe you are delaing with, if it's a 480 volt 3 phase motor then:
will it work ? probably, just like the welding cable will work.
does it meet NEC ? probably not... but more info would be in order.

ass-u-ming a 335 hp (this time you stated HP) motor would have a FLA of about 400 amps requiring 500 amp comductors. Parrell 3/0s in seperate conduits under normal ambient would be 400 amps.
Click to expand...

the contractor on a job where I work is running 2 sets parelled 4-0 3phase 480 v
runs to a 500 amp breaker
Click to expand...
However, 4/0cu is only good for 230amp. I see it as upsizing to 2 sets of 250kcm.
 
wire size

wire size

would you have to refer to table 430.250 to get the amper and since it is a continous duty add the 125 percent?
 
After the last two topics you posted, I get the feeling you are wanting someone to design the projects, if I am wrong, I apologize.
I would refer you to Art 430 on motors, and 310 on amapcities.
In your previous post I indcated the steps for sizing motor conductirs.
You indicate 10 years contractor experience so those sections should not be foreign.
You tell us how you would wire it, and how you obtained that and I will be glad to provide my opinion.
Someone else may approach differently.

(Mr. Moderator, if I overstepped my bounds I apologize.)
 
reply

reply

sorry this contractor is making me second guess myself. of course I would refer to 430.250 and use the amperes in the table then add 125 percent but I don't think he is doing that
 
augie47 said:
After the last two topics you posted, I get the feeling you are wanting someone to design the projects, if I am wrong, I apologize.
I would refer you to Art 430 on motors, and 310 on amapcities.
In your previous post I indcated the steps for sizing motor conductirs.
You indicate 10 years contractor experience so those sections should not be foreign.
You tell us how you would wire it, and how you obtained that and I will be glad to provide my opinion.
Someone else may approach differently.

(Mr. Moderator, if I overstepped my bounds I apologize.)
Click to expand...

Agreed.

IF this "contractor" is running parallel 4/0 (230amp) to a 500 amp breaker and the motor works out at 500amps. Doesn't it make sense the wire size should be the same? As I stated 4/0 is only good for 230amps it should be up-sized to 250 kcm. Or am I way off base here?
 
2 sets of 230 =460, next size up is 500 - doesn't that comply with 240.4 B ?

there are many motors for which the stated 3/0s would work, there's not enough info stated to know this is not correctly wired imho
 
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