Wire Amperage based on Straight Current Transmission

[kunk]

We have an Engineer saying that 3/0 wire will carry 239 amps in a straight current transmission. I can not find this calculation.

We are running the wire from the power company transformer underground to a meter pedastal then back underground to a panel with a 225 Amp Main breaker inside the building. They are saying we can use a 3/0 wire and a 320 Amp meter base to a 225 Amp MB.

 

[charlie b]

We have an Engineer saying that 3/0 wire will carry 239 amps in a straight current transmission.

I have no idea what this means. "Straight"? "Transmission"?

But it sounds like you are dealing with the utility side of the main service disconnect. The NEC rules do not apply there. What does the utility have to say?

 

[skeshesh]

I've also never heard of "straight current transmission" and a web search did not return any relevant results...

I gather from the OP that a utility engineer advised 3/0. If you want to push futher you can ask for a calc reference but as Charlie mentioned utility is its own AHJ. In addition cable ampacities are allowed to be calculated under qualified engineering supervision, take a look at 310.15(C).

 

[kunk]

Straight Current Transmission

Straight Current Transmission

I've also never heard of "straight current transmission" and a web search did not return any relevant results...

I gather from the OP that a utility engineer advised 3/0. If you want to push futher you can ask for a calc reference but as Charlie mentioned utility is its own AHJ. In addition cable ampacities are allowed to be calculated under qualified engineering supervision, take a look at 310.15(C).

This is not the power company. We are responsible to run from the power co. transformer to meter then to panel. I would think we would need to go by the 75 degree table.

 

[kunk]

The power company responsibility stops at the pole. The Electrician is responsible for the wire from pole to meter base and then to the panel.

I would think that this would fall under the 75 degree amperage chart.

 

[augie47]

What relationship does the engineer have with the job ?

 

[skeshesh]

This is not the power company. We are responsible to run from the power co. transformer to meter then to panel. I would think we would need to go by the 75 degree table.

I never said the power company is responsible for the installation. But I got the feeling that the engineer that's advising you was a utility engineer. I don't know any customer side engineers who would use a calculated ampacity for a 200-300A service. I would think the only time someone would be calculating ampacities is in special industrial applications and using software.

 

[iwire]

The power company responsibility stops at the pole. The Electrician is responsible for the wire from pole to meter base and then to the panel.

Are you sure of that?

In my area we often run underground from the pole or pad mount to the meter but that work is often under the NESC as the service point is at the meter.