800A Service Aluminum Feeders

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flectrician

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I found this old thread but didn't really get an answer I'm confident in.

800 Amp Service

I am going to figure Alu. conductors, would you run 2 pipes with #800 xhhw or more pipes / smaller wire. I had in my head #750 would work but looking at ampacities I don't think I can skip over the #800 when using the 800 or less exception. The service is 277/480 3 phase 800 amps.
forums.mikeholt.com

My drawings call for an 800A service with (2) runs of 600MCM. The customer has taken an alternate to install aluminum conductors to save cost. Would the following satisfy the requirements for an 800A service. (2) runs of 750MCM aluminum (385A*2=770A) fused at the next size up =800A.

My concern is that the wire will not be rated for the full 800A. The terminations are rated at 75 degrees. I realize I can swap the terminations for 90 degree and be home scot free, but if I'm able to, I'd like to do it the way described above.
 
(a) in your case, the service conductors must be sized to carry the calculated load so if the load is no more than 770 amps you meet Code
(b) changing "the terminations" to 90° does not necessarily allow you to use the 90° rating.... it's based on the device rating which would normally be 75°
 
augie47 said:
(a) in your case, the service conductors must be sized to carry the calculated load so if the load is no more than 770 amps you meet Code
(b) changing "the terminations" to 90° does not necessarily allow you to use the 90° rating.... it's based on the device rating which would normally be 75°
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(a) There is no load. Only building a service no panel.
(b) The device is the meter enclosure, and then the disconnect.
 
(a) with no load calculation, you may need to have 800 amp conductors.
(b) the disconnect is more than likely 75° thus requiring 75° rated conductors. Elecrtrofelons suggestion on (4) 250s i would be a good method.
 
augie47 said:
(a) with no load calculation, you may need to have 800 amp conductors.
(b) the disconnect is more than likely 75° thus requiring 75° rated conductors. Elecrtrofelons suggestion on (4) 250s i would be a good method.
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(a) This will be determined by whatever the load turns out to be when they create it, correct? If, for instance, they build one panel with a demand load totaling 680A, I will be a-okay with my 770A rated conductors. Right?
 
flectrician said:
(a) This will be determined by whatever the load turns out to be when they create it, correct? If, for instance, they build one panel with a demand load totaling 680A, I will be a-okay with my 770A rated conductors. Right?
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Correct. however, with no load calculation to verify, inspectors will often require the service conductors be rated no less than the overcurrent device.
 
How are you calling for an 800 amp service when you don't know the load? Seems backwards.... Also the panels are rated 75C and I believe some of the lugs may be rated 90C but since the equipment is label 75C you are stuck there. I don't think you will find equipment in that size that is rated 90C
 
Dennis Alwon said:
How are you calling for an 800 amp service when you don't know the load? Seems backwards.... Also the panels are rated 75C and I believe some of the lugs may be rated 90C but since the equipment is label 75C you are stuck there. I don't think you will find equipment in that size that is rated 90C
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The permit is for the building shell.
 
Besides what has already been stated, is there an engineer of record involved as well as plan review?

If there are engineered drawings, changing them without involving the designer could cause more issues.
 
I guess I should have asked if the alternate was offered by the designer.
 
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