Am I an idiot?

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Crohnos01

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OK, so here's the deal. I submitted calcs for review by the clients engineer and one of the comments that I got back said that my voltage drop calculation was wrong. Their engineer says that the voltage at a sub panel 200 feet from the MDP is the same as at the MDP? Did I fall asleep in class somewhere? Don't you always do a vd calc on a sub panel if for no other reason than to size the conductor and make sure you don't exceed the allowable drop?
 
Not real sure what the issue was but I don't see the voltage at the MDP and a sub panel 200 feet away being the same.
 
Perhaps the plans or engineer specified the same VD limit from service to MDP, or for branch ckts, as the MDP to subpanels.
 
Superconductors?

Superconductors?

Find out what the engineer is spec'ing for the panel feeders. I'd love to have some of those zero resistance cables!
 
Lol... I guess you have a point...no load would make a difference.....albeit a impractical one...

I had a retired EE friend of mine check my numbers to make sure I wasn't screwing up something stupid also... Apparently I wasn't. His only comment was that I was approaching max amperage rating on my 3/0 conductors for my feeder and maybe I wanted to bump up to 4/0 for any future expansion. However I am limited by an existing 2" PVC conduit that will keep me from running 4- 4/0 conductors.. Well, I suppose I could go to Cu and maybe get there, but the electrician is going to feel the pain financially since this is a DB project.
 
Crohnos01 said:
Lol... I guess you have a point...no load would make a difference.....albeit a impractical one...

I had a retired EE friend of mine check my numbers to make sure I wasn't screwing up something stupid also... Apparently I wasn't. His only comment was that I was approaching max amperage rating on my 3/0 conductors for my feeder and maybe I wanted to bump up to 4/0 for any future expansion. However I am limited by an existing 2" PVC conduit that will keep me from running 4- 4/0 conductors.. Well, I suppose I could go to Cu and maybe get there, but the electrician is going to feel the pain financially since this is a DB project.
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You may very well have acceptable voltage drop but if I understand correctly you have 200 amp circuit and 3/0 aluminum conductors. 3/0 aluminum only has an ampacity of 155 amps, and must be protected no more than 175 amps - the next higher standard overcurrent device.
 
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