400A Service Underground wire

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Horst1

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Now I understand why Engineers go to school for 6 years, so they can learn how to make the electrician correct their work... I have a new 400A commercial service, engineer calculated out the load at 154A (the 400A is by request of owner) So, the smart one designed this: 400A (320 continuous) meter can, behind that within 3' are 2 - 200A MB panels fed from double lugs on the meter can (2/0 cu). The meter can is fed 125' of 2/0 copper underground to the power company handhole. The smart one says that he only has to feed to the connected load, (which would only be 1/0 anyway) And that the 2 - 200A mains have nothing to do with the wire sizing...

Ok, I say, the 2/0 service wire is protected by 400A disconnect (equivelent) and that he must size for 400A, which means he can spec parallel runs of 250 KCmil AL. The 2/0 Cu at the meter cans is sufficient to feed each panel.

Now, I asked my inspector, before I went nose to nose with the smart one, and my inspector says I can actually go with parallel 4/0 AL, something about next standard size and Art 240... I really want to build this right, tell the engineer why and be smart enough to defend my position. Mostly because the owner will eat the additional cost and he is trying to save money... The 400A is necessary because they will utilize it in the future with a Deli/resturant added (although plans do not specify this).

So, any words of wisdom? Thanks.
 
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Horst1

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Oh My!!!

Oh My!!!

Wow, that 6 years paid off... I just read it and sure enough... Bizarre! Now what happens when the load increases to 350A after the resturant goes in... I mean besides the melting conductor part.... Thanks!

I'll tell you what, I will not build it.
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
Horst1 said:
Now what happens when the load increases to 350A after the resturant goes in... I mean besides the melting conductor part....
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You get to replace them. :grin:

The idea is that who ever adds load to the service in the future is required to do it within the code and that means doing load calcs to show that the conductors will not melt.

I'll tell you what, I will not build it.
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I would install this, after making sure the customer is well aware of the future costs, especially seeing as the customer asked for a 400 amp service.

IMO the service that the engineer has designed is not a 400 amp service it is at best a 175 amp 'service'
 
peter d

peter d

Senior Member
Location
New England
This situation is really no different than when the Poco provides and installs the underground conductors. They will usually run much smaller conductors than what the NEC calls for.

The difference is that the poco is responsible for them and will replace them when/if they melt down (which is not very likely.)

Is there any particular reason why the owner is requesting a 400 amp service?
 
mdshunk

mdshunk

Senior Member
Location
Right here.
peter d said:
Is there any particular reason why the owner is requesting a 400 amp service?
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Probably for the same reason some men have huge Rottweilers with spiked collars and drive pickup trucks with huge tires and suspensions. I reserve the customer's right to overkill the situation.
 
Awg-Dawg

Awg-Dawg

Senior Member
Location
Dayton Ohio
mdshunk said:
Probably for the same reason some men have huge Rottweilers with spiked collars and drive pickup trucks with huge tires and suspensions.
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There is just something about big wire/gear that people just like.

Never heard anyone say "Hey Jim, come look at my big water pipe":)
 
H

Horst1

Member
Owners Aspirations...

Owners Aspirations...

The service is based on the future growth of the property. The building is located on a major intersection. I have spoke with the owner and he is willing to go with 4/0 AL parallel (cost was a factor) and seems to understand the future costs would be double since everything would have to be cut back up, resoded, etc. As far as the Engineer goes... I guess he oversized a little with the 2/0 cu....
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
what future load ????

what future load ????

peter d said:
This situation is really no different than when the Poco provides and installs the underground conductors. They will usually run much smaller conductors than what the NEC calls for.

The difference is that the poco is responsible for them and will replace them when/if they melt down (which is not very likely.)

Is there any particular reason why the owner is requesting a 400 amp service?
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built many a 600-800 amp service to have POCO hit it with a pair of 4/0s from a 75 kva bank, based on the actual load. Most are still operating in the original state. They say they would bankrupt if the built everything to the customer's propsed future load.
 
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