New underground service

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noon9elec

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Bourne, MA
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Self employed Electrical Contractor
So its been awhile since I have done any type residential work, as my work over the last 3 years involves service only. No matter, but I am replacing an underground service 500 ft. long. While there is no significant load, I was thinking that a typical 4/0 URD, without reduced neutral would satisfy everyone. I was planning on a 200-amp panel, and I researched the 4/0 URD-rated for 308 amps. thats pretty much what was there before, I shouldn't have a problem, correct? Thanks
 
noon9elec said:
So its been awhile since I have done any type residential work, as my work over the last 3 years involves service only. No matter, but I am replacing an underground service 500 ft. long. While there is no significant load, I was thinking that a typical 4/0 URD, without reduced neutral would satisfy everyone. I was planning on a 200-amp panel, and I researched the 4/0 URD-rated for 308 amps. thats pretty much what was there before, I shouldn't have a problem, correct? Thanks
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That is probably fine. That would be about 3.5% VD at 70 amps. If that is an abnormal amount of electrical loads such as resistive heat, on demand water heater, etc, I might go a bit bigger but thats fine for the typical house. Not sure where you are getting 308 amps from. 4/0 AL is 180 amps, which you can next size up to 200, if the calculated load is under 180
 
noon9elec said:
So its been awhile since I have done any type residential work, as my work over the last 3 years involves service only. No matter, but I am replacing an underground service 500 ft. long. While there is no significant load, I was thinking that a typical 4/0 URD, without reduced neutral would satisfy everyone. I was planning on a 200-amp panel, and I researched the 4/0 URD-rated for 308 amps. thats pretty much what was there before, I shouldn't have a problem, correct? Thanks
Click to expand...


4/0 is not rated 308 amps. As stated if this is truly URD that it is not code compliant. Your supply company should carry some type of USE cable. It is rated 180 amps but is allowed for 200 amps for a residence.
 
noon9elec said:
So its been awhile since I have done any type residential work, as my work over the last 3 years involves service only. No matter, but I am replacing an underground service 500 ft. long. While there is no significant load, I was thinking that a typical 4/0 URD, without reduced neutral would satisfy everyone. I was planning on a 200-amp panel, and I researched the 4/0 URD-rated for 308 amps. thats pretty much what was there before, I shouldn't have a problem, correct? Thanks
Click to expand...
You say there is no significant load, don't know what level you call significant, but if under 100 you are probably fine.

NEC ampacity is going to be 180 amps on 4/0 aluminum. That don't mean the conductor can't carry more then that, it is just how much it can carry without starting to get into an operating temp that may start to compromise the 75C termination ratings.

Voltage drop is going to be present, but outside a few specific applications, NEC doesn't have any voltage drop requirements, just an informational note making some suggestions.
 
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