electric utility

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Brad Baxter

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electric utility told me that they are going to run 1 set of 350kcmil al to a 400amp service and meter socket. not in parallel so i said huh????????

I told him that we usually run 600kcmil al and he said they do not follow the same chart as us electricians. anyone ever heard of this?
 
Brad Baxter said:
electric utility told me that they are going to run 1 set of 350kcmil al to a 400amp service and meter socket. not in parallel so i said huh????????

I told him that we usually run 600kcmil al and he said they do not follow the same chart as us electricians. anyone ever heard of this?
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Utility work is not covered by the NEC. 90.2(B)(5)
 
In most case the utility will size their equipment at 50% of what the NEC is. In some situation that 4/0 would remain even if the service went from 400amp to 600amp.
 
Brad Baxter said:
electric utility told me that they are going to run 1 set of 350kcmil al to a 400amp service and meter socket. not in parallel so i said huh????????

I told him that we usually run 600kcmil al and he said they do not follow the same chart as us electricians. anyone ever heard of this?
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Yup, that's perfectly normal. It's the same way around here...a 400 amp service will get a 250 kcmil or 4/0 aluminum service lateral.

As mentioned the poco uses historical load data and not the NEC in sizing its conductors and transformers. Furthermore, if they do undersize something (very unlikely) they are there 24/7/365 to repair or replace it.
 
Who is installing the service cables from utility transformer to service panelboard/switchboard, utility company or building electric contractor? I know utility company size their service transformer based on their chart, and the connected load we provided to them. The service transformer utility company provided is much smaller than the service we applied/calcuated. It is the utility company's responsibility if the transformer burned out. If the service cables are installed by utility company, it is their responsibility to make sure the cable is big enough to handle the load and the main circuit breaker in switchboard will not be able to protect them. But I would think it is building electric contractor's responsibility to installed those service cables from service transformer to service panelboard/switchboard because I alway design the cable and conduit size for serice on single-line diagram.
 
You guys did a great job of explaining how the electric utilities install their services. I have nothing to correct, you guys are good.

We will install #4 Al for a 100 ampere overhead service, #2 for a 200, and 4/0 for a 400. For underground services, we use much larger conductors but they are always aluminum. :smile:
 
charlie said:
We will install #4 Al for a 100 ampere overhead service, #2 for a 200, and 4/0 for a 400. For underground services, we use much larger conductors but they are always aluminum. :smile:
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Out of curiosity, what does your company run for U/G service laterals on the 100, 200 and 400 amp services you mentioned?
 
peter d said:
Out of curiosity, what does your company run for U/G service laterals on the 100, 200 and 400 amp services you mentioned?
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4/0 for 100 & 200, either 4/0 or 500 kcmil for 400 (depends on the length of the lateral), 500 for up to 800, 2-500 for over 800 to 1600 amperes, all residential aluminum. 4/0 for 100 & 200, 500 for each multiple of 400 amperes to 1200 amperes, all commercial aluminum. Over 1200 amperes, the customer must supply the cable to a switchgear with internal metering transformers that are remotely located to the outside of the structure. :smile:
 
Our utility companys here do the same, but they quit using 4/0 on 400 amp laterals due to too many complaints of blinking lights when the A/C kicks on. Most underground here averages 150'-200'.
 
hillbilly1 said:
Our utility companys here do the same, but they quit using 4/0 on 400 amp laterals due to too many complaints of blinking lights when the A/C kicks on. Most underground here averages 150'-200'.
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I'm not sure where yer at, but I think my utility wouldn't care. In my old neighborhood everything was #6 solid AL coming down off the pole. I never figured it out but someone in the neighborhood had an ac unit that blinked all of the 20 or so houses on that Xfmr. I can only imagine what happened when I was welding. =)
 
480sparky said:
In my neck of the prairie, 2-2-4 for 100, 4/0-4/0-2/0 for 200 and 350/350/250 for 400.
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Are you from my neck of the woods, as we do the same as you?? We do run all aluminum.
Heck in some of our locations we will run two or three 2500 sq ft houses off a 350 underground secondary.
 
LarryFine said:
It may also be from an electric tank-less water heater.
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A residential customer who has a tank-less water heater is likely to be put onto a commercial rate because of the fluctuations if his neighbors complain. We will investigate and will fix the voltage problems but the cycling on and off of the tank-less will require a separate transformer to fix the neighbor's flicker problem. For that, the tank-less customers will get to pay a lot more for their power. :smile:
 
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