local electric coop

[roby]

I work for one of the largest electrical contractors in our area. We mainly build commercial and industrial buildings with fairly large sevices. Recently we built an 800 amp single phase, 240 vac service for a MRI clinic and resturant. We used an 800 amp meter center and split off with a 400 amp meter for each one. We pulled 3 500 kcmil copper wires to the breaker panel from each meter. The electric coop contracted the secondary from the pole underground to the meter center. They pulled parallel 350 kcmil AL for the 240 volt and
4/0 AL for the neutrals. Now I know this is not right. The boss, who is a master electrician asked why they did this. The coop's reply was, they can do what they want to. Is there anything we can do about this or do we just have to let them "do what they want to."

 

[charlie]

Re: local electric coop

Is there anything we can do about this or do we just have to let them "do what they want to."

OK, why do you want to do anything about this? If their cable burns up, it is outside - no problem, they have to fix or replace the cable. If the voltage drop is too great - no problem, they have a maximum voltage drop that is regulated, they have to replace the cable or move the transformer. If either on happens 40 years from now - no problem, they have to still fix it since they are responsible for the installation forever.

Let us look at your installation. How long is your guarantee? What happens if the load grows and you have too much voltage drop in the building? HMMM . . . I think they are charged for a service call and then a bill for the upgrade. What happens if a cable fails 30 years from now? HMMM . . . I think they are charged for a service call and then a bill for the upgrade.

Bottom line is that and electric utility will service an installation forever and you do not. Therefore, we get to size our cable for the load and you do not. The same applies to the transformation. We save money on the installation and once in a while (when we guess wrong) we have to fix our mistake.

Please do not take this the wrong way but a lot of electricians think there should be a level playing field, I submit to you that you would not want the playing field to be level.

 

[bob]

Re: local electric coop

The utility does not caculate load using the NEC.
Your caculated load to determine the main size will always be larger than the utility caculations. If the utiltiy used table 310-16, which they do not, the 4/0 would be rated at 180 amps x 2 = 360 amps. 360 x 240 volts = a demand
of 86 kw. Their caculations are base on the max demand. The rating of the 4/0 AL is probably higher than that given in table 310-16.