4000 amp service

[james wuebker]

Have a 4000 amp service. It's going to get relocated. Right now it has 10 sets of 500 mcm wires which is 3800 amps. Do I need to pull 600 mcm or is it OK to keep 500 mcm. I believe it should be 600 mcm wire but if I can pull 500's it would be OK with me.
Jim

 

[infinity]

Re: 4000 amp service

You would need 11 sets of 500 kcmil or 10 sets of 600 kcmil. Take a look at 240.4(C).

[ August 30, 2005, 04:13 PM: Message edited by: infinity ]

 

[charlie b]

Re: 4000 amp service

Not so fast. What is the calculated load? If it is between 3800 and 4000, then I agree with Infinity. If it is under 3800, and if you can set the main breaker to trip at 3800, then you can keep the 10 sets of 500's. If it is over 4000, then you have a different problem. If there is no service calculation, and if you don't choose to perform one, then you are back to Infinity's answer.

 

[ryan_618]

Re: 4000 amp service

Charlie, bare in mind that sizing conductors based on the adujustment is permitted only if 240.6(C) is complied with, otherwise you must follow 240.6(B).

 

[dillon3c]

Re: 4000 amp service



[ August 30, 2005, 05:19 PM: Message edited by: dillon3c ]

 

[don_resqcapt19]

Re: 4000 amp service

If there is more than one service disconnect, and the load is less than 3800 amps, then 230.90(A) Exception #3 will permit this installation. That is assuming that these are the service conductors and not feeder conductors.
Don

 

[james wuebker]

Re: 4000 amp service

Only 1 service disconnect. After looking over 240.6(c) I believe This main breaker is an adjustable-trip circuit breaker with a transparent,removable and sealable cover. This is a Sq. D breaker. I found this in my 2002 handbook in Exhibit 240.2. I think if using this type of breaker I can stick to my 500 mcm wire. Right now the max. load is only 2400 amps. Does anyone agree or should I just pull in 600 mcm wire.
Thanks!
Jim

 

[mdshunk]

Re: 4000 amp service

Originally posted by james wuebker:
Does anyone agree or should I just pull in 600 mcm wire.

Other than than possibly being wasteful and the price of copper, is there some reason why you would not want to feed this gear to it's full potential with 600's? I'm not sure what type of facility this is, but in manufacturing, that 2400 amp load today could easily be 3800 next year.

 

[highkvoltage]

Re: 4000 amp service

If you have to repull new wires I agree with the other poster that I would install the 600's for future loads. If you have to replace these again next year because you load is to much I would imagine somebody is not going to be happy. Another out would be install a spare conduit for future conductors. You can use 500's and always install another set if needed without to much cost in the future.
What size is you conduit that you are using. This also determines what you can do and what you can't. 4" all the above solutions work. 3 1/2" or 2 1/2" (3 - 500's are allowed) you are limited to use 500's and add a conduit.

 

[james wuebker]

Re: 4000 amp service

I don't think the load should go over 2700 amps because they are building another building to this and installing another 4000 amp service to it. This is a plastic injection molding company. Now if there wasn't another service going to be added then run the first service to it's max. Agree or disagree!
Thanks!
Jim

 

[tx2step]

Re: 4000 amp service

If this is an underground service, then you may also want to consider the load factor and Annex B.

There was a fairly involved discussion about this at the following thread:
http://www.mikeholt.com/cgi-bin/codeforum/ultimatebb.cgi?ubb=get_topic;f=3;t=001859;p=2

I recommend that you read this thread before you make a decision. One of the EE's there was describing situations where UG services burned up when the actual load was only about 60% of the normal capacity of the wire -- it was caused by overheating caused by the thermal characteristics of the duct bank and soil.

 

[charlie b]

Re: 4000 amp service

Originally posted by james wuebker:Now if there wasn't another service going to be added then run the first service to it's max. Agree or disagree!

Neither. I still think that the answer lies in a service calculation. Without that, you are guessing.

 

[james wuebker]

Re: 4000 amp service

charlie b, I know what they have and can have in the first biulding but the new one their not sure how many machines will be in there. I know in the new building 3 of the machines have 3 150 hp motors in each one and they are going to a/c the new building which is 40,000 sq. ft. A lot of secondary equipment. So they already have a figure that's around 2000 amps and they do believe that more machines will be put in this building.
Jim

 

[tx2step]

Re: 4000 amp service

Originally posted by james wuebker:
...I know what they have and can have in the first biulding...

Maybe today... but what about tomorrow? I've sure seen a lot of large manufacturers take unexpected and unanticipated directions and moves just a year or two after they've assured me of exactly what they had in mind to do in a particular facility. New machines and technology become available. New products or market demands open or change. Etc.

If they are paying for this, and are basing their decision on your recommendation, then I'd take the conservative route and install a fully rated entrance -- maybe even oversized if the load factor will be or might eventually be very high.

Why do you want to intentionally undersize the entrance capacity compared to the capacity of the existing service equipment?

What is your motivation for not making it fully rated? You must have a good reason, but I don't get it? Would you please clarify?

 

[james wuebker]

Re: 4000 amp service

The company wanted to go with what we needed for the first building and go the distance on the new building. Trying to save some money. I will let them know that I would like to go with the 600 mcm in both and then they will have their max. load available.
Thanks everyone!
Jim

 

[highkvoltage]

Re: 4000 amp service

Great tread. I have enjoyed reading how different people approach the same problem.

 

[pierre]

Re: 4000 amp service

Read Ryan's post again:


"(C) Devices Rated Over 800 Amperes. Where the overcurrent device is rated over 800 amperes, the ampacity of the conductors it protects shall be equal to or greater than the rating of the overcurrent device defined in 240.6 240.6."

240.6
3000, 4000, ...

notice the next smaller size ocpd is 3000 amps, not 3800.

Don't say to them you would like to install 600's, tell them it is required.

[ August 31, 2005, 10:14 PM: Message edited by: pierre ]

 

[rcwilson]

Re: 4000 amp service

Does 240.6 (C) "Restricted Access Adjustable Trip Circuit Breakers" apply here? (2002 Code)

IMO it could if the breaker has a cover over the trip unit that can be sealed with the breaker set at the 3800 A or lower long time pickup setting.

Regarding service calculations- I have never been able to guess the future load in an industrial building well enough to feel comfortable with the accuracy of service calculations. The error (or should I say uncertainty) in my calculations is probably 10% so I really couldn't tell the difference between a 4000A and a 3800 A service requirement.

A rule of thumb from my mentor- add up the motor loads, buy a transformer for 75% of that and it will run loaded at 70% or less. It has worked on our projects for the last 20 years.

I like the idea of running 500 kcmil and a spare conduit. Need to check Appendix B.

 

[pierre]

Re: 4000 amp service

I teach my students to read completely and not to stop when they think they have the answer.

I use the 05 mostly these days, as I am preparing myself for it's adoption in a few months.
Well I should take my own advice, as 240.6(C) is on the next page and I do believe it is permitted as Bob has asked.
Thanks for pointing that out Bob.