We are currently doing a job which requires us to upgrade an existing 1200 amp service to a 2000.There are existing 4 inch pipes ( 4 ) with parrallel 350 conductors. We planned to add 2 more 4 inch conduits and parrallel 500 conductors, to meet our 2000 amp needs. Does anyone have a better route for example adding more conduits for more 350 conductors instead of 500 mcm conductors. The 350 megged out fine and aare only 4 months old. Please give advice. Your help is greatly appreciated.
2000 amp SERVICE
- Thread starter butch
- Start date
- Status
- Location
- Massachusetts
Re: 2000 amp SERVICE
First do you know you can not mix sizes on each phase?
Add three conduits for a total of 7 sets of the 350s 7 x 310 amps = 2170 amps.
But can you land all of this?
Or scrap the 350s and have a party, add 1 conduit and run 5 sets of 600
420 x 5 = 2100 amps
[ March 13, 2003, 02:45 PM: Message edited by: iwire ]
First do you know you can not mix sizes on each phase?
Add three conduits for a total of 7 sets of the 350s 7 x 310 amps = 2170 amps.
But can you land all of this?
Or scrap the 350s and have a party, add 1 conduit and run 5 sets of 600
420 x 5 = 2100 amps
[ March 13, 2003, 02:45 PM: Message edited by: iwire ]
Re: 2000 amp SERVICE
310.4
The paralleled conductors in each phase, neutral, or grounded circuit conductor shall
(1) Be the same length
(2) Have the same conductor material
(3) Be the same size in circular mil area (4) Have the same insulation type
(5) Be terminated in the same manner
As the previous poster stated, they all have to be the same size, just wanted to throw the code reason why.
Your best bet would be to scrap the existing, and start anew. The conduits could more than likely be used, it would only require new wire, all of the same size.
Rick
310.4
The paralleled conductors in each phase, neutral, or grounded circuit conductor shall
(1) Be the same length
(2) Have the same conductor material
(3) Be the same size in circular mil area (4) Have the same insulation type
(5) Be terminated in the same manner
As the previous poster stated, they all have to be the same size, just wanted to throw the code reason why.
Your best bet would be to scrap the existing, and start anew. The conduits could more than likely be used, it would only require new wire, all of the same size.
Rick
- Location
- Massachusetts
Re: 2000 amp SERVICE
Thanks rdoan71 for typing that up, but do not forget that 310.4 goes on to explain that one set of phase conductors can be different from another set of phase conductors.
Not likely to apply here though.
Also the raceways have to be the same as each other.
[ March 13, 2003, 02:59 PM: Message edited by: iwire ]
Thanks rdoan71 for typing that up, but do not forget that 310.4 goes on to explain that one set of phase conductors can be different from another set of phase conductors.
Not likely to apply here though.
Also the raceways have to be the same as each other.
[ March 13, 2003, 02:59 PM: Message edited by: iwire ]
- Location
- Illinois
- Occupation
- retired electrician
Re: 2000 amp SERVICE
Remember that if the majority of the load is nonlinear, that the grounded conductor is current carrying, then we have to derate to 80% and this will require larger or more conductors.
Don
Remember that if the majority of the load is nonlinear, that the grounded conductor is current carrying, then we have to derate to 80% and this will require larger or more conductors.
Don
- Location
- Massachusetts
Re: 2000 amp SERVICE
From doing the math for the 1200 it did not seem like it was figured as a current carring conductor.
4 sets x 310 = 1240 x .8 = 992 amps he would have been already undesize.
Same for terminal ratings
4 sets x 260 = 1040
From doing the math for the 1200 it did not seem like it was figured as a current carring conductor.
4 sets x 310 = 1240 x .8 = 992 amps he would have been already undesize.
Same for terminal ratings
4 sets x 260 = 1040
doug glasscock
Member
- Location
- Virginia
Re: 2000 amp SERVICE
Don,
Is there a percent value tagged to the word "majority" in your post that says that the neutral conductor is current carrying as far as derating is concerned?
Don,
Is there a percent value tagged to the word "majority" in your post that says that the neutral conductor is current carrying as far as derating is concerned?
Re: 2000 amp SERVICE
How many current carrying conductors are there? If there are only three, then rdoan's statement is correct. If there is a grounded conductor, then you would have to derate according to 310.15 B 2 A.
If there isn't any grounded conductors, then why not put 6 500's & a ground in each existing 4" pipe? Depending on the number of bends and length of run, this may be an easier way than adding new conduit.
How many current carrying conductors are there? If there are only three, then rdoan's statement is correct. If there is a grounded conductor, then you would have to derate according to 310.15 B 2 A.
If there isn't any grounded conductors, then why not put 6 500's & a ground in each existing 4" pipe? Depending on the number of bends and length of run, this may be an easier way than adding new conduit.
- Location
- Illinois
- Occupation
- retired electrician
Re: 2000 amp SERVICE
Doug,
The wording come from 310.15(B)(4)(c). In my opinion, the grounded conductor must be counted as a current carrying conductor when the nonlinear load is over 50% of the total load.
Bob,
Yes, the original conductor sizing was too small if the grounded conductor is a current carrying conductor. I have no way of knowing if the original installation was calculated correctly. Your derating should start from the 90?C ampacity of the 350 which is 350 amps. That would result in a adjusted ampacity of 350(0.8) or 280 amps per conductor and a total of 1120 amps for the set of 4.
Don
Doug,
The wording come from 310.15(B)(4)(c). In my opinion, the grounded conductor must be counted as a current carrying conductor when the nonlinear load is over 50% of the total load.
Bob,
Yes, the original conductor sizing was too small if the grounded conductor is a current carrying conductor. I have no way of knowing if the original installation was calculated correctly. Your derating should start from the 90?C ampacity of the 350 which is 350 amps. That would result in a adjusted ampacity of 350(0.8) or 280 amps per conductor and a total of 1120 amps for the set of 4.
Don
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