# Best Practice for 1200 amps 600s or 350s



## VELOCI3 (Aug 15, 2019)

Southeast Power said:


> I have a design choice between using 4 sets of 350s or 3 sets of 600s copper.
> 
> Space isn't a concern, the run is under 50'.
> 
> ...




600’s. Less space, less labor, less overall cost. Think of the labor and material used for that 4th run of conduit


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## macmikeman (Jan 23, 2007)

I think we need to consider which one will contribute more to global warming and thereby flood Miami faster.


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## macmikeman (Jan 23, 2007)

I'm serious. These things need to be taken into consideration by all electrical designers.


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## gpop (May 14, 2018)

No real reason so it comes down to experience. You have lots of that so do the job in your head step by step and look for sticking points. 

Things like tugger wont fit so its a hand pull, No room for long sweeps, etc.


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## Southeast Power (Jan 18, 2009)

gpop said:


> No real reason so it comes down to experience. You have lots of that so do the job in your head step by step and look for sticking points.
> 
> Things like tugger wont fit so its a hand pull, No room for long sweeps, etc.


A tugger will work, I have been using double 45s on all of our underground.

We will be sliding the utility TX over a couple of feet and then setting a new ATS next to it. I'll cut a channel in the concrete if needed and just free wire underground from the TX to the ATS. 
The real job is to extend and re-terminate the existing 9 sets of conductors now in the TX into the ATS. Sucks for me I have to add a ground wire in each of the sets.


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## Southeast Power (Jan 18, 2009)

macmikeman said:


> I think we need to consider which one will contribute more to global warming and thereby flood Miami faster.


I do have to consider that we could be required to set our new equipment above some kind of FEMA flood elevation.
The coastal one we just poured was +11'


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## paulengr (Oct 8, 2017)

Labor will be less with 350s. Very difficult to bend 500+ without tools. Easy on 350. Material cost might be less too since PVC is very inexpensive.

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## Southeast Power (Jan 18, 2009)

paulengr said:


> Labor will be less with 350s. Very difficult to bend 500+ without tools. Easy on 350. Material cost might be less too since PVC is very inexpensive.
> 
> Sent from my SM-T350 using Tapatalk


I don’t mind 600s but it seems like every ache and pain I have, I can relate to working with 500s. I like getting wire put up quadplexed and phase colored it just gets too heavy to handle. I think 4- 50’ cuts of 350s with pulling eyes on them would make a quick job of the underground.


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## telsa (May 22, 2015)

I'd do everything under the Sun to not use 600 kCMIL copper conductors.

Running parallel conduits = less and less expense... either in the trench or O/H.

It's not even a close decision.

Better still, unless compelled -- go with aluminum -- 500 kCMIL -- 4 times over--- in 3" EMT.


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## Helmut (May 7, 2014)

Run is under 50'?

PVC costs is what? >$200 a run? Space is no concern?

Aluminum is easier to work with, IMO


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## flyboy (Jun 13, 2011)

Definitely smallest aluminum conductor you can get away with run in PVC raceways. I wouldn't even quote copper if it isn't spec'd.


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## Cow (Jan 16, 2008)

Put me in the camp of "not a fan of 600mcm".


Parallel 350CU or 500AL for us. I'd verify lugs at both ends before committing to one or the other though.



CU or AL, whatever the customer wants....


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## VELOCI3 (Aug 15, 2019)

Cow said:


> Put me in the camp of "not a fan of 600mcm".
> 
> 
> Parallel 350CU or 500AL for us. I'd verify lugs at both ends before committing to one or the other though.
> ...




If there are 4 runs then you can do 300 THHN in 2-1/2” sch40 PVC. In 25 years doing commercial and industrial I have never seen aluminum used. Not even in network service feeders from the utility. 


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## Southeast Power (Jan 18, 2009)

500 Aluminum is like 1.98 per foot
350 copper is 5.91 per foot


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## paulengr (Oct 8, 2017)

VELOCI3 said:


> If there are 4 runs then you can do 300 THHN in 2-1/2” sch40 PVC. In 25 years doing commercial and industrial I have never seen aluminum used. Not even in network service feeders from the utility.
> 
> 
> Sent from my iPhone using Tapatalk


Look up on the pole.



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## Cow (Jan 16, 2008)

VELOCI3 said:


> If there are 4 runs then you can do 300 THHN in 2-1/2” sch40 PVC.



300 CU is good for 285 amps. 4 sets doesn't get you to 1200 amps. The "round up rule" only works for 800 amps and less.


The only way your scenario would work is if Southeast Power was feeding a service using the six disconnect rule and his connected load was under (4x285)=1140 amps. 





VELOCI3 said:


> In 25 years doing commercial and industrial I have never seen aluminum used. Not even in network service feeders from the utility.



That hasn't been my experience.


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## VELOCI3 (Aug 15, 2019)

Cow said:


> 300 CU is good for 285 amps. 4 sets doesn't get you to 1200 amps. The "round up rule" only works for 800 amps and less.
> 
> 
> The only way your scenario would work is if Southeast Power was feeding a service using the six disconnect rule and his connected load was under (4x285)=1140 amps.
> ...




I’d like some more info on that rule. 

300’s at 75C is definitely 285A

300’s at 90C is 320A. Make sure your breaker and terminations and are 90C capable. 

Both ways work but certain conditions must be met. 


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## telsa (May 22, 2015)

VELOCI3 said:


> I’d like some more info on that rule.
> 
> 300’s at 75C is definitely 285A
> 
> ...


Such beasts don't exist.


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## Bird dog (Oct 27, 2015)

90C column is for derating only.


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## Helmut (May 7, 2014)

Southeast Power said:


> 500 Aluminum is like 1.98 per foot
> 350 copper is 5.91 per foot


Gee, I wonder what way you went?


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## DashDingo (Feb 11, 2018)

Of course aluminum 500’s would be the best choice.
But if it was spec copper.... 350’s all day.
Anything 500+ in copper is an absolute kock suckher 


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## Southeast Power (Jan 18, 2009)

Helmut said:


> Gee, I wonder what way you went?


I bid it with the tree fiddies :smile:


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